爆炸冲击波反射流场的理论计算方法

A theoretical method for the calculation of flow field behind blast reflected waves

爆炸冲击波遇到固壁,依次发生正规和非正规反射。本文中基于镜像方法,将爆炸冲击波在固壁反射等效为真实和虚拟爆炸流场的相互作用,建立了波后流场的理论计算方法。首先,假定反射波是以虚拟爆源为中心的圆弧,马赫杆是以爆心在固壁投影点为中心的圆弧。然后,根据爆炸自由场传播规律,利用基于几何近似的方法,建立流场中冲击波结构随时间演化的计算方法,确定任意时刻波后流场区域。最后,利用新发展的叠加模型LAMBR (LAMB revisied),将真实和虚拟爆炸流场进行叠加,给出波后流场中的压力、密度和速度等物理量。通过与数值模拟结果和已有数据进行对比,发现该方法得到的流场物理量分布、峰值等能够反映流场发展的主要规律,从而验证了该理论方法的合理性。而且,该理论方法所需的时间相较于数值模拟大大缩短。

Upon impinging on a rigid surface, the blast wave would go through regular and irregular reflection successively. A theoretical model is developed for the determination of the flow field behind the reflected wave, which is based on the method of image and identifies the field around blast wave reflection with that resulting from the interaction of real and imaginary bursts. Firstly, approximations of both reflected wave and Mach stems to circular arcs, centered on the imaginary burst point and ground zero respectively, are made. Then, given the blast free field, the method based on geometrical similarity is applied to calculate the temporal evolution of shock wave structures and differentiate different flow zones. Lastly, a newly developed addition model LAMBR (LAMB revisied) is employed to obtain the field parameters behind the reflected wave. The field parameter contours and peak values are in good agreement with the numerical results and the data from UFC 3-340-02, so the theoretical model is valid. And, the time needed for the theoretical calculation is much shorter than that for numerical simulation.