Answer to Question #130085 in Mechanics | Relativity for Ariyo Emmanuel

Question

What is a boundary layer? What causes a boundary layer to
develop?

Answer 1

Boundary layer is a region of flow of a viscous liquid (gas) with a small transverse thickness compared to the longitudinal dimensions, appearing at the surface of a streamlined solid body or at the interface of two liquid flows with different physical parameters (speeds, temperatures, chemical composition etc). The viscous effects become significant in the boundary layer.

The viscosity is responsible for no-slip condition and appearance of boundary layer. Namely, viscosity is a quantity that characterise internal frictional forces causing boundary level to develop.