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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Experimental Study on Two-Phase Flow in Horizontal Rectangular Minichannel wi...IJERA Editor
An experimental study was conducted to investigate two-phase air-water flow characteristics, in horizontal
rectangular minichannel with Y-junction. The width (W), the height (H) and the hydraulic diameter (DH) of the
rectangular cross section for the upstream side of the junction are 4.60 mm, 2.50 mm and 3.24 mm, while those
for the downstream side are 2.36 mm, 2.50 mm and 2.43 mm. The entire test section was machined from
transparent acrylic block, so that the flow structure could be visualized. Liquid single-phase and air-liquid twophase
flow experiments were conducted at room temperature. The flow pattern, the bubble velocity, the bubble
length, and the void fraction were measured with a high-speed video camera. Pressure profile upstream and
downstream from the junction was also measured for the respective flows, and the pressure loss due to the
contraction at the junction was determined from the pressure profiles. Two flow patterns, i.e., slug and annular
flows, were observed in the fully-developed region apart from the junction. In the analysis, the frictional pressure
drop data, the two-phase frictional multiplier data, bubble velocity data, bubble length data and void fraction data
were compared with calculations by some correlations in literatures. In addition, new pressure loss coefficient
correlations for the pressure drop at the junction has been proposed. Results of such experiment and analysis are
described in the present paper.
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.
Studies on impact of inlet viscosity ratio, decay rate & length scales in a c...QuEST Global
Modern aircraft engine designs are driven towards higher operating temperature and lower coolant flow requirements. During the flight mission, the hot gas path components encounter flows at different pressure, temperature and turbulence conditions. During design of such components, there is always an interest towards fundamental understanding of the impact of inlet turbulence on overall performance. The paper presents aerodynamic performance (stage efficiency) impact of stator inlet viscosity ratio, decay rate and length scales in a cooled turbine rig, based on CFD studies only. Through CFD studies, it is observed that an inlet length scale variation by 10 times could impact the aerodynamic efficiency by ~0.5% to 4% depending on the size of the length scale. Efficiency drops with higher flow length scales and turbulence intensity. The length scale effects are observed to be more predominant with high turbulence intensities than at low turbulence intensities. Similarly a viscosity ratio increase by 1000 times can decrease efficiency by < 0.5% in the lower bounds and can drastically increase to ~ 3% at higher bounds. The efficiency drop can be as much as 2.5 % for a decay rate change from 0.01 to 1 for viscosity ratio of 10000.
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
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
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.
Experimental Investigation on Impact of Jet on Vanes Pipe System to Determine...ijtsrd
The water coming out from the nozzle is called as a jet and when the impacted on the different surfaces and the change in momentum can be determined and the experiment is performed with the nozzle, different type of plates such as flat, Circular and semi circular and a spring scale connected to the balanced beam and different weights are used as counter weights, flow meter and pipes. In this paper during the experimentation of determining the coefficient of impact on the vanes plates some of the minor Losses occurred due to the presence of bend in the suction pipe and nozzle pipe line connectivity and the extra fitting such as valve to control the flow on the pipe are present, due to this the flow of water, velocity in the pipe are varied, an attempt is done with this experiment to determine some important minor losses ,major losses are neglected as length of pipe is short. The readings from the experiment on three different plates are conducted and readings are tabulated and compared. J Narendra Kumar | G Narasimhulu "Experimental Investigation on Impact of Jet on Vanes Pipe System to Determine the Minor Losses" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-6 , October 2020, URL: https://www.ijtsrd.com/papers/ijtsrd33507.pdf Paper Url: https://www.ijtsrd.com/engineering/mechanical-engineering/33507/experimental-investigation-on-impact-of-jet-on-vanes-pipe-system-to-determine-the-minor-losses/j-narendra-kumar
A Brief Study, Research, Design, Analysis on Multi Section Variable Camber WingIJERA Editor
Minimizing fuel consumption is one of the major concerns in the aviation industry. In the past decade, there
have been many attempts to improve the fuel efficiency of aircraft. One of the methods proposed is to vary the
lift-to-drag ratio of the aircraft in different flight conditions. To achieve this, the wing of the airplane must be
able to change its configuration during flight, corresponding to different flight regimes.In the research presented
in this thesis, the aerodynamic characteristics of a multisection, variable camber wing were investigated. The
model used in this research had a 160mm chord and a 200mm wingspan, with the ribs divided into 4 sections.
Each section was able to rotate approximately 5 degrees without causing significant discontinuity on the wing
surface. Two pneumatic actuators located at the main spar were used to morph the wing through mechanical
linkages. The multi-section variable camber wing model could provide up to 10 percent change in camber from
the baseline configuration, which had a NACA0015 section.The wing was tested in the free-jet wind tunnel at
three different Reynolds numbers: 322000, 48000, and 636000. Static tests were performed to obtain lift and
drag data for different configurations. Two rigid wings in baseline and camber configuration were built and
tested to compare the test data with variable camber wing. The wind tunnel test results indicated that the multisection
variable camber wing provided a higher lift than the rigid wing in both configurations whereas high drag
was also generated on the variable camber wing due to friction drag on the wing skin. The larger drag value
appeared on variable camber wing in baseline configuration than in cambered configuration resulting in lower
lift-to-drag ratio as compared to the baseline rigid wing whereas the variable camber wing in cambered
configuration had higher lift-to-drag ratio than the cambered rigid wing.
Smart Prediction Of Surface Finishing Quality Of En-8 Work Piece By Ann ModelIJERA Editor
Turning is a material removal process a subtractive form of machining which is used to create parts of circular
or rotational form of desired geometry/shape by removing unwanted material. Accuracy of any process depends
on involvement of operational variables. The operating parameters that contribute to turning process are Cutting
speed, Depth of cut, Feed rate. Vibrations, tool life, tool wear, surface finish and cutting forces etc are also in
direct relation with values selected for process parameters. So to improve the efficiency of process and quality
of the product it is necessary to control the process parameters. We have considered surface roughness the
parameters with main focus as it dictates the aesthetics and sometimes ergonomical characteristics of the
product. In this work a neural network is created using feed forward back propagation technique for simulation
of the process using the Matlab Neural network toolbox. So with assurance of accuracy of the predictive
capabilities of the neural network it was then used for optimization.
Windows used in FIR Filters optimized for Far-side Stop band Attenuation (FSA...IJERA Editor
It has been proposed that the Exponential window provides better side-lobe roll-off ratio than Kaiser window
which is very useful for some applications such as beam forming, filter design, and speech processing. In this
paper the second application i.e. design of digital nonrecursive Finite Impulse Response (FIR) filter by using
Exponential window is proposed. The far-end stopband attenuation is most significant parameter when the
signal to be filtered has great concentration of spectral energy. The filter should be designed in such a way so
that it can provide better far-end stopband attenuation (amplitude of last ripple in stopband). Digital FIR filter
designed by Kaiser window has a better far-end stopband attenuation than filter designed by the other previously
well known adjustable windows such as Dolph-Chebyshev and aramaki, which are special cases of
Ultraspherical windows, but obtaining a digital filter which performs higher far-end stopband attenuation than
Kaiser window will be useful. In this paper, the design of nonrecursive digital FIR filter has been proposed by
using Exponential window. It provides better far-end stopband attenuation than filter designed by well known
Kaiser window, which is the advantage of filter designed by Exponential window. The proposed schemes were
simulated on commercially available software and the results show the close agreement with proposed theory.
T E M U S I L A T U R A H M I Sp M B E K A S IPerdami Bekasi
SLIDE PRESENTASI dr. RIKI TSAN , TENTANG URGENSI PEMBENTUKAN PERDAMI CABANG BEKASI, PADA TEMU SILATURAHMI DOKTER SPESIALIS MATA SE BEKASI, 7 DESEMBER 2010, DI RESTORAN WULAN SARI, BEKASI
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.
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.
Experimental Study on Two-Phase Flow in Horizontal Rectangular Minichannel wi...IJERA Editor
An experimental study was conducted to investigate two-phase air-water flow characteristics, in horizontal
rectangular minichannel with Y-junction. The width (W), the height (H) and the hydraulic diameter (DH) of the
rectangular cross section for the upstream side of the junction are 4.60 mm, 2.50 mm and 3.24 mm, while those
for the downstream side are 2.36 mm, 2.50 mm and 2.43 mm. The entire test section was machined from
transparent acrylic block, so that the flow structure could be visualized. Liquid single-phase and air-liquid twophase
flow experiments were conducted at room temperature. The flow pattern, the bubble velocity, the bubble
length, and the void fraction were measured with a high-speed video camera. Pressure profile upstream and
downstream from the junction was also measured for the respective flows, and the pressure loss due to the
contraction at the junction was determined from the pressure profiles. Two flow patterns, i.e., slug and annular
flows, were observed in the fully-developed region apart from the junction. In the analysis, the frictional pressure
drop data, the two-phase frictional multiplier data, bubble velocity data, bubble length data and void fraction data
were compared with calculations by some correlations in literatures. In addition, new pressure loss coefficient
correlations for the pressure drop at the junction has been proposed. Results of such experiment and analysis are
described in the present paper.
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.
Studies on impact of inlet viscosity ratio, decay rate & length scales in a c...QuEST Global
Modern aircraft engine designs are driven towards higher operating temperature and lower coolant flow requirements. During the flight mission, the hot gas path components encounter flows at different pressure, temperature and turbulence conditions. During design of such components, there is always an interest towards fundamental understanding of the impact of inlet turbulence on overall performance. The paper presents aerodynamic performance (stage efficiency) impact of stator inlet viscosity ratio, decay rate and length scales in a cooled turbine rig, based on CFD studies only. Through CFD studies, it is observed that an inlet length scale variation by 10 times could impact the aerodynamic efficiency by ~0.5% to 4% depending on the size of the length scale. Efficiency drops with higher flow length scales and turbulence intensity. The length scale effects are observed to be more predominant with high turbulence intensities than at low turbulence intensities. Similarly a viscosity ratio increase by 1000 times can decrease efficiency by < 0.5% in the lower bounds and can drastically increase to ~ 3% at higher bounds. The efficiency drop can be as much as 2.5 % for a decay rate change from 0.01 to 1 for viscosity ratio of 10000.
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
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
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.
Experimental Investigation on Impact of Jet on Vanes Pipe System to Determine...ijtsrd
The water coming out from the nozzle is called as a jet and when the impacted on the different surfaces and the change in momentum can be determined and the experiment is performed with the nozzle, different type of plates such as flat, Circular and semi circular and a spring scale connected to the balanced beam and different weights are used as counter weights, flow meter and pipes. In this paper during the experimentation of determining the coefficient of impact on the vanes plates some of the minor Losses occurred due to the presence of bend in the suction pipe and nozzle pipe line connectivity and the extra fitting such as valve to control the flow on the pipe are present, due to this the flow of water, velocity in the pipe are varied, an attempt is done with this experiment to determine some important minor losses ,major losses are neglected as length of pipe is short. The readings from the experiment on three different plates are conducted and readings are tabulated and compared. J Narendra Kumar | G Narasimhulu "Experimental Investigation on Impact of Jet on Vanes Pipe System to Determine the Minor Losses" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-6 , October 2020, URL: https://www.ijtsrd.com/papers/ijtsrd33507.pdf Paper Url: https://www.ijtsrd.com/engineering/mechanical-engineering/33507/experimental-investigation-on-impact-of-jet-on-vanes-pipe-system-to-determine-the-minor-losses/j-narendra-kumar
A Brief Study, Research, Design, Analysis on Multi Section Variable Camber WingIJERA Editor
Minimizing fuel consumption is one of the major concerns in the aviation industry. In the past decade, there
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lift-to-drag ratio of the aircraft in different flight conditions. To achieve this, the wing of the airplane must be
able to change its configuration during flight, corresponding to different flight regimes.In the research presented
in this thesis, the aerodynamic characteristics of a multisection, variable camber wing were investigated. The
model used in this research had a 160mm chord and a 200mm wingspan, with the ribs divided into 4 sections.
Each section was able to rotate approximately 5 degrees without causing significant discontinuity on the wing
surface. Two pneumatic actuators located at the main spar were used to morph the wing through mechanical
linkages. The multi-section variable camber wing model could provide up to 10 percent change in camber from
the baseline configuration, which had a NACA0015 section.The wing was tested in the free-jet wind tunnel at
three different Reynolds numbers: 322000, 48000, and 636000. Static tests were performed to obtain lift and
drag data for different configurations. Two rigid wings in baseline and camber configuration were built and
tested to compare the test data with variable camber wing. The wind tunnel test results indicated that the multisection
variable camber wing provided a higher lift than the rigid wing in both configurations whereas high drag
was also generated on the variable camber wing due to friction drag on the wing skin. The larger drag value
appeared on variable camber wing in baseline configuration than in cambered configuration resulting in lower
lift-to-drag ratio as compared to the baseline rigid wing whereas the variable camber wing in cambered
configuration had higher lift-to-drag ratio than the cambered rigid wing.
Smart Prediction Of Surface Finishing Quality Of En-8 Work Piece By Ann ModelIJERA Editor
Turning is a material removal process a subtractive form of machining which is used to create parts of circular
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speed, Depth of cut, Feed rate. Vibrations, tool life, tool wear, surface finish and cutting forces etc are also in
direct relation with values selected for process parameters. So to improve the efficiency of process and quality
of the product it is necessary to control the process parameters. We have considered surface roughness the
parameters with main focus as it dictates the aesthetics and sometimes ergonomical characteristics of the
product. In this work a neural network is created using feed forward back propagation technique for simulation
of the process using the Matlab Neural network toolbox. So with assurance of accuracy of the predictive
capabilities of the neural network it was then used for optimization.
Windows used in FIR Filters optimized for Far-side Stop band Attenuation (FSA...IJERA Editor
It has been proposed that the Exponential window provides better side-lobe roll-off ratio than Kaiser window
which is very useful for some applications such as beam forming, filter design, and speech processing. In this
paper the second application i.e. design of digital nonrecursive Finite Impulse Response (FIR) filter by using
Exponential window is proposed. The far-end stopband attenuation is most significant parameter when the
signal to be filtered has great concentration of spectral energy. The filter should be designed in such a way so
that it can provide better far-end stopband attenuation (amplitude of last ripple in stopband). Digital FIR filter
designed by Kaiser window has a better far-end stopband attenuation than filter designed by the other previously
well known adjustable windows such as Dolph-Chebyshev and aramaki, which are special cases of
Ultraspherical windows, but obtaining a digital filter which performs higher far-end stopband attenuation than
Kaiser window will be useful. In this paper, the design of nonrecursive digital FIR filter has been proposed by
using Exponential window. It provides better far-end stopband attenuation than filter designed by well known
Kaiser window, which is the advantage of filter designed by Exponential window. The proposed schemes were
simulated on commercially available software and the results show the close agreement with proposed theory.
T E M U S I L A T U R A H M I Sp M B E K A S IPerdami Bekasi
SLIDE PRESENTASI dr. RIKI TSAN , TENTANG URGENSI PEMBENTUKAN PERDAMI CABANG BEKASI, PADA TEMU SILATURAHMI DOKTER SPESIALIS MATA SE BEKASI, 7 DESEMBER 2010, DI RESTORAN WULAN SARI, BEKASI
Experimental Investigations and Computational Analysis on Subsonic Wind Tunnelijtsrd
This paper disclose the entire approach to design an open circuit subsonic wind tunnel which will be used to consider the wind impact on the airfoil. The current rules and discoveries of the past research works were sought after for plan figuring of different segments of the wind tunnel. Wind speed of 26 m s have been practiced at the test territory. The wind qualities over a symmetrical airfoil are viewed as probably in a low speed wind tunnel. Tests were finished by moving the approach, from 0 to 5 degree. The stream attributes over a symmetrical airfoil are examined tentatively. The pressure distribution on the airfoil area was estimated, lift and drag force were estimated and velocity profiles were acquired. Rishabh Kumar Sahu | Saurabh Sharma | Vivek Swaroop | Vishal Kumar ""Experimental Investigations and Computational Analysis on Subsonic Wind Tunnel"" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-3 , April 2019, URL: https://www.ijtsrd.com/papers/ijtsrd23511.pdf
Paper URL: https://www.ijtsrd.com/engineering/mechanical-engineering/23511/experimental-investigations-and-computational-analysis-on-subsonic-wind-tunnel/rishabh-kumar-sahu
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.
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
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Abstract Water model experiments have been carried out in a 1/30th scaled down model of the 100 ton LD converter in order to investigate the effect of changing the lance height and the gas flow rate on the penetration depth of liquid with different exit diameters. It is found the penetration depth increases with decreasing nozzle diameter, decreasing the lance height and with increase the gas flow rate. Gas jets impinging onto a gas–liquid interface of a liquid pool are also studied using computational fluid dynamics modeling, which aims to obtain a better understanding of the behavior of the gas jets. The gas and liquid flows are modeled using the volume of fluid technique. The governing equations in the axisymmetric cylindrical coordinates are solved by the CFD simulation using FLUENT. The computed results are compared with experimental result and it isfound a good match with all the data. Keywords: LD process, Water Modeling, Penetration Depth, Volume of Fluid, CFD.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in 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
Effect of free surface and froude number on the protection length and turbule...eSAT Journals
Abstract An experimental study was carried out to investigate the effect of free surface, Froude and Reynolds numbers on the protection length and turbulence through compound transitions using Laser Doppler, in a rectangular channel. Measurements of turbulence are carried out along the compound transition, at different contraction ratios, at different bed slopes. Vertical transition in the bed were also changed. From the results, the protection length increases with the increase of the incoming Froude number, and increases with the increase of the relative height, while it increases with the increase of the contraction ratio. The steep slope has a major effect on the protection length. Free surface has a unique role in governing the turbulence in open channel flows. Within and downstream of the transition, the turbulence occurs primarily in the wall region. Within the transition, flow tends towards the critical state (Fr approaches close to 1) with a rise in the turbulence intensities in the free surface and the wall region which may be attributed to the flow tending towards critical state. At small values of Froude number Fr ≤ 0.22, the effect of Froude number on turbulence intensities and the free surface waves negligible. Keywords: Turbulence intensities- Laser Doppler-Protection length-Free surface-Relative height-Contraction ratio-Bottom slope-Froude number
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
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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
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the wake unsteadiness.
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.
Similar to Control of Suddenly Expanded Flow at Low Supersonic Mach Numbers (20)
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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.
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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.
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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.
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• 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.
Control of Suddenly Expanded Flow at Low Supersonic Mach Numbers
1. Zakir Ilahi Chaudhary et al. Int. Journal of Engineering Research and Applications www.ijera.com
ISSN: 2248-9622, Vol. 5, Issue 8, (Part - 5) August 2015, pp.24-33
www.ijera.com 24 | P a g e
Control of Suddenly Expanded Flow at Low Supersonic Mach
Numbers
Zakir Ilahi Chaudhary*, V. B. Shinde**, Syed Ashfaq***, S. A. Khan****
*(Research Scholar, Department of Mechanical Engineering, Datta Meghe College of Engineering, Airoli, Navi
Mumbai , India and Associate Professor, Department of Automobile Engineering, M H Saboo Siddik College of
Engineering, Mumbai, India.
** (Director, Amity School of Engineering & Technology (ASET), Registrar, Amity University, Mumbai,
(AUM), Maharashtra, India. On lien Professor in Mechanical Engg, DMCE, Airoli, Navi Mumbai, Maharashtra,
India.
****Department of Mechanical Engineering, Faculty of Engineering, International Islamic University, Gombak
Campus, Selangor, Kuala Lumpur, Malaysia.
ABSTRACT
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.
Keywords - Base pressure, Length-to-diameter ratio, Mach number, Nozzle pressure ratio, Sudden expansion
I. INTRODUCTION
In view of the developments in space flights and
missile technology worldwide by all the developed
nations as well as few developing countries, the base
flows at high Reynolds numbers continue to be an
important area of research. It is well known that the
base pressure and consequently the base drag at
transonic speed could be as high as 50 percent of the
total drag during the jet off conditions, however,
during the jet on (or power on) mode the effect of
base suction will be negligible as the pressure at the
base will be very high. Hence, if we are interested to
control the base pressure and ultimately the base drag
in case of blunt based projectiles and by doing so this
would lead to significant increase in the range of the
missiles or projectiles, and it will be of great help for
defense applications. Presently the world is facing the
energy crisis and any decrease in the value of the
base drag will be a welcome step. Since, we have
reached to a saturation stage as far as the
optimization in skin friction drag and wave drag are
concerned, there, is not much scope for further
investigation is left and controlling the base pressure
is the only area left to explore, hence, this study was
undertaken to control the base pressure with micro
jets. The prime objectives in this study are to control
the base pressure, to have smooth development of the
flow without oscillations in the duct, to minimize the
total pressure loss; the studies are conducted keeping
these features in mind. When we scan the literature
available it is found that scientists have made
attempts to control the base pressure by various
passive means, like; ribs, base cavities, ventilated
cavities at the blunt base, splitter plate, vortex locked
device, stepped base, boattailed bases, and so on.
Hence, in the present study the experiments were
conducted to control the base pressure as well as the
flow development in the enlarged duct was measured
to ensure that there is no negative effect of the
control on the flow field of the duct. It is well known
that whenever either passive or active controls are
used in the case of sudden expansion it mandatory on
the part of researchers to ensure that the flow field in
the enlarged duct is not aggravated and the flow field
with and without control are identical.
RESEARCH ARTICLE OPEN ACCESS
2. Zakir Ilahi Chaudhary et al. Int. Journal of Engineering Research and Applications www.ijera.com
ISSN: 2248-9622, Vol. 5, Issue 8, (Part - 5) August 2015, pp.24-33
www.ijera.com 25 | P a g e
Fig. 1: Sudden expansion flow field
Flow field of abrupt axi-symmetric expansion is
a complex phenomenon characterized by flow
separation, flow re-circulation and reattachment. A
shear layer into two main regions may divide such a
flow field, one being the flow recirculation region
and the other the main flow region. The point at
which the dividing streamline Strikes the wall is
called the reattachment point and the features of
sudden expansion flow field are shown in Fig. 1.
II. LITERATURE REVIEW
Kidd et al. [1] conducted Free-flight tests of
spin-stabilized projectiles and fin-stabilized missiles
with various stepped, flat and boattailed bases at
subsonic, transonic and supersonic Mach numbers.
They got the results which indicate that sub sonically
the addition of a stepped base can significantly
reduce the aerodynamic drag over that a flat base.
Khan and Rathakrishnan [2-6] done experimental
investigation to study the effectiveness of micro jets
under the influence of Over, Under, and Correct
expansion to control the base pressure in suddenly
expanded axi-symmetric ducts. They found that the
maximum increase in base pressure is 152 percent for
Mach number 2.58. Also they found that the micro
jets do not adversely influence the wall pressure
distribution. They showed that micro jets can serve as
an effective controller raising the base suction to
almost zero level for some combination for
parameters. Further, it was concluded that the nozzle
pressure ratio has a definite role to play in fixing the
base pressure with and without control. Ashfaq and
Khan [7] presented the results of experimental studies
to control the base pressure from a convergent nozzle
under the influence of favourable pressures gradient
at sonic Mach number. The area ratio (ratio of area of
suddenly expanded duct to nozzle exit area) studied
are 2.56, 3.24, 4.84 and 6.25. The L/D ratio of the
sudden expansion duct varies from 10 to 1. They
concluded that, unlike passive controls the favourable
pressure gradient does not ensure augmentation of the
control effectiveness for active control in the form of
micro jets. Wall pressure was measured and it is
found that the micro jets do not disturb the flow field
in the duct rather the quality of flow has improved
due to the presence of micro jets in some cases.
Ashfaq et al. [8] presented the results of experimental
studies to control the base pressure from a convergent
nozzle to ascertain the effect of level of expansion in
a suddenly expanded flow at sonic Mach number.
From the investigation it was found that unlike
passive controls the favourable pressure gradient
does not ensure augmentation of the control
effectiveness for active control in the form of micro
jets. To study the influence of micro jets on the
quality of flow in the enlarged duct wall pressure was
measured and it was found that the micro jets do not
disturb the flow field in the duct.
III. EXPERIMENTAL SETUP
The experimental set up of the present study is
shown in the Fig. 2. There are eight holes at the exit
periphery of the nozzle, four (marked m) were used
for base pressure (Pb) measurement, four of which are
(marked c) were used for control of base pressure. In
the control chamber the pressure energy was drawn
from the main settling chamber by employing a tube
connecting the main settling chamber with the control
chamber.
Further, the experimental setup was consisted of
an axi-symmetric convergent-divergent nozzle
having exit diameter as D1 followed by a concentric
axi-symmetric duct of larger diameter of diameter D2,
and the ratios of the diameter (i.e. D2/D1) are in the
range from 1.6 to 2.5. At the exit, diameter of the
nozzle was kept fixed (i.e. 10 mm) and the diameter
ratio of the model were 1.6, 1.8, 2.2, and 2.5. Brass
pipe was used to fabricate the suddenly expanded
ducts. The duct has a maximum L/D = 10 and the
lower L/Ds were achieved by cutting the length after
testing a particular L/D. However, the results
presented in this paper are for L/D = 4, 3, 2, and 1,
though the experiments were conducted for L/D = 10
to 1.
Fig. 2. Experimental setup
For measuring the pressure in the control
chamber, the stagnation pressure in the main settling
chamber and the pressure at the base, PSI model
9010 pressure transducer were used. It has 16
channels and pressure range is 0-300 psi. It displays
the reading after averaging 250 samples per second.
To interface the transducer with the computer,
3. Zakir Ilahi Chaudhary et al. Int. Journal of Engineering Research and Applications www.ijera.com
ISSN: 2248-9622, Vol. 5, Issue 8, (Part - 5) August 2015, pp.24-33
www.ijera.com 26 | P a g e
software is provided by the manufacturer. The user-
friendly menu driven software obtains data and
displays the pressure readings from all the 16
channels simultaneously on the computer screen.
The software is embedded with the facility to select
the units of pressure from a list of available options,
perform a re-zero/full calibration, etc. The transducer
is capable of selecting the number of samples to be
averaged, by means of dipswitch settings. It can
function well, up to 95 per cent humidity and
temperatures ranging from -20° to +60° Celsius.
IV. RESULTS AND DISCUSSIONS
The measured data consists of base pressure (Pb);
wall static pressure (Pw) along the duct and the nozzle
pressure ratio (NPR) defined as the ratio of
stagnation pressure (P0) to the back pressure (Patm).
All the measured pressures were non-
dimensionalized by dividing them with the ambient
pressure (i.e. the back pressure). In the present study,
the back pressure is the atmospheric pressure.
From the literature, it is found that in addition to area
ratio and the NPR, the inertia at the nozzle exit has a
very strong influence on the base pressure. To
quantify the increase in base pressure achieved with
control by micro jets, cross plots of base pressure in
the form of non-dimensional base pressure with the
non-dimensional step height of the suddenly
expanded duct are used for presenting the results.
To highlight the effect of diameter ratio, cross plots
of base pressure with diameter ratio as a function of
jet Mach number and NPR are presented in Figs.
3((a) to (j)), for L/D = 4 and NPRs from 3 to 11. It
should be kept in mind that, increase of diameter
ratio simply means that the additional relief is
available to the flow exiting from the nozzle. And,
this kind of relief will make the shock/expansion
waves at the nozzle lip to propagate comparatively
easily with the increase of diameter ratio. This
propagation of waves will result in change of
reattachment point with the duct and hence the
reattachment length. This variation in reattachment
length will have a definite role to play in dictating the
vortex strength at the base and hence on the base
pressure level.
Fig. 3 (a)
Fig. 3 (b)
Fig. 3 (c)
Fig. 3 (d)
Fig. 3 (e)
4. Zakir Ilahi Chaudhary et al. Int. Journal of Engineering Research and Applications www.ijera.com
ISSN: 2248-9622, Vol. 5, Issue 8, (Part - 5) August 2015, pp.24-33
www.ijera.com 27 | P a g e
Fig. 3 (f)
Fig. 3 (g)
Fig. 3 (h)
Fig. 3 (i)
Fig. 3 (j)
Fig. 3. Base pressure variation with Diameter Ratio
for L/D = 4
The results for NPR 11 are shown in Figs. 3((i)
to (j)) for the Mach numbers in the range from 1.1 to
1.5 clearly reflect the effect of relief on the base
pressure. All these jets are under expanded and hence
the free shear layer from the nozzle exit passes
through an expansion fan. In such situation increase
in reattachment length due to increase of diameter
ratio and hence the area ratio is seen to result in
decrease of base pressure for all the parameters of the
present study. Furthermore, the control is found to be
effective for these Mach number range taking the
base pressure to a higher value compared to the
corresponding case without control cases as seen in
Fig. 3(j) for Mach numbers 1.4 and 1.5. However, for
the similar situation at lower Mach numbers namely
1.1 and 1.2 the trend of continuous decrease in the
base pressure values continue but when micro jets
were activated neither they are able to influence the
flow field nor control results in substantial increase
or decrease of base pressure. It is also seen that with
increase in the Mach number from 1.1 to 1.2 results
in increase of base pressure this trend is on the
expected lines. It is well known from the literature
that the base pressure will increase with increase in
Mach number.
Similar results for NPR 9 are shown in Figs. 3((g) to
(h) for Mach number ranges 1.1 to 1.5. Here again
the base pressure behavior with diameter ratio is
similar to that for NPR 11, excepting that the
magnitudes of base pressure has come down as
compared to the values at NPR 11 when NPR comes
down from 11 to 9.
Base pressure results for NPR 7 are given in Figs.
3((e) to (f)) for Mach number ranges 1.1 to 1.5. Here,
at lower NPR namely at NPR = 7 the level of
expansion has changed considerably as compared to
the NPRs 9 and 11. And for higher NPRs in the range
11 and 9 the jets were highly under expanded and it is
found in the literature that whenever the jets are
under expanded control in the form of either passive
or active control becomes very effective and in the
present study also the same trend has been observed.
Further, it is seen that this effectiveness also,
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decreases with the decrease in the Nozzle Pressure
Ratio. The effect due to the transition from high level
of under expansion to a lower level of under
expansion is clearly seen here. As seen from Fig. 3(f)
that for Mach 1.5 the decreasing trend is arrested at
diameter ratio 2.2 and control effectiveness becomes
marginal. For lower Mach numbers 1.1 and 1.2 the
control effectiveness is only marginal.
Results for NPRs 3 and 5 at L/D = 4 are shown
in Figs. 3(a) to (d)). Here for Mach numbers 1.1 and
1.2 the flow is under expanded. Once the level of
under expansion has come down significantly the
trend of decrease in base pressure which was
observed for higher NPRs is no more visible,
however, up to diameter ratio 1.8 the similar trends
are maintained as earlier as seen in Fig. 3(d) for
Mach 1.5 and control reversal also takes place at the
same point whereas, the same behavior of the flow
takes place at diameter ratio 2.2 for Mach 1.4. From
Fig. 3(c) it is seen that at Mach 1.1 control reversal
takes place at diameter ratio 2.2, and there is
progressive growth in the value of the base pressure
from diameter ratio 1.8 to 2.2 and beyond the value
of the base pressure shoots up, but the decreasing
trend in the base pressure is reversed at the diameter
ratio 2.2, in case of Mach 1.2, the trend of decrease in
base pressure is the same except between diameter
ratio 2.2 there is sudden increase in the value of the
base pressure and control results in increase of base
pressure for all the parameters of the present study.
For NPR 3 the results are shown in Figs. 3((a) to (b)).
There is continuous increase in the magnitude of the
base pressure for Mach 1.1, 1.2, 1.5 and 1.4 as seen
in Fig. 3((a) to (b)), this change in trend is due to the
effect of level of expansion, length to diameter ratio,
and inertia level at the nozzle exit.
The strong effect of diameter ratio and area ratio
when the jets are almost correctly expanded is clearly
seen from these results exhibiting a mixed trend
reflecting both under and over expanded situation.
This is because when the jets are correctly expanded
there is an expansion fan at the nozzle exit due to the
increase in diameter ratio. This expansion fan has
control over the base pressure depending on the relief
it enjoys due to the diameter ratio.
From the results for L/D = 4 it is clear that the
control is effective when jets are under expanded and
the control effectiveness decreases with decrease in
the level of under expansion. These results indicate
that the control becomes effective in a field when
there is favorable pressure gradient exists. This is in
good agreement with the argument of available
literature as stated for the case of passive control.
Results for L/D = 3 are shown in Figs. 4((a) to
(j)). They show similar results for NPR 9 and 11 as it
was seen for L/D = 4, the only difference between the
present result and in the previous one is that all the
variables are same except that the L/D ratio has been
decreased from L/D = 4 to 3 as seen in Figs. 4((g) to
(j)). When the jets are operated at this decreased
length of L/D ratio = 3, the back pressure will
influence the flow in the suddenly expanded duct and
may marginally influence the base region. This
marginal influence is clearly seen as the nature of the
graphs are on the similar lines as that of at L/D = 4
with marginal increase in the magnitude of the base
pressure.
Fig. 4(f) presents the results for NPR 7 at Mach
1.4 and 1.5. For Mach 1.4 the results are same as that
of higher NPRs, whereas, for Mach 1.5 the trend is
similar up to diameter ratio 2.2 then there is sudden
increase in the value of the base pressure for the
reasons as explained above. Figs. 4((a) to (e))
presents the results for NPR 7 at Mach 1.1 and 1.2
Fig. 4(e) and NPR 3 and 5 are shown in Figs 4((a) to
(d)) for Mach 1.1, 1.2, 1.4, and 1.5 they are
representative of the similar results as that of higher
NPRs.
Fig. 4 (a)
Fig. 4 (b)
Fig. 4 (c)
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Fig. 4 (d)
Fig. 4 (e)
Fig. 4 (f)
Fig. 4 (g)
Fig. 4 (h)
Fig. 4 (i)
Fig. 4 (j)
Fig. 4. Base pressure variation with Diameter Ratio
for L/D = 3
Base pressure results for L/D = 2 in the NPR
range 11 to 3 are given in Figs. 5((a) to (j)). The
general behavior of base pressure with increase of
diameter ratio is similar to that for L/D = 4 for NPR 9
and 11 for NPR 7 at Mach 1.1 and 1.2 as shown in
Figs. 5((g) to (j)) and Fig. 5(e). However, the control
effectiveness is strongly influenced by the L/D, as
seen from these Figs. With decrease in L/D it is
interesting to see that the control has become very
effective in reducing the base pressure without
control case and when control were activated they
result in increase of base pressure for all the
parameters. Fig. 5(f) presents results for NPR = 7 at
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Mach 1.4 and 1.5. From the figure it is seen that for
Mach 1.4 the results are the same as we have
discussed earlier for higher NPRs and the control
results in increase of the base pressure, whereas, for
Mach 1.5 also the same trend of decrease in the base
continues till the diameter ratio 2.2 and then base
pressure abruptly increases. The primary reason for
this behavior is the level of expansion and the low
length to diameter ratio. Results for NPR 3 and 5 are
shown in Figs. 5((a) to (d)) and they represent the
similar results as we have discussed above for higher
NPRs namely 7, 9 and 11.
Fig. 5 (a)
Fig. 5 (b)
Fig. 5 (c)
Fig. 5 (d)
Fig. 5 (e)
Fig. 5 (f)
Fig. 5 (g)
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Fig. 5 (h)
Fig. 5 (i)
Fig. 5 (j)
Fig. 5. Base pressure variation with Diameter Ratio
for L/D = 2
The results for L/D = 1 are shown in Figs. 6((a)
to (j)) for NPRs 3 to 11. From the figure it is evident
that at NPRs 9 and 11 exhibit similar results as seen
earlier for L/D = 2 at NPRs 9 and 11.
Figs. 6((e) to (f)) shows the results for NPR 7 at
Mach 1.1, 1.2, 1.4 and 1.5. From the figure it is
evident that the results for Mach 1.1, 1.2, and 1.4 are
in no way different to that of for higher NPRs as
discussed above, whereas, for Mach 1.5 trend is same
to that of lower Mach number up to the diameter ratio
2.2 and beyond there is sudden jump in the value of
the base pressure and this result clearly indicates that
the this length is not sufficient for the flow to be
attached with the duct wall and then up to diameter
ratio 2.2 control results in increase of base pressure.
For NPR 5 the base pressure results are shown in
Figs. 6((c) to (d)). From the Fig. 6(d) it is seen that at
Mach 1.4 and 1.5 up to diameter ratio 1.8 the base
pressure decreases with increase in the diameter ratio
then there sudden jump in the value of base pressure,
this clearly indicates that the flow is no more attached
with the enlarged duct whereas, for Mach 1.1 and 1.2
that the base pressure decreases up to diameter ratio
1.8 then there is marginal increase in the base
pressure value and then sudden increase in base
pressure, which indicates that flow is detached with
the enlarged duct and control is only marginal for all
the cases in the present case. At NPR 3 Fig. 6(b) for
Mach 1.4 trend is same as discussed earlier but at
Mach 1.5 there is continuous increase in the value of
base pressure and flow is no more attached with the
duct wall. Similar results are seen in Fig. 6(a) and
flow seems to be no more attached with the duct wall.
However, the results for lower NPRs behave in
similar manner as those for L/D = 4, excepting that
the control effectiveness is very strongly influenced
by the reduced enlarged duct length. This is because
the base pressure is dictated by the free shear layer
reattachment and the reverse flow to the base region
from the boundary layer which grows downstream of
the reattachment point. Therefore, the duct length
which has got a very strong effect on boundary layer
growth has a definite influence on the base vortex as
well flow pattern at the base area which dictates the
base pressure level.
Fig. 6 (a)
Fig. 6 (b)
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Fig. 6 (c)
Fig. 6 (d)
Fig. 6 (e)
Fig. 6 (f)
Fig. 6 (g)
Fig. 6 (h)
Fig. 6 (i)
Fig. 6 (j)
Fig. 6. Base pressure variation with Diameter Ratio
for L/D = 1
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V. CONCLUSION
The results show that the effectiveness of the
Micro jets is marginal for some cases in controlling
the base pressure even under the influence of
favorable pressure gradient at lower NPRs namely 3
and 5. An important point to be observed that, unlike
passive controls the favorable pressure gradient need
not give desired results for active control in the form
of micro jets. However, for higher values of the
NPRs namely 9 and 11 the active control by micro
jets results in increase of base pressure for all the
values of the diameter ratios of the present studies. At
NPRs 5 and 7 the trends are different due to the level
of expansion, nature of waves present at the base,
relief available, L/D ratio and Mach numbers.
It is seen that most of the cases exhibit similar
behavior for higher as well as the lower L/Ds, and at
lower NPR and Mach numbers which means; that the
back pressure has not adversely influenced the flow
field in the base region as well as in the duct for L/D
= 4 and 3.
The minimum duct length required for the flow
to be attached with the enlarged duct seems to be L/D
= 2, for all the cases of the present study, it is also
found that for some combinations the flow attached
with the duct wall even at L/D = 1.
Hence the present results are case sensitive and
their behavior changes due the change in the shock
wave pattern when we alter the NPR, the Mach
number, L/D ratio and the diameter ratio.
All the non-dimensional base pressure presented
in paper is within an uncertainty band of ± 2.6 per
cent. Further, all the results are repeatable within ±
3 per cent.
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