稀薄流高超声速钝化前缘逆向射流流场特征研究

Flow field characteristics of opposing jet at blunted leading edge of hypersonic of rarefied flow

关键词:  逆向射流  临近空间  直接模拟蒙特卡洛  高超声速  稀薄气体

Key words:  Opposing jet  Near space  Direct simulation Monte Carlo  Hypersonic  Rarefied gas

摘要:

为准确预测稀薄过渡区逆向射流对稀薄大气的干扰流动特征，本文采用直接蒙特卡洛算法（DSMC），在自由流马赫数为7的情况下，对稀薄流中逆向射流干扰下的高超声速流动进行了数值模拟。计算中考虑了60~90 km高度的典型大气环境，研究了压比和自由流克努森数对压力、剪切力和热流密度的影响规律。结果表明，逆向射流改变了流场结构，且具有明显的热防护性能，但减阻效果不明显。逆向射流对高超声速稀薄来流的影响随压比的增加明显增强，形成的马赫盘大小也随之增加。高度的增加伴随稀薄效应不断增强，自由流克努森数增大，导致弓形激波厚度随高度增加而增加，壁面处的回流区范围不断减小至消失。这项研究初步揭示了稀薄流中逆向射流/高超声速流动相互作用的机制。

Abstract:

In order to accurately predict the interference flow characteristics between the opposing jet and the rarefied atmosphere in the rarefied transition region， the direct Monte Carlo algorithm （DSMC） is used to simulate the hypersonic flow under the interference of the opposing jet in the rarefied flow under the condition that the free flow Mach number is 7. The typical atmospheric environment of 60~90 km height is taken into account in the calculation， the effects of pressure ratio and Knudsen number of free flow on pressure， shear force and heat flux are studied. The results show that the opposing jet changes the structure of the flow field and has obvious heat protection performance， but the drag reduction effect is not obvious.The effect of opposing jet on hypersonic rarefied inflow increases with the increase of pressure ratio， and the size of the Mach disk also increases. With the increase of height， the rarefaction effect increases and the Knudsen number of free flow increases， so that the thickness of bow shock wave increases with the increase of height， and the reflux zone on the wall decreases and disappears. The results of this study provide physical insights into the mechanisms related to the interaction between opposing jets and hypersonic flows in rarefied flows.