Transient mixed convection from a vertical surface in a porous medium

An analysis is made of the unsteady mixed convection from a vertical flat plate in a fluid-saturated porous medium when the temperature on the surface is instantaneously changed from that of the surrounding fluid. A complete analysis is made of the governing equations at time t = 0, the steady state at large times and a series solution valid at small times is derived. A numerical solution of the full boundary-layer equations is then obtained for the whole transient until the forward integration approach is no longer well-posed. Results are presented to illustrate the occurrence of transients both when the buoyancy and free stream are in the same and opposing directions.