Compressible solver: Negative initial temperature error at low temperatures (216-223K)

Using SimScale Fluid Flow / CFD
1

Using the compressible solver at steady state with k-omega SST turbulence model. I am simulating external flow over a delta wing at high altitude conditions.

I have tried setting initial conditions, subdomain, and velocity inlet temperature to both 216K and 223K, but get the same FOAM FATAL ERROR: Negative initial temperature T0: -26.3 (at 216K) and T0: -14.3 (at 223K). The error occurs at the very first time step.

Interestingly the negative T0 value scales with the temperature — lower temperatures produce more negative T0 values, suggesting a fixed offset is being subtracted somewhere internally.

All temperature values are set in Kelvin. Pressure is set to 7,170 Pa (60,000ft altitude) and velocity inlet is 280 m/s.

Is there a minimum temperature limit in the compressible solver, or a known unit conversion issue at low temperatures?

Thank you for any responses.

3

Hi @BraylovesF1,

The limitation isn’t necessarily with temperature, but more so with velocity. The ‘compressible’ solver is pressure-based, which means that it can become unstable at speeds of approximately 0.7 Mach and greater.

It can be that you can stabilize the run with velocity ramping (like in this tutorial), but it can also be the case that you won’t be able to run it with the compressible solver.

A solver that handles that speed range better is “Multi-purpose” with compressibility enabled, so that would be my initial suggestion. Multi-purpose can go transonic/supersonic.

Cheers

4

Thank you so much, really appreciate your response!