[CFX-Post] - Boundary layer volume integration

Capn · January 15, 2014, 11:55

Hi everyone!
I'm doing some research on airfoils, and I have been trying to find a way to calculate the amount of entropy that is being generated in the boundary layers of an airfoil. The main idea is to be able do a breakdown of where in the airfoil (LE,TE, suction side, pressure side, etc.) we have the most losses.

The expressions I use are for a volumetric entropy generation rate (J/(K m3 s), and in order to get an understanding of which sections of the blade are the most detrimental for performance, I would like to integrate the generated entropy in the boundary layer volume.

The main approach I have considered:
Constructing a volume on and extending in the normal direction from the airfoil surface, with a height close to the boundary layer thickness. Then with CFX's own subroutines, I could perform a volume integration.
Question is, how to build a volume like that?

I'd be grateful for any suggestions on how to approach this issue! Or if there are any other post-processors that are capable of volume integration of this type.

Cheers!

singer1812 · January 15, 2014, 13:15

I suppose you could use isovolume. Few ways to use isovolume depending on how you set up your model. Generate it for values of y+ below what you deem correct, or generate it for values of wall distance below what you deem correct, or I could go on...

Pick a variable that will describe your BL, you can even generate your own based on your own criteria, and use isovolume to isolate it to the region you want.

January 15, 2014, 11:55	[CFX-Post] - Boundary layer volume integration	#1
Capn New Member Join Date: Jan 2014 Posts: 1 Rep Power: 0	Hi everyone! I'm doing some research on airfoils, and I have been trying to find a way to calculate the amount of entropy that is being generated in the boundary layers of an airfoil. The main idea is to be able do a breakdown of where in the airfoil (LE,TE, suction side, pressure side, etc.) we have the most losses. The expressions I use are for a volumetric entropy generation rate (J/(K m3 s), and in order to get an understanding of which sections of the blade are the most detrimental for performance, I would like to integrate the generated entropy in the boundary layer volume. The main approach I have considered: Constructing a volume on and extending in the normal direction from the airfoil surface, with a height close to the boundary layer thickness. Then with CFX's own subroutines, I could perform a volume integration. Question is, how to build a volume like that? I'd be grateful for any suggestions on how to approach this issue! Or if there are any other post-processors that are capable of volume integration of this type. Cheers!

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January 15, 2014, 13:15		#2
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 20	I suppose you could use isovolume. Few ways to use isovolume depending on how you set up your model. Generate it for values of y+ below what you deem correct, or generate it for values of wall distance below what you deem correct, or I could go on... Pick a variable that will describe your BL, you can even generate your own based on your own criteria, and use isovolume to isolate it to the region you want.