Effects of a reverse shock wave on neutrino oscillations in a new supernova model

It is known that in supernova explosions, there might be a reverse shock wave in addition to the forward shock wave during the explosion phase, when the mass of supernova is in a certain range. In this paper, we propose to add the reverse shock wave to the previous supernova model, in which only the forward shock wave was included,and thus obtain a new model. By analyzing the resonance condition as well as the density jump in the new model and using the Landau-Zener method, an expression for the crossing probability in high density matter(PH) is given.We proceed to study how PH varies with time and with neutrino energy when both the reverse shock wave and the forward shock wave are considered. From comparison with the previous results, where only the effects of the forward shock wave were considered, it is clear that the reverse shock wave brings significant changes to PH.     

Breakdown of hydrodynamics in a simple one-dimensional fluid

We investigate the behavior of a one-dimensional diatomic fluid under a shock wave excitation. We find that the properties of the resulting shock wave are in striking contrast with those predicted by hydrodynamic and kinetic approaches; e.g., the hydrodynamic profiles relax algebraically toward their equilibrium values. Deviations from local thermodynamic equilibrium are persistent, decaying as a power law of the distance to the shock layer. Nonequipartition is observed infinitely far from the shock wave, and the velocity-distribution moments exhibit multiscaling. These results question the validity of simple hydrodynamic theories to understand collective behavior in 1D fluids.     

Time-Asymptotic Behavior of Wave Propagation Around a Viscous Shock Profile

We study the nonlinear stability of shock waves for viscous conservation laws. Our approach is based on a new construction of a fundamental solution for a linearized system around a shock profile. We obtain, for the first time, the pointwise estimates of nonlinear wave interactions across a shock wave. Our results apply to all ranges of weak shock waves and small perturbations. In particular, our results reduce to the time-asymptotic behavior of constant state perturbation, uniformly as the strength of the shock wave tends to zero. The research of the first author was partially supported by NSC Grant 96-2628-M-001-011 and NSF Grant DMS-0709248. The research of the second author was partially supported by NSF Grant DMS-0207154 and UAB Advance Program, sponsored by NSF.     

Nonequilibrium and non-steady-state evolution of a shock state

Using numerical simulations, we study the evolution of silicon in the passage of a constant-pressure shock wave launched from an adjacent pusher. We examine also its optical characteristics of reflectivity and emission. Our finding points to the study of shocked interfaces as a novel means to explore nonequilibrium, non-steady-state behaviors of shock states and an alternative approach to assess electron-ion equilibration rate in a shock wave. It also reveals important structures in such a shock wave in contrast to its usual notion as a propagating discontinuity. This offers some possibilities for reconciling the different findings on the compressibility of deuterium.     

Conditions of the Formation of a Shock Wave under Cavitation in Hydrocarbon Solutions

Doklady Physics - We carried out a numerical study of the appearance of a shock wave during the collapse of a bubble in a hydrocarbon aqueous solution. The conditions for the appearance of a shock...     

Shock waves by a kinetic model of van der Waals fluids

We present a four-velocity kinetic model of van der Waals fluids. Although, from the physical point of view this model is very simple, mathematically it is quite complicated. Due to this complexity we performed various simplifications, which are also presented. We look for traveling wave solutions for these simplified versions. A discussion of the types of the states of rest is presented. We pay some attention to the monotonicity of the density component of the traveling wave. Finally, we compare the model's kinetic and hydrodynamic shock wave structures. The new feature is that kinetic effects alone are unable to kill the artificial phenomenon of impending shock splitting.     

The reflection of a finite amplitude wave from a curvilinear unsteady shock wave

The reflection of a wave of finite amplitude from a curvilinear unsteady shock wave has been analyzed. A formula connecting reflected wave parameters with that of the incident wave, curvature and shock wave intensity has been obtained in closed form.     

On generation of a shock wave in a hail protection setup

Problems of generation of a shock wave in a hail protection setup are considered. The results of oscillographing the shock wave by microphones arranges at different altitudes along the direction of its propagation are reported. The average velocity of the shock wave is determined. The processes occurring in the explosion combustion chamber are analyzed using the recorded oscillograms.     

Wave dynamics in a modified quintic complex Ginzburg-Landau system

We consider physical systems described by the modified quintic complex Ginzburg-Landau equation and its derivative forms and examine numerically the dynamics of its shock type wave solution. Discussions on the behaviours of this shock wave are introduced and it is shown how the ratios of diverse velocities of this wave could be exploited to explain and collect information concerning the spatial patterns formation in the system.     

Application of the wavenumber jump condition to the normal and oblique interaction of a plane acoustic wave and a plane shock

A kinematic approach is considered whereby the wavenumber jump conditions in conjunction with the appropriate dispersion relations is applied to the investigation of the normal and oblique interaction of a plane acoustic wave with a plane shock wave. For the normal interaction of an acoustic wave with a stationary plane shock a logarithmic shift in the wave spectra is obtained. For the normal interaction with a moving shock front it is shown that for shock Mach numbers above a critical value, the frequency of the transmitted wave becomes negative. This results in the fact that the crests of the transmitted signal arrive at a fixed observer in a reverse order to their generation. Finally, the oblique interaction of an acoustic wave with a stationary shock is considered. The “Snell's Law” for the transmitted wave is derived and two special angles of incidence are identified. The first is a no-refraction angle: i.e., the transmitted wave angle is the same as the incident wave angle. The second is a critical angle such that for incident angles greater than this critical angle there is no transmitted wave. A necessary and sufficient condition for the existence of a transmitted wave is derived in terms of the speed of sound and Mach number of the fluid and the frequency and tangential wavenumber component of the incident wave.The dynamics aspects of the interaction concerning the determination of the frequency independent transmission coefficients and shock displacements are determined for the simple case of the normal interaction with a moving shock as an illustration.     

Pressure fluctuations within a turbulent gas flow and their interaction with a shock wave

The interaction of a shock wave with a turbulent air flow is investigated experimentally. The turbulence was created with the aid of a grid. On its reflection from a perforated disc the wave propagated through a turbulent flow. The Mach number of the incident shock was equal to 1.9–4, the Mach number of the reflected wave was equal to 1.6–2.5. We found the autocorrelation functions of pressure fluctuations and their phase diagrams. The turbulent length scale of pressure fluctuations behind the incident shock was determined. The appropriate quantity behind the reflected wave is less of an order as compared with the previous case. It is established that the pressure behind the reflected wave in the turbulent flow is 7–8% higher as compared with the pressure in the laminar flow, if other conditions are the same.     

Numerical study of shock wave interaction in steady flows of a viscous heat-conducting gas with a low ratio of specific heats

Specific features of shock wave interaction in a viscous heat-conducting gas with a low ratio of specific heats are numerically studied. The case of the Mach reflection of shock waves with a negative angle of the reflected wave with respect to the free-stream velocity vector is considered, and the influence of viscosity on the flow structure is analyzed. Various issues of nonuniqueness of the shock wave configuration for different Reynolds numbers are discussed. Depending on the initial conditions and Reynolds numbers, two different shock wave configurations may exist: regular configuration interacting with an expansion fan and Mach configuration. In the dual solution domain, a possibility of the transition from regular to the Mach reflection of shock waves is considered.     

On the effect of conductivity of a shock-compressed gas on interferometric recording of parameters of motion of a liner

We report on the results of a study of the acceleration dynamics of an aluminum liner to a velocity of 5.5 km/s using continuous recording of velocity (velocity interferometer system for any reflector (VISAR) and Fabry-Perot interferometer) and motion trajectory (radiointerferometer and resistive transducer) in air and in a helium atmosphere. It is found that for liner velocities exceeding 4.0 and 5.0 km/s, the displacement of the shock wave front is recorded by the radiointerferometer in air and helium, respectively. At these velocities, the conductivities of air and helium behind the shock wave front are estimated.     

Passage of a Plane Shock Wave through the Region of a Glow Gas Discharge

Technical Physics - The interaction of a plane shock wave (M = 5) with an ionized plasma region formed before the arrival of a shock wave by a low-current glow gas discharge is considered...     

一类激波问题的间接匹配解

研究了一类非线性奇摄动方程的激波问题.利用间接匹配法，构造出激波在区间内的激波解. 关键词： 非线性方程 激波 间接匹配     

Rayleigh mechanism of local elevation of energy in propagation of a shock wave in an active medium

A mechanism of action of a shock wave on an active medium, which leads to an additional energy release source, is considered. This source moves together with the shock wave front and depends on the magnitude and direction of the electric field applied to the plasma and on the current density in the plasma. The study is a continuation of an earlier publication devoted to the propagation of weak shock waves. Here, we consider shock waves of an arbitrary intensity with an arbitrary mechanism of formation of an additional energy contribution due to variation of the parameters of the medium as a result of passage of the shock wave. Special cases of this effect are the propagation of a shock wave in a plasma and detonation burning.     

Computer simulation of perturbation of a shock wave in nitrogen by optical radiation

The possibility of a displacement of the front of a shock wave formed in a 1D nitrogen flow to the low gas pressure region (in front of the shock wave) upon absorption of the laser pulse energy in the region of the shock wave front is demonstrated using computer simulation based on the finite difference technique. The low-pressure region formed in the region of the initially high pressure under the action of a light pulse moves in the direction opposite to the direction of propagation of the shock wave front. Analysis is carried out for a typical experimental situation corresponding to the growth of carbon-nitride nanofilms.     

Numerical study of shock wave entry and propagation in a microchannel

The entry of a shock wave with the Mach number M_is = 2.03 into a microchannel and its further propagation is numerically studied with the use of kinetic and continuum approaches. Numerical simulations on the basis of the Navier ?? Stokes equations and the Direct Simulation Monte Carlo method are performed for different Knudsen numbers Kn = 8·10^?3 and 8·10^?2 based on the microchannel half-height. At the Knudsen number Kn = 8·10^?3, amplification of the shock wave after its entry into the microchannel is observed. Further downstream, the shock wave is attenuated, which is in qualitative agreement with experimental data. It is demonstrated that results predicted by a quasi-one-dimensional model (which ignores viscosity and heat conduction) of shock wave propagation over a channel with an abrupt change in the area agrees with results of numerical simulations on the basis of the Euler equations. In both cases, shock wave acceleration (amplification) after its entry into the microchannel is observed. At the Knudsen number Kn = 8·10^?2, the influence of the entrance shape on shock wave propagation over the microchannel is examined. Intense attenuation of the shock wave is observed in three cases: channel with sudden contraction, junction of two channels with an additional thin separating plate, and rounded junction in the form of a sector with an angle of 90° (quarter of a circumference). It is shown that the microchannel entrance shape can affect further propagation of the shock wave. The wave has the highest velocity in the case with a rounded entrance.     

Shock waves in a long-period optical fiber

The possibility of forming a shock wave of the pulse envelope has been investigated in a long-period or Bragg optical fiber with a system of two unidirectional linearly coupled waves. It has been demonstrated that, in principle, the possibility exists of forming a shock wave in a nonlinear optical fiber not only at the trailing edge but also at the leading edge of the wave packet. The origin of the formation of a shock wave depends substantially on the initial conditions providing excitation of the optical fiber.     

Propagation of cylindrical shock waves in a rotating atmosphere under the action of monochromatic radiation

Summary  A model of cylindrical shock waves is discussed in a non-uniform rotating atmosphere under the action of monochromatic radiation. We have assumed that the radiation flux moves through a rotating gas with constant intensity and the energy is absorbed only behind the shock wave which moves in opposite direction to the radiation flux.