Question

The boundary layer flow separates from the surface if (a) du/dy = 0 and dp/dx = 0 (b) du/dy = 0 and dp/dx > 0 (c) du/dy = 0 and dp/dx < 0 (d) The boundary layer thickness is zero

Answer 1

Boundary layer is the distance upto which there is a gradient in the velocity of the layer of the fluid flowing on the surface. So, the point where the boundary layer separates the surface, the velocity gradient in the y direction becomes zero and pressure gradient along the x direction becomes positive at the point of separation of boundary layer to the surface. So the correct answer is b)

b)du/dy=0 and dp/dx >0