FLOW OF A THIN LIQUID-FILM OVER A COLD HOT ROTATING-DISK

The unsteady flow of a liquid film on a cold/hot rotating disk is anal ysed by means of matched asymptotic expansion under the assumptions of radially uniform film thickness that varies with time. The velocity, temperature and rate of heat transfer are determined for both the case s. Two new non-dimensional parameters alpha and beta are defined and t he variation of the uniform film thickness with these two parameters a re shown graphically. Depending on alpha, a novel feature of flow reve rsal on the free surface of the film is obtained when the disk is heat ed from below axisymmetrically. A physical explanation of this flow re versal is also provided. It is further shown that heat flows from the disk to the film for R < R(c) and from the film to the disk for R > R( c) when the disk is cooled from below. These heat flow directions are reversed when the disk is heated from below. Moreover, in this case, h eat also flows from the free surface to the curve T(xi) = 0.