|February 22, 2014, 18:22||
how can I improve the y+ value?
Join Date: Oct 2013
Posts: 6Rep Power: 5
Hi, I'm working on a project that involves wind generation with a diffuser augmented wind turbine. I would like to know how can I improve the y+ value on the diffuser. It presents a value of 533 aprox on the y+.
|February 22, 2014, 19:25||
Join Date: Jun 2012
Posts: 312Rep Power: 7
There is a lot of literature which explains the definition of Y+. Here's a start:
It is a dimensionless wall distance. It is particularly important in turbulence modeling close to walls. High speed flows close to a wall produce higher Y+ values. The Y+ value you need depends on which turbulence model you use (if you're using one).
You can estimate how big or small your first cell height should be to obtain your desired Y+ by using tools such as this:
In your case if you want to reduce your Y+ you need to refine the mesh closer to the walls. After you've done this re-run the simulation on the refined mesh, and check the Y+ values again.
Just remember if as you refine you also increase the number of elements in your mesh and greatly increase the simulation time. Hence don't refine unless you have to. This goes in hand with a mesh sensitivity study.
|March 30, 2014, 18:05||
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 12,718Rep Power: 99
This generally indicates a coarse mesh. Higher than intended y+ also results from coarse meshes. The solution should be obvious.
But as for whether your current mesh is OK - do a sensitivity check and find out. You cannot tell from just an image.
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