Why do we need prism layers??

sam181087 · January 14, 2015, 00:58

How do prism layers resolve the boundary layer flow phenomena? Can tri/hex resolve the same efficiently if mesh is fine at the boundaries?

mprinkey · January 15, 2015, 10:27

Hex refinement at boundaries is generally preferred to prisms (aka wedges), but often the surface mesh is triangular. The goal of boundary layer refinement is to resolved the flow details. Those details are (usually) present only in the wall normal direction. So, while it is (in principle) possible to tet a boundary layer, the cell counts will be enormous and the mesh skewness, especially in the cells close to the wall, will be crippling.

On the other hand, simply extruding the tri-surface mesh into the flow domain using prisms avoids all of those issues. The flow can be well resolved in the wall normal direction while keep cell count and skewness under control.

sam181087 · January 15, 2015, 21:43

Thanks s lot ! It is useful information

student666 · February 11, 2015, 14:16

John C. Chien, who were you?!?

http://www.cfd-online.com/Forums/mai...shing-cfd.html

bye

January 14, 2015, 00:58	Why do we need prism layers??	#1
sam181087 New Member Sam Join Date: Dec 2012 Posts: 9 Rep Power: 13	How do prism layers resolve the boundary layer flow phenomena? Can tri/hex resolve the same efficiently if mesh is fine at the boundaries?

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January 15, 2015, 10:27		#2
mprinkey Senior Member Michael Prinkey Join Date: Mar 2009 Location: Pittsburgh PA Posts: 363 Rep Power: 25	Hex refinement at boundaries is generally preferred to prisms (aka wedges), but often the surface mesh is triangular. The goal of boundary layer refinement is to resolved the flow details. Those details are (usually) present only in the wall normal direction. So, while it is (in principle) possible to tet a boundary layer, the cell counts will be enormous and the mesh skewness, especially in the cells close to the wall, will be crippling. On the other hand, simply extruding the tri-surface mesh into the flow domain using prisms avoids all of those issues. The flow can be well resolved in the wall normal direction while keep cell count and skewness under control.

January 15, 2015, 21:43		#3
sam181087 New Member Sam Join Date: Dec 2012 Posts: 9 Rep Power: 13	Thanks s lot ! It is useful information

February 11, 2015, 14:16		#4
student666 Senior Member M. C. Join Date: May 2013 Location: Italy Posts: 286 Blog Entries: 6 Rep Power: 16	John C. Chien, who were you?!? http://www.cfd-online.com/Forums/mai...shing-cfd.html bye