The Effect of Adverse Pressure Gradient on the Structure of Turbulent Boundary Layer

Abstract

The effects of adverse pressure gradient (APG) on turbulent boundary layer flow are studied in this article using numerical methods. The values of pressure gradient are simulated by Clauser's parameter (β). The non-linear eddy-viscosity model (NLEVM) assumption has been employed to model turbulence. Moreover, applications have shown non-linear model to be far more reliable than the linear eddy-viscosity model (LEVM), particularly in flows subjected to APG and in other situations where normal straining is a major contributor to stress generation. Based on numerical solutions, turbulent intensity and turbulent shear stress and also mean velocity are calculated. The results show that the characteristics of turbulent boundary layer flows with APGs differ significantly from those of zero-pressure-gradient ordinary boundary layers. The numerical results show that more changes in the turbulent structure are induced directly by APG. The turbulent intensities and turbulent shear stress are increased by the effect of APG compared with flat plates under the same conditions. The numerical results also unveiled that the APG causes flow to be destabilized. The rate of integral parameters of the boundary layer such as momentum thickness and displacement thickness is increased as APG parameter increases and also when compared with the flat plate case. To validate the numerical results, a comparison has been made with previous experimental values and direct numerical simulation (DNS) data. Generally, good agreement has been obtained between numerical and measured values.