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How to initialize k and epsilon in RAS simulation via OpenFOAM

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Old   May 14, 2024, 12:18
Default How to initialize k and epsilon in RAS simulation via OpenFOAM
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mo magd
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I hope everything is going well.
I'm attempting to initialize my internal field and the boundary values for k and epsilon in an RAS simulation via OpenFOAM, but I'm unsure of how to proceed.
I've reviewed the examples in the tutorial folder to try and figure it out, but the way k and epsilon were initialized in those 0 folders struck me as odd. The values for epsilon seemed a bit high, as did those for k.
If k and epsilon represent the turbulent kinetic energy and turbulent dissipation rate, respectively, and we use the following formula for initialization:
k=1.5(UI)2
and
ϵ=cμ(k^(1.5)/l)
where I is the turbulence intensity (which is assumed to be 0.05) and l is the turbulent length scale.
According to these equations, if the fluid is initially at rest, k and epsilon should both be zero in the internal field, right? So why do I observe non-zero values in these tutorial folders for every case? Additionally, the method by which k and epsilon were calculated does not align with the values I would expect from these formulas.
Could someone please help me understand where I might be making a mistake?
Thanks!
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Old   June 18, 2024, 15:35
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Can you provide some details about the model and the values which you are mentioning about k and epsilon.
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Old   July 8, 2024, 22:20
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The presence of boundary layers, shear flows, or other flow features may affect the optimal initial conditions.
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