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Old   May 30, 2006, 03:56
Default compute bondary layer thickness
  #1
Ralf Schmidt
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Hi!

How to compute the thickness of the boundary layer??

Ok, it is the distance to the wall, where the vel. is 99% of the outer vel. It is possible to create a iso-surface for that value...

But what I want is a xy-plot (or a profile) on my surface of the B-L thickness.

Any Idea?

Ralf

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Old   May 30, 2006, 04:28
Default Re: compute bondary layer thickness
  #2
Steve Silvester
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Hi,

You could do an iso-clip on a plane normal to the surface using clip values of 99% max velocity and a min a tiny fraction lower. That'll create a surface restricted to your boundary layer thickness which you can then use to create an xy plot on plotting thickness (whatever your co-ordinate normal to the surface is) against position. That does it, I'm fairly sure theres a few ways to go about this though.

Regards

Steve
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Old   May 31, 2006, 07:35
Default Re: compute bondary layer thickness
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Ralf Schmidt
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Thank you, I've got it working now...

BUT maybe one can help my with another Problem: What free stream vel. should I use for computation?

I simulate a very simple case: turbulent flow over a plate (2D, incompressible calculation (air))

- pressure outlet BC at the top of my domain and at the right side, and a

- vel. inlet BC at the left side (the plate is at the bottom).

Now (because of displacement due to the B-L. ) the vel. above the plate increases to a value about 5% higher than the inlet vel.

What value should I take as free stream vel.???

The top side of the domain has a distance of about 35 times the BL-thickness from the plate. Is that distance to small?? Or are the BC wrong?

Any idea?

Ralf
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