Suppressing a Laminar Flow Separation Zone by Spark Discharge at Mach Number M = 1.43

The influence of flow perturbations generated by an electric discharge on the region of interaction between a shock wave and laminar boundary layer in the flow on a flat plate at a Mach number of M = 1.43 has been experimentally studied. The oblique shock wave generated by a wedge mounted above the plate induced separation of the flow, while perturbations in the flow were introduced by a spark discharge on the model plate surface. It is established that the discharge leads to the formation of turbulent and thermal spots. The turbulent spot suppresses the separation zone, while the thermal spot leads to a local increase in the boundary layer thickness in the interaction zone.

     

The interaction of shock waves with a boundary layer on a sharp plate and a blunted plate

The interaction of shock waves with a turbulent boundary layer on a sharp plate and a blunted plate is numerically investigated. The shock waves in the flow are generated by wedges installed on the flat plate. The flow is simulated by the dynamic equations of a viscous perfect gas. The effect of the blunting radius of the plate’s leading edge and the wedge angle on the flow field and the local aerodynamic coefficients is shown. The calculated results are in agreement with the experimental data.     

Interaction of shock wave with subsonic heated layer

The problem of attenuation of an incident shock wave on the passage through a heated layer of finite thickness has been considered by numerical methods. Three possible regimes of interaction of the incident shock wave with the heated layer are revealed. It is shown that a significant decrease in intensity of the incident shock wave is caused by its interaction with a heated subsonic jet trace.     

Shock wave reflection and diffraction on a convex double wedge

We have numerically simulated the interaction of a shock wave with a convex double angle within the framework of a model of inviscid non-heat-conducting gas. The main attention is paid to the stage of a two-shock diffraction configuration on the second face of the wedge. Special features of flow under various condi-tions of diffraction are revealed. We also propose an explanation of the appearance and behavior of a purely gasdynamic layer formally resembling the viscous boundary layer.     

Shock focusing upon interaction of a shock with a cylindrical dust cloud

Propagation of a strong plane shock wave through air containing a cylindrical cloud of low-concentration quartz dust is numerically modeled using Euler’s equations. A one-velocity single-temperature model of dust-air mixture is used. Refraction of incident shock and formation and focusing of transversal shocks are described. Two qualitatively different interaction regimes–external and internal–are found to take place for different dust concentration values. The dependence of peak shock focusing point position and relative shock focusing intensity on volume concentration of dust in the range of from 0.01 to 0.15% is determined. With an increase of dust concentration, the peak focusing point draws near the cloud edge and moves inside the cloud, while focusing intensity significantly rises.     

Mathematical Simulation of the Supersonic Gas Flow Over a Wedge with an Attached Shock Wave and High-Temperature Effects

Journal of Engineering Physics and Thermophysics - The development of a supersonic gas flow over a wedge in the process of interaction of a plane shock wave with the wedge was mathematically...     

Formation of triple shock configurations with negative reflection angle in steady flows

Triple configurations of shock waves with negative reflection angles are considered. These configurations have been observed in quasi-steady cases of shock wave reflection from a planar wedge in real gases, while in steady cases three-shock configurations are only known to occur with positive reflection angles. Boundaries for the appearance of a three-shock configuration with a negative reflection angle in steady cases are analytically determined as dependent on the initial Mach number of the flow, angle of incidence, and adiabatic index. The formation of a three-shock configuration with a negative reflection angle in a steady flow must lead to a change in the character of the wave pattern, and under certain conditions it can lead to instability.     

New derivation of the exact solution for the diffraction of a cylindrical or spherical pulse by a wedge

By means of the Cagniard-de Hoop technique applied to the two or three dimensional Green's function of the reduced wave equation with boundary conditions imposed on the faces of a wedge of arbitrary angle, a closed form expression is deduced for the field due to the diffraction of an incident cylindrical or spherical pulse by the wedge. A solution, which is valid in all regions of space whether a shadow zone exists, is presented for either Dirichlet or Neumann boundary conditions. The approach adopted herein is seen to be more concise and straightforward than earlier methods as results previously secured in the corresponding time-harmonic problem are effectively utilized.     

Peculiarities of reflected shock wave bifurcation on a needle

The axisymmetric bifurcation of a reflected shock wave interacting with the boundary layer on a 79-mm-long needle with a diameter of 1.1 mm has been studied. The needle, oriented in counterflow direction, was mounted at the axis on the end wall of a shock tube with 98 × 98-mm section. Experimental data on the parameters of reflected shock wave bifurcation are presented for CO₂ at an initial pressure of 4 kPa and Mach number M = 2.5 of the incident shock wave. The obtained data are compared to experimental parameters of the reflected shock wave bifurcation on side walls of the shock tube. Experimental data were obtained by schlieren imaging of flow patterns and high-speed photography with a DICAM-Pro camera in the double-frame recording mode.     

Scattering of a light wave by a thin fiber on or near a prism: experiment and analytical theory

We have performed an experiment of the scattering of the near field on a prism created by a laser wave, evanescent wave (EW), or plane wave (PW) of an incident angle slightly larger than or smaller than the critical angle, by a thin fiber of subwavelength diameter set above the prism, and we made an analytical theory of an adapted model for the experiment. We have been able to analyze the experimental data exactly by the model theory better than any other theory we have ever known. The importance of the multiple interaction of the wave between the fiber and the surface and also the close similarity of the scattering characteristics between the EW and the PW mentioned above have been acknowledged by the analysis of the data obtained.     

The effect of MHD interactions on the input shock waves in a supersonic diffuser

The interaction with an external magnetic field modifies the variation of the shock wave configuration in a pure inert gas plasma at the entrance of a supersonic diffuser. The phenomenon was studied using an experimental setup based on a shock tube with a flat nozzle and the model supersonic diffuser. The experiments were conducted in krypton, for the shock wave Mach number in the shock tube M=7.8 and the Mach number at the nozzle exit M=4.2. The gasodynamic discontinuities and their structural variations induced by the magnetic induction changes were by visualized by the schlieren method and by photography of the intrinsic emission accompanying the process. Three regions of the MHD interaction affecting the shock wave configuration in the gas flow were revealed.     

Correlations study in shock wave/turbulent boundary layer interaction

The shock waves/turbulent boundary layer interaction is a problem of critical importance that is frequently encountered in designing flying vehicles. Presently, the most topical issue is the investigation of nonstationary phenomena (in particular, low-frequency effects) involved in this interaction. We have experimentally studied separated flows in the zone of interaction between an obliquely incident shock wave and a turbulent boundary layer at a Mach number of M = 2. Correlation data in the separation zone and the upstream flow were obtained. It is established that low-frequency oscillations in the reflected shock are related to the pulsation in the inflow boundary layer.     

兰姆波检测参数曲线的应用研究

为了推广应用兰姆波进行无损检测,对兰姆波检测参数曲线进行了研究。通过对兰姆波频率特征方程的对称模式和反对称模式两种情况进行算法分析,用VC++软件加以编程实现,设计了专门用于绘制兰姆波参数曲线的软件,同时依据激励角频散曲线设计了兰姆波换能器的斜楔结构参数,并制作了兰姆波换能器,进而解决了兰姆波检测参数曲线的绘制和应用问题,所绘制的参数曲线适用于不同材质、不同型号的金属薄板兰姆波检测。     

The propagation and reflection of finite amplitude cylindrically symmetric shear waves in a hyperelastic incompressible solid

Summary We consider axially symmetric shear waves propagating in an incompressible hyperelastic thick-walled cylindrical shell, whose strain energy function is expressible as a truncated power series in terms of the basic strain invariants. A continuous pulse is initiated at the interior boundary of the cylinder by surface tractions of finite duration. The pulse propagates away from the interior boundary, then reflects from the outer boundary, and subsequently reflects back and forth between the two boundaries of the cylinder. We analyze shock development of the first incident and first reflected wave. The incident pulse can break before it reaches the outer boundary. Using Whitham's nonlinearization technique, we determine conditions under which the incident wave breaks and which shock waves can subsequently occur. Similar calculations are carried out for the first reflection. The formulas obtained for the incident pulse provide accurate estimates of the breaking distance and time, and the location of the shock paths, for any incident shock waves that occur. Results obtained for the reflected wave cannot be used to make similar estimates, but they do reveal that once the pulse has completely left the outer boundary, the possible shock that can occur is the same as for the incident wave. Our analysis is carried out for axial shear waves. A similar analysis can be done for torsional shear waves, but not for combined axial and torsional shear wave propagation. We illustrate the conclusions of our shock analysis with numerical solutions obtained using a relaxation scheme for systems of conservation laws. Numerical results are obtained for axial shear and for combined axial and torsional shear. These results indicate that the shock behavior indicated by our analysis of axial shear is also valid for combined axial and torsional shear wave propagation.     

Modeling the dynamics of several particles behind a propagating shock wave

The interaction of a shock wave in a gas phase with a system of particles moving in this gas has been numerically simulated. The wave pattern of the nonstationary interaction of the propagating shock wave with these particles is described in detail. The mathematical model and computational technology employed is compared with experimental data on the dynamics of particles behind the shock wave. It is established that the approximate model of separate particles used to calculate relaxation of their velocities unsatisfactorily operates in the presence of a mutual influence of particles, whereby one particle can occur in the aerodynamic shadow of an adjacent particle.     

双Wollaston棱镜的光程差及其色散

深入研究了的光程差与棱镜楔角以及空间变量-入射角三者的关系,并进行了计算机模拟.发现了对方解石构成的双Wollaston棱镜,光程差有较大的变化范围,光程差和入射角的关系有较好的线性的条件是:棱镜楔角在22°附近,入射角在-50°到10°范围内变化.然后对光程差的色散特性进行了分析和计算机模拟,结果表明,双Wollaston棱镜的光程差明显依赖于光波长,根据拟合结果它们的关系可以用三阶多项式来表述.本结果为偏振型空间调制干涉光谱仪的设计和应用提供了理论依据.     

Skew shock wave on a gas-solid body interface

The interaction between a skew shock wave (SSW) and a plane surface of a solid body is considered. Break decay (BD) on the gas—solid body interface at an arbitrary angle of impact is calculated within the limits of applicability of the hydrodynamic theory of shock waves.     

Analytical and experimental evaluation of energies during shock wave loading

Analytical expressions were developed using gas dynamic equations to evaluate the energy associated with the incident shock wave (incident energy) and the reflected shock wave (remaining energy) for a shock tube experiment. The real time deformation profile of the specimen being loaded by a shock tube was also used to calculate the deformation energy. A shock wave loading on a homogeneous aluminum panel in a simple shock tube experiment was used to illustrate the implementation of these methods.     

Shock adiabat,phase diagram,and viscosity of mercury at a pressure up to 50 GPa

The results of measurements of shear viscosity of mercury under shock compression, obtained in [1]by the method of decay of small perturbations preassigned at the shock wave front, are considered in the light of new data on the phase diagram, isothermal compressibility, and equation of state for mercury in the high-pressure region. It is demonstrated that the measured value of viscosity η = 0.8 kPa s at a shock compression pressure of 44 GPa (which differs from the initial state under normal conditions by a factor of 5 × 10⁵) corresponds to the transition of mercury under shock compression to the solid state..