Hello, thank you for the reply.
This is a link to the project: Low Re Aerodynamics
A bit of context: I’m a professor at the University of Delaware, developing a fluid mechanics assignment for our 3rd years students (optimize drag for low Re external flow). Right now, I’m just debugging it using a sphere as the aerodynamic object, designed to a low Re of about 0.0001 (mu = 1 Pa-s, sphere volume = 1m^3, rho = 0.0001 kg/m3, V = 1 m/s). There is known analytic result D = 6PimuVR which in this case works out to be 11.69 N. I’m also cutting the sphere into either 1/4 or 1/5 to exploit the axisymmetry (so I’m expecting Drag = 11.69N/4 = 2.9N (for 90deg wedge) or 2.3N (for 72deg wedge).
At this point, I’m not expecting to replicate that number, but I would like the simulations to converge with respect to a number in a reasonable number of iterations. I’ve tried a number of different meshes, all of which have good quality elements, and some which are quite fine. The residuals generally converge quite well, but the Result Control (i.e. Drag = Total Force in Y) doesn’t not.