The diffraction of a shock wave over a stationary body is a problem of interest associated with the starting of shock tubes and expansion tubes which are well suited to studies of hypersonic flows. However, these facilities are characterized by very short test times. The transient parameters during the establishment of the detached bow shock in such impulsive facilities are important for both data processing and experimental design. In the present study, numerical simulations are conducted to investigate the diffraction of a normal shock wave over a sphere and the subsequent transient phenomena in a viscous perfect-gas flow field. The incident shock Mach number ranges from 3 to 5 with a specific heat ratio of 1.4. Based on the theoretical description of the reflected shock position during bow shock formation, approximate solutions for the time histories of the stagnation-point heat flux are also derived. The analytical and numerical results agree well. The results show that the stagnation-point pressure and heat flux approach their steady-state values much more rapidly than the shock detachment distance does.

冲击波在静止物体上的衍射是与激振管和膨胀管的启动相关的关注问题，激振管和膨胀管非常适合于高超声速流的研究。但是，这些设备的特点是测试时间非常短。在这种冲动设备中建立分离的弓形激波期间的瞬态参数对于数据处理和实验设计均很重要。在本研究中，进行了数值模拟，以研究正常冲击波在球体上的衍射以及在粘性完美气体流场中的后续瞬态现象。入射冲击马赫数为3至5，比热比为1.4。根据对弓形激波形成过程中反射激波位置的理论描述，还推导出了滞点热通量时间历史的近似解。分析和数值结果吻合得很好。结果表明，停滞点压力和热通量比减震距离要快得多地接近其稳态值。