"A Study on Shock Wave Self-Excited Oscillation in Supersonic Flows"

本研究的目的是研究超音速流动中的冲击波自激振荡。因此，许多带有冲击波的超音速流已经通过实验和计算进行了研究。重点是基于对超音速流动中激波自激振荡的流动结构和流动物理的物理理解。对于研究项目，本研究选择并研究了以下八个主题，并且本研究的目标已经完成。 ：(1)研究了冲击波/湍流边界层中冲击波的自激振荡。流动分离不均匀且相当不稳定。此外，不稳定特征与马赫数无关。采用LIF的新型流动可视化技术用于密度等值线的测量。(2)研究了超音速流中反向射流冲击波的自激振荡。数值模拟与实验结果非常吻合。测量红色压力脉动表明主频率随射流总压力变化。(3)研究了超音速射流与壁面的相互作用流场。由于喷嘴出口与壁面的距离不同，相互作用的流型和激波振荡型态发生剧烈变化。(4)对超音速混合流场进行了研究。还进行了数值模拟，结果与实验非常吻合。提出了超声速混合新技术并证明了其性能。(5)在热和化学非平衡条件下研究了冲击波引起的气动加热。揭示了高温对气动加热的影响。(6)研究了钝体前方激波产生的气动加热问题。事实证明，薄膜冷却具有足够的降低气动加热的能力。(7)对再入飞行器瓦片间隙产生的空腔流进行了峰值压力和峰值加热的研究。捕获了带有嵌入激波的振荡腔流。(8)研究了塞式喷嘴周围带有嵌入激波的超音速流动。研究了塞式喷嘴形状对阻力的影响，并通过优化喷嘴形状实现了阻力的大幅降低。较少的

The purpose of the present study is to investigate the shock wave self-excited oscillation in supersonic flows. Hence, many supersonic flows with shock waves have been experimentally and computationally studied. The emphasis is based on the physical understanding of the flow structure and flow physics of shock wave self-excited oscillation in supersonic flows. For the research projects eight topics are selected and studied in the present study as follows and the objectives of the present study have been completed. :(1) Self-induced oscillation of shock wave in shock wave/turbulent boundary layer have been studied. The flow separation is not uniform and quite unsteady. Also the unsteady features are independent on mach number. The new flow visualization technique by LIF is installed for the measurement of density contour.(2) Self-induced oscillation of shock wave in opposing jet in supersonic flow have been studied. Numerical simulations show quite good agreement with experiments. Measu … More red pressure fluctuations show that dominant frequency changes due to total pressure of jet.(3) Interacting flow field between supersonic jet and wall has been studied. The interacting flow pattern and shock wave oscillation pattern changes drastically due to the distance between the nozzle exit and wall.(4) The supersonic mixing flow fields have been studied. Numerical simulations have been also conducted resulting quite good agreement with experiments. The new technique for supersonic mixing has been proposed and demonstrated its capability.(5) Shock wave induced aerodynamic heating has been studied with thermally and chemically nonequilibrium conditions. High temperature effects on aerodynamic heating have been revealed.(6) Aerodynamic haeting problems generated from shock wave ahead of the blunt body have been studied. Film cooling has proved to have sufficient capability for reducing aerodynamic heating.(7) Cavity flow generated by the gap of the tile of the reentry vehicle has been studied with peak pressure and peak heating. Oscillatory cavity flows with embedded shock waves have been captured.(8) Supersonic flows with embedded shock wave around plug nozzle have been studied. The effect of the shape of plug nozzle on the drag is investigated and the drastic reduction of the drag is obtained by optimal nozzle shape. Less