Gennady N. Markelov

Numerical Modeling of Near-Continuum Flow over a Wedge with Real Gas Effects

Effects of vibrational relaxation and dissociation on the standoff distance of the bow shock wave on a wedge are numerically examined with the use of the kinetic (DSMC method) and continuum (Navier-Stokes equations) approaches. A hypersonic flow around the wedge is computed for Knudsen numbers about 5 x 10 -4 in a wide range of wedge angles both for a monatomic gas (argon) and a diatomic reacting and nonreacting gas (nitrogen). DSMC computations are based on three different real gas effect models. The kinetic and continuum results for the standoff distance are in good agreement for argon and nonreacting nitrogen. The influence of vibration-dissociation coupling on the results of numerical simulations is analyzed. Sensitivity of simulation results to chemical reaction rate constants is also estimated. Numerical simulations show that dissociation is responsible for the nonlinear form of the dependence of the standoff distance on the wedge angle, which qualitatively agrees with available experimental data.

Numerical study of 2D/3D micronozzle flows

Methods for creating thrusters with very low thrust using micronozzles have been actively developed recently. The flow in such nozzles is characterized by low Reynolds numbers and, as a consequence, by high viscous losses. DSMC calculations for flows in plane and three-dimensional micronozzles have been conducted in the present paper. A comparison of DSMC results with available experimental data of the nozzle performance is presented. It is proposed to increase the efficiency of micronozzles by helium injection to the near-wall flow region at the throat. This leads to a significant increase in the gas velocity near the nozzle wall and in the specific impulse.

Aerodynamics of space station “Mir” during aeroassisted controlled descent

Future descent of space station “Mir” requires the choice of an optimal configuration (positions of solar arrays) which allows one to minimize the disturbing aerodynamic torques and maximize the drag. The aerodynamic characteristics of two configurations with required positions of solar arrays are studied by engineering and statistical methods along the descent trajectory. The study showed that a decrease in the flight altitude from 200 to 130 km does not exert a noticeable effect on the magnitude of the force and moment coefficients and also revealed the reasons decreasing the accuracy of the engineering prediction.

Rarefaction effects on separation of hypersonic laminar flows

A hypersonic monoatomic gas (argon) flow around a hollow cylinder flare was numerically simulated for low-to-moderate Reynolds numbers. A shock wave induced by the flare causes the formation of a separation region, and flow rarefaction near the leading edge affects the separation extent. The continuum (Navier–Stokes equations) and kinetic (the DSMC method) approaches were used to study the influence of the Mach number and wall-to-freestream temperature ratio on the flow structure and separation. To take into account rarefaction effects, slip boundary conditions are used for the Navier–Stokes solver.

HYPERSONIC BOUNDARY LAYER ANALYSIS COMPARISON OF VELOCI TY MEASUREMENTS AND MONTE -CARLO CALCULATIONS

* Research scientist, Theoretical and Applied Optics Department. † Research scientist, Fundamental and Experimental Aerodynamics Department. ‡ Senior research scientist, Physical Instrumentation and Sensing Department. § Scientific director, Office National d’Etudes et de Recherches Aerospatiales. ¶ Senior research scientist, Institute of Theoretical and Applied Mechanics. # Professor, Institute of Theoretical and Applied Mechanics. Associate fellow. INTRODUCTION