Heat transfer in the forced laminar wall jet

The mean flow and stability characteristics of a plane, laminar wall jet were investigated experimentally for a constant wall temperature boundary condition. The streamwise mean velocity and temperature profiles and the downstream development of the hydrodynamic and thermal boundary layer thicknesses were obtained through simultaneous hot and cold wire measurements. Even at relatively low temperature differences, heating or cooling of the surface sufficiently altered the mean velocity profile in the inner region to produce significant effects on the jet stability. Selective forcing of the flow at the most amplified frequencies produced profound effects on the velocity and temperature fields and hence the time-averaged shear stress and heat transfer. Large amplitude excitation of the flow at high frequencies resulted in a reduction in the maximum skin friction by as much as 65% with an increase in the maximum wall heat flux as high as 45%. The skin friction and wall heat flux were much less susceptible to low frequency excitation.