| Description |
xi, 69 leaves : illustrations (some colored) ; 29 cm |
| Summary |
"The thermal management of hypersonic air-breathing vehicles presents formidable challenges. Reusable thermal protection systems (TPS) are one of the key technologies that must be improved in order to use hypersonic vehicles as practical, long-range transportation systems. Active cooling systems, such as transpiration cooling, must be considered for affordable, long duration flights to achieve efficient temperature reduction and coolant mass saving. With this technique, it is important to understand the physics that characterize the boundary layer and its interaction with the vehicle's surface. This current study numerically investigates the effectiveness of a variable-velocity transpiration strategy (developed recently in a joint effort by the research groups in University of Texas at Arlington and Missouri S&T) for fully laminar, transitional, and fully turbulent flows over a 2-D blunt body with a cylindrical leading edge and a wedge region. The transitional flow cases are evaluated for a range of transition locations to see the influence of this parameter on the variable transpiration strategy introduced. For all flow types presented in this study, a saw-tooth wall velocity distribution (variable transpiration strategy) is compared to a uniform-velocity transpiration approach. An equal amount of coolant usage has been imposed in order to compare the cooling effectiveness between both strategies for various flow types in different regions of the body. The results suggest that the uniform-velocity transpiration allows a reduction of 68% in the stagnation point heat flux and 77% for variable-velocity transpiration with respect to the no-transpiration case in both laminar and turbulent flow cases. The computational results also show that the efficiency of the transpiration cooling is much higher in laminar flow compared to turbulent flow in regions downstream of the stagnation point. In such regions, for turbulent flows, the amount of total coolant must be increased by approximately 110% to match the cooling efficiency observed in laminar flows. In addition to the analysis of cooling effectiveness, the thermal response of TPS material with the variable transpiration strategy is also investigated for both fully laminar and fully turbulent flows"--Abstract, leaf iii. |
|
