高超声速飞行器激波控制减阻技术

针对高超声速飞行器巨大的激波阻力,采用数值方法研究了由钝头体、气动杆和侧向喷流构成的组合模型的减阻性能。侧向喷流将弓形激波推离气动杆,组合模型的再附激波明显弱于传统气动杆模型,其阻力系数比气动杆模型低了33.52%,从而验证了本文组合模型优异的减阻效率。进行了组合模型的影响因素分析,随侧向喷流总压比和气动杆的长度的增加,再附激波强度减弱,减阻效率升高,但减阻效率的变化速率逐渐减小。随喷口位置向下游移动,再附激波逐渐增强,减阻效率降低,且减阻效率的变化速率逐渐增加。此外本文还研究了以上参数对流场结构及钝头体压力峰值位置的影响。     

Numerical validation and parametric investigation on the cold flow field of a typical cavity-based scramjet combustor

The three-dimensional coupled implicit Reynolds Averaged Navier–Stokes (RANS) equations and the two equation standard k–ε turbulence model has been employed to numerically simulate the cold flow field in a typical cavity-based scramjet combustor. The numerical results show reasonable agreement with the schlieren photograph and the pressure distribution available in the open literature. The pressure distribution after the first pressure rise is under-predicted. There are five shock waves existing in the cold flow field of the referenced combustor. The first and second pressure rises on the upper wall of the combustor are predicted accurately with the medium grid. The other three shock waves occur in the core flow of the combustor. The location of the pressure rise due to these three shock waves could not be predicted accurately due to the presence of recirculation zone downstream of the small step. Further, the effect of length-to-depth ratio of the cavity and the back pressure on the wave structure in the combustor has been investigated. The obtained results show that there is an optimal length-to-depth ratio for the cavity to restrict the movement of the shock wave train in the flow field of the scramjet combustor. The low velocity region in the cavity affects the downstream flow field for low back pressure. The intensity of the shock wave generated at the exit of the isolator depends on the back pressure at the exit of the combustor and this in turn affects the pressure distribution on the upper wall of the combustor.     

Transient analysis of counterflowing jet over highly blunt cone in hypersonic flow

Understanding the characteristics of various Counterflowing jets exiting from a nose cone is crucial for determining heat load reduction and usage of this device in various conditions. Such jets can undergo several flow regimes during venting, from initial supersonic flow, to transonic, to subsonic flow regimes as the pressure of jet decreases. A bow shock wave is a characteristic flow structure during the initial stage of the jet development, and this paper focuses on the development of the bow shock wave and the jet structure behind it. The transient behavior of a sonic counterflow jet is investigated using unsteady, axisymmetric Navier–Stokes solved with SST turbulence model at free stream Mach number of 5.75. The coolant gas (Carbon Dioxide and Helium) is chosen to inject into the hypersonic air flow at the nose of the model. The gases are considered to be ideal, and the computational domain is axisymmetric. The jet structure, including the shock wave and flow separation due to an adverse pressure gradient at the nose is investigated with a focus on the differences between high diffusivity coolant jet (Helium) and low diffusivity coolant jet (CO₂) flow scenarios.     

数值模拟侧向超声速单喷流干扰流场特性

采用数值方法研究了平板上超/高超声速来流与超声速横向喷流相撞引起的复杂干扰流场特性。所建立的单介质冷喷流数值模拟方法,经过了表面多方位压力分布测量结果、纹影显示的激波结构以及表面油流图谱表现的表面分离范围的实验验证。根据数值模拟与实验对比的结果,合理地描述了喷流干扰流场压力分布以及表面、空间结构特性,并分析了压力比对流场结构和特性的影响。     

Influences of the turbulence model and the slot width on the transverse slot injection flow field in supersonic flows

Transverse slot injection scheme is very important for the mixing process between the air and the fuel in supersonic flows. The effect of the turbulence model and slot width on the transverse slot injection flow field has been investigated numerically based on the grid independency analysis, and the predicted results have been compared with the experimental data available in the open literature. The obtained results show that the grid scale makes only a slight difference to the wall pressure profiles for all jet-to-crossflow pressure ratios employed in this study, and the wall pressure profile with low jet-to-crossflow pressure ratio is predicted accurately by the RNG k–ε turbulence model, the SST k–ω turbulence model for the flow field with high jet-to-crossflow pressure ratio. High jet-to-crossflow pressure ratio can increase the jet penetration depth in supersonic flows, and the gradient of the length of the upstream separation region is larger than that of the height of the Mach surface. At the same time, when the jet-to-crossflow pressure ratio is maintained constant, the jet penetration depth increases with the increase of the slot width.     

Fine structure of interplanetary shock fronts from the data of the BMSW instrument of the PLASMA-F experiment

The paper is concerned with studying the thickness of fronts of 38 interplanetary shocks detected by the BMSW instrument, which is a part of the scientific payload of the SPEKTR-R spacecraft, which was launched into a highly elliptical orbit in 2011. The main parameters of the interplanetary shocks have been calculated as follows: the ratio of thermal pressure to magnetic pressure before the front β, the angle between the shock front normal and the undisturbed magnetic field θ_Bn, the ratio of the shock propagation velocity to the magnetosonic velocity in the undisturbed region M_ms, and the shock front velocity relative to the Earth. It has been shown that the front thickness determined from the plasma parameters approximately matches the front thickness obtained from the magnetic field measurements and lies between 0.5 and 5 proton inertial lengths. In some events, the oscillations have been observed (upstream and downstream of the shock) in plasma parameters and in the magnetic field data. The length has been found to be between 0.5 and 6 proton inertial lengths for the preceding oscillations and between 0.5 and 10 proton inertial lengths for the following oscillations. The average value of the proton inertial length is 62 km.     

Statistical properties of the fluxes of energetic ions and solar wind in the region of intersection of shock wave fronts in the distant heliosphere

The character of statistical distributions of the intensity of energetic charged particles, solar wind flux, and the interplanetary magnetic field strength is analyzed using the data obtained by the Voyager 1 and Voyager 2 spacecraft in the distant heliosphere. A comparison of the distributions in the region of crossings of shock wave fronts in 1991 and in 2004 is carried out, and their similarities and differences are discussed.     

Results of the early orbit manoeuvres of the ampte-uks

The Active Magnetospheric Particle Tracer Explorers (AMPTE) program consists of three satellites which were launched on 16th August 1984. The scientific aim of the mission is to inject lithium and barium tracer ions inside and outside the Earth's magnetosphere and to detect and monitor these ions as they diffuse through the inner magnetosphere. The first of these three satellites, the U.S. Charge Composition Explorer (CCE) was launched into an elliptical orbit of apogee 8 R_e. The other two satellites are the West German Ion Release Module (IRM) and the U.K. Subsatellite (UKS), both of which were launched on the same vehicle into a highly elliptical orbit of apogee 18 R_e. At discreet intervals during the mission the IRM will release ions into the solar wind, and the movement of these ions will be monitored by the UKS. Depending on the particular scientific requirement, the UKS has to be positioned accurately at a given distance behind the IRM. Initially the UKS has to be located 100 km behind the IRM, and held there for ～9 months. It will then be moved a distance of ～1 R_e behind the IRM. In order to manoeuvre the UKS around its orbit, a cold gas jet system is incorporated on the satellite, allowing impulses to be applied both along and perpendicular to the orbit velocity vector. The orbit control system also has to cater for relative orbit changes due to air drag at perigee, as the IRM and the UKS have different $\text{area}\text{mass}$ ratios. This paper presents an account of the orbit control system implemented on the UKS, together with the mathematical approach adopted, and results from manoeuvres made in the first weeks of the mission.     

Numerical investigation on the shock wave transition in a three-dimensional scramjet isolator

The scramjet isolator, which is used to prevent the hypersonic inlet from disturbances that arise from the pressure rise in the scramjet combustor due to the intense turbulent combustion, is one of the most critical components in hypersonic airbreathing propulsion systems. Any engineering error that is possible in the design and manufacturing procedure of the experimental model, and the intense heat release in the scramjet combustor, may cause the performance of the isolator to decrease, leading to its lack of capability in supporting the back pressure. The coupled implicit Reynolds Averaged Navier–Stokes (RANS) equations and the two-equation standard k?ε turbulent model have been employed to numerically simulate the flow fields in a three-dimensional scramjet isolator. The effects of the divergent angle and the back pressure on the shock wave transition and the location of the leading edge of the shock wave train have been estimated and discussed. The obtained results show that the present numerical results are in very good agreement with the available experimental shadow-pictures, and the numerical method is more suitable for capturing the shock wave train and predicting the location of the leading edge of the shock wave train in the scramjet isolator than the present two-dimensional numerical methods. This is due to the small width-to-height ratio of the isolator and the intense three-dimensional flow structures. On increasing the divergent angle of the scramjet isolator, the static pressure along the central symmetrical line of the isolator decreases sharply. This is due to the strong expansion wave generated at the entrance of the isolator, and when the divergent angle of the isolator is sufficiently large, namely 1.5°, a zone of negative pressure is formed just ahead of the leading edge of the shock wave train. At the same time, the shock wave train varies from being oblique to being normal, and then back to oblique. With an increase in the prescribed back pressure at the exit of the scramjet isolator, the leading edge of the shock wave train moves forward towards the entrance of the isolator, and when the back pressure is sufficiently large, unstart conditions in the hypersonic inlet can take place if the shock train reaches the inlet.     

Determination of vibrational CO2 distributions in thermodynamically-nonequilibrated rarefied flows by use of radiational characteristics in the 15 μm band

A method for determination of the vibrational distributions and populations of individual vibrational levels of vibrationally-nonequilibrated carbon dioxide in bend-stretch manifold and asymmetric stretching mode was developed and substantiated. The method is based on the measurements of integrated radiation intensity in the wide spectral intervals of the 15 μm CO₂ band and total emissivities of its appropriate Q-branches. Computations of radiation intensities and emissivities in P and R-branches were performed by using vibrational-rotational band models and in Q-branches by the direct “line-by-line” integration.It was shown that vibrational temperature of CO₂ asymmetric stretching mode may be determined from the measurements of integrated radiation intensity of the 15 μm band. The populations of individual levels of the bend-stretch manifold may be obtained from the measurements of total emissivities of some Q-branches of the 15 μm band.The procedure of the CO₂ lower vibrational levels populations determination under the conditions typical of 18 μm and 9–11 μm CO₂ laser cavities is described.     

前缘水平投影可控的乘波体设计方法研究

结合流线追踪技术和密切面混合函数提出了一种前缘水平投影可控的乘波体设计方法,并完成了前缘水平投影为超椭圆的乘波体(Waverider-F)和超椭圆前缘转超椭圆后缘的乘波体(Waverider-FT)设计。二者具有较高的容积效率,前缘对应的轴向投影近似为余弦曲线。通过数值仿真验证了设计方法的有效性,设计点时Waverider-F的乘波特性良好且保持了基准流场的特点,Waverider-FT前部完全乘波,后部两侧诱导激波使流场变形且形成高压区,接力点时二者的乘波特性也较好。另外,二者具有较高的升阻比和预压缩效率,设计点时无粘升阻比分别为3.46和2.88。与Waverider-F相比,Waverider-FT的升力、阻力和出口增压比都明显增加,而升阻比、俯仰力矩和出口总压恢复系数降低。有粘条件下,设计点的升阻比由2.91降为2.41,对应的出口总压恢复系数降低了5.8%。     

Acceleration of solar cosmic rays and the fine spectral structure of type II radio bursts

On the basis of data, obtained by means of the ground-based solar service RSTN (Radio Solar Telescope Network) and the geostationary satellite system GOES, the relationship between the solar cosmic rays (SCR) intensity I _p with the proton energy E _p > 1 MeV and parameters of meter-decameter type II radio bursts in the frequency range of 25–180 MHz is studied. The process of proton acceleration by shock waves was characterized by the frequency drift velocity of radio bursts V _mII and the relative difference between radio emission frequencies at the first two harmonics b. It is shown that the coefficient of correlation between I _p and b increases with E _p growing from 0.40 to 0.70, while a similar coefficient between I _p and V _mII does not exceed 0.30. Indications in favor of the two-stage SCR acceleration model are obtained.     

Variations of the magnetopause position versus the level of geomagnetic activity (according to data of the INTERBALL-1 Satellite for 1995–1997)

The variations in the deviation of the observed position of the magnetosphere boundary from its mean position predicted by the Shue at al., 1997 (Sh97) model [7] are studied as a function of the substorm activity level (the AE-index value) and magnetic storm intensity (the value of the corrected D _st ^* index). The results obtained make it possible to state that the amplitude of motion of the magnetospheric boundary on the dayside and in the low-latitude tail is small. It is likely that the position of the boundary is either independent of the AE and D _st ^* indices or this dependence is weak. At the same time, the boundary of the high-latitude tail shifts inward on the average by 1.5R _E with an increase of the AE-index in the case of absence of magnetic storms (contraction of the magnetospheric tail). On the contrary, in the presence of magnetic storms, this boundary shifts outward by up to 3R _E with an increase of the AE-index (inflation of the magnetospheric tail). It is also shown that the boundary of the high-latitude tail moves outward with an increase of the D _st ^* index, both at low substorm activity and in periods of high substorm activity. The amplitude of the outward motion of the high-latitude tail of the magnetosphere is by a factor of two higher for moderate magnetic storms with strong substorms than for moderate magnetic storms with weak substorms.     

Photochemical initiation of gaseous detonations

Direct initiation of detonations in gaseous mixtures of C₂H₂-O₂, H₂-O₂ and H₂-Cl₂ in the pressure range of 10–150 torr using flash photolysis was studied. Similar to blast initiation using a concentrated powerful energy source, it was found that for photochemical initiation, there exists a certain threshold of flash intensity and energy for each mixture at any given initial pressure and composition below which a deflagration is formed. At the critical threshold, however, a fully developed detonation is rapidly formed in the immediate vicinity of the window of incident UV radiation. However, at super critical flash energies, the amplitude of the detonation formed decreases and combustion of the entire irradiated volume approaches a constant volume explosion. It was found that photo-chemical initiation requires both a certain minimum peak value of the free radical concentration generated by the photo-dissociation as well as an appropriate gradient of this free radical distribution. The minimum peak radical concentration permits rapid reaction rates for the generation of strong pressure waves, while the gradient is necessary for the amplification of the shock waves to a detonation. If the gradient is absent and the free radicals are uniformly distributed in the mixture, then the entire volume simply explodes as in a constant volume process. The present study reveals that the mechanism of photochemical initiation is one of proper temporal synchronization of the chemical energy release to the shock wave as it propagates through the mixture. In analogy to the LASER, the term SWACER is introduced to represent this mechanism of Shock Wave Amplication by Coherent Energy Release. There are strong indications that this SWACER mechanism is universal and plays the main role in the formation of detonations whenever a powerful concentrated external source is not used to generate a strong shock wave in the explosive.     

真实气体效应对高超声速轨道器气动特性的影响

基于一个7组元6反应动力学模型，采用NND差分格式求解化学反应Navier-Stokes方程，数值研究高超声速轨道器的绕流特性。重点讨论了轨道器气动特性在真实气体效应作用下对不同来流状态和不同舵偏角的敏感性。研究表明：真实气体效应主要发生在物面附近很薄的激波层内，缩短了激波的脱体距离，使激波层变薄，流动变量的梯度变大；空气的离解和电离导致轨道器的阻力系数比完全气体计算值低，压心位置前移。小攻角下，升力系数和俯仰力矩系数的真实气体计算值高于完全气体计算值，大攻角情形则相反。此外，小攻角时真实气体效应产生小低头力矩，而大攻角时产生小抬头力矩。单就舵面而言，真实气体效应使其阻力系数增大，使其升力系数和俯仰力矩系数在小攻角且非负舵偏角时变小，在大攻角且负舵偏角时变大。特别地，真实气体效应仅在零攻角且零舵偏角时对舵面的压心位置产生较大影响。     

单喷管火箭自由喷流噪声数值模拟

利用非定常燃气流场数值模拟方法，研究超声速喷流核心区及其外围亚声速区燃气流动态分布和流动特性，在此基础上利用欧拉方程条件的伽辽金有限元方法以及FWH方法，实现并完成喷流噪声传播特性、辐射特性数值模拟。喷流噪声数值模拟结果显示：燃气流推进初期，强喷流噪声区域紧随燃气流前锋；燃气流场相对稳定后，强喷流噪声区域主要位于燃气流等能区末稍，一些小尺度试验的燃气流激波系附近也存在较强喷流噪声。这些强喷流噪声主要由燃气流前锋带动的大涡动态卷吸、燃气流强湍流脉动以及激波扰动引起。受数值模拟网格分辨率影响，当前仅能保持中低频段声压级数值模拟结果与实测结果总体接近。     

Effect of reflected ions on the formation of the structure of interplanetary quasi-perpendicular shocks for Mach numbers lower than the first critical mach number

Based on the data of the BMSW instrument installed on the of SPEKTR-R spacecraft, as well as according to the data of instruments of the WIND spacecraft, etc., using two examples, the paper has studied the role of ions reflected from the front and associated structural features of quasi-perpendicular interplanetary shocks (IS) with the Alfvén Mach number М _A lower than the first critical Mach number М _c1 . It has been shown that BSs with the finite parameter 0.1 < β₁ < 1 contain a small fraction of reflected protons, which play a significant role in forming the front structure (β₁ is the ratio of gas-to-magnetic pressure before the shock front). In particular, in the case of a perpendicular shock recorded on August 24, 2013 (the angle between the magnetic field direction and the normal to the front θ_Bn ≈ 85°), an IS with a small Mach number (М_A ≈ 1.4) and small β₁ ≈ 0.2 is shown that the interactions of reflected ions with inflowing solar wind may result in the collisionless heating of ions in front of and behind it. The case of the oblique (θ_Bn = 63°) IS on April 19, 2014 with a small Mach number (М ^A ≈ 1.2) and small β₁ ≈ 0.5 has been investigated. It has been found that, before the front, there is a sequence of trains of magnetosonic waves, the amplitude of which decreases to zero upon increasing their distance from the front. The mechanism of their formation is associated with the development of instability caused by the ions reflected from the front.     

化学非平衡效应对返回舱再入气动力特性的影响

高空高马赫数条件下,化学非平衡效应将对飞行器气动特性产生影响,影响飞行器气动布局优化和飞行弹道设计。文章通过三维化学非平衡流动求解程序,针对再入返回器开展数值研究与机理分析,通过对比完全气体模型和化学非平衡气体模型获得的气动力参数,揭示化学非平衡效应对流场结构和气动力特性的影响和规律。结果表明,对Apollo的气动力计算结果验证了模型和计算方法;化学非平衡效应影响下,激波层内化学反应消耗大量能量,致使激波脱体距离减小,气体压缩性增强;典型状态高度为70 km,Ma=30条件下,化学非平衡效应导致返回器升力系数增大约6%、阻力系数增大约1.3%～3.3%、升阻比增大3%左右、俯仰力矩系数增大,从而使配平攻角减小约2.5＆#176;;通过机理分析,发现化学非平衡效应影响下表面压力系数发生变化的原因是飞行器周围激波形状及驻点压力改变,表现为气体沿流线经激波层、压缩区和膨胀区的历程变化;对于钝体形状的返回器,迎风面前体压力系数增加和后体压力系数降低,造成轴向力和法向力系数增大。     

Estimation of the current density and analysis of the geometry of the current system surrounding the Earth

The results of an investigation of the distribution of plasma pressure, pressure gradients, and magnetic field near the equatorial plane in the plasma ring surrounding the Earth under magneto-quiet conditions are presented. Observational data obtained during the international THEMIS mission are used. The picture of the distribution of transverse-current density near the equatorial plane was obtained under assumption of observing the magnetostatic balance condition at geocentric distances from 6 to 12R _E. In estimating the integral transverse current it was accepted that in daytime sector the magnetic-field minima on magnetic field lines are not localized in the equatorial plane. Estimates of the integral transverse current were obtained, which demonstrate the possibility of closing nighttime transverse currents at geocentric distances of up to ～12R _E inside the magnetosphere, which form a high-latitudinal continuation of the ring current.