[Nek5000-users] Pipe Roughness

[nek5000-users at lists.mcs.anl.gov]

The typical way would be to change explicitly the surface geometry, 
either by changing the location of the mesh (i.e. "surface" fitted) or 
by some type of immersed boundary method. For the first method, the 
approach certainly depends on the type (and scale) of the intended 
roughness, for instance there might be the possibility to use a neknek 
approach to decouple the mesh in the pipe centre and the one close to 
the surface.

For the immersed boundary method, there is a simple, but apparently 
quite efficient way that could be suitable for dissimilar roughness 
(i.e. small scale), see e.g. here:

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.3.044605

You might also try out approaches based on wall models with a specific 
slip velocity as e.g. done in atmospheric boundary layers, as e.g.
https://aip.scitation.org/doi/10.1063/1.4994603

Hope this helps,
PHilipp

On 2018-07-11 15:22, nek5000-users at lists.mcs.anl.gov wrote:
> 
> Dear all,
> 
> Can anybody tell me how to take into account the roughness of the pipe? 
> Do I have to change the geometry or there is something easier?
> 
> Any help would be greatly appreciated,
> 
> Ali
> Embry-Riddle Aeronautical University
> 
> 
> 
> 
> 
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