Learning Forum

[Rana Abdo]

I have a rough plate solid gometry having micron peaks and vallys that form the roughness the plate is 1.5 metre and the peaks and vallys are in microns so how can i mesh the plate to make the solver see the micron peaks and vallys i am using ansys fluent meshing is there any way to do so without making the mesh size very small meshing takes to long and also the number of cells becom very large and hence processing takes too much time 

I have been wondering if i can scale these peaks and vallys only on the plate but how can i rescale them once again while not changing the plate size just only the peaks and vallys is there any option in fluent ?

[Rob]

There are a couple of things to consider here. 

• If you don't resolve the roughness with VERY small cells you won't actually capture the roughness. 
• Most CAD kernals don't work too well at the micron level. Scaling may avoid the issue, but you'd need to scale in the "up" direction and then hope the mesh wasn't too skewed when rescaling in the solver. 

Why do you need to resolve the roughness, but at the same time don't want to spend the cell count to actually resolve the roughness? 

[Rana Abdo]

My pc wont handle this large memory 

Also if the geomtry itsself has errors face errors because its not smooth and the error says remove or recreate the surface in space claim how can i solve this issue i must have that surface with its shape

[Rana Abdo]

And also what do you mean by scaling in the up direction do you mean scaling the entire plate with  domain ?

[Rob]

If you don't have compute resource to handle meshing the roughness then what are you going to run the model on? Depending on what you're doing can you model a 1mm2 section in detail and user periodic boundaries or similar? If so, scale the 1mm2 section up to 1m2 to avoid the tolerance issues and try that. 

Or have a look at the wall roughness options in Fluent and do what almost everyone else does and adjust the sandgrain roughness values.