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Specifically I mean for complex applications it may be difficult to generate mesh that meets y requirement everywhere.
But in general, the formulation of the v2-f was develop to handle resolved flows better than other 2 equation formulations of the k-e. H header they reference some newer papers, which I haven't read, but it's possible that they discuss near wall handling of v2 and f for y But in general, the formulation of the v2-f was develop to handle resolved flows better than other 2 equation formulations of the k-e. H header they reference some newer papers, which I haven't read, but it's possible that they discuss near wall handling of v2 and f for y Ok, my understanding is the same, the v2f turbulence model is a socalled "low"-Re turbulence model (also for high Re-Numbers in the core flow) with no use of any wall functions, because of a resolved boundary layer.
Since I've been working with the v2f model for a while, I wanted to share with you some thoughts about the wall conditions.
For the v2f model implemented in openfoam, the boundary conditions at the wall for low-re cases are: k=1e-10 v2=1e-10 f=1e-10 (because of the code-friendly modification by Lien) nut=nut Low Re Wall Function(i.e. epsilon = 2*nu*k1/y1^2, where k1 and y1 are the cell-center values at the wall.
Now I want to use v2f for my "real" case, which is flow through fuel bundle of nuclear reactor.
To be more specific, in my case fuel bundle is an array of 55 fuel rods which are held together with spacer grid (in the middle of sketch geo.jpg).
The wall function implemented in openfoam is supposed to take care of it (epsilon Low Re Wall Function).
Benchmark will be done with experimental measurements of velocity fields behind mixing vanes, so I'm not interested in skin frictions...
The Durbin paper I reference discusses this at length. Since my real case is quite big and contains a lot of vanes inside a tube, I cannot afford very dense mesh in the boundary layer.
My point is, if you're going to use a wall-function with the v2-f, which will effectively override the benefit of the v2-f model, it's seems pointless to use it. So my next step is using wall functions, which are also implemented in that v2f turbulent model... I don't know much about the v2f turbulent model yet, but I checked the Description in the v2f.
Dear all, I'd just like to add my small piece of insight in this issue, after also struggling to understand the OF wall functions.
It turns out that there was a bug in the epsilon Low Re Wall Function up to and including version 2.4.x, causing erratic behavior of this wall function.