COMSOL modeling of toroidal flow

dameyawn

I'm having lots of difficulty modeling toroidal flow in COMSOL. What I'm eventually getting at is a simulation of a semicircular canal, but am attacking the problem one step at a time.

The most fundamental model would just be cylindrical flow that wraps around in a circle, w/o no inlet/outlet i.e. a toroid.

Then I try to impart an initial radial velocity so that I can generate video watching the flow decline due to viscous forces at the wall. I've also tried to create a force field that varies w/ radius (toroid centered at (0,0) ).

Both methods error me to no end. Some solvers at least converge, but the results look whacky.

Any tips? Maybe a better way to model it would be a regular cylinder where the inlet's conditions were dtermined by the outlet's...?

Thanks...