Effect of Rotational Motion on Jet-Impingement Cooling. The Tornado Effect onHairpin Vortices in Turbulent Convective Cooling

摘要

The overall objective of the program is to enhance the effectiveness of turbinecooling by exploiting the presence and structures of vortices. Program A is concerned with jet impingement cooling and addresses the effects of bulk fluid rotation on jets, their vortical structures and cooling. A low-speed rotating water tunnel has been constructed for flow-visualization study of impinging jets in rotation: in addition, a rotating air rig was also constructed. The results show that the Contour of the impinging jet is crucial in determining the jet trajectory and both the favorable and adverse effects of rotation have been identified in the context of impingement cooling. Program B is concerned with convective and film-cooling. It focuses upon the so-called tornado effect, or the corewise transport of heat through the legs of hairpin vortices, which could lead to enhanced cooling in turbulent flows. An explicit confirmation of the effect have been established by ain water and unsteady heat transfer measurements in air. (AN).