This academic article discusses numerical flow simulation of an elbow draft tube using STAR-CCM+ software. It summarizes the steps taken which include geometric modeling of the draft tube, mesh generation, specification of parameters like material properties and boundary conditions, and setting up the implicit unsteady simulation. Results of the simulation like pressure and velocity variations along the draft tube over different time steps are presented. Key findings are that pressure and velocity distributions are affected by time step size, with smaller time steps showing more uniform distributions. Performance metrics like head recovery and efficiency of the draft tube are computed and seen to decrease initially with time step before leveling off.
The presentation gives glances of the importance of CFD analysis in engineering design with an illustration/ case study. For more details, follow the webinar "Role of CFD in Engineering Design" on https://www.learncax.com/knowledge-base/blog/by-author/ganesh-visavale
The Powerpoint presentation discusses about the Introduction to CFD and its Applications in various fields as an Introductory topic for Mechanical Engg. Students in General.
The presentation gives glances of the importance of CFD analysis in engineering design with an illustration/ case study. For more details, follow the webinar "Role of CFD in Engineering Design" on https://www.learncax.com/knowledge-base/blog/by-author/ganesh-visavale
The Powerpoint presentation discusses about the Introduction to CFD and its Applications in various fields as an Introductory topic for Mechanical Engg. Students in General.
1. Introduction to Kinematics
2. Methods of Describing Fluid Motion
a). Lagrangian Method
b). Eulerian Method
3. Flow Patterns
- Stream Line
- Path Line
- Streak Line
- Streak Tube
4. Classification of Fluid Flow
a). Steady and Unsteady Flow
b). Uniform and Non-Uniform Flow
c). Laminar and Turbulent Flow
d). Rotational and Irrotational Flow
e). Compressible and Incompressible Flow
f). Ideal and Real Flow
g). One, Two and Three Dimensional Flow
5. Rate of Flow (Discharge) and Continuity Equation
6. Continuity Equation in Three Dimensions
7. Velocity and Acceleration
8. Stream and Velocity Potential Functions
Finite element method in solving civil engineering problemSaniul Mahi
The applications of Finite Element Method in solving Civil Engineering problem and the merits of using a finite element procedure over the other methods.
Check out this video ▶https://youtu.be/gtqBQQ-V-T4 for an explanation of this slide.
IS 456:2000 is an important code for every civil engineer and also for every exam aspirant. This code gives various provisions for a concrete structure consisting of elements like beams, slabs, columns, footing. This slide gives a comprehensive summary of all the important code provisions that are usually asked in many examinations.
B.TECH. DEGREE COURSE
SCHEME AND SYLLABUS
(2002-03 admission onwards)
MAHATMA GANDHI UNIVERSITY,mg university, KTU
KOTTAYAM
KERALA
Module 1
Introduction - Proprties of fluids - pressure, force, density, specific weight, compressibility, capillarity, surface tension, dynamic and kinematic viscosity-Pascal’s law-Newtonian and non-Newtonian fluids-fluid statics-measurement of pressure-variation of pressure-manometry-hydrostatic pressure on plane and curved surfaces-centre of pressure-buoyancy-floation-stability of submerged and floating bodies-metacentric height-period of oscillation.
Module 2
Kinematics of fluid motion-Eulerian and Lagrangian approach-classification and representation of fluid flow- path line, stream line and streak line. Basic hydrodynamics-equation for acceleration-continuity equation-rotational and irrotational flow-velocity potential and stream function-circulation and vorticity-vortex flow-energy variation across stream lines-basic field flow such as uniform flow, spiral flow, source, sink, doublet, vortex pair, flow past a cylinder with a circulation, Magnus effect-Joukowski theorem-coefficient of lift.
Module 3
Euler’s momentum equation-Bernoulli’s equation and its limitations-momentum and energy correction factors-pressure variation across uniform conduit and uniform bend-pressure distribution in irrotational flow and in curved boundaries-flow through orifices and mouthpieces, notches and weirs-time of emptying a tank-application of Bernoulli’s theorem-orifice meter, ventury meter, pitot tube, rotameter.
Module 4
Navier-Stoke’s equation-body force-Hagen-Poiseullie equation-boundary layer flow theory-velocity variation- methods of controlling-applications-diffuser-boundary layer separation –wakes, drag force, coefficient of drag, skin friction, pressure, profile and total drag-stream lined body, bluff body-drag force on a rectangular plate-drag coefficient for flow around a cylinder-lift and drag force on an aerofoil-applications of aerofoil- characteristics-work done-aerofoil flow recorder-polar diagram-simple problems.
Module 5
Flow of a real fluid-effect of viscosity on fluid flow-laminar and turbulent flow-boundary layer thickness-displacement, momentum and energy thickness-flow through pipes-laminar and turbulent flow in pipes-critical Reynolds number-Darcy-Weisback equation-hydraulic radius-Moody;s chart-pipes in series and parallel-siphon losses in pipes-power transmission through pipes-water hammer-equivalent pipe-open channel flow-Chezy’s equation-most economical cross section-hydraulic jump.
1. Introduction to Kinematics
2. Methods of Describing Fluid Motion
a). Lagrangian Method
b). Eulerian Method
3. Flow Patterns
- Stream Line
- Path Line
- Streak Line
- Streak Tube
4. Classification of Fluid Flow
a). Steady and Unsteady Flow
b). Uniform and Non-Uniform Flow
c). Laminar and Turbulent Flow
d). Rotational and Irrotational Flow
e). Compressible and Incompressible Flow
f). Ideal and Real Flow
g). One, Two and Three Dimensional Flow
5. Rate of Flow (Discharge) and Continuity Equation
6. Continuity Equation in Three Dimensions
7. Velocity and Acceleration
8. Stream and Velocity Potential Functions
Finite element method in solving civil engineering problemSaniul Mahi
The applications of Finite Element Method in solving Civil Engineering problem and the merits of using a finite element procedure over the other methods.
Check out this video ▶https://youtu.be/gtqBQQ-V-T4 for an explanation of this slide.
IS 456:2000 is an important code for every civil engineer and also for every exam aspirant. This code gives various provisions for a concrete structure consisting of elements like beams, slabs, columns, footing. This slide gives a comprehensive summary of all the important code provisions that are usually asked in many examinations.
B.TECH. DEGREE COURSE
SCHEME AND SYLLABUS
(2002-03 admission onwards)
MAHATMA GANDHI UNIVERSITY,mg university, KTU
KOTTAYAM
KERALA
Module 1
Introduction - Proprties of fluids - pressure, force, density, specific weight, compressibility, capillarity, surface tension, dynamic and kinematic viscosity-Pascal’s law-Newtonian and non-Newtonian fluids-fluid statics-measurement of pressure-variation of pressure-manometry-hydrostatic pressure on plane and curved surfaces-centre of pressure-buoyancy-floation-stability of submerged and floating bodies-metacentric height-period of oscillation.
Module 2
Kinematics of fluid motion-Eulerian and Lagrangian approach-classification and representation of fluid flow- path line, stream line and streak line. Basic hydrodynamics-equation for acceleration-continuity equation-rotational and irrotational flow-velocity potential and stream function-circulation and vorticity-vortex flow-energy variation across stream lines-basic field flow such as uniform flow, spiral flow, source, sink, doublet, vortex pair, flow past a cylinder with a circulation, Magnus effect-Joukowski theorem-coefficient of lift.
Module 3
Euler’s momentum equation-Bernoulli’s equation and its limitations-momentum and energy correction factors-pressure variation across uniform conduit and uniform bend-pressure distribution in irrotational flow and in curved boundaries-flow through orifices and mouthpieces, notches and weirs-time of emptying a tank-application of Bernoulli’s theorem-orifice meter, ventury meter, pitot tube, rotameter.
Module 4
Navier-Stoke’s equation-body force-Hagen-Poiseullie equation-boundary layer flow theory-velocity variation- methods of controlling-applications-diffuser-boundary layer separation –wakes, drag force, coefficient of drag, skin friction, pressure, profile and total drag-stream lined body, bluff body-drag force on a rectangular plate-drag coefficient for flow around a cylinder-lift and drag force on an aerofoil-applications of aerofoil- characteristics-work done-aerofoil flow recorder-polar diagram-simple problems.
Module 5
Flow of a real fluid-effect of viscosity on fluid flow-laminar and turbulent flow-boundary layer thickness-displacement, momentum and energy thickness-flow through pipes-laminar and turbulent flow in pipes-critical Reynolds number-Darcy-Weisback equation-hydraulic radius-Moody;s chart-pipes in series and parallel-siphon losses in pipes-power transmission through pipes-water hammer-equivalent pipe-open channel flow-Chezy’s equation-most economical cross section-hydraulic jump.
LMS Imagine.Lab Amesim / STAR-CCM+ co-simulation - Thermal analysis of a comb...Siemens PLM Software
This presentation introduces the co-simulation capabilities between LMS Imagine.Lab Amesim and Star-CCM+, two products from the Simcenter portfolio of Siemens PLM Software. This slideset also presents a concrete example of these co-simulation capabilities with the thermal analysis of a combustion chamber.
For more information, please visit our website:
siemens.com/plm/simcenter
Optimization of Closure Law of Guide Vanes for an Operational Hydropower Plan...Dr. Amarjeet Singh
This paper addresses the optimization of twostage closure law of guide vanes in an operational
hydropower plant of Nepal. The mathematical model
has been established in commercial software Bentley
Hammer, whose correctness has been validated by
comparing the results with the data of experimental
load rejection test. The validated mathematical model
has been employed to find the parameters of optimum
closure pattern, which minimizes the non-linear
objective function of maximum water pressure and
maximum rotational speed of turbine.
REVIEW OF FLOW DISTRIBUTION NETWORK ANALYSIS FOR DISCHARGE SIDE OF CENTRIFUGA...ijiert bestjournal
A computational fluid dynamics (CFD) analysis has been conducted to find the pressure losses for dividing and combining fluid flow through a junction of discharge system. Simulations are performed for a range of flow ratios and equations are developed for pressure loss coefficients at junctions. A mathematical model based on s uccessive approximations then would be employed to estimate the pressure losses. The proposed CFD based strategy can be used for the analysis of all the three pipe branches of s ome diameter are selected along with equal length so that only the effect of bend angle can be st udied. The effect of bend angle,pipe diameter,pipe length,reynolds number on the resistan ce coefficient is studied. The software used is CATIA for modeling and ANSYS fluent for analysis purpose.
Role of Simulation in Deep Drawn Cylindrical PartIJSRD
Simulation is widely used in forming industry due to its speed and lower cost and it has been proven to be effective in prediction of formability and spring back behavior. The purpose of finite element simulation in the sheet metal forming process is to minimize the time and cost in the design phase by predicting key outcomes such as the final shape of the part, the possibility of various defects and the flow of material. Such simulation is most useful and efficient when it is performed in the early stage of design by designers, rather than by analysis specialists after the detailed design is complete. The accuracy of such simulation depends on knowledge of material properties, boundary conditions and processing parameters. In the industry today, numerical sheet metal forming simulation is very important tool for reducing load time and improving part quality. In this paper finite element model for the deep-drawing of cylindrical cups is constructed and the simulation results are obtained by using different simulation parameters, i.e. punch velocity, coefficient of friction and blank holder force of the FE mesh-elements and these results are compared with experimental work.
FLOW DISTRIBUTION NETWORK ANALYSIS FOR DISCHARGE SIDE OF CENTRIFUGAL PUMPijiert bestjournal
A computational fluid dynamics (CFD) analysis has been conducted to f ind the pressure losses for dividing and combining fluid flow through a junction of discharge system. Si mulations are performed for a range of flow ratios and equations are developed for pressure loss coeff icients at junctions. A mathematical model based on successive approximations then would be employed to estim ate the pressure losses. The proposed CFD based strategy can be used for the analysis of all the thr ee pipe branches of some diameter are selected along with equal length so that only the effect of bend angle can be studied. The effect of bend angle,pipe diameter,pipe length,Reynolds number on the resistance coeffi cient is studied. The software used is CATIA for modeling and ANSYS fluent for analysis purpose.
Numerical Investigation of Turbulent Flow over a Rotating Circular Cylinder u...IJERA Editor
Recent advancements in the field of computational fluid mechanics and the availability of high performance with regard to rotating software computing cylinders (RCs) have drawn attention to the field of flow accelerated corrosion. (FAC). Current studies aim to numerically predict turbulent flow characteristics around the rotating cylinder and the concomitant effects on the wall shear stresses and local mass fraction of inhibitors that are directly related to corrosion rate. This 3-D numerical investigation was carried out using the commercial CFX package from which the where SST turbulence model was selected to compute the unknown Reynolds stresses term in the incompressible and viscid form of the Navier-Stokes equation. The effect of three different cylinder rotation speeds and three brine temperatures on the wall shear stress and on brine mixing is reported. Results of the simulations revealed that both cylinder rotation speed and the temperature of the brine significantly affect wall shear stress and mixing of the inhibitor that in turn affects corrosion rate
A computational approach for evaluating helical compression springseSAT Journals
Abstract Helical compression springs are generally synthesized and evaluated by determining the maximum torsional stress, fatigue life, natural frequency, and/or load loss due to stress relaxation. To this end, researchers have developed finite element analysis (FEA) modeling methods to simulate the design performance of helical compression springs. The intent of this paper was to make a useful contribution to the published works for evaluating round wire helical compression springs. Specifically, commercially available FEA software was used to construct a structural model of a helical compression spring to simulate its full range of compression. The proposed FEA modeling methodology considers coil-to-coil contact and the end coils were modeled as rigid surfaces. With 9 mm of compression, the predicted spring rate correlated with the analytically calculated value to within 5%. Keywords: Helical compression spring, machine component design, spring FEA
Simulations Of Unsteady Flow Around A Generic Pickup Truck Using Reynolds Ave...Abhishek Jain
Above Research Paper can be downloaded from www.zeusnumerix.com
The research paper aims to replicate the wind tunnel test of General Motors pick-up truck using CFD analysis. The pickup is a blunt body and simulation reveals vortex shedding from the edges of the vehicle downstream. The unsteadiness of this phenomenon is seen in the oscillation of residue. The paper shows matching of velocity magnitude downstream of the vortex. Authors - Bahram Khalighi (GM, USA), Basant Gupta et al Zeus Numerix.
Simulation of Deep-Drawing Process of Large Panelstheijes
The article deals with the analysis of formability of deep-drawing DC06 steel sheets. The aim of the investigations is to verify possibilities of formability of sheet metal with thickness of 0.85 mm. The mechanical parameters of the sheets have been determined in uniaxial tensile and bulge tests. The numerical simulations using AUTOFORM has been carried out for two drawpiece models. Obtained results can be used during the simulation of real forming process.
Computational Estimation of Flow through the C-D Supersonic Nozzle and Impuls...IJMTST Journal
In this paper, CFD analysis of flow within, Convergent – Divergent rectangular super sonic nozzle and super sonic impulse turbine with partial admission have been performed. The analysis has been performed according to shape of a super sonic nozzle and length of axial clearance and the objective is to investigate the effect of nozzle-rotor interaction on turbine’s performance. It is found that nozzle-rotor interaction losses are largely dependent on axial clearance, which affects the flow within nozzle and the extent of flow expansion. Therefore selecting appropriate length of axial clearance can decrease nozzle-rotor interaction losses. The work is carried in two stages:1) Modeling and analysis of flow for rectangular convergent divergent super sonic nozzle. 2) Prediction of optimal axial gap between the nozzle and rotor blades by allowing the above nozzle flow. In the present work, using a finite volume commercial code, ANSYS FLUENT 14.5, carries out flow through the convergent divergent nozzle study. The nozzle geometry is modeled and grid is generated using ANSYS14.5 Software. Computational results are in good agreement with the experimental ones.
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Search and Society: Reimagining Information Access for Radical FuturesBhaskar Mitra
The field of Information retrieval (IR) is currently undergoing a transformative shift, at least partly due to the emerging applications of generative AI to information access. In this talk, we will deliberate on the sociotechnical implications of generative AI for information access. We will argue that there is both a critical necessity and an exciting opportunity for the IR community to re-center our research agendas on societal needs while dismantling the artificial separation between the work on fairness, accountability, transparency, and ethics in IR and the rest of IR research. Instead of adopting a reactionary strategy of trying to mitigate potential social harms from emerging technologies, the community should aim to proactively set the research agenda for the kinds of systems we should build inspired by diverse explicitly stated sociotechnical imaginaries. The sociotechnical imaginaries that underpin the design and development of information access technologies needs to be explicitly articulated, and we need to develop theories of change in context of these diverse perspectives. Our guiding future imaginaries must be informed by other academic fields, such as democratic theory and critical theory, and should be co-developed with social science scholars, legal scholars, civil rights and social justice activists, and artists, among others.
UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
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Numerical flow simulation using star ccm+
1. Civil and Environmental Research www.iiste.org
ISSN 2224-5790 (Paper) ISSN 2225-0514 (Online)
Vol.3, No.6, 2013 - Selected from International Conference on Recent Trends in Applied Sciences with Engineering Applications
34
Numerical Flow Simulation using Star CCM+
Upendra Rajak, Dr. Vishnu Prasad, Dr. Ruchi Khare
Department of Civil Engineering, M.A. National Institute of Technology, Bhopal, MP, India
*E-mail: upendrarajak86@gmail.com
Phone No: +91 9753509775
ABSTRACT
The accuracy of numerical simulation of any physical process depends on the technique adopted for the
simulation and the software used. Many software i.e., ANSYS, PHONICS, NUMECA, STAR-CCM+, etc. have
been developed to solve the governing equations in discretizing the flow domain. Each software has its own
capabilities and limitations. In the present work, STAR-CCM+ has been used for numerical simulation in draft
tube of hydraulic turbine and result are presented in graphical and tabular form.
Keyword: Elbow draft tube, numerical flow simulation, efficiency, head loss.
Nomenclature
γ specific weight of water(N/m3)
P03 total pressure inlet (kPa)
P05 total pressure outlet (kPa)
V03 inlet velocity (m/s)
V05 outlet velocity (m/s)
HLD head loss (m)
HRLD total relative loss (%)
HRD head recovery (m)
ηD draft tube efficiency(%)
g acceleration due to gravity (m/s2
)
D inlet diameter (m)
H height of draft tube (m)
L length of draft tube (m)
INTRODUCTION
The design of any physical flow system is based on some assumption for simplicity but the flow behavior is to
checked before making the actual system[2].The computational fluid dynamics is efficient and cost effective
tool for flow simulation in comparison to experimental testing approach which is time consuming and expensive.
With the advancement of computational techniques, and also computer speed, the researchers are seeking answer
to the complexity in flow by Simulating the flow by approximate solution of governing equation in specified
domain.
In 2004, CD-adapco introduces a new product, STAR-CCM+, “CCM” stands for Computational Continuum
Mechanics from STAR-CD. STAR-CCM+ is fully integrated tool allows user to build geometry as well as
provides engineering physics simulation inside a single integrated package[5, 8]. There is inbuilt geometry
modeler within the STAR-CCM + environment, as well as it has facility to import external CAD models and
modifying them before running the simulation. In STAR-CCM+ analysis of the flow behavior is possible while
the simulation is running [6,7]. It can be applied for the solution of Aerospace, Automotive, Biomedical,
Chemical, Power Generation. It can also be used for the numerical flow simulation of various hydraulic machine,
pumps and turbines etc.
One of the important components of reaction turbine, from the aspect of efficiency is draft tube, which connects
runner exit to tail race and converts major part of kinetic energy coming out from runner into pressure energy
and therefore has direct impact on the total efficiency of hydroelectric power plant [2, 4].The present work deals
with the implicit unsteady flow simulation of elbow draft tube of a reaction turbine using Star CCM+. The
analysis is carried out for velocity and pressure variation with different Courant numbers.
2. Civil and Environmental Research www.iiste.org
ISSN 2224-5790 (Paper) ISSN 2225-0514 (Online)
Vol.3, No.6, 2013 - Selected from International Conference on Recent Trends in Applied Sciences with Engineering Applications
35
GEOMETRIC MODELING
The fig. 1 shows the geometric model of elbow draft tube of length (L) 11.0 m, inlet diameter (D) 1.726 m and
height (H) 2.542 m.
MESHING
The size and shape of element and density of meshing affects the accuracy of numerical simulation. The mesh
continua has been used for selection of mesh model and to define the base size of mesh.
Fig.2 shows the tetrahedral volume mesh of draft tube generated in STAR-CCM+. Different types of mesh
models are available in STAR-CCM+ to carry the meshes on surface inside flow domain.
PARAMETER SPECIFICATIONS
The following properties parameters are to be define for simulation:
Material
The material property like density, viscosity etc. are to be defined.
Implicit Unsteady model
Segregated fluid energy and segregated models are only applied for implicit unsteady flow[1]. This model is
alternative to explicit unsteady. The choice between models is based on the time scales of the phenomena of
interest at each time-step. Implicit unsteady model uses implicit solver, its function is to control the update at
each physical time for the calculation. It also controls the time-step size.
Region & boundary condition
Volume domains in space that are completely surrounded by boundaries is termed as regions. The inlet velocity
in three directions are defined as inlet boundary condition. The value of velocity are given in table.
TABLE NO.1
X(m/s) Y(m/s) Z(m/s)
Inlet velocity -0.0422 0.0148 -7.69
Inlet reference pressure 1 (atm.)
Outlet relative pressure 0 (atm.)
The static pressure equal to 1atm has been taken as outlet boundary conditions.
Derived parts
Fig.1 MODEL OF DRAFT TUBE
Fig.3.MESH MODEL OF DRAFT TUBE
3. Civil and Environmental Research www.iiste.org
ISSN 2224-5790 (Paper) ISSN 2225-0514 (Online)
Vol.3, No.6, 2013 - Selected from International Conference on Recent Trends in Applied Sciences with Engineering Applications
36
A derived part is created using one or more other parts as parent parts, or inputs, and it is dependent on these
parent parts. If any of the parent parts change, all parts depending on those parent parts are automatically
recalculated and redisplayed to reflect the change [6].
Editing and addition can be done in derived parts to examine the solution, derived parts get its data from the
input parent data. Here in the present example streamline and iso- surface is used as derived parts.
Turbulence Models
The turbulence are used to capture the turbulence scale to predict the turbulence behavior. The selection of
model depends on nature of boundaries of and Reynolds number[7].
The segregated flow implicit solver, K-Epsilon Turbulence are defined as the solving parameters in the present
example.
TERMINATION OF SIMULATION
The computations for simulation are to be stopped after it meets some specific requirements like number of
iteration, value of residuals etc.
In this criteria it specifies how long the solution should run and under what conditions it should stop iterating
and/or marching in time. Each enabled criterion is evaluated at the completion of every iteration and time step
and a check is used to determine if the requirement of all the criteria are met to stop the solver.
Maximum physical time
Maximum physical time step define the total time step in analysis. In this present work 8 step has been taken as
the maximum physical time.
Maximum step
Maximum number of iteration in steady-solver and unsteady-solver analysis can be set as an stopping criteria to
stop the simulation.
FORMULE USED FOR CALCULATION
The following formula used for calculation of head loss, head recovery, efficiency, and relative loss[3]:
Head loss in draft tube
03 05( )
LD
P P
H
γ
−
=
Head recovery in draft tube
2 2
03 05( )
2
RD LD
V V
H H
g
−
= −
draft tube Efficiency of the
2
03
2
100RD
D
gH
V
η = ×
Relative loss
2
03
2
100LD
RLD
gH
H
V
= ×
RESULT AND DISCUSSIONS
The pressure and velocity distributions in the flow domain are obtained from numerical simulation. These are
used for computation of head loss and efficiency of draft tube.
The viscous flow unsteady analysis has been carried out in draft tube of length 11.0 m, height 2.542 m and
diameter 1.726 m and result are presented in tabular and graphical form. The boundary conditions are kept same
for time steps. It is seen that the velocity at the centre of the outlet is more than the velocity at the periphery of
the outlet. The values of velocity and pressure were calculated using the report on mass flow average basis as a
field function.
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37
TABLE NO.2
Average value of Pressure and Velocity.
Time
step
Inlet Middle section Outlet
Velocity
(m/s)
Pressure
(kPa)
Velocity
(m/s)
Pressure
(kPa)
Velocity
(m/s)
Pressure
(kPa)
0.2 7.7 4.67 3.306 2.391 1.684 1.525
0.25 7.7 6.49 3.563 3.322 1.444 1.084
0.5 7.7 8.43 4.356 5.434 1.833 1.951
1.0 7.7 8.10 4.331 5.164 1.879 2.029
1.5 7.7 9.22 4.266 6.288 2.341 3.112
2.0 7.7 9.38 4.242 6.429 2.528 3.663
2.5 7.7 8.54 4.328 5.468 2.066 2.459
3.0 7.7 9.2 4.238 6.243 2.537 3.653
Fig.13. (a): Pressure contour at 0.2 sec time step
Fig.13. (b) Pressure contour at 1.5 sec time step
Fig.13. (c): Pressure contour at 3.0 sec time step
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The Fig.13 a, b, and c shows the variation of total pressure distribution on longitudinal plane created from inlet
to outlet in draft tube at different time steps of 0.2 sec, 1.5 sec, and 3.0 sec respectively. If is seen that in fig.
13(a), the maximum and minimum pressure values are 8.5kPa and -1.4kPa. The pressure variation in fig. 13(b) is
between 13.11KPa and -7.4KPa while in fig. 13(c), the variation is between 13.80KPa and -7.46KPa. This
indicates that at small time step, the pressure variation is less and become nearly constant at higher time steps.
The variations of velocity for different time steps of 0.2 sec, 1.5 sec, and 3.0 sec are shown in fig. 14(a), (b) and
(c) respectively on the same longitudinal plane. It is observed that velocity decreases from inlet to outlet in all
cases due to enlargement of flow area. The velocity distribution is more uniform at small time step. It is more at
outlet at where pressure is low.
Fig.14. (a):Velocity contour at 0.2 sec time step
Fig.14. (b): Velocity contour at 1.5 sec time step
Fig.14. (c): Velocity contour at 3.0 sec time step
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Fig.15(a) Fig.15(b)
Fig.15 (a, b) pressure contour at inlet and outlet (0.2 sec) time step.
Fig.(c) Fig.(d)
Fig.15 (c, d) pressure contour at inlet and outlet (1.5 sec) time step.
Fig.(e) Fig.(f)
Fig.15 (e, f) pressure contour at inlet and outlet (3.0 sec) time step.
Figures 15(a) to (f) show the pressure contours at inlet and out for different time steps. At inlet, pressure is
maximum at centre and decreases towards periphery for all time steps. The pressure distribution at outlet for
time step of 0.2 sec indicates that pressure decreases gradually from bottom to top. As the time step is increased,
pressure distribution become becomes very uneven and gives min pressure at bottom and maximum at sides of
outlet section,
Fig.16. (a): velocity stream line at 0.2 sec time step
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The streamline of flow are shown in Fig.16 (a) to (c) at different time steps of 0.2 sec, 1.5 sec, and 3.0 sec
respectively. The above figure shows the maximum swirl at 3.0 sec as compared to 0.2 sec and 1.5 sec. It is seen
that stream lines are nearly parallel at 0.2 sec time steps and as the time step is increased, flow becomes very
turbulent with eddies as given in fig. 16 (b) and (c).
Fig.16. (b): velocity stream line at 1.5 sec time step
Fig.16. (c): velocity stream line at 3.0 sec time step
Fig.17. (a): Draft tube head recovery with time step.
Fig.17. (b): Draft tube efficiency with time step.
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The head or energy recovery in draft tube and its efficiency decreases with increase in time steps initially and
becomes constant after time step of 1.5 sec in fig. 17(a) and (b). The head loss and relative head loss in fig. 17(c)
and (d) has reverse pattern to that of head recovery and efficiency with time step.
CONCLUSIONS
It is seen from the results of numerical simulation in draft tube that time step has significant effect on pressure
and velocity distribution and also on the hydraulic performance of draft tube. The variation of pressure and
velocity from inlet to outlet are similar to theoretical energy change with flow area. STAR-CCM+ may be very
useful tool for performance of hydraulic systems and design optimization.
REFERENCE
1. ARPE Jorge, “Pressure Wall Measurement in The Whole Draft Tube Steady and Unsteady Analysis”,
Proceeding of the XXI IAHR Syposium on Hydraulic Machine and Systems September 9-12, 2002,
Lausanne.
2. Khare Ruchi, Prasad Vishnu, Mittal Sushil Kumar, “Effect of Runner Solidity on Performance of Elbow
Draft Tube”, Energy Procedia 14(2012), pp 2054-2059.
3. M.F Gubin, “Draft Tubes of Hydraulic Station”, Amerind Publishing Company Pvt. Ltd, 1973 .
4. Prasad Vishnu, Khare Ruchi, Abhas Chincholikar, “Hydraulic Performance of Elbow Draft Tube for
Different Geometric Configurations Using CFD”, IGHEN-2010, Oct.21-23, 2010, AHEC, IIT Roorkee,
India.
5. Used Software STAR-CCM+(6.06.016).
6. STAR-CCM+(6.06.016) user manual.
7. https://cd-adapco.secure.force.com
8. http://en.wikipedia.org/wiki/CD-adapcom
9. http://www.cdadapco.com/products/starccmplus
Fig.17. (c): Draft tube head loss with time step
Fig.17. (d): Draft tube relative loss with time step
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