Boundary layer flows over (a) smooth and (b) rough surfaces.

Transfer of mass and momentum at rough and porous surfaces, Journal of Fluid Mechanics

Surfaces with different wavelengths but the same amplitude. (a) and (b)

Laminar Flow Airfoil

Boundary Layer Transition - an overview

Turbulent boundary-layer flow over regular multiscale roughness, Journal of Fluid Mechanics

If flow separation occurs, does it always accompanies a wake region? I mean, behind the flow separation, does the region always have a wake region whose pressure is low? - Quora

Skin friction coefficient distribution along the wall for the 480 × 240

Drag and Lift in Fluids - The Engineering Projects

What is a boundary layer? Explain with a sketch development of boundary layer over a smooth plate. - Quora