Boundary Layer

Jing_min · February 21, 2012, 08:39

Hi
I use f3d 9.3.2. I have modeled a simple spillway. I want to know how to calculate the boundary layer thickness along the spillway?
(There is no output for that)

Thanks!!!

JBurnham · February 21, 2012, 11:49

You'll have to compare the velocity in each cell along the spillway surface to the free-stream velocity (or use the average velocity for the top few cells of flow). When the near-wall velocity reaches 99% of the free-stream velocity, that height above the wall is conventionally assumed to be the boundary layer thickness (e.g., Schlichting "Boundary Layer Theory"). The accuracy of the measurement will be on the order of the cell size. You could use a "neutral file" (see the manual) to specify a number of points and get velocity output for just those points.

February 21, 2012, 08:39	Boundary Layer	#1
Jing_min New Member Jing Join Date: Dec 2011 Posts: 20 Rep Power: 14	Hi I use f3d 9.3.2. I have modeled a simple spillway. I want to know how to calculate the boundary layer thickness along the spillway? (There is no output for that) Thanks!!!

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February 21, 2012, 11:49		#2
JBurnham Senior Member Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 17	You'll have to compare the velocity in each cell along the spillway surface to the free-stream velocity (or use the average velocity for the top few cells of flow). When the near-wall velocity reaches 99% of the free-stream velocity, that height above the wall is conventionally assumed to be the boundary layer thickness (e.g., Schlichting "Boundary Layer Theory"). The accuracy of the measurement will be on the order of the cell size. You could use a "neutral file" (see the manual) to specify a number of points and get velocity output for just those points.