INFLUENCE OF SHEAR-LAYER DYNAMICS ON IMPINGEMENT HEAT-TRANSFER

Measurements of convective heat transfer coefficients on a flat plate with an air jet impinging on it perpendicularly are made to investigat e the influence of some governing parameters. Particular attention is focused on the effects of the shear layer dynamics. For certain flow c onditions and/or test arrangements, coherent structures and/or recircu lation currents are observed affecting the distribution of the heat tr ansfer coefficients. Measurements of wall temperature as well as of ad iabatic wall temperature of the stream are made by means of an infrare d scanning radiometer, and the heat transfer coefficients are calculat ed by means of the so-called heated thin foil technique. The data are reduced in dimensionless form as Nusselt numbers and compared with dat a from the available literature. Both spatial distributions and averag ed values of the Nusselt number are discussed. A new explanation for t he second peak in the local Nusselt number is proposed.