Supercomputer model of dynamical dusty gas with intense momentum transfer between phases based on OpenFPM library

The paper considers the solution of model gas-dynamic problems (propagation of plane sound wave, one-dimensional shock tube problem, three-dimensional problem of a point explosion in a continuous medium) in the case of a gas-dust medium. The interaction of dust and gas was taken into account using the IDIC method within the SPH method used to solve gas-dynamic equations. An important feature of the work is the use of the open computational package OpenFPM, which makes it easy to carry out parallel computations. The main advantage of this package is the ready-made (implemented by the authors of the package) and intuitive, automatically parallelizable vector data structures, the use of which is identical both in the case of calculations on a personal computer and in the case of using supercomputer resources. The paper analyzes the efficiency of parallelization of numerical solutions of the considered problems.

Longitudinal and transverse waves

“Longitudinal and transverse waves” discusses vector-amplitude waves in isotropic media, as exemplified by plasma waves and by plane sound waves. Transverse and longitudinal polarizations are identified with amplitudes that are divergence-free or curl-free. These conditions pick out polarization states that are “pure”, meaning not contaminated by the other possibility.

Multi-Domain Boundary Element Method for Sound Scattering on a Partly Perturbed Water Surface

The problem is the scattering of a plane sound wave at a rough water-air interface. The purpose of this paper is to describe in detail the method and demonstrate its work with simple examples. The main advantage of this approach is that there are no limits on the relation between the shape of the surface and the incident wave, so we can consider large Rayleigh parameter, shading, multiple scattering. The solution of the Helmholtz equation in the form of an integral over the boundary is used only in the inner domain, in the outer domain the separation of variables is used to obtain a nonlocal integral boundary condition on the artificial boundary.

Velocity and Absorption Coefficient of Sound Waves in Classical Gases

The velocity and absorption coefficient of plane sound waves in classical gases are obtained by solving the Boltzmann kinetic equation. This is done within the linear response theory as a reaction of the single-particle distribution function to a periodic external field. The nonperturbative dispersion equation is derived in the relaxation time approximation and solved numerically. The obtained theoretical results demonstrate an universal dependence of the sound velocity and scaled absorption coefficient on the variable wт , where w is the sound frequency, and т−1 is the particle collision frequency. In the region of wт ∼ 1, a transition from the frequent- to rare-collision regime takes place. The sound velocity increases sharply, and the scaled absorption coefficient has a maximum – both theoretical findings are in agreement with the data.