How to define the turbulent k near the wall ?
hello everyone, :)
I wish to define the solution of the turbulent kinematic energy solution near the wall, in Fluent.
My case is standard k-e with standard wall function.
From the ansys help we can see that the k-equation is solved in the whole domain including near the wall, while the epsilon adjacent to the wall is calculated from the near-wall equ with is derived from the local equilibrium hypothesis.
After the solution I found that the production of k (Gk) is zero everywhere on the wall, which is very different from the Gk equ based on the local equilibrium hypothesis.
I wish to give a definition of the k in order to force the local equilibrium near the wall. Could anybody give some advice how i can do this?
Many thanks!! :)
There is no fluctuation on the wall ( the velocity is always zero) so that the turbulent kinetic energy k vanishes on the wall.
I saw in many literatures they specified the value of k on the wall, which is, to give a Diriclet boundary for the equation. For example, some can specify the k as u*^2/sqrt(Cmu), which is, to force the local equilibrium on the wall. Or some can give a zero k on the wall.
I checked the results of the Fluent on an external flow around a cylinder with k-e and standard wall function. When I compared the computed k to the "u*^2/sqrt(Cmu)" , I saw in the wake region the computed value differed a lot. I wonder whether this would be a key point to cause the differences between my results and those in the literatures.
So I wish to specify the k on the wall, in the Fluent, eg. though a UDF~~
Could anybody shed some light~~:)
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