Learning Forum

[sjohn]

I am running a single phase transient simulation of a hot gas flowing through three circular inlets into a thrust chamber (without nozzle) with a single outlet. The viscous model is SST k-omega. The inlets are mass-flow inlets with a specified temperature. The surface containing the inlets is set to mixed heat loss and is a thin wall. The simulation has run for about 2000 time steps but the mass-averaged inlet temperature is about 1/3rd of what I had specified in the inlet boundary condition panel. The gas material is set to calculate density using ideal gas law and the operating density is set to zero as per Fluent recommendation. The outlet boundary condition contains a gauge pressure (0 psi). 

When the same model was run with the gas density set to a constant, the mass-averaged inlet temperature was as specified in the inlet boundary condition. Can someone explain why the mass-averaged inlet temperature is different in the two scenarios?

[Essence]

Hello,

Please check which temperature (static or total) has been specified at the inlets. If you are calculating static temperature at inlets, then use Area-weighted average instead or Mass-weighted average. If it is total temperature, use Mass-weighted average.

Please check the mesh once for it's minimum orthogonal quality, y+ values, growth rate etc.