Turbulence terms change during thermal-only stage of de-coupled simulation


After a flow-only stage of a simulation, the flow calculation is stopped and the heat transfer or scalar calculation is started. 

The values of the two turbulence quantities, Turbulent Kinetic Energy (TKE) and Turbulent Energy Dissipation (TED), sometimes change during the thermal-only or scalar-only stage of a simulation. 

The flow equations are not being solved, so this is unexpected behavior.



The turbulence parameters are computed during Thermal-only and/or Scalar-only solutions (when the flow solution is frozen) because the thermal and scalar equations require turbulence data to estimate eddy viscosity and other turbulence values. These small changes in TED and TKE are due to round-off when turbulence quantities are re-computed.  

Because the flow values (Velocity components and pressure) do not change, the TED and TKE values change to different values due to the round-off at restart. These variations at restart are normally small and have a negligible impact on overall results. 


Simulation CFD