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-   -   Compressible Fluid Flow in COMSOL Multiphysics (http://www.cfd-online.com/Forums/main/15962-compressible-fluid-flow-comsol-multiphysics.html)

 BBG November 4, 2008 01:59

Compressible Fluid Flow in COMSOL Multiphysics

Hey all,

I am trying to figure out how to do compressible fluid flow with turbulence in COMSOL to determine the lift and drag coefficients for airfoils. I am able to do so for laminar incompressible flow, but of course these are not the correct results.

So far, I have used the Chem Engineering - Non-Isothermal Flow and Convection and Conduction application modes. The Non-Isothermal Flow mode is using the k-e Turbulence Model.

The non-default subdomain settings for the Non-Isothermal Flow are as follows: a) Dynamic Viscosity is 1.52*10^-5 kg/ms b) Initial Pressure is 23842 Pa c) Streamline diffusion off

The non-default boundary settings for the Non-Isothermal Flow are as follows: a) An inlet, an outlet, and the rest are set to the default logarithmic function wall. b) Non-linear weak constraints are on

For the Convection and Conduction: a) All sides are set to Thermal Insulator b) Thermal conductivity, density, heat capacity are set to certain values. c) Heat source is set to Q = p_time+u*px+v*py d) Temperature is initiated

First off, when I try to solve it it returns with the error "Failed to find a solution:

The relative residual (1.3e-006) is greater than the relative tolerance.

Returned solution has not converged."

What does that mean and how can I fix it?

And finally, the temperature is constant around the cylinder/airfoil, however the temperature and velocity fields are not. Why is this? Shouldn't the temperature be changing?