boundary conditions for simpleFoam calculation
1 Attachment(s)
Hello everyone,
I am currently simulating the airflow over a car. I know what the results should look like, but after changing the boundary condition numerous times I am still unable to get realistic results (tried with both kepsilon model and komega model). I posted a picture of my simulation below (blended out some walls) as well as added the boundary conditions. fvSchemes and fvSolution were taken from either the motorbike tutorial (for k omega model) or pitzDaily tutorial (k epsilon model). I am calculating with simpleFoam. R, omega and k were also taken from these tutorials. Appreciate the help :). Patrick P.S Which model (k epsilon / k omega model) is better for this calculation? epsilon: Code:
Code:
dimensions [0 2 -1 0 0 0 0]; Code:
dimensions [0 2 -2 0 0 0 0]; Code:
dimensions [0 1 -1 0 0 0 0]; Code:
dimensions [0 2 -2 0 0 0 0]; Code:
dimensions [0 0 -1 0 0 0 0]; Code:
dimensions [0 2 -2 0 0 0 0]; |
problem solved
|
Do you like your drag results?
|
I haven't had the chance to implement liftDrag from OF 1.2. I have to do that when I have time. If you know a different way to calculate the drag coefficient with OF please share :).
|
functions
{ forces { type forces; functionObjectLibs ("libforces.so"); outputControl timeStep; outputInterval 1; patches (OBJECT_OBJECT); pName p; Uname U; log true; rhoName rhoInf; rhoInf 1.17; magUInf 0.0045; CofR (1.25 0 4); } forceCoeffs { type forceCoeffs; functionObjectLibs ("libforces.so"); outputControl timeStep; outputInterval 1; patches (OBJECT_OBJECT); pName p; Uname U; log true; rhoName rhoInf; rhoInf 1.17; magUInf 0.0045; CofR (1.25 0 4); liftDir (0.0 1.0 0.0); dragDir (1.0 0.0 0.0); pitchAxis (0 0 0); lRef 0.5; Aref 12.56; } I use something like this in my /system/controlDict file. You must alter for your case, but this is a start. I'm not sure in which version that a forces function object (vocabulary?) was introduced off-hand. Regards, Ben Racine |
The following thread is the reference for the above statements.
http://www.cfd-online.com/Forums/ope...es-v1-6-a.html |
Hey Ben,
Thanks for the code. I tried it and it worked without any problems. I have a couple of question regarding this code. 1. Which patches should I use for my simulation? Do I use every patch that defines the vehicle (I split the car into multiple parts: wheels, windshields and so on)? 2. And what is lRef? How do I calculate it? 3. Do you know a method for calculating Aref? Appreciate the help :) Patrick Wang |
1. Which patches should I use for my simulation? Do I use every patch that defines the vehicle (I split the car into multiple parts: wheels, windshields and so on)? Yes
2. And what is lRef? How do I calculate it? I believe it's the the length-scale used for finding Re number. 3. Do you know a method for calculating Aref? Aref is probably best done by doing a 2D frontal area projection of your surface model in some CAD package... as I believe it's typical to use frontal area in vehicle aerodynamics when calculating drag coefficients. Hope this helps and someone can correct if I'm wrong anywhere. Ben |
baklanton
Hi Patrick,
I am also experiencing an issue which is similar to the one you explained in your first post. Could you please explain how you solved it? Thank you! |
All times are GMT -4. The time now is 18:47. |