# Inlet Turbulence parameters k/omega by timeVarying Velocity

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 March 11, 2016, 07:35 Inlet Turbulence parameters k/omega by timeVarying Velocity #1 New Member   Stefan Join Date: Oct 2015 Posts: 24 Rep Power: 10 Dear Formers, i got a transient RANS model which needs a timeVarying Inlet-Velocity (Valve open/close) It varies between 0 and 4 m/s. (arranged with timeVaryingUniformFixedValue and a txt file) My question is now according the turbulence parameters k and omega (k-w-sst-Model)? What is the best type of Inlet BC therefore? I had the following thoughts: If I calculate and implement fixedValues at the inlet it is fixed for all the simulation time what is not really true because the velocity and so k (=1.5*(U*I)^2 changes over the time. That may leeds to convergence problems??? The other option is to use turbulenceIntensityKineticEnergieInlet for k and defining an Intensity. But here I got bad feelings according the case if U=0 so k=0 and there might show up an dividing /0 Same for omega with turbulentMixingLengthFrequency. What is the most stable definition? Would be greate if somebody could help me out! Thank you in advance Stefan

 March 11, 2016, 07:36 #2 New Member   Stefan Join Date: Oct 2015 Posts: 24 Rep Power: 10 Another idea: Would it make sense to make timedependendValue-Files for k and omega like as for the velocity?

March 11, 2016, 15:03
#3
Member

Eric Robertson
Join Date: Jul 2012
Posts: 95
Rep Power: 14
Quote:
 Originally Posted by StefanW Another idea: Would it make sense to make timedependendValue-Files for k and omega like as for the velocity?
You probably should vary the freestream turbulence parameters along with the velocity. Though you only ramp up the inflow velocity by a small amount, there is of course much evidence that your choice of freestream turbulence parameters affect the solution. So, what you choose to do actually depends on what you're looking to accomplish.

 Tags k-omega, k-w-sst, omega, rans modelling, turbulence parameters