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Questions tagged [cfd]

questions about computational fluid dynamics

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Wall functions and separation in turbine blade simulation

I am simulating a turbine and I have some question about standard wall function in FLUENT. Standard wall function requires $y^+$ value between 30 to 60 on the blade. but the following quote states: ...
user19061's user avatar
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4 votes
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483 views

How should I set the turbulent prandtl number in a turbulent compressible flow simulation?

I'm working on simulating compressible fluid flow over a flat plate with turbulence. The energy equation for compressible flow with turbulence requires modeling a turbulent heat flux of the form $$...
Paul's user avatar
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156 views

Assign a name to surface in CAD STEP file

I have a CAD model designed in FreeCAD and need to export it to a STEP file (neutral CAD format) to be used in numerical anaysis software. I would like to assign names to selected surfaces in order to ...
FliegenderZirkus's user avatar
2 votes
2 answers
193 views

Imposing/ensuring a constant mass flow rate in turbulent flow simulation

I'm trying to simulate using Finite Elements (non commercial software) the Tube Bundle benchmark problem: http://cfd.mace.manchester.ac.uk/ercoftac/doku.php?id=cases:case078&s[]=tube&s[]=...
Terry's user avatar
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Convergence problem in RANS simulation of unsteady flow

I am simulating an air flow through a two dimensional rectangular channel. The channel splits into two channels, one of them is followed by a 90 degree bend downwards and leads into a cylindrical ...
Simon Henn's user avatar
2 votes
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307 views

OpenFOAM simpleFoam calculation of flow around object leads to strange result

I calculated the flow around an object using OpenFOAM's simpleFoam and wanted to evaluate it's drag coefficent. Actually the drag coefficient is in a reasonable ...
Axel's user avatar
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196 views

Airfoil meshing using ANSYS

Logged in a little time ago i have a new question. So I am trying to mesh an arifoil geometry using ANSYS meshing. Airfoil number is NACA 84-M profile. Running 2-D simulation my main objective is to ...
Theodosis Koutsoukos's user avatar
2 votes
0 answers
103 views

Regarding the ITTC Guidelines for Ship CFD applications

I was reading through the ITTC – Recommended Procedures and Guidelines - Practical Guidelines for Ship CFD Applications (https://ittc.info/media/4196/75-03-02-03.pdf) document and this little thing ...
ASPVL's user avatar
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Flow rate at the vent exit

I am working on a vent. The vent is attached to a box and is designed to extract air out of the box using the venturi effect. Air is made to flow over the vent which creates a significant pressure ...
jaisingh's user avatar
2 votes
0 answers
917 views

How to simulate an exhaust fan condition in ANSYS Fluent?

I'm trying to simulate a model which has one inlet and three outlets, and I'm passing air through it. Now, I want one of the outlets to have exhaust fan. I see options of exhaust fan and outlet-vent ...
Giri's user avatar
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Obtaining the correct flat plate turbulent boundary layer thickness in a CFD simulation

I used a commercial CFD software to simulate incompressible turbulent flow of air over a flat plate. I setup a 2D domain 1.5m long in the x direction and .2m in the y direction. The boundary ...
Paul's user avatar
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How is the reaction progress variable $c$ coupled with Temperature equation while solving the SIMPLE algorithm in CFD?

While solving the Navier-Stokes equation using SIMPLE algorithm, we solve the transport equation for additional scalar at the last step according to the SIMPLE's procedure. We need to add a new ...
Manish's user avatar
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problem in the calculation of pressure drop for an axial turbine

I am simulating an axial turbine. In this turbine, there are two domains. The first domain is the piping before and after the blade and the second domain contains the turbine blades. The domain ...
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Why is the turbulent kinetic energy $k=\overline{v_1'^2}+\overline{v_2'^2}+\overline{v_3'^2}$ even in 2D cases?

I'm writing an essay which partly includes writing about the Reynolds stress model where the dissipation term $\varepsilon_{ij}$ is assumed to be isotropic (since dissipation mostly occurs at small ...
Erik Sahlin's user avatar
1 vote
1 answer
68 views

What is the side way force on a flat membrane place perpendicular to the flow of current on one side, and stagnant water on the other

So basically imagine a plate being placed parallel to the direction of flow of water with water flowing with a certain velocity on one side of the plate and on the other side it is almost stagnant. ...
Uttarayana's user avatar
1 vote
1 answer
233 views

Pressure drop in a CFD simulation of an air flow too small

I am simulating a turbulent air flow through a rectangular channel with the goal to match measured velocity profiles and the static pressure at certain points. My problem is that the pressure drop in ...
Simon Henn's user avatar
1 vote
0 answers
55 views

Why does Roe Average use enthalpy?

If my understanding is correct, Roe averaging is supposed to be a linearization of the nonlinear flux jacobian. For the Euler equations, one can compute the roe average as depending on density, ...
Rubio Hawk's user avatar
1 vote
0 answers
41 views

How to unserstand Correct boundary condition at outlet for incompressible flow?

I am simulating flow around a model. This model have an inlet and an outlet. Flow is incompressible. I know that value of pressure at the outlet is very much different from ambient pressure(Operating ...
user19061's user avatar
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How to solve mesh error for narrow surfaces in Ansys Meshing?

I am simulating a spherical grooved bearing….e.g. A bearing that has spiral grooves on the ball. Please see the following figures. There is a kind of lubricant between ball and cup, so as to prevent ...
Am ir's user avatar
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Is RotCFD or Ansys Fluent better to capture the wake pattern far downstream of a flow in the case of a rotating blade?

My main constraint is that the wake pattern to be worked on is far downstream. Which one will give me more accurate results? Will these two work well for the far wake at all?
user16357's user avatar
1 vote
2 answers
461 views

What is reason of low axial velocity at tip and hub of an axial turbine?

I am analyzing results of my turbine simulation. I have created one line from hub to casing at downstream of the flow...please see the following figures. I want to investigate along this line how the ...
user19061's user avatar
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1 vote
0 answers
64 views

Is it possible that entropy generation decreases with decreasing turbine efficiency(First Low efficiency )?

I simulated an axial turbine(Wells turbine). Now I have faced with strange problem. Performance of any turbine can be improved if the losses are identified and minimized. Several losses can be ...
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1 vote
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72 views

How do I set Reciprocating and Rotation motion in Fluent or CFX?

I want to model the following case(Attached picture) This case have reciprocating and rotation motion. Is it possible that this case models in Fluent or CFX without writing Code? How i set this ...
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1 vote
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How to set up the boundary between volumes in a simulated turbine

I am simulating a turbine and I have some doubts about the correctness of my approach. In this turbine, there are three volumes: The two volumes are the piping before and after the blade and the ...
user19061's user avatar
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1 vote
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58 views

periodic rotational conditions in Fluent

I have one question: In Fluent, should be generated same mesh in rotational faces for creating periodic rotational conditions? Is there a way that unmatched meshes are applied for creating periodic ...
user19061's user avatar
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1 vote
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74 views

Boundary layer is not captured well in axial turbine blade simulation

I am simulating an axial turbine, I tried different mesh topologies and all give me almost the same number. In fact, Boundary layer is not captured well, Reynolds number is equal to $4.4 \times 10^5$ ...
user19061's user avatar
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1 vote
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415 views

Is the convergence of solution ok in Fluent?

I am simulating an axial turbine by using Fluent. The convergence of solution is monitored by checking the residuals of the numerically solved governing equations. Moreover, in order to judge the ...
user19061's user avatar
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1 vote
1 answer
2k views

Boundary conditions for Stream function-Vorticity method

I have used a MATLAB finite difference code to solve a lid driven cavity flow, based on a Stream function-Vorticity formulation of the viscous, incompressible Navier Stokes equations. Details about ...
Torben's user avatar
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0 answers
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How to discretize the Navier Stokes diffusive term on a quadtree mesh with staggered gird?

I'm currently trying to build a CFD code using the quadtree data structure. Everything is pretty much sorted out except for the diffusive term in the momentum equation. I have looked for so many ...
Momo's user avatar
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0 answers
79 views

Best Practice for Multiple Zones in ANSYS Design Modeler for a 3D Structured Mesh for Fluent Simulation

I am building a structured mesh in a rectangular domain to model the flow over a wing with impinging jets at the root over the surface in the spanwise direction. I've tried building unstructured ...
WnGatRC456's user avatar
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1 answer
73 views

CFD numerical methods (FEA, FVM, FDM,…)

I just read the answer from this question and have a question please: What I read: Computational Fluid Dynamics (CFD) refers to the use of the numerical techniques to solve fluid dynamical problems. ...
James's user avatar
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0 votes
0 answers
53 views

Why does CFD over predict shockwave in comparison to wind tunnel?

I ran a CFD simulation of Mach=0.85 flow over an aerofoil and noted that my Cp (coefficient of pressure) plot over predicts the shockwave in comparison to experimental data? Can someone please explain ...
Lerman's user avatar
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0 votes
0 answers
110 views

SU2 vs OpenFoam for highly unsteady aerodynamics. Suggestions?

I am trying to simulate aerodynamic interactions between high speed propeller downwash and wings of a cruising aircraft. Confused between OpenFoam and SU2. Open to other opensource software ...
Pamraat Parmar's user avatar
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0 answers
28 views

Thermal Undershooting In SLM Simulation on Ansys Fluent

I am creating a SLM simulation of basalt on Ansys Fluent. I have enabled laminar viscosity, solidification and melting, and the energy equation. The heat flux is applied to the top wall through the ...
user347553's user avatar
0 votes
0 answers
24 views

How to preserve edge grading of rotated edges in ICEM CFD?

I have a 2D axisymmetric geometry for which I am generating block-structured mesh in ICEM. I am converting this 2D block setup to a 3D block setup by rotating the 2D blocks using a dedicated option in ...
ishan_ae's user avatar
0 votes
0 answers
30 views

Which, if any, CFD methods would be best for predicting performance of a sailboat?

I am interested in using a CFD simulator to calculate the performance potential of a sailboat. And not just a single boat, but of multiple boats of different configurations and hull shapes. If I know ...
bcardarella's user avatar
0 votes
1 answer
49 views

Typical Runoff velocity values

I am computing runoff velocities for rainfall falling over an area using St-Venant 1D momentum equation. I wanted to have some idea if my computed velocities are within a reasonable range of what one ...
user1889930's user avatar
0 votes
0 answers
35 views

approximate equation for temperature drop near wall in contact with fluid

I am concerned about the following problem and so far I am not able to find a solution. Let us consider an environment at a temperature $T_a$ and the inner surface of a not insulating wall in contact ...
FST's user avatar
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0 votes
1 answer
56 views

Sharp Edged Pipe with Negative Pressure

I want to calculate the 2D pipe flow with sharp edged contraction pipe (below figure). The fluid is water, the model is steady state k-epsilon. The boundary condition is velocity inlet (8.47ft/s = 2....
Kinnikuman's user avatar
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0 answers
87 views

Density or Pressure based solver CFD

I’m currently trying to simulate the 2d cross section of a bullet using Ansys Fluent but am really confused about which solver type to use- density or pressure based? Conditions: Transonic (M=0.8) ...
Eddie's user avatar
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0 votes
0 answers
46 views

Is there a CFD program that can simulate the motion of a non rigid body through fluid?

Is there a CFD program that can simulate motion of a conveyor belt underwater? Aproximating it as a moving rigid plate is not gonna work.
Francis L.'s user avatar
0 votes
2 answers
206 views

Heat transfer coefficient in forced convection and its dependence of temperature

I'm working on a Ansys Fluent of an Aluminium coil annealing furnace with the goal of estimating the heat transfer coefficients at different temperatures and ventilator/fan speed conditions. The ...
Ash's user avatar
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0 answers
126 views

Why am I getting an ever increasing value of power co-efficient (Cp) with the increase of TSR in Vertical axis wind turbine simulation?

I am trying to get the bell-shaped Cp vs TSR graph in my 2D simulation of the H-Darrieus vertical axis wind turbine (using a sliding mesh model). However, I am always getting an ever increase of Cp ...
MMT's user avatar
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0 votes
2 answers
130 views

Interpretation of dx/dt and u in CFD

I am currently studying CFD and I have a question about how I should interpret the term u and dx/dt. I would like to find that out in the textbook, but I could not. When I solve 1D Euler Equation with ...
mumu's user avatar
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0 votes
1 answer
95 views

Isn't the Newton's cooling law for heat convection too macroscopic for CFD simulations?

In CFD (Computational Fluid Dynamics) simulations, the space is discretised into a huge number of tiny cells and, therefore, one has the opportunity to use a model of heat transfer that takes into ...
Élio Pereira's user avatar
0 votes
0 answers
200 views

Can we run ANSYS Fluent/OpenFOAM simulations in AWS or any free server?

I was planning to run some FSI related simulations. But the computation capacity that I have is not sufficient. But I had heard that there is a possibility to create instances in the Amazon EC2 or the ...
Vinay5forPrime's user avatar
0 votes
0 answers
30 views

Why is CGNS not used in CSM?

The CGNS format appears to be only applied in CFD (computational fluid dynamics). Why is it not applied in CSM (computational solid mechanics)? Is there any technical reason? The hierarchical ...
Elon Musk's user avatar
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0 votes
0 answers
32 views

Solution diverges for Converging-Diverging Nozzle

I am trying to run a CFD simulation for an ASTAR nozzle but cannot get the solution to converge. These are the steps I took to try and run the simulation. I made the geometry in Solidworks and ...
mojojojo's user avatar
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0 votes
0 answers
166 views

Interpolation at a face, Finite Volume Method in Computational Fluid Dynamics

I am learning CFD and I have come across an example in which the thermal conductivity needs to be interpolated at a face between two rectangular cells. The face weighting factor is given as: $$g = \...
TheBirdman's user avatar
0 votes
0 answers
77 views

Tempreture distribution in a furnace

I am simulating a furnace as follows: Is it possible to capture temperature distribution in this furnace without designing intake fan? Which kind of boundary conditions can replace with intake fan? ...
user19061's user avatar
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