Sound Shock Waves Research Articles

Journal-related Activities and Other Special Activities at the 2022 American Society of Anesthesiologists Meeting

Journal-related Activities and Other Special Activities at the 2022 American Society of Anesthesiologists Meeting

Effect of the Sound Source Position Error on Distribution Characteristics of Underwater Shock Wave Bunching Sound Field

Curved reflection bunching technique of underwater plasma sound source (UPSS) uses the geometric characteristics of the curved reflector to reflect and bunching intense sound shock wave, so the center position error of the sound source is one of the important factors affecting the bunching performance of the shock wave. In this paper, the cause of the sound source position error is analyzed in detail, and nonlinear finite element software ANSYS/LS-DYNA (dynamic analysis software developed by LSTC) is used to establish the model of the shock wave bunching sound field. Through numerical simulations, the shock wave bunching sound field distribution characteristics under the influence of different position errors are comprehensively simulated, and the bunching performance of the shock wave and its influence law are deeply analyzed according to the simulation results. It provides guidance for reasonably controlling the machining error and installation error of the reflector and discharge electrode, estimating the effective discharge times of the discharge electrode, and formulating the design process.

Evolution of imploding cylindrical second sound waves in superfluid 4He

The use of cylindrical imploding pulses allows to produce locally larger temperature and vortex line densities and provides also information on the interplay between thermodynamic and geometric factors. Above a certain fairly low level of temperature perturbation second sound shock waves followed by a superfluid vorticity field are generated. To understand the flow and heat transfer it is therefore of great interest to measure both the spatial and the temporal evolution of the temperature and of the vortex line density. The temperature was measured using superconducting bolometers and a newly developed method to deduce the vortex line density from the amplitude variation of short test pulses was used. The observed influence of the intensity and duration of the heat input and initial vortex line density level on the flow characteristics will be presented. The experimental observations will be compared with our numerical calculations and also in the case of very small heat pulses (acoustic case) with analytical calculations.

Apparatus for the non-contact disintegration of conrements present in a body

An apparatus for the non-contact disintegration of concrements present in a body by means of sound shock waves generated by spark discharge between two electrodes (3, 4) in a focus (F 1 ) of at least one liquid-filled rotationally symmetrical reflector (2) formed in a reflector block, said sound shock waves being focussed in a focal point (F 2 ) situated outside the reflector (2). Between the focus (F 1 ) and the focal point (F 2 ), in a region (3) bounded by an imaginary conical surface defined by the edge R of the reflector (2) and the focus (F,), there is positioned an object (20) intercepting sound shock waves impinging thereon.

Influence of quantum turbulence on the evolution of moderate plane second sound heat pulses in helium II

Recent experiments have shown the existence of a very strong temperature overshoot behind a propagating second sound shock wave close to the heated surface. The ratio of the temperature overshoot to the shock wave amplitude depends strongly on the rest time between two consecutive heat pulses. These results can be reproduced by a simple theoretical model using only the Gorter-Mellink mutual interaction force and a vortex line density (VLD) evolution equation. The evolution equation is taken to be that proposed by Vinen as extended to include spatial dependence. The drift velocity of the VLD is assumed to have a specific form, and the initial VLD is chosen as a parameter. Experimental observations and existing physical considerations led to the formulation of the used theoretical model. The quantitative agreement between the theoretical calculations and experiments is fair for an overshoot ratio below about 3. At stronger heat pulses the agreement is only qualitative. The model describes well the mechanism of development of a hot layer close to the heated surface and the evolution of the counterflow velocity and temperature field behind the second sound shock wave and indicates possible improvements of the theoretical model.

Nonlinear fourth sound

The two-fluid model for He II is used to derive the Mach number dependence on shock strength for weak fourth sound shock waves. The shock structure profile is found to be a hyperbolic tangent with shock thickness proportional to shock strength. The steepening coefficient is evaluated, and methods for producing nonlinear fourth sound are discussed.

On the interaction of second sound shock waves and vorticity in superfluid helium

Two second sound shock waves were propagated successively into initially quiescent superfluid helium. With long separation times the waveforms are identical, but with shorter times the flow behind the second shock decays anomalously, revealing the presence of fluid disturbances produced near the heater by the first pulse. In order to study the vortical nature of these disturbances, second sound shocks were produced in rotating superfluid helium. Propagation of shocks both along and normal to the axis of rotation was studied, the former case proving to be similar to the experiment with successive shocks.

Converging second sound shock waves in superfluid helium

A spherical heater and conical channel are used to produce converging second sound shock waves. Arrival time and temperature jump data verify the validity of the weak shock relations. The calculated relative velocities (around 10 m/sec) are the largest ever produced in bulk superfluid helium. Comparison of converging and straight channel experiments shows unambiguously that the phenomena associated with the breakdown of superfluidity in second sound shock experiments occur near the heater, not in the bulk fluid.

A HeI-HeII Interface and Second Sound Shock Waves near the Superfluid Transition

Etude basee sur le modele phenomenologique de Guinzburg-Landau dependant du temps. L'interface He I-He II et les ondes de choc du second son pres de la transition superfluide sont des solutions kinks des equations

Fourth sound shock waves in 3HeB

Abstract The relative density of the superfluid component of 3He is expected to be significantly depressed by flow. For this reason the distortion of a finite amplitude fourth sound wave exhibits an unusual amplitude dependence. For waves of sufficiently large initial amplitude, a fully developed shock wave will contain two discontinuities per wavelength. Waves of amplitude twenty times greater than the threshold for this unusual behavior have been reported in the literature.

Wave Coupling Across a Shock Wave in a Fully Ionized Gas

This paper presents a theory of the coupling between electron-acoustic, ion-acoustic, and electromagnetic plane waves at an idealized shock front in a two-fluid, fully ionized, inviscid plasma. The equations of hydrodynamics and Maxwell's equations are used to derive the dispersion equation relating the frequency and propagation constant of possible modes of propagation in a plasma. Boundary conditions which must hold at the shock front in the presence of an incoming perturbation are then derived, and the amplitudes of predicted wave modes generated at the boundary are calculated. A generalized Poynting vector is used to calculate energy coupling ratios for the waves. In agreement with previous work on sound-shock wave interaction in neutral gases, we find enhanced ion-acoustic transmission in the present work. In addition, we also find enhanced propagation in the electron-acoustic coupled mode.