[Marco D'Ario]

Hi, I have been doing CFDs for some months now using SU2 and INC_RANS, for incompressible fluid and symmetric particles (concave spheres generated by adding many cones on the surface of the sphere, see attachment for example). I am interested in the CD of those particles against the one for spheres of the same Re.

With my settings, I can perfectly recapitulate the CD of a sphere, with a 2% error.

I recently discovered how to normalize the CD that SU2 returns, but for some of those particles (particularly those with many spikes), I get a lower CD than one of the spheres for Re<100. The CD can be as low as 20% lower than the one of a Sphere. From what I understand, this is impossible, as only asymmetric objects would have a lower CD when facing the flow towards the lower area of impact.

Did anyone have a similar problem before, or think that those results are correct or can suggest what I might be doing wrong?

I have been on this 24/7 for the past weeks and I checked every line of my code multiple times and I am 99% sure that what I am missing is not in my code. Again, my sphere behaviour is pristine.

Thanks so much.