Flow and heat transfer of Ostwald-de Waele fluid over a variable thickness rotating disk with index decreasing

Abstract

This paper investigates the flow and heat transfer of Ostwald-de Waele fluid over a variable thickness rotating disk with style of z=a (r/R0+1)−m. Boundary layer governing partial equations are reduced to a set of semi-similarity ordinary differential equations by modified local von Kármán’s transformation and then solved by Runge–Kutta method coupled with multi-shooting technique. The effects of involved parameters (Ostwald-de Waele fluid physical power law exponent, disk thickness index, Prandtl number) on velocity and temperature fields, local skin friction coefficient and Nusselt number are presented graphically. Some new phenomena are found. Results indicate that, unlike the flat rotating disk, the local radial skin friction coefficients and tangential decrease with the fluid physical power law exponent increases, the peak in the radial velocity rises which is significantly distinct from the results of a power-law fluid over a flat rotating disk. As disk thickness index m increases, the local radial skin friction coefficient increases while local tangential skin friction coefficient decreases, the local Nusselt number decrease, both the thickness of velocity and temperature boundary layer increase.