[kassiotis]

Hello everybody,

I try to solve the benchmark proposed ans studied by Schäfer and Turek in this paper. I have found some linked topic here and here, but they don't really answer my questions.

For the moment, I consider the first case proposed in the benchmark (steady simulation, parabolic input velocity with max 0,3m/s leading to a Reynold number around 20).

You will find here some pictures of typical meshes I use:





And the "annoying" results:



As one can see, the velocity field is not really physical as the flow don't want to enter the fine mesh surrounding the cylinder.

I use icoFoam with steadyState time integration scheme. The initial condition are zero velocity and pressure fields (according to the description of the benchmark). I'm doing one time step (Is the steady solution independant of the size of the time step ?). For PISO algorithm I tried many solution with high number of orthogonal and nonOrthogonal correctors (let's say respectively 300 and 20)...leading to more time expensive computation but not really better results. I also checked the mesh with the checkMesh utility:

Mesh non-orthogonality Max: 44.01408683 average: 11.32517179
Non-orthogonality check OK.

My question are the following:
1 - is it absolutely necessary to compute first a solution with potential foam (as proposed in one of the thread)?...I think it will not really respect the benchmark proposed I my case.
2 - Do you see any mistake in my procedure?
3 - Is they a way to link the non-orthogonality results obtained by checkMesh to the number of orthogonal and nonOrthogonal correctors.
4 - Other question : in the paper by Schäfer and Turek they speak about a recirculation area that as to be measured. What is this? Is they an easy way to automatically measure this in OpenFoam (not seeing the results in paraFoam)?

Thank you for any help or comments.