[crizpi21]

Hi,

I am trying to run a simple case of the flow around a 2D square (side=0.5m) with rounded edges inside a rectangular domain using Pimplefoam solver. My objective is to calculate the drag coefficient at the walls of the square for different radius of curvature of the square.

For a particular radius (case1: r=0.2m), my drag coefficient is fairly stable after 40 s. However, if I decrease the radius (case2: r=0.1m), the drag coefficient oscillates a lot around the "mean" value. See attached drag_coeff_plot.
[Note that magnitude of drag coefficient in both cases is different since for more rounded edges, Cdrag should be lower]

From my understanding, as drag coefficient dependes on forces, which are obtained from pressure, the problem is with pressure calculation.

The only thing that I am changing between both cases is the mesh, that has to be adapted for the different radius, so the size of the cells around the square may not be the same. However, I have done "checkMesh" and non-orthogonality and aspect ratio are very similar in both cases. Find attached files.

I have also plotted the residuals for p (see residuals_p attached file) and they look a bit different, but I do not know if this could be causing the difference.

Can you think about any possible reason why I am obtaining this huge variations in drag coefficient in case2? Maybe I should modify some parameters in my fvSolution and fvSchemes files? I can post them if necessary.

Any tip would be helpful, I am really stuck with this.

Thanks in advance.

Cristina