Further detailed analysis about shock wave reflection outside Laval nozzle in different working states

When ratio of environmental pressure to total pressure increases from design state to third limit condition (normal shock at the outlet of nozzle), there are different shock wave phenomena outside the Laval nozzle. According to extant theory about shock wave reflection, the working range between design condition and the third limit condition was subdivided into several sections: strong oblique shock wave condition, Mach reflection condition, regular reflection and dual solution domain. Three critical ratios of environmental pressure to total pressure were proposed and determined to replace flow-deviation angle for estimating different Laval nozzle working statuses. Varying tendency of these critical ratios of Laval nozzle in various aspect ratios were also given with a figure. The pressure ratios corresponding regular reflection, Mach reflection and strong oblique wave in a planar Laval nozzle with aspect ratio 5 were 0.0841, 0.0959 and 0.2005 respectively, and then the accuracy of these values were verified with numerical simulation.