Questions tagged [cfd]

questions about computational fluid dynamics

42 questions with no upvoted or accepted answers
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1answer
254 views

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: ...
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0answers
427 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 $$...
2
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0answers
34 views

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 ...
2
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0answers
152 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 ...
2
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0answers
39 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 ...
2
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0answers
90 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 ...
2
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0answers
61 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 ...
2
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0answers
61 views

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 ...
2
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0answers
628 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 ...
2
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0answers
245 views

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 ...
2
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0answers
207 views

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 ...
2
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0answers
67 views

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 ...
1
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1answer
26 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. ...
1
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1answer
42 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 ...
1
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0answers
21 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, ...
1
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3answers
572 views

How do drag and downforce in a rear spoiler of a car vary with angle of attack?

I ran an two aerodynamic simulations, one for a spoiler angle of 0 deg and the other for the same spoiler declined at 30 deg. The results showed a considerable increase in downforce, but only a slight ...
1
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0answers
307 views

ANSYS Fluent - Using Patch to set initial conditions, should I set the pressure and velocity or only one property to generate shock waves in a pipe?

I am fairly new to CFD and I am working in ANSYS Fluent. I am trying to model two specific shock waves in opposite directions in a length pipe. The shock waves need to be traveling at specific Mach ...
1
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0answers
22 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 ...
1
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0answers
200 views

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 ...
1
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0answers
39 views

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?
1
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2answers
359 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 ...
1
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0answers
59 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 ...
1
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0answers
64 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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0answers
35 views

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 ...
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0answers
54 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 ...
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0answers
73 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 $4.4 \times 10^5$ ...
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0answers
363 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 ...
1
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1answer
1k 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 ...
0
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0answers
27 views

Exporting CFD wind simulation in urban area

I need to perform somewhat specific wind simulations, but I have never touched a CFD software before. The scenario is, there is a part of a city, several buildings and I need to simulate the wind in ...
0
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0answers
50 views

How to simulate gas-liquid mixing in a bioreactor in ANSYS Fluent?

I thank you for taking a look. I'm a beginner with so much love to simulate fluids as fluid visualizations fascinate me. My learning has been only through youtube, forums. So, please excuse my naivety ...
0
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0answers
71 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 ...
0
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0answers
27 views

Where is Wizard in Solidworks Flow simulation?

would anyone knows why my wizard in Solidworks 2016 flow simulation is missing, I am starting to learn flow simulation because of my study, I am still a beginner, I tried testing it 1 time with my ...
0
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1answer
48 views

How to compute velocity distribution in the developing boundary layer on the cylinder

Air flows perpendicular to the axis of a cylinder $a=1$ cm in diameter. Air speed upstream of the cylinder is $U=6.72$ mm/s and its kinematic viscosity is $2.1×10^{-5}$ at 350 K. I want to obtain the ...
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0answers
18 views

Finding the momentum source using divergence theorem

I have the following question: I understand how to use the divergence theorem but I'm not sure how I would find the momentum source, am I supposed to find the integral of grad U?
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0answers
19 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 ...
0
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0answers
26 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 ...
0
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0answers
76 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 = \...
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0answers
57 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? ...
0
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0answers
137 views

What is the exact meaning of "static and dynamic torque"?

I have the following parameters in my project. enter link description here I submitted a paper. Now, one of the Reviewer's comments is as follows: Validation is not enough and convincing. The CFD ...
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0answers
364 views

Why is there negative static pressure in contour?

I studied a paper about turbine and i seen that there is negative static pressure in contour. Why does this happen? Wave Energy Harvesting Turbine: Performance Enhancement
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0answers
53 views

Flow through manifold: convergence issues

I try to simulate flow through a manifold with multiple inlets & outlets but I'm facing convergence issues. I know that it may be due to poor quality mesh, but my mesh statistics are: Minimum ...
-1
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1answer
223 views

Velocity inlet boundary condition in Ansys Fluent

Ansys Fluent offers a very simplified version of boundary conditions. So if I know the velocity at the inlet, I need not care about pressure and vice versa. What I am having trouble with is that I ...