Classification of shock wave reflections from a wedge. Part 2: Experimental and numerical simulations of different types of Mach reflections

Classification of various types of the reflections of a shock wave over straight wedge is supposed. The idea about entire reflection phenomenon as a result of interaction of two processes—the shock wave refection process and the flow deflection process—serves as a basis for the classification. To recognize the types of reflection, changes in the shapes of the reflected wave, Mach stem and contact surface are taken into account. The boundaries and domains of existence for various types of reflection are reported. New names for some types of reflection are proposed.     

Effect of multiple ion reflections on the structure of an ion-sound shock wave

It is shown that multiple ion reflection, arising as a result of collisional dissipation, from a shock front can produce an ion-sound shock wave with an arbitrarily large Mach number. For an exponentially small number of reflected ions, the ion-sound shock wave “degenerates” into a collisionless quasishock wave. The comparative role of viscosity and sound dispersion with different initial nonisothermality of the plasma is discussed. Zh. Tekh. Fiz. 69, 52–56 (December 1999)     

Impact of incident Mach wave on supersonic boundary layer

Results of an experimental study of the excitation of high-intensity disturbances by a weak external shock wave in laminar boundary layer on flat-plate models with sharp and blunted leading edges at М = 2.5 are reported. The field of disturbances produced by a 2D sticker in turbulent boundary layer on the wall of wind-tunnel test section in the free stream is shown to have the form of an N-wave. It is found that, on the blunted plate, the intensity of pulsations produced by weak external shock waves in boundary layer several times exceeds the intensity of pulsations produced in boundary layer on the model with a sharp leading edge.     

Classification of shock wave reflections from a wedge. Part 1: Boundaries and domains of existence for different types of reflections

Classification of various types of the reflections of a shock wave over straight wedge is supposed. The idea about entire reflection phenomenon as a result of interaction of two processes—the shock wave refection process and the flow deflection process—serves as a basis for the classification. To recognize the types of reflection, changes in the shapes of the reflected wave, Mach stem and contact surface are taken into account. The boundaries and domains of existence for various types of reflection are reported. New names for some types of reflection are proposed.     

Study of cerium phase transitions in shock wave experiments

Cerium has a complex phase diagram that is explained by the presence of structural phase transitions. Experiments to measure the sound velocities in cerium by two methods were carried out to determine the onset of cerium melting on the Hugoniot. In the pressure range 4–37 GPa, the sound velocity in cerium samples was measured by the counter release method using manganin-based piezoresistive gauges. In the pressure range 35–140 GPa, the sound velocity in cerium was measured by the overtaking release method using carbogal and tetrachloromethane indicator liquids. The samples were loaded with plane shock wave generators using powerful explosive charges. The onset of cerium melting on the Hugoniot at a pressure of about 13 GPa has been ascertained from the measured elastic longitudinal and bulk sound velocities.     

Autapse-induced target wave,spiral wave in regular network of neurons

Autapse is a type of synapse that connects axon and dendrites of the same neuron, and the effect is often detected by close-loop feedback in axonal action potentials to the owned dendritic tree. An artificial autapse was introduced into the Hindmarsh-Rose neuron model, and a regular network was designed to detect the regular pattern formation induced by autapse. It was found that target wave emerged in the network even when only a single autapse was considered. By increasing the(autapse density) number of neurons with autapse, for example, a regular area(2×2, 3×3, 4×4, 5×5 neurons) under autapse induced target wave by selecting the feedback gain and time-delay in autapse. Spiral waves were also observed under optimized feedback gain and time delay in autapses because of coherence-like resonance in the network induced by some electric autapses connected to some neurons. This confirmed that the electric autapse has a critical role in exciting and regulating the collective behaviors of neurons by generating stable regular waves(target waves, spiral waves) in the network. The wave length of the induced travelling wave(target wave, spiral wave), because of local effect of autapse, was also calculated to understand the waveprofile in the network of neurons.     

Effect of external power supply to a shock layer on the shock wave structure

A physical model that describes the structure of a 1D shock wave in a gas containing a moving heat source is put forward. A stationary equation for the profile of a shock wave in a gas with an arbitrary-shape heat source that is at rest relative to this wave is derived. Analytical solutions to this equation make it possible to analyze the flow pattern in the case of external power supply.     

Underwater Mach wave radiation from impact pile driving: theory and observation

The underwater noise from impact pile driving is studied using a finite element model for the sound generation and parabolic equation model for propagation. Results are compared with measurements using a vertical line array deployed at a marine construction site in Puget Sound. It is shown that the dominant underwater noise from impact driving is from the Mach wave associated with the radial expansion of the pile that propagates down the pile after impact at supersonic speed. The predictions of vertical arrival angle associated with the Mach cone, peak pressure level as function of depth, and dominant features of the pressure time series compare well with corresponding field observations.     

Impact of the external energy supply to the shock layer region on the shock wave parameters

A system of equations describing supersonic gas flow in the presence of a heat source near the shock front is obtained. Relations between the gas parameters in disturbed and undisturbed regions, which generalize the classical Hugoniot-Rankine relations, are derived. Formulas for calculation of the flow parameters in the presence of an energy supply to the shock layer region are presented. It is demonstrated that there exists a critical intensity of energy supply at which the system of equations of the conservation laws for the gas parameters on both sides of the shock layer possesses no stationary solution.     

Study of the fine structure of charged particles flows in the bow shock wave

The paper presents a study of the bow shock wave based on the data from an energy ion spectrometer installed on board the satellite Prognoz 8. In the experiment both the vector of total ion flux and the ion energy spectra were measured, the energy range being from 0·16 to 4·2 keV with the time resolution of about 1 sec. The paper describes a statistical data processing of basic parameters from several consecutive shock wave crossings, following each other in short time intervals. The results, compared with the behaviour of other parameters characteristic for this region, enable to draw a qualitative conclusion about the processes responsible for fast thermalization in the region after the shock wave front.Presented at the Fifth Scientific Assembly of IAGA in Prague, 1985.We would like to express our thanks to Dr. Russel who kindly supplied the data from ISEE-3 mag. field measurements. We are grateful to Dr. Vaisberg for many valuable suggestions concerning data processing and interpretation.     

部分道路关闭引起的交通激波特性研究

本文根据实际交通中经常遇到的交通事故或部分道路施工等情况, 建立了部分道路关闭的交通流模型. 采用平均场理论分析和确定性NS元胞自动机规则分别对模型进行解析和数值模拟, 结果表明, 系统存在三种稳定的物理状态:低密度相、激波相和高密度相, 并找到了系统发生相变的临界密度. 理论分析和数值模拟能很好地符合.     

激光引致激波演化数值研究

在高重复频率激光推进的研究中,激波的合并是发生在激波演化后期的,同时由于脉冲间隔短,脉冲宽度对流场演化的影响也需要详细研究。考虑了激光辐照过程对流场演化的影响,通过数值计算对激波演化特性进行了研究。结果表明,初期波阵面的椭球形状逐渐转化为一个球形,球心与击穿点的距离随时间逐渐减小并最终趋于稳定。基于激波合并的应用,当激波马赫数在1~2之间时,给出了激波波阵面半径随时间的变化规律,以及激波高压区长度和波峰压强随激波波阵面半径变化规律的经验公式。     

回旋行波放大器输出端反射对其稳定性的影响

 基于回旋行波放大器的线性理论和反射边界条件,建立了渐变输出端存在反射时回旋行波放大器模型,分析了TE₀₁圆电模基波回旋行波放大器输出端反射对其增益、返波起振长度、返波起振电流和返波起振频率的影响。结果表明,随着反射增强,线性增益降低,返波起振长度和起振电流减小,返波起振频率的变化较小;反射增强将在一定程度内影响放大器的稳定性。     

回旋行波放大器输出端反射对其稳定性的影响

基于回旋行波放大器的线性理论和反射边界条件,建立了渐变输出端存在反射时回旋行波放大器模型,分析了TE01圆电模基波回旋行波放大器输出端反射对其增益、返波起振长度、返波起振电流和返波起振频率的影响。结果表明,随着反射增强,线性增益降低,返波起振长度和起振电流减小,返波起振频率的变化较小;反射增强将在一定程度内影响放大器的稳定性。