Детонация горючей газовой смеси при взаимодействии ударной волны с эллиптической областью тяжелого инертного газа

On the basis of the Euler equations, the interaction of a shock wave in a combustible gas with an elliptical bubble of an inert gas of increased density is numerically simulated within a plane two-dimensional formulation. The finite-volume Godunov-type method of the second order of approximation is applied. Gas combustion is modeled using the Korobeinikov-Levin two-stage kinetics. Various values of the Mach number of the incident wave and the elongation of the inert bubble are considered, and the refraction and focusing of the incident shock are described. Qualitatively different regimes of gas detonation initiation have been found, including direct initiation by a strong wave, ignition upon reflection of an average-intensity wave from the gas interface, and upon focusing of secondary shock waves at lower shock Mach numbers. The dependence of the ignition mode on the shock intensity and the shape of the bubble is determined.

Intensity-Dependent Dispersion in Nonlinear Phononic Layered Systems

Phononic crystals are typically considered to operate in regimes where a linear constitutive relationship provides an adequate representation. For high intensity wave propagation, however, weak nonlinearities can affect performance. For example, a cubic nonlinearity gives rise to frequency shifting and thus a shift in band gap location. In the study of nonlinear optics, a cubic term has been treated using a quasi-linear constitutive relationship with intensity dependent properties. This technique is explored herein for generating nonlinear dispersion relationships for the elastic case. In addition, a perturbation method developed previously for discrete systems, used in conjunction with a finite element discretization, is proposed as an alternative dispersion analysis tool. Simulations of the fully nonlinear governing equations are provided as validation of the predicted dispersion curves.

Radiation pressure on a dielectric surface

The radiation pressure on an insulating dielectric medium should be calculable from the force acting on the polarization vector P. The well-known force proposed by Gordon (Phys. Rev. A, 8, 14 (1973) disappears in the case of a steady-state plane wave. A new form of force explicitly involving the polarization vector is proposed and applied to determine the partition of the incident momentum among the reflected and transmitted wave, and the dielectric medium. The momentum of electromagnetic wave in a dielectric medium thus found is consistent with the classical relationship, wave momentum flux density = wave intensity/wave velocity.

Stochastic heating in ultra high intensity laser-plasma interaction

Stochastic instabilities are studied considering the motion of one particle in a very high intensity wave propagating along a constant homogeneous magnetic field, and in a high intensity wave propagating in a nonmagnetized medium perturbed by one or two low intensity traveling waves. Resonances are identified and conditions for resonance overlap are studied. The part of chaos in the electron acceleration is analyzed. PIC code simulation results confirm the stochastic heating.