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how to set URANS turbulence model in unsteady flow simulation

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Old   April 25, 2017, 08:52
Default how to set URANS turbulence model in unsteady flow simulation
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Zheng Liu
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Hi FOAMERS,

I am new of turbulence modeling. I am quite confused in setting the boundary conditions of turbulence models.

For example, the k-epsilon model in steady state conditions, if I want the inlet turbulence kinetic energy having the intensity of 5%, I can set the inlet type to be turbulenceIntensityKineticEnergyInlet with the key word "intensity". For the value of turbulence kinetic energy, it can be calculated based on the formula " k = 1.5(U * I)^2 ", where U is the mean flow velocity, I the turbulence kinetic energy (see: https://www.cfd-online.com/Wiki/Turb...ary_conditions).

However, in unsteady flow conditions, the inlet flow velocity is keep changing. My question is, in URANS model, is the inlet turbulence kinetic energy (also dissipation rate) also varying with time? If so, How to set the boundary conditions since the turbulence kinetic energy is not a constant value?

Thanks in advance
Zheng
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