UNSTEADY-FLOW BETWEEN 2 ROTATING-DISKS WITH HEAT-TRANSFER

The flow of a viscous incompressible fluid between two parallel discs which at time t are spaced a distance H(1 - alpha-t)1/2 apart and are rotating with angular velocities proportional to (1 - alpha-t)-1 has been studied. Account is taken of the heat transfer between the two discs. The governing Navier-Stokes equation and energy equation are transformed to a set of ordinary differential equations. Approximate and exact solutions to these equations giving temperature distribution are obtained in the case where the upper disc is isothermal and the lower disc is either isothermal or subject to a constant heat flux beta. It is found that the temperature of the fluid increases with the decrease of both the Prandtl number Pr and the parameter beta individually, keeping the other constant. It is established that the rotation of the two discs has a very small effect on the temperature of the fluid and the heat transfer process, while the rapid normal motion of the upper disc (R2 greater-than-or-equal-to 1) has a dominant effect on the temperature of the fluid and the heat transfer process. The results show rather good agreement between the approximate and exact solutions.