Unknown failure solving airfoils

Submitted by Antonio Ramirez on July 9, 2012 - 11:38

Questions

Hello,
I´m trying to obtain the preassure coeficient of some airfoil designs. After creating the design with Caedium builder, I follow the steps described in the tutorial for a NACA 0012 airfoil in RANS flow.
The problem came when I applied the solver and this message showed up.

"Warning:
volume_32 [www.7383.5] RANS Flow: Failed
Solver singularity: smoothSolver: Solving for epsilon, Initial residual = -1.#IND, Final residual = 1.#QNAN, No Iterations 100"

Please, could someone tell me what I'm doing wrong and how can I solve it?

Best regards.
Antonio.

Unexpected problem.

Submitted by Antonio Ramirez on October 22, 2012 - 10:57.

Hello,
Today I´ve been using caedium as usual but in this last simulation this problem was shown:

Warning:
volume_13 [www.4686.5] RANS Flow: Failed
Unexpected process exit.
The system can not find the specified path.

How can I solve it?
Thank you.

Check and reset default paths to MS MPI and OpenFOAM

Submitted by symscape on October 22, 2012 - 12:30.

Is that the entire message? Did it mention which specified path it could not find?

Have you changed any preferences? It could be either the path to MS MPI (assuming you are running on Windows) or the path to OpenFOAM is wrong.

Check and reset to defaults the following preference (File->Preferences) paths in the Properties Panel:

Application->MPI, default = C:\Program Files\Microsoft HPC Pack 2008 R2\Bin\mpiexec
Physics->OpenFOAM, default = C:\Program Files\Caedium\openflow

Use Flow Over a Rotating Wheel with Moving Ground as a template

Submitted by symscape on July 9, 2012 - 13:32.

The tutorial "Transonic Flow Over the NACA 0012 Airfoil" uses a special one cell thick mesh. Instead I suggest you use the tutorial "Flow Over a Rotating Wheel with Moving Ground" as a template. You will need to:

Replace the wheel with your airfoil
Make sure you position the airfoil in the center of the symmetry plane with a good distance between the airfoil and the top and bottom faces

Note the bottom face needs to be assigned as a Slip or Symmetry Local boundary condition rather than a Wall.

Still doesn't work.

Submitted by Antonio Ramirez on July 11, 2012 - 10:55.

First of all I would like to thank you for your help.
As you said I tried to solve my airfoil with this method but the same message is shown. I have no experience using the programme so I don´t really know where the problem come from.
Maybe someone could check my model and verify where is my mistake.
One more time thank you.

Try the tutorials first

Submitted by symscape on July 11, 2012 - 11:28.

Take a step back, have you successfully completed the original tutorials "Wheel in a Box" and "Flow Over a Rotating Wheel with Moving Ground"?

If so, try working through the FAQ "How do I fix mesh and solver failures?"

Done! :)

Submitted by Antonio Ramirez on July 25, 2012 - 13:10.

Thank you very much. Recently I found the problem and now it works perfectly!
Best regards.
Antonio Ramírez.

Force tool.

Submitted by Antonio Ramirez on September 6, 2012 - 09:46.

Hello,

I have a quick question about the force tool in vector variables.
When I apply this tool on a face, what is the value that I obtain? The sum of all the forces acting along the face? The average value of the force?
And by the way, how can I obtain the point of action of this force?

Once again, thank you very much.
Antonio Ramirez

Force definition

Submitted by symscape on September 6, 2012 - 10:28.

Force is a vector sum (integral) of A.(n.p + tau), where A is the area, n is the normal, p is the pressure, and tau is the shear stress for each element on a face respectively. To obtain the lift or drag on an object you need to create a group of the entire closed set of faces. For more details see "Lift Force and Drag Force".

If by "point of action" you mean the axis of zero moment (torque) then there is no automated way to determine it.

Symscape