Flow of a Viscoplastlc Fluid on a Rotating Disk

The equations describing the flow of a viscoplastic fluid on a rotating disk are de-rived and are solved by perturbation technique and nurmerical computation respectively for 2 cases.This makes it possible to calculate the thickness distribution of film.Twokinds of distribution of thickness have been found.For the viscoplastic fluid for whichboth viscosity and yield stress are independent of radial coordinate r,the thickness h decreases with increasing r.For a Bingham fluid for which both viscosity and yieldstress are function of time and r.the thickness h increases with increasing r.