A Multi-space Interrelation Theory for Correlating Aerodynamic Data from Hypersonic Ground Testing

Prediction of aerodynamic force/heating acting on hypersonic vehicles in flight conditions with experimental data is a critical yet challenging step in developing hypersonic vehicles. A multi-space interrelation (MSI) theory and its correlation algorithms have been presented. MSI considers the flight condition as an ideal wind tunnel and then aims at detecting an inherent invariant of aerodynamic data from different wind tunnels. The invariant detection is carried out by special supervised self-learning schemes, adaptive space transformation (AST), and/or parse-matrix evolution (PME). The invariant is then used to predict the aerodynamic force/heating coefficients. The study indicates that the multi-space interrelation theory agrees well with physical phenomena. The correlation algorithm can make use of hypersonic wind-tunnel experimental data effectively, and the correlation function is capable of unifying all the experimental data in an analytical form. With the proposed theory and algorithm, one can expect to find a reliable correlation formula with high accuracy based on plenty of wind-tunnel experimental data, provided that the physical condition has not essentially changed

Wave dynamic processes induced by a supersonic projectile dischargingfrom a shock tube

A numerical study on wave dynamic processes occurring in muzzle blast flows, which are created by a supersonic projectile released from the open-end of a shock tube into ambient air, is described in this paper. The Euler equations, assuming axisymmetric flows, are solved by using a dispersion-controlled scheme implemented with moving boundary conditions. Three test cases are simulated for examining friction effects on the muzzle flow. From numerical simulations, the wave dynamic processes, including two blast waves, two jet flows, the bow shock wave and their interactions in the muzzle blasts, are demonstrated and discussed in detail. The study shows that the major wave dynamic processes developing in the muzzle flow remain similar when the friction varies, but some wave processes, such as shock-shock interactions, shock-jet interactions and the contact surface instability, get more intensive, which result in more complex muzzle blast flows.</p

Numerical studies on the effect of the key parameter to hypersonic “pitch-up anomaly”

高温真实气体效应所引起气体比热比γ的降低被认为是导致航天飞机"上仰异常"的主要原因.为详细研究此问题,本文数值求解了Euler方程,化学反应源项采用有限速率模型,考虑了5个组分、17个基元反应.研究结果表明采用低比热比气体CF4作为实验气体会导致膨胀区的压力分布与真实气体效应的影响规律不一致,并不能反映出"上仰异常"现象的本质.在高温真实气体效应的影响下,化学反应所带来的影响大于振动激发的影响,对于y方向半模压力积分Cay来说是3.8倍,而对于半模力矩积分系数Cam来说是1.7倍.对比分析表明,热化学反应导致的比热比分布不均衡是导致"上仰异常"现象出现的根本原因

中国科学院力学研究所高温气体动力学国家重点实验室;

由于激波和燃烧的耦合作用,气相爆轰波的波面后方会出现横向运动的激波,从而形成胞格爆轰波结构。对于超声速气流中的斜爆轰波,其胞格结构比正爆轰波更加复杂,研究者对此还缺乏深入的认识。采用无粘Euler方程和单步化学反应模型对斜爆轰波进行了数值模拟,重点研究了活化能和诱导斜爆轰波楔面角度对于波面胞格结构的影响。模拟发现存在两种斜爆轰结构,一种的特点是只存在单向横波,另一种是存在双向的横波。其中在双向横波的结构后方,首次在斜爆轰结构中发现了波后未反应气团的存在。利用统计方法对斜爆轰中横波的产生过程进行分析,结果表明两种结构的产生过程受到不同因素的影响,为斜爆轰波结构的预测提供了依据

Numerical simulation of deflagration to detonation transition in a straight duct: Effects of energy release and detonation stability

Numerical simulation based on the Euler equation and one-step reaction model is carried out to investigate the process of deflagration to detonation transition (DDT) occurring in a straight duct. The numerical method used includes a high resolution fifth-order weighted essentially non-oscillatory (WENO) scheme for spatial discretization, coupled with a third order total variation diminishing Runge-Kutta time stepping method. In particular, effect of energy release on the DDT process is studied. The model parameters used are the heat release at q = 50,30,25,20,15,10 and 5, the specific heat ratio at 1.2, and the activation temperature at Ti = 15, respectively. For all the cases, the initial energy in the spark is about the same compared to the detonation energy at the Chapman-Jouguet (CJ) state. It is found from the simulation that the DDT occurrence strongly depends on the magnitude of the energy release. The run-up distance of DDT occurrence decreases with the increase of the energy release for q = 50 similar to 20, and increases with the increase of the energy release for q = 20 similar to 5. This phenomenon is found to be in agreement with the analysis of mathematical stability theory. It is suggested that the factors to strengthen the DDT would make the detonation more stable, and vice versa. Finally, it is concluded from the simulations that the interaction of the shock wave and the flame front is the main reason for leading to DDT.</font

高焓激波风洞喷管流场数值研究

本文利用数值求解多块结构网格条件下的轴对称热化学非平衡Navier-Stokes 方程的方法，针对JF-10 氢氧爆轰驱动高焓激波风洞上调试的典型实验状态，数值模拟了高焓风洞锥形喷管的流场状态，给出了相应实验状态下，喷管出口及轴线方向各参数的分布，同时探索了焓值对喷管流场状态参数的影响。结果表明，喷管出口截面均匀区域达到出口截面直径的75%，能够提供足够的模型试验区域；出口气流已处于冻结流状态，气体成分和空气有一定差别，实验中这一点须予以考虑

壁面催化效应数值研究

高超声速飞行器壁面催化效应会导致激波层中原子在壁面处复合释热,加剧周围气动热环境。针对高超声速流动壁面催化特性,选择不同飞行马赫数及高度条件,采用完全催化和非催化两种条件对球锥模型壁面热流率进行数值模拟计算,研究壁面催化效应对气动热的影响规律。结果表明,固定飞行高度时,壁面催化效应对气动热的影响随马赫数增加而加强,Ma 25条件下驻点处完全催化与非催化热流比值高达1.92。壁面催化效应不仅会影响壁面附近的流场特性及组分分布状态,而且对整个激波层都有一定的影响作用

马赫数无关原理对高超声速热化学反应流的适应性研究

通过求解考虑热化学非平衡的5组分,17个基元反应的N-S方程,对马赫数无关原理对高超声速热化学反应流的适应性进行了研究。模型采用高超声速常用的柱状钝头体。对比量热完全气体、热化学非平衡气体下激波角、沿流线压力分布、阻力系数的差异,得出真实气体效应下马赫数无关原理依然适用的结论。通过对阻力系数的进一步分析研究知,真实气体效应是通过能量向振动能、化学能的从新分配机制来影响阻力系数的变化,且其所引起的阻力系数变化总体来说比较小;在M>15时,向化学能的分配为主导因素

基于分子发射光谱的温度测量技术及其应用

本文基于CN自由基所固有的分子结构特征,通过光谱理论计算了CN自由基B~2∑~+→X~2∑~+电子带系发射光谱的谱线强度,并结合实际的光谱实验,分析了谱线的自然展宽、碰撞展宽、多普勒展宽以及仪器展宽等各种展宽因素对谱线线型的影响,从理论上计算了任意转动温度、振动温度以及谱线展宽线型条件下CN自由基B~2∑~+→X~2∑~+电子带系发射光谱的强度分布,为测量等离子体的转动温度和振动温度提供理论依据。基于上述光谱理论分析结果,实验中利用光学多通道分析仪对不同延时时刻等离子体的发射光谱进行分析,通过理论计算光谱与实验光谱进行拟合,从而得到等离子体的转动温度和振动温度随时间的变化过程,并根据温度的变化..

复现高超声速飞行条件下10°尖锥标模气动力特性试验研究

综述了应用中科院力学所的JF12长试验时间激波风洞中,在复现40km高度,飞行马赫数7的试验条件下,开展的10°尖锥标模天平测力试验研究结果