Propagation of pressure waves in two-phase flow

We deal with a pressure wave of finite amplitude propagating in a gas and liquid medium or in the fluid in an elastic tube. We study the effects of pipe elasticity on the propagation velocity of the pressure wave. Pressure waves of finite amplitude progressing in the two-phase flow are treated considering the void fraction change due to pressure rise. The propagation velocity of the two-phase shock wave is also investigated, and the behavior of the reflection of the pressure wave at the rigid wall is analyzed and compared to that in a pure gas or liquid. The results are compared to experimental data of a pressure wave propagating in the two-phase flow in a vertical shock tube.     

Propagation of guided waves in pressure vessel

Pressure vessels usually operate under extremes of high/low temperatures and high pressures. Defect, such as crack and corrosion, can result in leakage or rupture failures, even catastrophic incidents. Guided wave-based structural health monitoring (SHM) technology is one of the most prominent options in non-destructive evaluation and testing (NDE/NDT) techniques. Propagation of guided waves in a typical pressure vessel is systematically investigated in this study for the application of guided wave-based SHM. Shape of the pressure vessel is a cylinder with two end caps. Because of geometric similarity, theory of guided wave propagation in the cylinderical structure is analyzed to study dispersive features of guided waves in the pressure vessel. Dispersion curves of three different types of guided wave modes, viz. the longitudinal, torsional and flexural modes, are calculated using theoretical method. Based on the analyses and experimental wave signals, central frequency and wave parameters of incident wave are optimized. Effect of contained liquid on propagation of guided waves, especially the L(0, 2) mode, in the pressure vessel is further investigated to minimize energy leakage of the wave to the contained liquid. The analytical method, finite element analysis (FEA) and experiments are applied to study propagation characteristics of guided waves in the pressure vessel, so as to demonstrate the feasibility of guided wave-based non-destructive evaluation and testing (NDE/NDT) for such kind of complex structures.     

不同自燃模式对压力波动形成的影响

在内燃机中,HCCI(均值混合气压燃)爆震、汽油机常规爆震、汽油机超级爆震都是由未燃混合气自燃引起的化学能突然释放,从而产生振荡燃烧,但其压升率及压力振荡幅值却截然不同。为了阐明其中机理,根据上述的带震荡的燃烧压力波变化规律,提出以实验测得的放热率为基础的“能量注入法”,建立了3种自燃模式。通过对能量方程中的热源项进行分类改变,进而对3种自燃模式进行数值模拟、对其产生的压力波动进行比较分析。模拟结果表明,不同震荡特征的燃烧压力波源于不同的自燃模式,从而导致其宏观表现的压升率以及压力波振荡幅值有极大的差异。以放热率为基础的“能量注入法”能准确、快捷地探究内燃机燃烧室中压力波的形成与传播。     

Interaction of unsteady pressure waves and perforated baffles

The results of experiments to investigate the interaction of plane shock waves with a triangular pressure profile and perforated baffles are presented. The parameters of the reflected waves are determined and the amplitude and impulse attenuation coefficients are measured as functions of the permeability of the barrier. The quenching coefficients are determined for the case of two baffles arranged in series.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 174–176, November–December, 1987.     

Interaction of pressure waves with a wet foam

Brest. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 5, pp. 78–83, September–October, 1994.     

Atmospheric pressure waves in the field of volcanology

Atmospheric pressure waves are a notable phenomenon associated with explosive volcanic eruptions. They can provide us with information about eruption processes that are useful both scientifically and practically. In this paper, we give a brief review of studies that have been carried out on this phenomenon in the field of volcanology. Then, we introduce a prototype tool called ‘MOVE’ (Mobile Observatory for Volcanic Explosions). It is a remote-controlled vehicle carrying various instruments to observe pressure waves and the eruption processes. PACS 91.40.Dr · 91.40.Ft · 93.65.+e · 93.85.+qThis paper was based on work presented at the 2nd International Symposium on Interdisciplinary Shock Wave Research, Sendai, Japan on March 1–3, 2005.     

Simple waves in a plasma with anisotropic pressure

Fast and slow simple waves are studied in the framework of the anisotropic magnetohydrodynamics of Chew, Goldberger, and Low [1]. Baranov [2] has constructed fields of integral curves for fast and slow waves and in two special cases has shown that such waves break in the compression section. The possibility of breaking of a slow wave in a rarefaction section was noted by Akhiezer et al. [3]. However, their general relations in simple waves [3] have been shown to be incorrect [2, 4]. In the present paper the nature of the variation of the longitudinal and transverse plasma pressures is determined, and the problem of the breaking of fast and slow waves is completely solved. Conditions under which a slow wave breaks in a rarefaction section are found. A fast wave always breaks in a rarefaction section.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 181–183, July–August, 1988.     

Interaction of pressure waves with orifices inside ducts

Summary Reflected and transmitted pressure waves are generated by the interaction which takes place when an incident pressure wave reaches an orifice placed inside a duct, with initial steady flow through the orifice before this interaction.In this paper a theoretical approach for relating reflected and transmitted pressure waves with orifice geometry, initial steady flow conditions and incident pressure wave is outlined.Several experiments were carried out with different incident shock wave intensities and orifice sizes; theoretical and experimental results are then compared and the agreement is quite good.Some anomalous phenomena observed during such experiments are reported.

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Sommario Quando un'onda di pressione raggiunge un orifizio intubato, attraversato da un flusso preesistente, ne nascono un'onda trasmessa e un'onda riflessa.Nel presente lavoro si affronta teoricamente il problema di correlare l'intensità di tali onde riflessa e trasmessa alle caratteristiche geometriche dell'orifizio, al flusso preesistente, ed all'intensità dell'onda incidente; si confrontano poi tali risultati teorici con quelli ottenuti sperimentalmente su diversi orifizi quando l'onda incidente sia un'onda d'urto, ottenendone un buon accordo. Si segnalano inoltre alcuni fenomeni anomali osservati sperimentalmente.

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=A/A _p The indexes 1, 2, 3, 4, 5, 6,e,ee refer to Fig. 1.     

Transmission of pressure waves in partially saturated soils

A split-Hopkinson pressure bar (SHPB) was used to experimentally determine stress-transmission coefficients and wave speeds for dry and moist 50/80 silica soil specimens. Results show that for a constant input pressure the transmitted pressure and wave speed increase to a maximum at approximately five- to ten-percent moisture content. Then, both wave speed and transmission ratio decrease with increasing moisture content down to the approximate values of dry soil. Preliminary analysis indicates that these trends can be explained by the effects that saturation and soil capillarity have on effective stress in the soil.Paper was presented at the 1987 SEM Fall Conference on Experimental Mechanics, held in Savannah, GA on October 25–28.     

Transient waves generated by a moving oscillatory pressure on a sloping beach

A uniform asymptotic analysis of the unsteady wave motion generated by a moving oscillatory pressure distribution on a sloping beach of slope angle /4 is given. Our method of investigation gives important information regarding the nature, number and distribution of the resulting wave pattern. The effect of the sloping beach on the waves is exhibited.     

Large-scale edge waves generated by a moving atmospheric pressure

Long waves generated by a moving atmospheric pressure distribution, associated with a storm, in coastal region are investigated numerically. For simplicity the moving atmospheric pressure is assumed to be moving only in the alongshore direction and the beach slope is assumed to be a constant in the on-offshore direction. By solving the linear shallow water equations we obtain numerical solutions for a wide range of physical parameters, including storm size (2a), storm speed (U), and beach slope (α). Based on the numerical results, it is determined that edge wave packets are generated if the storm speed is equal to or greater than the critical velocity, U_cr, which is defined as the phase speed of the fundamental edge wave mode whose wavelength is scaled by the width of the storm size. The length and the location of the positively moving edge wave packet is roughly Ut/2 ≤ y ≤ Ut, where y is in the alongshore direction and t is the time. Once the edge wave packet is generated, the wavelength is the same as that of the fundamental edge wave mode corresponding to the storm speed and is independent of the storm size, which can, however, affect the wave amplitude. When the storm speed is less than the critical velocity, the primary surface signature is a depression directly correlated to the atmospheric pressure distribution.     

Stationary simple waves in a plasma with anisotropic pressure

Stationary simple waves in a plasma with anisotropic pressure are investigated on the basis of the hydrodynamic equations of Chew, Goldberger, and Low. In Sec. 1, for the case where the vectors of the average flow velocity and the magnetic field intensity are parallel, the system of equations is reduced to two quasilinear equations for the velocity components. In Sec. 2 the equations for the characteristics are obtained, the system being assumed to be hyperbolic. For the special case of irrotational flow the character of simple waves in flows adjacent to various contours is studied. Section 3 contains a qualitative investigation of changes in the flow parameters in simple waves. In Sec. 4 the possibility of a transition to an unstable state of the plasma is studied.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 12–19, March–April, 1971.The author thanks V. B. Baranov for the formulation of the problem and for his advice and constant attention to the work and also A. G. Kulikovskii for discussion of the results.     

Generation and propagation of pressure waves in supersonic deep-cavity flows

The mechanism behind cavity-induced pressure oscillations in supersonic flows past a deep rectangular cavity is not well understood despite several investigations having been carried out. In particular, the process by which the pressure wave is generated and the path of the pressure wave propagating inside the cavity remains unclear. In the present study, the pressure waves around a deep rectangular cavity over which nitrogen gas flows at a Mach number of 1.7 are visualized using the schlieren method. The length of the cavity is 14.0?mm. The depths of the cavity are selected as 20.0?and 11.7?mm, corresponding to length-to-depth ratios of 0.70 and 1.2, respectively. The pressure waves propagating inside as well as outside the cavity have been successfully visualized using a high-speed camera, and the propagation pattern of these waves is found to be different from that previously predicted by numerical simulation and from those expected in previous oscillation models. In addition, the pressure oscillation near the trailing edge of the cavity is also measured using semiconductor-type pressure transducers simultaneously with the capture of the schlieren images. As a result, the relationship between the shear-layer motion, pressure-wave generation, and pressure oscillation at the trailing edge of the cavity is clarified experimentally.     

On the propagation of pressure waves in saturated porous media

The problem of the propagation of pressure waves through compressible porous media saturated with a slightly compressible fluid is considered. By using Darcy's law the problem is reduced to a mixed initial-boundary value problem for an equation of the heat conduction type with a nonlinear term. The method of quasi-characteristics is used to solve this equation numerically. Solutions of the wave propagation problem for media with different permeability coefficients are presented. A solution of the inverse problem of determining the permeability coefficient using wave-pulse test data is constructed on the basis of a set of solutions of the direct problem.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, pp. 81–84, November–December, 1996.