This document summarizes a numerical investigation of flow characteristics in a C-shaped subsonic diffuser. The study validated experimental results from a C-shaped diffuser with an area ratio of 1.273 and 30 degree turn angle using computational fluid dynamics software. A series of parametric simulations were then conducted, varying the area ratio from 1.25 to 2 and turn angle from 30 to 75 degrees. The simulations found that static pressure recovery increased with higher area ratios but decreased with higher turn angles, while total pressure loss remained relatively constant with parameter changes.
A Numerical study of Flow through Sigmoid DuctIJERA Editor
Curved diffusers are an integral component of the gas turbine engines of high-speed aircraft. These facilitate
effective operation of the combustor by reducing the total pressure loss. The performance characteristics of
these diffusers depend on their geometry and the inlet conditions. In the present investigation the distribution of
mean velocity, static pressure and total pressure are experimentally studied on a S-shape Diffusing Duct of
45°/45° angle of turn with an area ratio of 1.65 aspect ratio 3.95 keeping inlet width 55 mm with centre line
length 460 mm. The experimental results then were numerically validated with the help of Fluent. The velocity
distribution shows that generation of secondary motion in the form of counter rotating vortices within the 1st half
of the diffuser. The secondary motion changes their sense of rotation after the inflexion plane of the test
diffuser. The maximum values of the mass average static Pressure recovery and total pressure loss are 36% and
13% compared to the predicted results of 39% and 11% respectively, which shows a good agreement between
the experimental and predicted results.
Flow Investigation inside A Curved Square DuctIJERA Editor
This paper presents the results of an experimental work with measurement of wall static pressure of 90°C shaped Curved duct. The test duct is made up of transparent perspex sheets to facilitate the flow visualization study. The duct has an inlet to exit area ratio of 1.0 with centerline distance of 750 mm. The inlet aspect ratio of the test duct has been fixed at 1.0. The velocities for the proposed investigations are to be measured by using a Pitot tube.Wall pressures are measured with the help of an inclinedmanometer with the inclination of 35°. The manometer had two tubes emanating from it: one left open to the atmosphere and the other connected to the steel pipes attached to the four walls of the curved duct. The difference in the readings helped us calculate the static pressure and thereby the normalized pressure. Wall pressure distribution along the curved and parallel walls of the duct at 0°, 22.5°, 45°, 67.5° and 90° measuring sections was measured. All the experimental data has been processed by an Intel i3 CPU, 3 GB RAM PC and analyzed to give the distribution of static pressure in the square duct.The main purpose of this investigation is to show the development of secondary flow which happens when the flow takes place through the bend in the curvature. This secondary flow arises as a result of a centrifugal force acting when the flow moves through the bend. The investigation is carried out at three different velocities 20 m/s, 40 m/s and 60 m/s. The distribution of normalized pressure which is the ratio of static pressure to the dynamic pressure is mapped and shown in the form of contours by using the software package SURFER.The trend of wall static pressure development on the walls of C shaped duct shows that as the flow proceeds towards the curvature, there exists a high pressure gradient between the outside face and inside face due the centrifugal force acting along the curvature. This shows the bulk shifting of flow towards the inside face. This is due to the generation of secondary motion in a plane perpendicular to the primary flow.
CFD Simulation of Swirling Effect in S-Shaped Diffusing Duct by Swirl Angle o...IOSR Journals
Abstract: The present study involves the CFD analysis for the prediction of swirl effect on the characteristics
of a steady, incompressible flow through an S-shaped diffusing duct BY KEEPING SWIRL ANGLE OF 10˚. The
curved diffuser considered in the present case has S-shaped diffusing duct having an area ratio of 1.9, length of
300 mm and turning angle of 22.5°/22.5°. The static pressure, total pressure, velocity and turbulence intensity
were accounted. The improvement is observed for both, clockwise and anti-clockwise swirl, the improvement
being higher for clockwise swirl. Flow uniformity at the exit is more uniform for clockwise swirl at the inlet.
Keywords: Curved diffusers, intake ducts, swirling flow, secondary flows, pressure recovery
A Computational Investigation of Flow Structure Within a Sinuous DuctIJERA Editor
In the present investigation the distribution of mean velocity are experimentally studied on three constant area
rectangular curved ducts with an aspect ratio of 2.4. First one is C-shape, second one is S-shape and third one
is a DS-shape duct. The experiment is carried out at mass averaged mean velocity of 40m/s for all the ducts.
The velocity distribution shows for C-duct, the bulk flow shifting from outer wall to the inner wall along the
flow passage and for S-duct, the bulk flow shifting from outer wall to the inner wall in the first half and from
inner wall to the outer wall in the second half along the flow passage of curved ducts are very instinct. Due to
the imbalance of centrifugal force and radial pressure gradient, secondary motions in the forms of counter
rotating vortices have been generated within both the curved duct. For DS-duct the velocity distributions shows
the Bulk of flow shifting from inner watt to outer wall in the first bend and third bend of the duct and outer wall
to inner wall in the second bend and forth bend of the duct along the flow passage is very instinct. Flow at end
of the DS-duct is purely uniform in nature due to non existence of secondary motion. The experimental results
then were numerically validated with the help of Fluent, which shows a good agreement between the
experimental and predicted results for all the ducts
Flow Development through a Duct and a Diffuser Using CFDIJERA Editor
In the present paper an extensive study of rectangular cross-sectioned C-duct and C-diffuser is made by the help of 2-D mean velocity contours. Study of flow characteristics through constant area duct is a fundamental research area of basic fluid mechanics since the concepts of potential flow and frictional losses in conduit flow were established. C-ducts are used in aircraft intakes, combustors, internal cooling systems of gas turbines, ventilation ducts, wind tunnels etc., while diffuser is mechanical device usually made in the form of a gradual conical expander intended to raise the static pressure of the fluid flowing through it. Flow through curved ducts is more complex compared to straight duct due to the curvature of the duct axis and centrifugal forces are induced on the flowing fluid resulting in the development of secondary motion (normal to the primary flow direction) which is manifested in the form of a pair of contra-rotating vortices. For a diffuser in addition to the secondary flow, the diverging flow passage, which causes an adverse stream wise pressure gradient, can lead to flow separation. The combined effect may result n non uniformity of total pressure and total pressure loss at the exit. A comparative study of different turbulent models available in the Fluent using y as guidance in selecting the appropriate grid configuration and turbulence models are done. Standard k-ε model and RSM models are used to solve the closure problem for both the constant area duct and the diffuser. It has been observed that the Standard k-e model predicts the flow through the constant area duct and the diffuser within a reasonable domain ofthe y range.
Numerical Investigation of Single Stage of an Axial Flow Compressor for Effec...IJERA Editor
In present work, a compressor configuration is taken from literature which will be studied for aspect ratio (ratio between length of blade to chord length) influence over performance. Performance in the sense is pressure ratio of compressor. The aspect ratio of the blade is an important parameter and has a strong influence on the performance of axial flow compressor. There are so many literatures available on influence of design parameters of axial flow compressor over its performance. Few literatures only are available for effects of aspect ratio of blade over performance of compressor. A study is proposed to be carried out to verify the effect of aspect ratio on the performance of single stage subsonic compressor through ANSYS-CFX software. The analysis will be carried out for the constant tip diameter of the compressor rotor blade having an aspect ratio 1, 2 and 3 and to obtain the pressure loss and flow parameters of the compressor stage. Further increase in aspect ratio will lead to structural problem of compressor. Therefore, there will be optimum aspect ratio between 2 and 3. Simulation will be conducted to aspect ratios of 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8 and 2.9 to find optimum ratio using ANSYS-CFX commercial CFD software.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A Numerical study of Flow through Sigmoid DuctIJERA Editor
Curved diffusers are an integral component of the gas turbine engines of high-speed aircraft. These facilitate
effective operation of the combustor by reducing the total pressure loss. The performance characteristics of
these diffusers depend on their geometry and the inlet conditions. In the present investigation the distribution of
mean velocity, static pressure and total pressure are experimentally studied on a S-shape Diffusing Duct of
45°/45° angle of turn with an area ratio of 1.65 aspect ratio 3.95 keeping inlet width 55 mm with centre line
length 460 mm. The experimental results then were numerically validated with the help of Fluent. The velocity
distribution shows that generation of secondary motion in the form of counter rotating vortices within the 1st half
of the diffuser. The secondary motion changes their sense of rotation after the inflexion plane of the test
diffuser. The maximum values of the mass average static Pressure recovery and total pressure loss are 36% and
13% compared to the predicted results of 39% and 11% respectively, which shows a good agreement between
the experimental and predicted results.
Flow Investigation inside A Curved Square DuctIJERA Editor
This paper presents the results of an experimental work with measurement of wall static pressure of 90°C shaped Curved duct. The test duct is made up of transparent perspex sheets to facilitate the flow visualization study. The duct has an inlet to exit area ratio of 1.0 with centerline distance of 750 mm. The inlet aspect ratio of the test duct has been fixed at 1.0. The velocities for the proposed investigations are to be measured by using a Pitot tube.Wall pressures are measured with the help of an inclinedmanometer with the inclination of 35°. The manometer had two tubes emanating from it: one left open to the atmosphere and the other connected to the steel pipes attached to the four walls of the curved duct. The difference in the readings helped us calculate the static pressure and thereby the normalized pressure. Wall pressure distribution along the curved and parallel walls of the duct at 0°, 22.5°, 45°, 67.5° and 90° measuring sections was measured. All the experimental data has been processed by an Intel i3 CPU, 3 GB RAM PC and analyzed to give the distribution of static pressure in the square duct.The main purpose of this investigation is to show the development of secondary flow which happens when the flow takes place through the bend in the curvature. This secondary flow arises as a result of a centrifugal force acting when the flow moves through the bend. The investigation is carried out at three different velocities 20 m/s, 40 m/s and 60 m/s. The distribution of normalized pressure which is the ratio of static pressure to the dynamic pressure is mapped and shown in the form of contours by using the software package SURFER.The trend of wall static pressure development on the walls of C shaped duct shows that as the flow proceeds towards the curvature, there exists a high pressure gradient between the outside face and inside face due the centrifugal force acting along the curvature. This shows the bulk shifting of flow towards the inside face. This is due to the generation of secondary motion in a plane perpendicular to the primary flow.
CFD Simulation of Swirling Effect in S-Shaped Diffusing Duct by Swirl Angle o...IOSR Journals
Abstract: The present study involves the CFD analysis for the prediction of swirl effect on the characteristics
of a steady, incompressible flow through an S-shaped diffusing duct BY KEEPING SWIRL ANGLE OF 10˚. The
curved diffuser considered in the present case has S-shaped diffusing duct having an area ratio of 1.9, length of
300 mm and turning angle of 22.5°/22.5°. The static pressure, total pressure, velocity and turbulence intensity
were accounted. The improvement is observed for both, clockwise and anti-clockwise swirl, the improvement
being higher for clockwise swirl. Flow uniformity at the exit is more uniform for clockwise swirl at the inlet.
Keywords: Curved diffusers, intake ducts, swirling flow, secondary flows, pressure recovery
A Computational Investigation of Flow Structure Within a Sinuous DuctIJERA Editor
In the present investigation the distribution of mean velocity are experimentally studied on three constant area
rectangular curved ducts with an aspect ratio of 2.4. First one is C-shape, second one is S-shape and third one
is a DS-shape duct. The experiment is carried out at mass averaged mean velocity of 40m/s for all the ducts.
The velocity distribution shows for C-duct, the bulk flow shifting from outer wall to the inner wall along the
flow passage and for S-duct, the bulk flow shifting from outer wall to the inner wall in the first half and from
inner wall to the outer wall in the second half along the flow passage of curved ducts are very instinct. Due to
the imbalance of centrifugal force and radial pressure gradient, secondary motions in the forms of counter
rotating vortices have been generated within both the curved duct. For DS-duct the velocity distributions shows
the Bulk of flow shifting from inner watt to outer wall in the first bend and third bend of the duct and outer wall
to inner wall in the second bend and forth bend of the duct along the flow passage is very instinct. Flow at end
of the DS-duct is purely uniform in nature due to non existence of secondary motion. The experimental results
then were numerically validated with the help of Fluent, which shows a good agreement between the
experimental and predicted results for all the ducts
Flow Development through a Duct and a Diffuser Using CFDIJERA Editor
In the present paper an extensive study of rectangular cross-sectioned C-duct and C-diffuser is made by the help of 2-D mean velocity contours. Study of flow characteristics through constant area duct is a fundamental research area of basic fluid mechanics since the concepts of potential flow and frictional losses in conduit flow were established. C-ducts are used in aircraft intakes, combustors, internal cooling systems of gas turbines, ventilation ducts, wind tunnels etc., while diffuser is mechanical device usually made in the form of a gradual conical expander intended to raise the static pressure of the fluid flowing through it. Flow through curved ducts is more complex compared to straight duct due to the curvature of the duct axis and centrifugal forces are induced on the flowing fluid resulting in the development of secondary motion (normal to the primary flow direction) which is manifested in the form of a pair of contra-rotating vortices. For a diffuser in addition to the secondary flow, the diverging flow passage, which causes an adverse stream wise pressure gradient, can lead to flow separation. The combined effect may result n non uniformity of total pressure and total pressure loss at the exit. A comparative study of different turbulent models available in the Fluent using y as guidance in selecting the appropriate grid configuration and turbulence models are done. Standard k-ε model and RSM models are used to solve the closure problem for both the constant area duct and the diffuser. It has been observed that the Standard k-e model predicts the flow through the constant area duct and the diffuser within a reasonable domain ofthe y range.
Numerical Investigation of Single Stage of an Axial Flow Compressor for Effec...IJERA Editor
In present work, a compressor configuration is taken from literature which will be studied for aspect ratio (ratio between length of blade to chord length) influence over performance. Performance in the sense is pressure ratio of compressor. The aspect ratio of the blade is an important parameter and has a strong influence on the performance of axial flow compressor. There are so many literatures available on influence of design parameters of axial flow compressor over its performance. Few literatures only are available for effects of aspect ratio of blade over performance of compressor. A study is proposed to be carried out to verify the effect of aspect ratio on the performance of single stage subsonic compressor through ANSYS-CFX software. The analysis will be carried out for the constant tip diameter of the compressor rotor blade having an aspect ratio 1, 2 and 3 and to obtain the pressure loss and flow parameters of the compressor stage. Further increase in aspect ratio will lead to structural problem of compressor. Therefore, there will be optimum aspect ratio between 2 and 3. Simulation will be conducted to aspect ratios of 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8 and 2.9 to find optimum ratio using ANSYS-CFX commercial CFD software.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Effect of Geometric Configuration on Performance of Uniflow CycloneIJERD Editor
Reverse flow cyclones find wide applications in many industries however, they require a high
expenditure of energy and large pressure drops, which can be better overcome by uniflow cyclones. A
laboratory unit of Uniflow Cyclone has been developed with 45 mm inlet diameter. The performance
parameters pressure drop and total efficiency were studied for the effect of geometric configuration. The present
study includes the effect of 4 different geometric parameters on performance of uniflow cyclone. The geometric
variation of test cyclones includes the Inlet velocity, Vane angles, Outlet to inlet diameter ratio and Separation
lengths. The overall experimental results yield and investigated the optimal conditions for uniflow cyclone
performance is 450 vane angle, 0.5 outlet to inlet diameter ratio, 3D separation length and 9-10 m/s inlet
velocity. The experimental pressure drop values are validated with the model equations available in literature
and well matched for Ramachandran model.
Control of Suddenly Expanded Flow at Low Supersonic Mach NumbersIJERA Editor
In the present study the experiments were conducted to control the base pressure from a convergent-divergent
nozzle at low supersonic Mach numbers to assess the effectiveness of active control mechanism in the form of
micro jets at different expansion level. The parameters considered in the present study are the diameter ratio,
length to diameter ratio (L/D), Nozzle Pressure Ratio (NPR), and the Mach number. The diameter ratio selected
for the present study are 1.6, 1.8, 2.2, and 2.5. Experiments were conducted for nozzle pressure ratio (NPR)
from 3 to 11. The L/D ratio of the enlarged duct was varied from 10 to 1, and results are presented for L/D 4, 3,
2, and 1. The Mach numbers of the present studies are 1.1, 1.2, 1.4, and 1.5. The results show that the Micro jets
are very effective and are able to raise the base pressure value to a considerable level under the influence of
favorable pressure gradient except at lower NPR 3. At NPRs 5 and 7 for some cases the trends differ due to the
level of expansion, nature of waves present in the base region, relief available to the flow, L/D ratio of the
enlarged duct and the Mach numbers. It is seen that most of the cases exhibit similar behavior for the L/Ds in
the range 4 and 3, which means; that the back pressure has not adversely influenced the flow field in the base
region as well as in the duct. The minimum duct length required for the flow to be attached is L/D = 2, even
though in some cases flow is attached with duct wall. With this it can be stated that the micro jets can be an
alternative for the for base pressure control.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A Computational Analysis of Flow StructureThrough Constant Area S-DuctIJERA Editor
This paper presents the results of an experimental work with measurement of mean velocity contours in 2-D form and validation of the same with numerical results based on the y+ approach at fully developed flow for various turbulent models like, k-ε model, k-ω model, RNG k-ε model and Reynolds Stress Model (RSM), are used to solve the problem. All the turbulence models are studied in the commercial CFD code of Fluent. The experiment is carried out at mass averaged mean velocity of 40m/s and the geometry of the duct is chosen as rectangular cross-section of 45°/45° curved constant area S-duct. In the present paper the computational results obtained from the different turbulence models are compared with the experimental results. In addition to this for validation of the numerical simulation near wall treatments for fully developed flow or log-law region are also investigated for wall 30<y+><300 in the region where turbulent shear dominates. It is concluded from the present study that the mesh resolving the fully turbulent region is sufficiently accurate in terms of qualitative features. Here RSM turbulence model predicts the best results while comparing with the experimental results.RSM model also predicts the flow properties more consistently because it accounts for grid independence test.
A Computational Analysis of Flow Development through a Constant Area C- DuctIJERA Editor
This paper represents the results of an experimental work with measurement of mean velocity along with total pressure contours in 2-D form and validation of the same with numerical results based on the wall y+ approach for various turbulent models like, Spalart Alamras, k-ε model, k-ω model and RSM models are used to solve the closure problem. The turbulence models are investigated in the commercial CFD code of Fluent using y+ as guidance in selecting the appropriate grid configuration and turbulence model. The experiment is carried out at mass averaged mean velocity of 40m/s and the geometry of the duct is chosen as rectangular cross-section of 90 curved constant area duct .In the present paper the computational results obtained from different turbulence models are compared with the experimental result along with the near-wall treatments are investigated for wall y+<30>30 in the fully turbulent region. It is concluded in the present study that the mesh resolving the fully turbulent region is sufficiently accurate in terms of qualitative features. Here RSM turbulence model predicts the best results while comparing with the experimental results.
Numerical Study of Flow Separation Control by Tangential and Perpendicular Bl...CSCJournals
In this study, tangential and perpendicular steady blowing at the trailing edge of NACA 0012 airfoil is investigated numerically to flow separation control and to study the effects of blowing amplitude and blowing coefficient on airfoil aerodynamic characteristics. Flow was fully turbulent with the Reynolds number of 5105 and the turbulent employed model was the Menter’s shear stress model. Blowing on airfoil is modeled in tangential (tangential blowing) and perpendicular (perpendicular blowing) form and length of blowing jet is 3.5 percent of chord length. Considering previous studies, blowing jet is optimum in two distances on the airfoil surface, one around 40 percent and the other around 80 percent of chord length from the leading edge, which in this study blowing jet is placed at 80 percent of the chord length from the leading edge. Blowing velocity from 0.1 to 0.5 is considered of freestream velocity. Results of tangential blowing show that by increasing amplitude of blowing, lift and drag coefficients changes are inconsiderable. Maximum increase of lift to drag ratio in amplitude of 0.5, around 16.5 percent, but in perpendicular blowing lower amplitude of blowing is more appropriate. Also tangential blowing has no effect on stall angle and cause gradual stall of NACA 0012 airfoil, whereas perpendicular blowing improve stall angle from 14 to 16 degrees.
Influence of number of impeller and diffuser blades on the pressure recovery ...eSAT Journals
Abstract Impeller is a very important element in rotating devices to deliver energy to/from the fluid. The diffusers are essential for effective transformation of the kinetic power produced by the rotor in a centrifugal fan. Hence the flow in the impeller and diffuser passages is the important phenomenon in optimizing the performance. These impeller and diffuser flow passages are the most complex regions to predict the flow behavior. With the advanced development of Particle Image Velocimetry as well as convenient numerical CFD tools, it has become possible to reach at an accurate result well-matched with the real behavior of the flow. Hence, in this work moving mesh technique is used to get a numerical solution for the estimation of actual flow manner. Numerous research works have been done recently to get the physics of fluid flow through impeller and diffuser, both numerically and experimentally. But it is found from the literature that the study on the performance of the fan by changing the number of impeller and diffuser blades together in a combination has not been the emphasis of attention in these works. Hence a numerical analysis has been carried out in this paper to comprehensively lookout the fluid interaction in impeller-diffuser as well as to envisage the flow behavior of the fan by changing the number of impeller and diffuser blades together in combination. For the same number of impeller blades, it is found from the analysis that a higher static pressure rise coefficient is achieved at the outlet of the fan for smaller number of diffuser blades. It is also found that larger the number of impeller blades, larger is the static pressure rise coefficient for the same number of diffuser blades, hence performance gets improved. Key Words: Unsteady flow, Recirculation zone, Turbulence, Impeller vane, Diffuser vane, Static pressure rise.
CFD Simulation and Analysis of Fluid Flow Parameters within a Y-Shaped Branch...IOSR Journals
Plumbing system use pipe fittings to connect straight pipe or tubing section for regulating or measuring fluid flow. Y (wye)-shape fitting is one of the important component in the plumbing system. A wye branch allows splitting a branch line equally in two directions. The opening sizes can vary for different situations for instance in situation where a large main line needs to be split into two smaller branches. The wye shape fitting will convert into T shape fitting when the included angle between two pipe branches is 180°. In the present work, effect of angle of turn/bend for a Y-shape pipe will be studied computationally using ANSYS CFX software. For the analysis, all the three pipe branches of 1 inch internal diameter are selected along with equal length so that only the effect of bend angle at 450, 600, 900 and 1800 can be studied. Water as a fluid is selected which flows through the plumbing system. The effect of bend angle, pipe diameter, pipe length, Reynolds number on the resistance coefficient is studied. It was observed that resistance coefficient vary with the change in flow
Experimental Studies, Geometry Acquisition and Grid Generation Of Diesel Engi...meijjournal
A typical diesel engine port is of complicated geometry . This paper addresses the experimental studies of
intake port of a four cylinder diesel engine for different vacuum pressures and valve lift positions. In this
study the cylinder head is experimented through a paddle wheel flow setup which gives the flow coefficient
and swirl number as output. The main scope of the work is to understand the flow behaviour through the
intake port and finally to determine mean flow coefficient and mean swirl number for different valve lift
ratios L/D, where L is valve lift and D is bore diameter. This paper also addresses the geometry acquisition
and grid generation for three dimensional Computational Fluid Analysis for flow filed computation and
obtain a calibrated CFD code for future design once the code is validated with experimental results
Effect of Geometric Configuration on Performance of Uniflow CycloneIJERD Editor
Reverse flow cyclones find wide applications in many industries however, they require a high
expenditure of energy and large pressure drops, which can be better overcome by uniflow cyclones. A
laboratory unit of Uniflow Cyclone has been developed with 45 mm inlet diameter. The performance
parameters pressure drop and total efficiency were studied for the effect of geometric configuration. The present
study includes the effect of 4 different geometric parameters on performance of uniflow cyclone. The geometric
variation of test cyclones includes the Inlet velocity, Vane angles, Outlet to inlet diameter ratio and Separation
lengths. The overall experimental results yield and investigated the optimal conditions for uniflow cyclone
performance is 450 vane angle, 0.5 outlet to inlet diameter ratio, 3D separation length and 9-10 m/s inlet
velocity. The experimental pressure drop values are validated with the model equations available in literature
and well matched for Ramachandran model.
Control of Suddenly Expanded Flow at Low Supersonic Mach NumbersIJERA Editor
In the present study the experiments were conducted to control the base pressure from a convergent-divergent
nozzle at low supersonic Mach numbers to assess the effectiveness of active control mechanism in the form of
micro jets at different expansion level. The parameters considered in the present study are the diameter ratio,
length to diameter ratio (L/D), Nozzle Pressure Ratio (NPR), and the Mach number. The diameter ratio selected
for the present study are 1.6, 1.8, 2.2, and 2.5. Experiments were conducted for nozzle pressure ratio (NPR)
from 3 to 11. The L/D ratio of the enlarged duct was varied from 10 to 1, and results are presented for L/D 4, 3,
2, and 1. The Mach numbers of the present studies are 1.1, 1.2, 1.4, and 1.5. The results show that the Micro jets
are very effective and are able to raise the base pressure value to a considerable level under the influence of
favorable pressure gradient except at lower NPR 3. At NPRs 5 and 7 for some cases the trends differ due to the
level of expansion, nature of waves present in the base region, relief available to the flow, L/D ratio of the
enlarged duct and the Mach numbers. It is seen that most of the cases exhibit similar behavior for the L/Ds in
the range 4 and 3, which means; that the back pressure has not adversely influenced the flow field in the base
region as well as in the duct. The minimum duct length required for the flow to be attached is L/D = 2, even
though in some cases flow is attached with duct wall. With this it can be stated that the micro jets can be an
alternative for the for base pressure control.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A Computational Analysis of Flow StructureThrough Constant Area S-DuctIJERA Editor
This paper presents the results of an experimental work with measurement of mean velocity contours in 2-D form and validation of the same with numerical results based on the y+ approach at fully developed flow for various turbulent models like, k-ε model, k-ω model, RNG k-ε model and Reynolds Stress Model (RSM), are used to solve the problem. All the turbulence models are studied in the commercial CFD code of Fluent. The experiment is carried out at mass averaged mean velocity of 40m/s and the geometry of the duct is chosen as rectangular cross-section of 45°/45° curved constant area S-duct. In the present paper the computational results obtained from the different turbulence models are compared with the experimental results. In addition to this for validation of the numerical simulation near wall treatments for fully developed flow or log-law region are also investigated for wall 30<y+><300 in the region where turbulent shear dominates. It is concluded from the present study that the mesh resolving the fully turbulent region is sufficiently accurate in terms of qualitative features. Here RSM turbulence model predicts the best results while comparing with the experimental results.RSM model also predicts the flow properties more consistently because it accounts for grid independence test.
A Computational Analysis of Flow Development through a Constant Area C- DuctIJERA Editor
This paper represents the results of an experimental work with measurement of mean velocity along with total pressure contours in 2-D form and validation of the same with numerical results based on the wall y+ approach for various turbulent models like, Spalart Alamras, k-ε model, k-ω model and RSM models are used to solve the closure problem. The turbulence models are investigated in the commercial CFD code of Fluent using y+ as guidance in selecting the appropriate grid configuration and turbulence model. The experiment is carried out at mass averaged mean velocity of 40m/s and the geometry of the duct is chosen as rectangular cross-section of 90 curved constant area duct .In the present paper the computational results obtained from different turbulence models are compared with the experimental result along with the near-wall treatments are investigated for wall y+<30>30 in the fully turbulent region. It is concluded in the present study that the mesh resolving the fully turbulent region is sufficiently accurate in terms of qualitative features. Here RSM turbulence model predicts the best results while comparing with the experimental results.
Numerical Study of Flow Separation Control by Tangential and Perpendicular Bl...CSCJournals
In this study, tangential and perpendicular steady blowing at the trailing edge of NACA 0012 airfoil is investigated numerically to flow separation control and to study the effects of blowing amplitude and blowing coefficient on airfoil aerodynamic characteristics. Flow was fully turbulent with the Reynolds number of 5105 and the turbulent employed model was the Menter’s shear stress model. Blowing on airfoil is modeled in tangential (tangential blowing) and perpendicular (perpendicular blowing) form and length of blowing jet is 3.5 percent of chord length. Considering previous studies, blowing jet is optimum in two distances on the airfoil surface, one around 40 percent and the other around 80 percent of chord length from the leading edge, which in this study blowing jet is placed at 80 percent of the chord length from the leading edge. Blowing velocity from 0.1 to 0.5 is considered of freestream velocity. Results of tangential blowing show that by increasing amplitude of blowing, lift and drag coefficients changes are inconsiderable. Maximum increase of lift to drag ratio in amplitude of 0.5, around 16.5 percent, but in perpendicular blowing lower amplitude of blowing is more appropriate. Also tangential blowing has no effect on stall angle and cause gradual stall of NACA 0012 airfoil, whereas perpendicular blowing improve stall angle from 14 to 16 degrees.
Influence of number of impeller and diffuser blades on the pressure recovery ...eSAT Journals
Abstract Impeller is a very important element in rotating devices to deliver energy to/from the fluid. The diffusers are essential for effective transformation of the kinetic power produced by the rotor in a centrifugal fan. Hence the flow in the impeller and diffuser passages is the important phenomenon in optimizing the performance. These impeller and diffuser flow passages are the most complex regions to predict the flow behavior. With the advanced development of Particle Image Velocimetry as well as convenient numerical CFD tools, it has become possible to reach at an accurate result well-matched with the real behavior of the flow. Hence, in this work moving mesh technique is used to get a numerical solution for the estimation of actual flow manner. Numerous research works have been done recently to get the physics of fluid flow through impeller and diffuser, both numerically and experimentally. But it is found from the literature that the study on the performance of the fan by changing the number of impeller and diffuser blades together in a combination has not been the emphasis of attention in these works. Hence a numerical analysis has been carried out in this paper to comprehensively lookout the fluid interaction in impeller-diffuser as well as to envisage the flow behavior of the fan by changing the number of impeller and diffuser blades together in combination. For the same number of impeller blades, it is found from the analysis that a higher static pressure rise coefficient is achieved at the outlet of the fan for smaller number of diffuser blades. It is also found that larger the number of impeller blades, larger is the static pressure rise coefficient for the same number of diffuser blades, hence performance gets improved. Key Words: Unsteady flow, Recirculation zone, Turbulence, Impeller vane, Diffuser vane, Static pressure rise.
CFD Simulation and Analysis of Fluid Flow Parameters within a Y-Shaped Branch...IOSR Journals
Plumbing system use pipe fittings to connect straight pipe or tubing section for regulating or measuring fluid flow. Y (wye)-shape fitting is one of the important component in the plumbing system. A wye branch allows splitting a branch line equally in two directions. The opening sizes can vary for different situations for instance in situation where a large main line needs to be split into two smaller branches. The wye shape fitting will convert into T shape fitting when the included angle between two pipe branches is 180°. In the present work, effect of angle of turn/bend for a Y-shape pipe will be studied computationally using ANSYS CFX software. For the analysis, all the three pipe branches of 1 inch internal diameter are selected along with equal length so that only the effect of bend angle at 450, 600, 900 and 1800 can be studied. Water as a fluid is selected which flows through the plumbing system. The effect of bend angle, pipe diameter, pipe length, Reynolds number on the resistance coefficient is studied. It was observed that resistance coefficient vary with the change in flow
Experimental Studies, Geometry Acquisition and Grid Generation Of Diesel Engi...meijjournal
A typical diesel engine port is of complicated geometry . This paper addresses the experimental studies of
intake port of a four cylinder diesel engine for different vacuum pressures and valve lift positions. In this
study the cylinder head is experimented through a paddle wheel flow setup which gives the flow coefficient
and swirl number as output. The main scope of the work is to understand the flow behaviour through the
intake port and finally to determine mean flow coefficient and mean swirl number for different valve lift
ratios L/D, where L is valve lift and D is bore diameter. This paper also addresses the geometry acquisition
and grid generation for three dimensional Computational Fluid Analysis for flow filed computation and
obtain a calibrated CFD code for future design once the code is validated with experimental results
An Investigation on the Performance Characteristics of a Centrifugal CompressorIJERD Editor
The design and off-design performance characteristics of single stage centrifugal compressor
consisting of 12 vanes impeller interfacing with 11 vanes diffuser have been studied experimentally and
numerically. The impeller has been designed and developed with radial exit, 30o inlet blade angle (with
tangent), 77 mm diameter and the discharge volute considering constant mean flow velocity. The performance
of the compressor at varying capacity (60 to 120 % of design) by controlling the discharge valve and with the
variation of rotating speed (15000 to 35000 rpm) by regulating speed of the coupled gas turbine has been
conducted at the recently developed test rig. The numerical simulation has been done by adopting viscous
Reynolds Average Navier-Stokes (RANS) equations with and without Coriolis Force & Centrifugal Force in
rotating reference frame (impeller) and stationary reference frame (casing) respectively utilizing CFD software
Fluent 14. The flow around a single vane of impeller interfacing with single vane of diffuser, the rotational
periodicity and sliding mesh at the interfacing zone between rotating impeller and stationery diffuser are
considered. Non dimensional performance curves derived from experimental and numerical results are
presented and compared. The numerical results are found to match very closely with the experimented data near
the design point and deviation is observed at the both side of the designed operating point. Non-uniform
pressure profiles towards the impeller exit and strong cross flow from blade to blade are detected at low flow
operating conditions. Total pressure, static pressure and velocity distributions at design and off design
operation obtained from the CFD results are analysed and presented here.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
This is a self-contained three-day short course on the fundamentals of tactical missile design. It provides a system-level, integrated method for missile aerodynamic configuration/propulsion design and analysis and addresses the broad range of alternatives in meeting cost and performance requirements. The methods presented are generally simple closed-form analytical expressions that are physics-based, to provide insight into the primary driving parameters. Configuration sizing examples are presented for rocket-powered, ramjet-powered, and turbojet-powered baseline missiles. Typical values of missile parameters and the characteristics of current operational missiles are discussed, as well as the enabling subsystems and technologies for tactical missiles, the development process, and the current/projected state-of-the-art. The attendees will vote on the relative emphasis of the topics. Over thirty videos illustrate missile development activities and missile performance. Finally, each attendee may design, build, and fly an air-powered rocket that illustrates some of the course design methods.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Analysis of cross flow induced vibration in an inline and staggered configura...eSAT Journals
Abstract
In many engineering applications like heat exchanger, radiator, evaporator, nuclear power plant and thermal power plant, arrangement of tubes is very crucial. Fluid elastic instability forms the basis for deciding the type of arrangement and tube spacing but the phenomenon of vortex induced vibration is random in nature. Tube spacing also plays a critical role in different types of arrangement. Different type of application requires different tube spacing and the range of tube spacing vary from 1 to 6. Vortex Induced Vibration in cross flow around the inline and staggered arrangement of the tube arrays is experimentally studied for varying P/d (tube spacing) ratio. It is observed that with the increase in the velocity, the amplitude displacement increases. As the amplitude displacement of the tube reduces, the pitch over diameter ratio is increased from 2 to 4. It is also observed that between inline and staggered arrangement, the amplitude displacement of staggered arrangement is more compared to inline arrangement for same tube spacing.
Keywords: Vortex Induced Vibration, Inline Arrangement, Staggered Arrangement, Regression Analysis
3 ijaems jun-2015-17-comparative pressure drop in laminar and turbulent flowsINFOGAIN PUBLICATION
The study of Turbulent flow characteristics in complex geometries receives considerable attention due to its Importance in many engineering applications and has been the subject of interest for researchers. Some of these include the energy conversion systems found in same design of heat exchangers, nuclear reactor, solar collectors & cooling of industrial machines and electronic components. Flow in channels with baffle plates occurs in many industrial applications such as heat exchangers, filtration, chemical reactors, and desalination. These baffles cause turbulence which leads to increases friction within the pipe or duct and leads significant pressure drop.
This work is concern with the comparative flow and pressure distribution analysis of a smooth and segmented Baffles pipe. In which pressure drop during the flow is examined and with the help of hydrodynamic characteristics performance is predicted with the help of Finite element volume tool ANSYS- Fluent, where simulation is been done. The goal is to carry out evaluating pressure drop across the pipe using different turbulent model and at simulation is done for wide range of Reynolds number in both laminar and turbulent flow regimes. The FEV results are validated with well published results in literature and furthermore with experimentation. The FEV and experimental results show good agreement.
CFD and EXPERIMENTAL ANALYSIS of VORTEX SHEDDING BEHIND D-SHAPED CYLINDERAM Publications
The flow around bluff bodies is an area of great research of scientists for several years. Vortex shedding is
one of the most challenging phenomenon in turbulent flows. This phenomenon was first studied by Strouhal. Many
researchers have modeled the various objects as cylinders with different cross-sections among which square and
circular cylinders were the most interested sections to study the vortex shedding phenomenon. The Vortex Shedding
frequency depends on different aspects of the flow field such as the end conditions, blockage ratio of the flow passage,
and width to height ratio. This case studies the wave development behind a D-Shaped cylinder, at different Reynolds
numbers, for which we expect a vortex street in the wake of the D-Shaped cylinder, the well known as von Kármán
Street. This body typically serves some vital operational function in aerodynamic. In circular cylinder flow separation
point changes with Reynolds number but in D-Shaped cylinder there is fix flow separation point. So there is more
wake steadiness in D-Shaped cylinder as compared to Circular cylinder and drag reduction because of wake
steadiness.In the present work CFD simulation is carried out for flow past a D-Shaped cylinder to see the wake
behavior. The Reynolds number regime currently studied corresponds to low Reynolds number, laminar and
nominally two-dimensional wake. The fluid domain is a two-dimensional plane with a D-Shaped cylinder of
dimensions B=90mm, H=80mm and L=200mm. CFD calculations of the 2-D flow past the D-Shaped cylinder are
presented and results are validated by comparing with Experimental results of pressure distribution on cylinder
surface. The experimentation is carried out using small open type wind tunnel. The flow visualization is done by
smoke visualization technique. Results are presented for various B/H ratios and Reynolds numbers. The variation of
Strouhal number with Reynolds number is found from the analysis. The focus of the present research is on reducing
the wake unsteadiness.
Effect of height of triangular siil on the performance of stilling basin modeleSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Numerical simulation of Pressure Drop through a Compact Helical geometryIJERA Editor
Pipes are used in every industrial thermo-fluid equipment and systems, such as tubes, ducts, heat exchangers, air conditioning and refrigerating systems etc. Flatter velocity profiles and more uniform thermal environments are extremely desirous factors for improved performance of these flow reactors and heat exchangers. One means of achieving it in laminar flow systems is to use mixers and flow inverters. In the present study a new device is introduced by changing the dean number of fluid flowing in helically coiled tubes. The objective is to study velocity profile and pressure drop in the proposed device made up from the configurations of changing radius. Pressure drop in straight, helical coil and compact helical geometry configuration were compared using computational fluid dynamics software (FLUENT) results.
EXPERIMENTAL and ANALYTICAL ANALYSIS of FLOW PAST D-SHAPED CYLINDERAM Publications
The study of flow past the bluff body is very important in aerodynamics. The D-Shaped cylinder is one of the
bluff bodies which serve some vital operational function in aerodynamic. So it is necessary to study the flow past the DShaped
cylinder. In this paper the flow past D-Shaped cylinder of dimensions B=90mm, H=80mm, and L=200mm is
studied experimentally and analytically. The analytical results are validated with experimental results. The flow
parameter drag co-efficient is calculated for different Reynolds number using Drag co-efficient relation and results of
drag co-efficient are validated with experimental results. Based on the experimental and analytical results, the drag coefficient
of circular cylinder and D-Shaped cylinder are compared. The Strouhal number is calculated using Strouhal
number co-relation for different Reynolds number and results of Strouhal number are validated with previous results
from literature. The experimentation is carried in small open type wind tunnel. The Reynolds number regime currently
studied corresponds to low Reynolds number. The present research involves the calculation of drag co-efficient for DShaped
cylinder. This experiment is based on existing wind tunnel that is already developed. The focus of the present
research is on finding the drag co-efficient both by experimentally and analytically.
Diffusers are extensively used in centrifugal
compressors, axial flow compressors, ram jets, combustion
chambers, inlet portions of jet engines and etc. A small change in
pressure recovery can increases the efficiency significantly.
Therefore diffusers are absolutely essential for good turbo
machinery performance. The geometric limitations in aircraft
applications where the diffusers need to be specially designed so
as to achieve maximum pressure recovery and avoiding flow
separation.
The study behind the investigation of flow separation in a planar
diffuser by varying the diffuser taper angle for axisymmetric
expansion. Numerical solution of 2D axisymmetric diffuser model
is validated for skin friction coefficient and pressure coefficient
along upper and bottom wall surfaces with the experimental
results of planar diffuser predicted by Vance Dippold and
Nicholas J. Georgiadis in NASA research center [2]
.
Further the diffuser taper angle is varied for other different
angles and results shows the effect of flow separation were it is
reduces i.e., for what angle and at which angle it is just avoided.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
2. International Journal of Mechanical Engineering Research and Development (IJMERD), ISSN 2248 –
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used in wind tunnels, compressor crossover, air conditioning and ventilation ducting systems,
plumes, draft tubes, etc.
The objective of the present study is to investigate the flow characteristics within a
circular C-shaped diffuser. The research work on curved diffuser was initiated from the study
of curved duct. The earliest experimental work on curved ducts has been reported by
Williams et al. [1] in the beginning of the last century. It was reported that the location of the
maximum axial velocity is shifted towards the outward wall of the curved pipe.
The effect of the centrifugal force on the pressure gradient was studied by Dean [2, 3].
He established a relation between viscous force, inertia force and the curvature by a non
dimensional number known as Dean Number.
Experimental investigation on circular 90° and 180° turn curved ducts was carried out
by Rowe et al. [4] and reported the generation of contra rotating vortices within the bends..
Enayet et al. [5] investigated the turbulent flow characteristics through 90° circular
curved duct of curvature ratio 2.8. It was observed that the thickness of the inlet boundary
layer has a significant role on the generation of secondary motion within the duct.
Kim and Patel [6] have investigated on a 90° curved duct of rectangular cross section.
It was reported that the formation of vortices on the inner wall due to the pressure driven
secondary motion originated in the corner region of curved duct.
The earliest work on curved diffuser was reported by Stanitz [7]. The diffuser was
designed based on potential flow solution for two-dimensional, invisid, incompressible and
irrotational flow. The evaluation of the performance of these diffusers was on the basis of
wall static pressure only.
The first systematic studies on 2-D curved subsonic diffusers were carried out by Fox
& Kline [8]. The centerline of the diffuser was taken as circular with a linearly varying area
distribution normal to the centerline. They established a complete map of flow over a range
of the L/D ratio and at different values of ∆β.
Parson and Hill [9] investigated on three 2-D curved diffusers of As = 10 of various
combination of ratio between the centerline length and inlet width. They observed that the
streamline curvature affects the flow development substantially within the curved diffuser.
A qualitative measurement of the mean flow quantities in a 40° curved diffuser of
rectangular cross section of Ar = 1.32 and inlet As = 1.5 have been reported by McMillan
[10]. The result clearly showed the development of strong counter rotating vortices between
two parallel walls, which dominate the flow and performance characteristics.
Majumdar et al. [11] experimentally studied the flow characteristics in a large area
ratio curved diffuser with splitter vanes installed at different angles to the flow at the inlet of
the diffuser. It was observed that splitter vanes deflect the flow towards the convex wall and a
pair of contra rotating vertices generated at the flow passage.
Yaras [12] experimentally investigated the flow characteristics of 90° curved diffuser
with strong curvature having Ar =3.42 for different values of inlet boundary layer thickness
and turbulence intensity. Measurements were taken by the help of seven-hole pressure probe.
He observed that the performance parameters were almost independent by the variations in
the inlet boundary layer.
Majumdar et al. [13] experimentally studied the turbulent characteristics in a curved
diffuser. They observed that the stream wise bulk flow shifted towards the outward wall in
the downstream of the diffuser, which was mainly due to the influence of centrifugal force.
Moreover, one pair of contra-rotating vortices was identified at 30° turns in the flow passage.
The overall static pressure recovery was observed as 5l%.
Majumdar et al. [14] conducted an experiment on 180° bend rectangular diffusing
duct. They measured the wall pressure, velocity and turbulence intensity along the flow
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passage of the diffusing duct. The observation clearly showed the formation of vortical
motions between the two parallel walls. The overall pressure recovery was found about 48%
MATERIALS AND METHODOLOGY
A test rig for the present investigation has been constructed at Fluid Mechanics &
Machinery Laboratory of Power Engineering Department Jadavpur University to investigate
the flow characteristics within a circular cross sectioned C-shape diffuser. The geometry of
the test diffuser is shown in Fig. 1. with co-ordinate system and measurement locations. The
entire set up was fabricated from mild steel sheet except the test diffuser.
The test diffuser was designed with increase in area from inlet to exit and it
distributed normal to the centerline as suggested by Fox and Kline [8]. The test diffuser was
designed based on an area ratio of 1.273 and centerline length of 225 mm. The test diffuser is
made of fiber glass reinforcement plastic. Centerline was turned at 37.5° from inlet to exit
with inlet diameter of 78 mm.
In order to avoid the pressure losses and flow distortion at the inlet and exit, two
constant area connectors were attached at the inlet and exit of the test diffuser. A pre-
calibrated five-hole pressure probe was used to obtain detailed flow parameters like mean
velocity and its components, total and static pressure and secondary motions along the entire
length of the diffuser. Ambient air was used as working fluid.
For measuring mean velocity and its components and static and total pressure surveys
along the entire cross section of curved diffuser, the test piece was divided into five planes,
one at Section H, at Central horizontal plane, the Inlet section one diameter upstream of the
test diffuser, two planes, Section A and Section B at 12.5° and 25° turn along the length of
the diffusing passages and the fifth plane, Section C is at the mid point of the exit duct. The
details of measured planes are shown in Fig. 1. For measurement of flow parameters the five
hole pressure probe was inserted through a 8 mm drilled hole provided at four locations,
namely , 0°, 45°, 90°, and 315° angle as shown detail in Fig.1.
FIGURE 1 Geometry of test diffuser and measuring locations
The pre-calibrated five hole pressure probes was mounted in a traversing mechanism
and the probe inserted into the flow field through 8 mm diameter drilled hole provided at the
4. International Journal of Mechanical Engineering Research and Development (IJMERD), ISSN 2248 –
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wall. The probe was placed within 1 mm of solid surface for the first reading. The probe was
then moved radially and placed at the desired location as shown in Fig. 1.
Instrumentation for the present study was chosen such that the experimental errors
are minimum and also to have quick response to the flow parameters.
The pre-calibrated hemispherical tip five-hole pressure probe used for the present
study. The probe was calibrated and using non null technique was used to measure the flow
parameter.
All the five sensing ports of the probe were connected to a variable inclined multi tube
manometer. The readings were recorded with respect to atmospheric pressure. The mean
velocity and components of mean velocity distribution have been drawn with the help of
SURFER software
The assessment of errors resulting from the readings of the present five hole pressure
probe was made as a function of all incidence angles for all flow characteristics in all the
probe sectors and discussed in details[15], [16].
RESULTS AND DISCUSSIONS
The flow characteristics have been evaluated by mass average mean velocity, between
the curved walls, total pressure and static pressure of the flow at various cross sections.
Measured flow quantities have been presented in the form of 2-D profiles. All the velocities
and pressures were normalized with respect to the inlet mass average velocity and inlet
dynamic pressure respectively.
MEAN VELOCITY CONTOUR
The normalized mean velocity distribution in the form of contour plots at various
sections of the curved diffuser has been discussed here and shown in Fig.2.
Mean velocity at Section H as shown in Fig.2(a) indicates that the high velocity fluid
occupies the flow area close to convex wall (cv) as the flow proceeds from inlet to exit. Flow
is also diffused in the downstream direction due to increase in cross-sectional area. Low
velocity fluid increasingly accumulates close to the concave wall (cc) indicating a complex
flow development dominated by combined effected of flow diffusion and centrifugal force.
However, for a better understanding, this flow development can be observed through contour
plots at Inlet Section, Section A, Section B and Section C as shown in Fig.2(b), (c), (d), (e).
The mean velocity contour at Inlet Section is shown in Fig.2(b) and it indicates that
the flow is nearly symmetrical in nature throughout the entire cross-sectional area.
The mean velocity contour of Section A, shown in Fig.2(c), indicates the overall
diffusion of velocity particularly near the concave wall of this section and also reveals the
shifting of the high velocity fluid close to the convex wall. These are mainly due to combined
effect of the inertia force and centrifugal action on the flow.
The mean velocity distribution in Section B is shown in Fig.2(d). The figure shows
that the overall diffusion takes place at this section. The flow pattern at this section has
changed compared to the preceding section. An appreciable diffusion across the entire section
is observed from this figure. It is also observed that the high velocity core has occupied major
part of the central area of the cross section and this is mainly due to the tendency of the flow
to move towards concave wall due to inertia. As a result, low velocity fluid is pushed towards
the convex wall indicating the accumulation of low momentum fluid at this section.
The mean velocity distribution of Section C is shown in Fig.2(e). The figure depicts
that the high velocity core is shifted towards concave wall and it occupies a substantial
portion of the cross sectional area. The low velocity fluid close to the convex wall, as
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compared with the observation at Section B, occupies more area at Section C. Comparing the
velocity distribution lines about the mid horizontal plane, it can be observed that the flow is
symmetrical between top and bottom surfaces; it indicates the development of similar types
of flow about the vertical plane. In a closed conduit, this phenomenon is only possible if the
directions of flow in the two halves are opposite in nature (counter rotating flows), which is a
natural phenomenon of flow through curved duct of any cross-section. Over an above it,
increase in the cross-sectional area has further complicated the flow development.
(a) Section H
(b) Inlet section (c) Section A (d) Section B (e) Section C
FIGURE 2 Mean velocity contour
PRESSURE RECOVERY & LOSS COEFFICIENT
The variation of normalized coefficients of mass averaged static pressure recovery
and total pressure loss based on the average static and total pressures at different sections of
C-shape diffuser are shown in Fig.3. The figure shows that the coefficient of pressure
recovery increases continuously up to the Section A, subsequently the increase takes place
with a lesser gradient up to the Section B, and then again increases in a steeper gradient. The
overall coefficient of mass averaged static pressure recovery is nearly 35% for this test
diffuser.
The coefficient of mass averaged total pressure loss increases rapidly in the curved
diffuser up to the Section A. Then it increases steadily and marginally up to Section C. The
overall mean value of the coefficient of mass averaged total pressure loss is nearly 14% for
this test diffuser.
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FIGURE 3 Variation of mass average pressure recovery and loss coefficients
NUMERICAL VALIDATION
In the present study a preliminary investigation was carried out using different
turbulence models available in FLUENT. Based on the Intensive investigation it was found
that Standard k – ε model of turbulence provides the best result and results obtained from
computational analysis match both in qualitatively and quantitatively with the experimental
results. It is to be noted here that the inlet profiles obtained during experiment are fed as an
inlet condition during the validation with FLUENT. Some of the validation figures are shown
in Fig. 4(a), Fig. 4(b), Fig. 4(c) and Fig. 4(d) respectively.
All four figures indicate that the mass averaged mean velocity contours obtained by
computational and experimental investigations, which shows a qualitative matching to each
other. However, a slight mismatch can be observed at convex side of 10º of Section H and at
the 45º plane of Section A close to the top surface.
This could be due to the complicated nature of flow at those planes, which was not
properly predicted by the process of computer simulation.
The mean velocity distribution at the Section B and Section C are shown in Fig. 4(c) and Fig.
4(d) show a reasonably good agreement of the computational investigation with the
experimental results. These agreements confirm that the CFD code using Standard k-ε model
can predict the flow and performance characteristics reasonably well for similar geometries
with similar boundary conditions
Experimental Computational
(a) Section H
Experimental
7. International Journal of Mechanical Engineering Research and Development (IJMERD), ISSN 2248 –
9347(Print) ISSN 2228 – 9355(Online), Volume 1, Number 2, May- October (2011)
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(b) Section A (c) Section B (d) Section C
Computational
FIGURE 4 Comparison of normalized velocity distribution at Section H, Section A,
Section B and Section C obtained through Computational and Experimental
investigation.
Figure 5 shows the comparison of performance parameters like coefficient of static pressure
recovery and coefficient of total pressure loss obtained through experimental and
computational investigation. From the figure it has been observed that coefficient of pressure
recovery Cpr for the computational investigation was obtained as 38% compared to the
experimental investigation, which obtained as 35%. Similarly the coefficient of pressure loss
is obtained as 13% in computation investigation compared to the 14% of experimental study.
This shows very good matching of the predicted results with the experimental one.
These agreements confirm that the CFD code using Standard k – ε model can predict
the flow and performance characteristics reasonably well for similar geometries with same
boundary conditions
FIGURE 5 Comparison of performance parameters obtained through computational and
experimental investigation
8. International Journal of Mechanical Engineering Research and Development (IJMERD), ISSN 2248 –
9347(Print) ISSN 2228 – 9355(Online), Volume 1, Number 2, May- October (2011)
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PARAMETRIC INVESTIGATION
To obtain a more insight of the performance parameters an intense parametric study
of pressure recovery/loss coefficient for different area ratio with angle turn diffusers were
carried out.
For this purpose area ratios 1.25, 1.5, 1.75 and 2 with the angle of turns 30º, 40º, 50º,
60º, 70º and 75º C-shape diffusers have chosen.
From this investigation it is observed from Fig.6 that for the increase in area ratio
static pressure recovery increases sharply upto area ratio 2 but with the increase of angle of
turn pressure recovery decreases steadily except for area ratio 1.25 and 1.5 where for increase
of angle of turn from 30º to 40º pressure recovery increase sharply then for further increase of
angle of turn it decreases steadily.
The coefficient of total pressure loss almost remains constant with the change in area
ratio and angle of turn for similar inlet conditions.
FIGURE 6 Variation of mass average pressure recovery and loss coefficients.
CONCLUSION
Based on the present investigation following conclusion have drawn for the present
paper.
i. High velocity fluids shifted and accumulated at the concave wall of the exit section.
ii. The mass average static pressure recovery and total pressure loss for the curved test
diffuser is continuous from Inlet section to Section C.
iii. Performance parameter like coefficient of mass average static pressure recovery
and coefficient of mass average total pressure loss are 35% and 13% respectively.
iv. A comparison between the experimental and predicated results for the annular curved
diffuser show good qualitative agreement between the two.
v. The coefficient of mass averaged static pressure recovery and total pressure loss are
obtained as 38% and 14% in predicted results and in the experimental results their
values obtained as 35% and 13% respectively, which indicate a good matching
between the experimental and predicted results
9. International Journal of Mechanical Engineering Research and Development (IJMERD), ISSN 2248 –
9347(Print) ISSN 2228 – 9355(Online), Volume 1, Number 2, May- October (2011)
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vi. From the parametric investigation it is observed that for the increase in area ratio upto
2.0, static pressure recovery increases sharply But with the increase of angle of turn
pressure recovery decreases steadily except for area ratio 1.25 and 1.5 where for
increase of angle of turn 30º to 40º pressure recovery increase sharply then for further
increase of angle of turn it decreases steadily.
vii. Among the different turbulence models within the fluent solver a standard k-ε model
shows the good results and predicts the flow and performance characteristics well for
annular curved diffusing ducts with uniform flow at inlet.
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NOMENCLATURE
Ar Area ratio D Inlet diameter of the Diffuser
As Aspect ratio L Centerline length of the Diffuser
CC Concave or outward wall Re Reynolds number
CPR Coefficient of pressure recovery ∆ β Angle of turn of the center line
CV Convex or inward wall