激波驱动的气固两相流的动态压力测量

利用水平圆柱形激波管对激波驱动的可压缩性气固两相流进行了试验研究.利用压电式压力传感器、电荷放大器、示波器及计算机组成的压力信号测试系统, 对激波与颗粒作用前后的气相参数进行测量及分析. 试验中测得了激波在管中的传播速度, 波后气流的压力, 反射激波、透射激波的压力和速度等. 分别考察颗粒、装载比、驱动气源以及入射激波马赫数等因素的差异对气相参数的影响.试验结果表明: 激波与颗粒群相互作用时, 会产生反射激波和透射激波,其强度与驱动气源、颗粒大小、颗粒装载比等参数有关;激波衰减率随着装载比、马赫数的增大而减小. 研究指出,在颗粒群被激波加速的初始阶段, 颗粒间的弹性碰撞起着重要的作用.      

爆轰驱动高焓激波膨胀管性能研究

介绍了中国科学院高温气体动力学实验室JF-16爆轰驱动高焓激波膨胀管的研制进展及其性能测试结果. 性能研究主要测量了入射激波速度和压力曲线. 根据入射激波速度,应用Mirels的黏性激波管理论计算了超高速试验气流的运动速度,然后应用Gaseq软件计算了试验气流的热力学参数. 研究结果表明:在16.35\,m长的JF-16激波膨胀管中获得了流速7\,000\,m/s以上的稳定试验气流,试验时间为50$\sim$100$\mu$s, 试验气流总焓30\,MJ/kg左右.      

秦岭公路隧道2号竖井地应力与岩爆分析

利用水平圆柱形激波管对激波驱动的可压缩性气固两相流进行了试验研究. 利用压电式压力传感器、电荷放大器、示波器及计算机组成的压力信号测试系统, 对激波 与颗粒作用前后的气相参数进行测量及分析. 试验中测得了激波在管中的传播速 度, 波后气流的压力, 反射激波、透射激波的压力和速度等. 分别考察颗粒、装载 比、驱动气源以及入射激波马赫数等因素的差异对气相参数的影响. 试验结果表明: 激波与颗粒群相互作用时, 会产生反射激波和透射激波, 其强度与驱动气源、颗粒大小、颗粒装载比等参数有关; 激波衰减率随着装载比、马赫数的增大而减小. 研究指出, 在颗粒群被激波加速的初始阶段, 颗粒间的弹性碰撞起着重要的作用.     

测量低密度气流速度和运动激波马赫数的火花放电法

本文在讨论了各种测量气流速度的方法,特别是Miller的放电法基础上,提出了一种测量低密度流场气流速度和运动激波马赫数的改进方法。本方法采用双曝光技术,有助于提高测量精度;在结构上和电路上的改进,克服了低密度流场中漏电问题。该方法适用于气流速度1200m/s以上,密度约0.05kg/cm~3的高速瞬态流场中的气流速度和运动激波马赫数的测量。     

单次脉冲爆轰发动机工作过程的数值模拟

通过求解14组分和19个基元反应的CH4-O2-N2详细化学反应动力学机理的二维轴对称Navier-Stokes方程,对爆轰管内半球形高温火团引发的爆轰过程和爆轰波进入外流场后的全流场分布进行数值模拟。模拟结果显示了爆轰波在管内的成长、稳定传播、进入尾喷管后衰减为激波和进入外流场的全过程,以及爆轰管出口端附近区域的复杂涡与激波的相互作用。对轴线上的压力分布和封闭端的压力等进行了讨论,为脉冲爆轰发动机的开发研制提供参考信息。     

含灰气体激波结构的实验观察

利用激波管实验对含灰气体激波结构作了研究。在灰粒负荷率低于0.4及激波马赫数低于1.5的范围内测量了压力、激波速度及灰粒浓度。激波后冻结及平衡压力可用R-H关系很好地加以计算,但松弛区长度则较基于球定常运动的计算值短得多。实验中观察到耗散激波结构并发现灰尘的存在减少气流中的压力脉动。激波传播速度与基于“等效气体”模型计算值相符。     

多障碍物通道中激波诱导气相爆轰的数值研究

应用数值模拟方法，研究了直通道中激波经过多块矩形障碍物时诱导 H2/O2混合气体起爆的物理机制. 研究表明：在前导激波强度不足以诱导波后气 体直接起爆的条件下，经过激波压缩的可燃气体也可能在远离激波的障碍物之间的凹槽部位 起爆；障碍物表面产生的压缩波、膨胀波和气流滑移面对可燃气体的起爆、爆轰波的形成和 传播过程有重要的影响；添加不同稀释比的氮气可以影响爆轰波后流场的温度分布；增加障 碍物的间距可以改变可燃气起爆位置.     

基于多层分块算法的激波干扰流场预测

激波-激波干扰流场预测是超声速乃至高超声速流动中最具挑战性的问题之一. 特别地, 第IV类激波干扰由于其在壁面驻点附近产生极高的热载荷而备受关注. 本文针对圆柱诱导的弓形激波和入射斜激波的干扰问题, 分别基于量热完全气体模型和考虑振动激发的热完全气体模型, 数值求解有黏二维可压缩NS方程, 分析了高温气体效应对激波干扰流场结构, 以及第IV类激波干扰流场状态参数的影响. 接着, 本文基于一种具有广义可分离特性的遗传算法 (多层分块算法), 给出能够预测不同气体模型下第IV类激波干扰流场三波点的坐标位置、超声速射流的几何形状等特征性几何结构的数学模型, 进一步获得高温气体效应对激波干扰类型转变准则影响的定量化评估. 激波干扰类型转变准则面上的多组临界工况的激波干扰流场结构以及壁面压力和壁面热流分布的对比结果表明, 不同气体模型下的激波干扰类型和流场结构差异较为显著, 获得的定量化预测模型对工程中气动热环境的预测具有一定的参考价值.      

瓦斯/空气预混气体爆燃流场测试系统多参数耦合同步控制实验方法

为了更精确地获得爆炸激波管内瓦斯/空气预混气体爆燃过程中，激波形成过程、压力和火焰传播速度以及火焰与惰性阻燃剂相互作用的流场演化图像。通过分析激波管测试系统中多个目标的时间响应特征及控制方式，利用超高速相机、光电倍增管、时间延时器、固态继电器、电荷放大器和数据采集系统等设备，设计实验方案，分别对激波管中瓦斯/空气预混气体爆燃高压点火系统的响应时间和惰性介质阻燃剂喷射系统的响应时间进行测试。实验结果表明电火花点火的响应时间为微秒量级，而阻燃剂喷射系统的响应时间为毫秒量级，以响应时间为依据，通过设置精确的延迟时间实现多目标同步控制，为完成激波管内瓦斯/空气预混气体爆燃过程的微观流场显示奠定基础。     

激波喷出过程和在林带中的传播

运用激波管技术研究了激波从管口喷出和在林带中传播这两个基本问题。给出了三方面的结果 :揭示了激波从管口喷出时的复杂流场 ,显示了主激波弯曲和衰减 ,二次激波的形成和合拢 ,涡环的长大和发展 ,以及涡环前缘出现正激波等基本物理现象 ;显示了激波在林带中的传播过程 ,取得了激波遇林地的反射 ,马赫杆形成 ,激波与林冠的相遇 ,林冠对涡环的阻滞效应等纹影照片 ;沿激波在林地的传播方向测量了地面压力 ,证实林带有明显的消波效应。     

Reconstruction of velocity fields from wall pressure measurements in a shock wave/turbulent boundary layer interaction

We present here experimental results in a shock wave/turbulent boundary layer interaction at Mach number of 2.3 impinged by an oblique shock wave, with a deflection angle of 9.5°, as installed in the supersonic wind tunnel of the IUSTI laboratory, France. For such a shock intensity, strong unsteadiness are developing inside the separated zone involving very low frequencies associated with reflected shock motions.The present work consists in simultaneous PIV velocity fields and unsteady wall pressure measurements. The wall pressure and PIV measurements were used to characterize the pressure distribution at the wall in an axial direction, and the flow field associated. These results give access for the first time to the spatial-time correlation between wall pressure and velocity in a shock wave turbulent boundary layer interaction and show the feasibility of such coupling techniques in compressible flows. Linear Stochastic Estimation (LSE) coupled with Proper Orthogonal Decomposition (POD) has been applied to these measurements, and first results are presented here, showing the ability of these techniques to reproduce both the unsteady breathing of the recirculating bubble at low frequency and the Kelvin–Helmholtz instabilities developing at moderate frequency.     

Interaction of a shock with a sphere suspended in a vertical shock tube

Shock wave interaction with a sphere is one of the benchmark tests in shock dynamics. However, unlike wind tunnel experiments, unsteady drag force on a sphere installed in a shock tube have not been measured quantitatively. This paper presents an experimental and numerical study of the unsteady drag force acting on a 80 mm diameter sphere which was vertically suspended in a 300 mm x 300 mm vertical shock tube and loaded with a planar shock wave of M _s = 1.22 in air. The drag force history on the sphere was measured by an accelerometer installed in it. Accelerometer output signals were subjected to deconvolution data processing, producing a drag history comparable to that obtained by solving numerically the Navier-Stokes equations. A good agreement was obtained between the measured and computed drag force histories. In order to interpret the interaction of shock wave over the sphere, high speed video recordings and double exposure holographic interferometric observations were also conducted. It was found that the maximum drag force appeared not at the time instant when the shock arrived at the equator of the sphere, but at some earlier time before the transition of the reflected shock wave from regular to Mach reflection took place. A negative value of the drag force was observed, even though for a very short duration of time, when the Mach stem of the transmitted shock wave relfected and focused at the rear stagnation point of the sphere.Received: 31 March 2003, Accepted: 7 July 2003, Published online: 2 September 2003     

Application of fast-responding pressure-sensitive paint to a hemispherical dome in unsteady transonic flow

The current work focuses on the development and application of fast-responding polymer/ceramic pressure-sensitive paint (PSP) as an advanced surface pressure measurement technique for unsteady flow fields in large-scale wind tunnels. To demonstrate the unsteady PSP technique, the unsteady surface pressure distribution over a hemispherical dome placed in the United States Air Force Research Laboratory’s Trisonic Gasdynamics Facility (TGF) was studied by phase-locking to the characteristic frequency in the flow caused by an unsteady separated shear layer shed from the dome. The wind tunnel was operated at stagnation pressures of 23.92 and 71.84 kPa, with the test section flow at Mach 0.6. Under the two operating conditions, the predominant shear layer frequency was measured to be 272 and 400 Hz, respectively. The quasi-periodic shear layer frequency enabled a phase-averaged method to be employed for capturing the unsteady shock motion on the hemisphere. Unsteady pressure data resulting from this technique are shown to correlate well with measurements acquired by conventional measurement techniques. Measurement uncertainty in the phase-averaging technique will be discussed. To address measurement uncertainties from temperature sensitivity and model movement, a new implementation of an AC-coupled data representation is offered.     

Unsteady flow around models in an electromagnetic shock tube

Results of experimental studies of the unsteady flow around models of a stream moving behind the front of a very strong shock wave excited in an electromagnetic shock tube are presented. The flow establishment time in the stagnation-point region of blunt bodies is found.     

Time-resolved stereo PIV measurements of shock–boundary layer interaction on a supercritical airfoil

Time-resolved stereo particle-image velocimetry (TR-SPIV) and unsteady pressure measurements are used to analyze the unsteady flow over a supercritical DRA-2303 airfoil in transonic flow. The dynamic shock wave–boundary layer interaction is one of the most essential features of this unsteady flow causing a distinct oscillation of the flow field. Results from wind-tunnel experiments with a variation of the freestream Mach number at Reynolds numbers ranging from 2.55 to 2.79 × 10⁶ are analyzed regarding the origin and nature of the unsteady shock–boundary layer interaction. Therefore, the TR-SPIV results are analyzed for three buffet flows. One flow exhibits a sinusoidal streamwise oscillation of the shock wave only due to an acoustic feedback loop formed by the shock wave and the trailing-edge noise. The other two buffet flows have been intentionally influenced by an artificial acoustic source installed downstream of the test section to investigate the behavior of the interaction to upstream-propagating disturbances generated by a defined source of noise. The results show that such upstream-propagating disturbances could be identified to be responsible for the upstream displacement of the shock wave and that the feedback loop is formed by a pulsating separation of the boundary layer dependent on the shock position and the sound pressure level at the shock position. Thereby, the pulsation of the separation could be determined to be a reaction to the shock motion and not vice versa.     

带喷流激波针流动特性实验研究

采用动态测力、动态测压和纹影等风洞实验技术,对加装了带喷流激波针的钝头体的绕流特性、稳定和非稳模态的形成条件和机理进行了研究.结果表明:带喷流激波针流场存在稳态和非稳态两种模态,超声速喷流的压比大于临界压比时流动处于稳定模态,反之则为非稳模态;增大激波针长度可减小钝头体阻力,但达到一定长度后,进一步减阻的效果不再显著;增大喷流压比能够有效减弱再附激波强度,有利于缓解单独激波针的肩部热斑问题;非稳模态下波系自激振荡对再附激波在钝头体表面所围的区域影响剧烈,振荡是周期性的,且存在确定的主导频率,主导频率随喷流压力比增大而减小;自激振荡的产生是由于喷流出口周围的反压在喷流压比小于临界压比时无法获得持续的平衡而导致.      

Characteristics of an annular vertical diaphragmless shock tube

Abstract. This paper reports on the characteristics of a compact vertical diaphragmless shock tube, which was constructed and tested in the Shock Wave Research Center to study experimentally the behavior of toroidal shock waves. It is 1.15 m in height and has a self-sustained co-axial vertical structure consisting of a 100 mm i.d. outer tube and an 80 mm o.d. inner tube. To create a ring shaped shock wave between the inner and outer tubes, a rubber sheet is inserted to separate a high pressure driver gas from a test gas, which is bulged with auxiliary high pressure helium from the behind. When the rubber membrane is contracted by the sudden release of the auxiliary gas so as to break the seal, shock waves are formed. Special design features of the shock tube are described and their role in producing repeatable shock waves is discussed. Its special opening characteristics make possible the production of annular shaped shock waves that are unlikely met with a conventional tube that uses rupturing diaphragms. Performance of the shock tube is evaluated in terms of the shock wave Mach numbers and the measured flow properties. It eventually showed a higher degree of repeatability and the scatter in the shock wave Mach numbers Ms was found to be 0.2% for Ms ranging from 1.1 to 1.8. The shock wave Mach number so far measured agreed very well with the simple shock tube theory. Received 3 February 1999 / Accepted 6 April 2000     

The formation of a secondary shock wave behind a shock wave diffracting at a convex corner

This paper deals with the formation of a secondary shock wave behind the shock wave diffracting at a two-dimensional convex corner for incident shock Mach numbers ranging from 1.03 to 1.74 in air. Experiments were carried out using a 60 mm 150 mm shock tube equipped with holographic interferometry. The threshold incident shock wave Mach number () at which a secondary shock wave appeared was found to be = 1.32 at an 81° corner and = 1.33 at a 120° corner. These secondary shock waves are formed due to the existence of a locally supersonic flow behind the diffracting shock wave. Behind the diffracting shock wave, the subsonic flow is accelerated and eventually becomes locally supersonic. A simple unsteady flow analysis revealed that for gases with specific heats ratio the threshold shock wave Mach number was = 1.346. When the value of is less than this, the vortex is formed at the corner without any discontinuous waves accompanying above the slip line. The viscosity was found to be less effective on the threshold of the secondary shock wave, although it attenuated the pressure jump at the secondary shock wave. This is well understood by the consideration of the effect of the wall friction in one-dimensional duct flows. In order to interpret the experimental results a numerical simulation using a shock adaptive unstructured grid Eulerian solver was also carried out. Received 1 May 1996 / Accepted 12 September 1996     

Study of unsteady flow past bodies behind shock waves

Several theoretical and experimental studies have been devoted to the problem of the nonstationary action of the stream behind a shock wave on bodies of varied shape. In particular, in [1], the pressure and density are calculated for flow about bodies of the more typical shapes in the initial stage of the process. The basic relations which accompany the interaction of shock waves are considered in [2, 3]. The analysis of the phenomena of diffraction of shock waves on the sphere, cylinder, and cone is presented in [4]. Problems of unsteady flow about a wing are examined in [5, 6]. A detailed review of the foreign studies on unsteady flow is given in [7]. Of great practical interest is the question of the time for flow formation and the magnitudes of the unsteady loads during this period. Experimental investigations have been made recently [8, 9] in which some criteria are presented for estimating the bow shock formation time for supersonic flow about the sphere and cylinder with flat blunting. However the question of the formation time of the stationary pressure on the body surface is not referred to in these studies and no relationship is shown between the transient position of the reflected wave and the corresponding unsteady pressure on the surface. Moreover, in [8] the dimensionless time criterion is determined very approximately, independently of the Mach number of the shock wave. The present study was undertaken with the object of determining the basic criteria which characterize unsteady flow about bodies behind a plane shock wave which has time-independent parameters, and clarification of the shock wave reflected from the body and the pressure on the surface of the body during the transient period. The most typical body shapes were studied: 1) a cylinder with flat face aligned with the stream; 2) a spherically-blunted cylinder; and 3) a cylinder transverse to the stream. The experiments were conducted in a conventional shock tube using the single-diaphragm scheme. The measurements of the pressure on the models and the velocity of the incident shock wave were made using the technique analogous to that of [10, 11]. A highspeed movie camera was used to record the pattern of the wave diffraction on the body. The Mach number of the incident shock wave varied in the range from M=1.5 to M≈6.0, which corresponded to a range of Mach numbers M_∞ of the stream behind the shock wave from 0.6 to 2.1. The calculations of the required gas dynamic parameters for high temperatures were made with account for equilibrium dissociation of the air on the basis of the data of [10, 12, 13]. The magnitude of the relative maximal shock wave standoff Δ at the stagnation point obtained in the present experiments was compared with the values of Δ from other studies. In the case of the flat-blunted cylinder it was in good agreement with the results of [8–14], and in the case of the spherically-blunted cylinder and the transverse cylinder it was in agreement with the results of [15].     

Attenuation of shock waves propagating in polyurethane foams

Shock wave attenuation in polyurethane foams is investigated experimentally and numerically. This study is a part of research project regarding shock propagation in polyurethane foams with high-porosities = 0.951 ~ 0.977 and low densities of ρc = 27.6 ~55.8 kg/m³. Sixty Millimeter long cylindrical foams with various cell numbers and foam insertion condition were installed in a horizontal shock tube of 50 mm i.d. and 5.4 mm in length. Results of pressure measurements in air/foam combination are compared with CFD simulation solving the one-dimensional Euler equations. In the case of a foam B fixed on shock tube wall, pressures at the shock tube end wall increases relatively slowly comparing to non-fixed foam, free to move and a foam A fixed on shock tube wall. This implies that elastic inertia hardly contributes to pressure build up. Pressures behind a foam C fixed on shock tube wall decrease indicating that shock wave is degenerated into compression wave. Dimensionless impulse and attenuation factor decrease as the initial cell number increases. The momentum loss varies depending on cell structure and cell number.