Expert: Paul Soderman - 8/24/2006

Question
Respected sir ,


            please explain about boundry layer sepration?.  

Answer
Fluid flow along a duct or over a surface will be retarded at the wall by viscosity.  The thin layer of retarded flow is the boundary layer, which of course has the least momentum adjacent to the wall.  If a streamwise pressure gradient develops along the wall, such as will occur in a diffuser or on a curved wall that is curving away from the flow, the flow along the wall will separate from the wall if it does not have enough momentum to overcome the pressure gradient.  By separation, we mean that the streamlines will diverge away from the surface.  In the separated region, backflow and turbulence will fill the void.