Formation mechanism of the reflected shock wave over curved surfaces.

对曲面上的激波反射现象进行了实验和理论研究。实验中使用的模型是普通的圆形、圆柱形、凹形和凸形楔形，以及模拟前者的阶梯形模型。采用阶梯模型研究了圆柱形楔体上反射波的形成过程。本课题组将这种阶梯状模型的实验方法称为多步法，并用纹影装置拍摄了反射波结构。通过将其与阶跃模型上的激波反射进行比较，可以从物理上更好地理解圆柱楔体上反射波的形成机理。特别是阐明了凹面圆柱楔体上的反射波在反射点外非常微弱的原因。详细阐述了所谓的跃迁规则反射(TRR)的结构和形成机理。通过考虑阶跃产生的压缩波的行为，提出了一个过渡楔形角的解析式，该公式与实验结果吻合较好，并研究了一些参数(初始楔形角、入射激波马赫数和曲率半径)对过渡楔形角的影响。为了研究这种影响，已经进行了实验。当凹楔体的初始楔角增大时，推导出的零初始楔角的解析式不能给出正确的值。提出了一种计算过渡楔形角的理论方法，并与实验结果吻合较好。与另一种方法的比较表明，该方法是一种更好的预测过渡楔形角的方法。

Shock reflection phenomena over curved surfaces have been investigated both experimentally and theoretically. The models used in this experiment are ordinary circular cylindrical concave and convex wedges and step-like models which simulate the former. The step-like models were used to investigate the process of reflected wave formation over circular cylindrical wedges. The present experimental method by use of step-like models are dubbed method of multiple steps by our research group.The reflected wave structure has been photographed with a schlieren apparatus. The formation mechanism of the reflected wave over circular cylindrical wedges is physically well understood by comparing it with shock reflection over step-like models. In particular, the reason why the reflected wave over a concave circular cylindrical wedge is very weak away fl.om the reflection point is elucidated. Moreover the structure and the formation mechanism of the so-called transitioned regular reflection (TRR) are illustrated in detail. By considering the behavior of the compression wave issued from the step, an analytical formula for the transition wedge angle is proposed and found in good agreement with thc experiment.We were also interested in the effect of some parameters (initial wedge angle, incident shock Mach number and radius of curvature) over the transition wedge angle. The experiment has been performed to investigate such effects. When the initial wedge angle of the concave wedge increases, the analytical formula derived for zero initial wedge angle does not give the correct value. A theoretical method to calculate transition wedge angle was proposed and in good agreement with experiment. Comparison with another method shows this is a far better method for predicting the transition wedge angle.