UNSTEADY HEAT TRANSFER IN LAMINAR BOUNDARY LAYER OVER A FLAT PLATE

The thermal response of an incompressible, laminar boundary layer over a semi-infinite flat plate due to a step change in either the wall temperature or wall flux is investigated. A new analytical method of finding solutions valid for all times is presented. Results for wall flux or wall temperature transients are displayed graphically for Prandtl numbers ranging from 0·01 to 100. It is demonstrated that, for a restricted range of Prandtl number (0·72 to 100), the time required for the thermal layer to achieve steadiness varies inversely with the free stream velocity and directly with 1 3 power of the Prandtl number. For an ideal gas of constant Prandtl number with linear viscosity-temperature relation of the Chapman-Rubesin description, the incompressible results for both cases can be directly applied when the fluid properties are properly interpreted. © 1968.