[Nimish]

Hello,

I am running a duct flow analysis with compressible air using LES. The duct length (along X) and height (along Y) is considerably larger than the depth (along Z) of the duct. The duct has inlet, outlet, opening and wall boundary conditions (BCs) as shown below. Also, the planes along the depth direction have symmetry BCs. The inlet velocity BC is specified as the profile data using outlet velocity output from the steady state analysis, and also the the domain is initialized using steady state analysis.

opening
__________________________________
inlet __________________________________ outlet
wall

At low Mach numbers (~0.1), the analysis runs without any problem. When I rerun the problem with higher Mach number (~0.4), with same mesh and same boundary conditions, the analysis gives "floating point exception: overflow" error. I ran the low Mach number problem using "constant property air" and no heat transfer. For the higher Mach number, I am using air as compressible gas, and "total energy" as the heat transfer model.

When I process the results just below this error, the streamlines show the flow going from inlet to the opening. The Y velocity component is supposed to be very small compared to the X velocity component, because majority of the flow is expected to be along the duct length.

I think the mesh refinement might not be sufficient to handle LES type simulation. I am going to try refining the mesh, and improving mesh quality, but wanted to know if someone can offer any additional direction to look into. ANy help will be greatly appreciated.

Thanks.