Numerical solution of the problem of shock tube flow development with transverse diaphragm withdrawal

The time-dependent two-dimensional perfect gas flow which occurs in a channel with a constant cross-section as a result of the transverse withdrawal of a diaphragm to provide an initial pressure difference is studied numerically using a second-order-accurate method. The evolution and interaction of the main wave disturbances is analyzed in detail on the basis of the solutions obtained. Volgograd. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.2, pp. 147–154, March–April, 1994.     

激波管聚酯膜片变形过程分析

使用聚酯薄膜作为激波管膜片,通过施加不同压力的激波管实验,获得了膜片厚度及多张膜片的组合方式对膜片所能承受最大压力的影响。利用高速相机对激波管膜片从开始变形到破坏的全过程进行拍摄,使用三维DIC软件获得膜片在变形过程中的位移场。实验发现了膜片会出现圆弧反翘并快速破坏的特别现象,并以此为特征将变形过程分为2个阶段。给出任意厚度膜片第1阶段圆弧变形的数学规律及第2阶段圆弧反翘的形状特征,以及全过程中膜片厚度变化的数学规律。     

Contact zone during the noninstantaneous opening of a diaphragm in a shock tube

The structure and nature of motion of the contact zone during the noninstantaneous opening of a diaphragm in a shock tube are analyzed for the case of Re and equal adiabatic indices of the propelling and propelled gases. It is shown that the temperature profiles in the contact zone are self-similar, and an expression is obtained for the trajectory of the interface of the gases in the contact zone.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 159–161, November–December, 1976.     

Density distribution in rarefaction wave produced by rupture of diaphragm in a shock tube

The effect of the finite time of opening of the diaphragm in a shock tube on the formation of the rarefaction wave was investigated experimentally. The density distribution in the rarefaction wave was measured in relation to the coordinate and time and was compared with the known self-similar solution.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 2, pp. 130–131, March–April, 1972.     

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.     

Hypersonic flow structure in a large-scale multi-diaphragm shock tube

The results of an experimental and theoretical study of the structure of the shock wave and the gas flow behind it are presented, together with data on the duration of the high-temperature working flows, the contact zones and the regions of uniform cold-flow parameters in the large (channel diameter 0.5 m, length 200 m, gas tank diameter 3 m, length 23 m) interchangeable-nozzle shock tube of the Central Scientific Research Institute of Mechanical Engineering.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 158–165, September–October, 1993.     

Nonideal effects behind reflected shock waves in a high-pressure shock tube

Abstract. Shock tubes often experience temperature and pressure nonuniformities behind the reflected shock wave that cannot be neglected in chemical kinetics experiments. Because of increased viscous effects, smaller tube diameters, and nonideal shock formation, the reflected-shock nonidealities tend to be greater in higher-pressure shock tubes. Since the increase in test temperature () is the most significant parameter for chemical kinetics, experiments were performed to characterize in the Stanford High Pressure Shock Tube using infrared emission from a known amount of CO in argon. From the measured change in vibrationally equilibrated CO emission with time, the corresponding ddt (or for a known time interval) of the mixture was inferred assuming an isentropic relationship between post-shock temperature and pressure changes. For a range of representative conditions in argon (24–530 atm, 1275–1900 K), the test temperature 2 cm from the endwall increased 3–8 K after 100 s and 15–40 K after 500 s, depending on the initial conditions. Separate pressure measurements using a shielded piezoelectric transducer confirmed the isentropic assumption. An analytical model of the reflected-shock gas dynamics was also developed, and the calculated 's agree well with those obtained from experiment. The analytical model was used to estimate the effects of temperature and pressure nonuniformities on typical chemical kinetics measurements. When the kinetics are fast (s), the temperature increase is typically negligible, although some correction is suggested for kinetics experiments lasting longer than 500 s. The temperature increase, however, has a negligible impact on the measured laser absorption profiles of OH (306 nm) and CH (216 nm), validating the use of a constant absorption coefficient. Infrared emission experiments are more sensitive to temperature and density changes, so nonuniformities should be taken into account when interpreting ir-emission data. Received 25 April 2000 / Accepted 8 September 2000     

Critical effects resulting from reaction-induced changes in viscosity

Chemical reactions induce changes in viscosity, this effect being quite pronounced in the case of polymerization processes. The fact that the coefficient of viscosity changes as the degree of chemical advancement increases gives rise to specific hydrodynamic effects in a flowing liquid. Some of these effects are discussed in the present paper.Translated from Zhurnal Prikladnoi Mekhaniki i Technicheskoi Fiziki, No. 2, pp. 168–172, March–April, 1975.The author wishes to thank V. G. Abramov and A. M. Stolin for valuable advice and suggestions.     

Heat flux measurement over a cone in a shock tube flow

This paper is the part 2 of our previous thin film heat transfer measurements. In the first report we measured time variations of heat flux over a cylinder placed in a shock tube flow and compared experimental results with CFD results, Saito et al. (Shock Waves 14:327–333, 2004). We report a result of heat transfer measurements over an 86° apex angle cone surface impinged by a Ms = 2.38 shock wave in air with distributed thin film transfer gauges along cone surface and its comparison with results of numerical simulations. We performed double exposure holographic interferometric observation, and also from the heat transfer measurement and numerical simulation, confirmed the presence of delayed transition from regular to Mach reflection over the cone. The numerical estimation of delayed transition distance from the apex agreed very well with experimental one.      

高温激波管化学非平衡流动数值模拟研究

为了预测氢氧定容燃烧驱动的高温激波管性能,需要准确分析激波管非定常化学非平衡流动过程.本文在破膜前的驱动段定容燃烧以及破膜后的化学非平衡流动数值模拟中,引入双时间步长方法,发展高温激波管化学非平衡流动数值模拟方法,该方法在时间上具有二阶精度.计算结果与目前存在的激波管流动解析解以及零维化学反应系统的数值解进行了比较,吻合较好.对于典型高温激波管状态,采用有限体积方法离散准一维流动Euler控制方程,并通过将流动过程和化学反应动力学过程耦合求解,获得了激波管内部的化学非平衡流动特征.     

Near-wall imaging using toluene-based planar laser-induced fluorescence in shock tube flow

A quantitative thermometry technique, based on planar laser-induced fluorescence (PLIF), was applied to image temperature fields immediately next to walls in shock tube flows. Two types of near-wall flows were considered: the side wall thermal boundary layer behind an incident shock wave, and the end wall thermal layer behind a reflected shock wave. These thin layers are imaged with high spatial resolution (15μm/pixel) in conjunction with fused silica walls and near-UV bandpass filters to accurately measure fluorescence signal levels with minimal interferences from scatter and reflection at the wall surface. Nitrogen, hydrogen or argon gas were premixed with 1–12% toluene, the LIF tracer, and tested under various shock flow conditions. The measured pressures and temperatures ranged between 0.01 and 0.8 bar and 293 and 600 K, respectively. Temperature field measurements were found to be in good agreement with theoretical values calculated using 2-D laminar boundary layer and 1-D heat diffusion equations, respectively. In addition, PLIF images were taken at various time delays behind incident and reflected shock waves to observe the development of the side wall and end wall layers, respectively. The demonstrated diagnostic strategy can be used to accurately measure temperature to about 60 μm from the wall.     

Microsize and initial pressure effects on shock wave propagation in a tube

In this paper, the shock wave propagation in a channel with a micrometric hydraulic diameter is numerically simulated for an initial Mach number \(M_{s}=2.61\) . The obtained values of the Mach number along the tube are compared to experimental and numerical data given in the literature. The microscale effects on the flow behavior, such as shock wave attenuation and pressure increase behind the shock wave, are amplified by further reducing the scaling ratio (or Reynolds number) of the flow. This reduction is obtained by either decreasing the hydraulic diameter \(D_\mathrm{H}\) or the initial driven gas pressure \(P_1\) . Under these conditions, the flow behavior changes drastically.     

The interaction between shock waves and foam in a shock tube

An experimental study and a numerical simulation were conducted to investigate the mechanical and thermodynamic processes involved in the interaction between shock waves and low density foam. The experiment was done in a stainless shock tube (80 mm in inner diameter, 10 mm in wall thickness and 5 360 mm in length). The velocities of the incident and reflected compression waves in the foam were measured by using piezo-ceramic pressure sensors. The end-wall peak pressure behind the reflected wave in the foam was measured by using a crystal piezoelectric sensor. It is suggested that the high end-wall pressure may be caused by a rapid contact between the foam and the end-wall surface. Both open-cell and closed-cell foams with different length and density were tested. Through comparing the numerical and experimental end-wall pressure, the permeability coefficients α and β are quantitatively determined.     

A numerical simulation of boundary layer effects in a shock tube

A numerical scheme is used to investigate boundary layer effects in a shock tube. The method consists of a mixture of Roe's approximate Riemann solver and central differences for the convective fluxes and central differences for the viscous fluxes and is implicit in one space dimension. Comparisons are made with experimental data and with solutions obtained via boundary layer equations. Examination of the calculated flow field explains the observed behaviour and highlights the approximate nature of boundary layer solutions.     

环形激波聚焦流场特性的数值研究

针对环形激波聚焦过程产生的高温、高压特性,采用间断有限元方法模拟了环形激波在同轴圆柱形激波管内的聚焦流场特性。计算结果表明,采用间断有限元方法能够有效地捕捉激波聚焦过程形成的二次激波、涡环、三波交点和球面双马赫反射等主要流动特征。此外,通过改变环形管道内外半径对聚焦流场进行模拟发现,环形管道外径对中心轴线上聚焦峰值压力的大小和位置影响较小,环形管道内径对中心轴线上聚焦峰值压力的大小和位置影响较大。计算结果可以为工程应用提供一定的理论指导。