Hi, I'm calculating 3D viscous imcompressible flow of sphere using vortex method. I know that flow are axi-symmetric below Reynols number 200. But I get asymmetrical flow result at Reynolds number 50. Here I do not consider stretching term. So I'm wondering that asymmetrical flow result happen because i do not consider stretching. If I put stretching term into calculation, Will flow are axi-symmetric? Thank you for reading

The stretch term in that low Reynolds number range is essentially zero anyway. So putting it explicitly equal to zero will not change the flow characteristics. Since the particles are undoubtedly distributed non-uniformly, there will be a "degree" of asymmetry. It is not clear from your message how asymmetric your flow is, 0.1%, 1%, 10%, ... off the symmetry?

The details of your implementation are very important. You need to explain how you're generating vorticity, how you're accounting for diffusion, and how you're evaluating the velocity field. Asymmetry could also develop due to lack of temporal/spatial resolution.

I have simulated flow over a sphere with our vortex code, and it is, for all practical purposes, symmetric up to the limit for that regime

Adrin Gharakhani