Unsteady hydromagnetic flow and heat transfer of a viscous fluid near a suddenly accelerated flat surface

摘要

The unsteady boundary layer flow and heat transfer near a suddenly accelerated flat surface in an unbounded mass of hydromagnetic viscous fluid with the combined influence of the magnetic field, viscous dissipation, internal heat generation/absorption and thermal radiation have been investigated. A new similarity transformation is recommended, which transforms the hydromagnetic boundary layer equations into a set of non-linear ordinary differential equations. These equations are then solved numerically using the finite-difference method for some values of the governing parameters that involve unsteadiness parameter , heat source/sink parameter , Eckert number E, magnetic interaction parameter M, radiation parameter N and Prandtl number Pr. The influence of these parameters on the velocity as well as the temperature field is investigated in detail. In particular, the impact of viscous dissipation (measured through E), which is a strong function of constant reference temperature Tref, on the temperature field has been investigated in different situations. This entails considering the value of Tref as positive or negative depending on whether the surface temperature is higher or lower than the fluid temperature. The analysis reveals that there exists a critical value of E depending upon the values of the other physical parameters for which the surface heat flux vanishes. Below this critical value, heat flows either from the surface to the fluid or from the fluid to the surface depending on whether Tref or 0.