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Abhishek July 31, 2006 17:36

urgent: 2d laminar boundary layer simulation
I am trying to perform simulation of boundary layer of viscous laminar flow over a cylinder by writing my own code. I cannot understand how to deal with the interaction of the viscous (boundary layer) and inviscid region.

Can I just use for the whole fluid domain the simplified equation of navier-stokes equation for boundary layer in which the pressure gradient is replaced by using bernoulli's equation for free stream.

Please suggest.

Thanks Abhishek

wen long July 31, 2006 22:21

Re: urgent: 2d laminar boundary layer simulation
Check out Cebeci's book.

not cheap, but you can find it in laboratory.

Need to match: 1)velocity 2)pressure 3)zero shear at the outer edge of the boundary layer.

For strick sense of interaction, the outer flow and bl flow needs to be coupled and solved together.

From outer to bl: outer flow gives velocity and pressure gradient to drive the boundary layer flow. The bl equation is essentially 2 point bc diffusion equation in the vertial direction. Two point bc diffusion equation needs 2 boundary conditions: one at the wall which is velocity=0. The other one at the boundary layer outer edge which is velocity=U_outer. But the location of the outer edge is still unknown, so you need one more: shearstress --> 0 to find the thickness of the bl.

From bl to outer flow: once you find the thickness (location of the boundary layer outer edge), you need to go back and re-solve the outer flow for velocity and pressure, because the outer flow boundary should be placed at the interface.

Abhishek August 1, 2006 19:17

Re: urgent: 2d laminar boundary layer simulation
Wen Long,

Thanks for the explanation. Can you please explain in more detail of how to calculate the boundary layer thickness.

Thanks Abhishek.

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