Dmitry L. Reviznikov

Two-phase shock layer in a supersonic dusty gas flow

The problems of the numerical simulation of a dusty supersonic flow past a blunt body is examined. The model of a two-phase shock layer is presented. The Euler description of the gas phase and the Lagrange description of the dispersed phase that is used in combination is the basis of the present model. The complete variant of a discrete-elemental method, i.e., the direct numerical simulation of a dynamic admixture, is used. The effect of collisional and collisionless foreign particles on to the carrying gas flow and heat transfer is studied, as well as the direct impact of a two-phase gas flow onto a streamlined surface, by considering particle collisions and the dispersed phase’s reverse impact on the gas phase.

Numerical Simulation of Heterogeneous Flows and Heat-Mass Transfer in Complex Domains on Rectangular Grids

This paper is concerned with numerical simulation of two-phase flows in complex computational regions. Both nozzle flow and jet-obstacle interaction are considered. The presence of dispersed phase (solid or liquid particles) may lead to specific thermal and erosional interaction of inertial particles with the nozzle walls and the obstacle material. The latter makes the conjugated problem much more complicated. Therefore, we consider the complete flow field in the nozzle-jet-obstacle system. The present work is a continuation of the recent study by the authors [1, 2]. A unified approach to the general problem of a two-phase nozzle-jet-obstacle flow is suggested. In this approach, both the continuous and dispersed phase behavior is calculated using the fixed rectangular grids. The solution of transient conduction equation in the solid is also carried out on rectangular grids. Both dynamics and heating/cooling of particles are calculated using the discrete-element method in Lagrangian variables. The computational model includes many mechanical effects such as collisions of particles with each other, reflection of particles from the wall surface and the feedback effect of the dispersed phase on the gas flow. The distinctive feature is the direct numerical simulation of dispersed phase dynamics, where each single real particle in the flow has its computational counterpart. All governing equations for continuous fields are solved on rectangular grids using a ghost-cell immersed boundary method. This method provides discretization of the appropriate boundary conditions via a procedure of polynomial approximation. Such approach works well for both the incompressible and compressible flows. Rectangular grids allow a straightforward implementation of high order TVD and ENO schemes for the numerical simulation of gas flows. The immersed boundary method is perfectly suited for the problems within a computational domain of varying geometry, since it doesn’t require rebuilding the grid after each boundary movement. This feature was successfully used in the numerical simulation of erosive destruction of the circular cylinder in the two-phase flow [2], where the mass carried away from the body resulted in moving boundaries. The current work incorporates the previous methods and algorithms into the software package allowing the numerical investigation of heterogeneous flows in more complex configurations.Copyright

A NEW CONCEPT OF A SOLAR PROBE SHIELDING FROM INTENSE THERMAL RADIATION OF THE SUN

An effect of shielding of an intense solar radiation towards a solar probe with the use of micron-sized particles generated during ablation of a special composite thermal protection material is estimated on the basis of an approximate solution to a conjugate heat transfer problem. The spectral radiative properties of particles are calculated using the Mie theory, and the two-flux model is used for the radiative transfer calculations in the particle cloud. A computational model for the dynamics, heating, and evaporation/sublimation of small particles takes into account the drag force from a rarefied gas moving from the sublimating composite material, the light pressure effect and the radiative heating/cooling of absorbing and scattering particles. A preliminary numerical heat transfer analysis indicates that implementation of silicon carbide or similar particles into a thermal protection and the resulting generation of a rarefied particle cloud can be considered as a promising way to protect the solar probe from the intense thermal irradiation. This shielding effect is expected to be important to decrease the minimum working distance of the space vehicle from the solar photosphere.

Meshfree Computational Algorithms Based on Normalized Radial Basis Functions

In this paper, new methods for solving mathematical modelling problems, based on the usage of normalized radial basis functions, are introduced. Meshfree computational algorithms for solving classical and inverse problems of mathematical physics are developed. The distinctive feature of these algorithms is the usage of moving functional basis, which allows us to adapt to solution particularities and to maintain high accuracy at relatively low computational cost. Specifics of neural network algorithms application to non-stationary problems of mathematical physics were indicated. The paper studies the matters of application of developed algorithms to identification problems. Analysis of solution results for representative problems of source components (and boundary conditions) identification in heat transfer equations illustrates that the elaborated algorithms obtain regularization qualities and allow us to maintain high accuracy in problems with considerable measurement errors.