The effect of transient wall suction and blowing on stagnation point flow and heat transfer
Abstract
The effects of transient blowing and suction on stagnationpoint flow and heat transfer are analyzed. The transient momentum and thermal boundarylayer equations are reduced by asymptotic integration to firstorder differential equations governing the transient wall shear and heat flux behavior. The wallshear and heatflux maxima are found to lag behind the minima in blowing velocity in the case of oscillatory blowing about a nonzero mean, and the oscillation amplitudes of the wall shear and heat flux are found to decrease from their quasisteady values as the oscillation frequency increases. At very high frequencies, the wallshear and heatflux phase lags are shown to approach zero while the oscillation amplitudes approach reduced constant values; the heatflux phase lag is found to increase with increasing Prandtl number. It is shown that the time required to attain steadystate wall shear and heat flux increases with the level of blowing or suction under conditions of a rapid shutoff or turnon in blowing or suction, and that a momentary interruption of blowing can be very detrimental to the thermal protection of a surface.
 Publication:

American Society of Mechanical Engineers
 Pub Date:
 May 1975
 Bibcode:
 1975asme.confR....K
 Keywords:

 Boundary Layer Control;
 Heat Transfer;
 Stagnation Point;
 Thermal Boundary Layer;
 Transient Oscillations;
 Wall Pressure;
 Asymptotic Methods;
 Blowing;
 Boundary Layer Equations;
 Differential Equations;
 Heat Flux;
 RungeKutta Method;
 Shear Flow;
 Suction;
 Two Dimensional Boundary Layer;
 Wall Flow;
 Fluid Mechanics and Heat Transfer