extreme temperatures

Andrew Garrard

I am trying to solve an atypical tubomachines problem. The reason that it is atypical is that the stator baffles come extremely close to the rotor blades (i.e. < 1mm). The rotor diameter is 100 mm and so there is a very large change in length scale. The problem requires 3 dimensions and the solution to the energy equation. I am using a hex grid, which is tricky given the change in length scales, and I am about at the limit of what my machine can cope with (8 Million elements). When I set all wall B.Cs (there are no inlets and outlets in the initial case) to either no heat flux or 300 K, an initial fluid temperature of 300 K and no viscous heating, I get temperatures hitting the limits of 1 and 5000K in some cells. This situation is unphysical. I would like to be able to run the simulation as a time dependent, compressible problem, but at the moment the iterations are too long to consider running transient (and don't converge anyway) and the extreme temperatures destroy the ideal gas model.

If anyone has any suggestions I would be interested to hear them. Trying different ideas to solve the problem takes a long time due to grid size.