THE INFLUENCE OF VORTICAL STRUCTURES ON THE THERMAL FIELDS OF JETS

In this investigation we explore the effect of unsteady vortical struc tures on the adiabatic wall temperature distribution in an impinging ' et Treating first the simpler case of a free jet, we introduce a conce ptual model for the separation of the total temperature, appealing to the dynamics of particle pathlines and vortex rings in the jet. The pr esence of a region of higher total temperature on the inside of the je t and a region of lower total temperature toward the jet periphery, pr edicted by the model, exhibits good agreement with the experimental da ta taken at high subsonic Mach number. The results from a numerical si mulation further confirm the theoretical expectations. Through a simil ar argument, we show that when a thermally insulated flat plate is ins erted into the jet, the wall temperature distribution is modified by t he presence of secondary vortical structures, which are induced near, and swept over, the plate surface. When the plate is near the jet nozz le, a region of lower wall temperature, attributable to these addition al vortices, is observed in the experimental data. When the plate is f urther from the nozzle, no secondary vortices are formed and no region of lowered wall temperature is measured. Self-sustaining acoustic res onance, when it occurs, is found to alter significantly this picture o f the wall temperature distribution. Although the scope of this work i s limited to free and impinging jets, this present topic, along with t he previously reported mechanism of the Eckert-Weise effect, exemplifi es the wider family of problems in which unsteady vortical structure s trongly affects the wall temperature and heat transfer.