An experimental study on the equilibrium boundary layer subjected to favourable pressure gradient (Effect of pressure gradient on law of the wall)

Abstract

Effect of favorable pressure gradient on the wall similarity in turbulent boundary layer has been investigated experimentally. An appropriately adjusted pressure gradient produces an equilibrium boundary layer of which momentum thickness Reynolds number is constant. The wall shear stress was measured by three methods, which are direct measurement, Preston tube and Sublayer plate. A modified log-law considered the effects of the inertia and pressure gradient terms in the boundary layer equation gives better representation for the mean velocity profile subjected to favorable pressure gradient at finite Reynolds number. The velocity scale us applied to the modified log-law representation seems to be more relevant for turbulent intensity profile as well as mean velocity profile.

Keywords

• turbulent flow
• boundary layer
• law of the wall
• log-law
• favorable pressure gradient