The important concept of the boundary layer is introduced. We study the
laminar, thermal and turbulent boundary layers and also derive a system of boundary
layer equations. The concept of the boundary layer thickness is considered and the
separation of the boundary layer is discussed. The general profile of the average
velocity of the turbulent flow near a smooth wall, and the effects of roughness are
being studied. The notion of the roughness parameter is defined.
Keywords: Boundary layer, Boundary layer separation, Boundary layer
thickness, Friction velocity, Prandtl number, Roughness parameter, Thermal
boundary layer, Turbulent boundary layer, Viscous sublayer.
