Papers by Gennady Markelov
Journal of Aircraft, 2000
ABSTRACT
9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, 2006
The key to the explanation of most phenomena associated with the 'activity' of comets is the prop... more The key to the explanation of most phenomena associated with the 'activity' of comets is the proper understanding of processes taking place within a thin layer around the nucleus/cometary atmosphere interface. As a comet is heated by the Sun, the highly variable dusty atmosphere is formed due to sublimation of volatile components of the cometary nucleus and lifting of nonvolatile grains. We believe that a cometary nucleus can be described as a body of high porosity and low density. The solar radiation can penetrate to a substantial skin depth. Thus both energy absorption and sublimation in the uppermost porous layer have a volumetric character. Due to intermolecular collisions in the innermost coma, backflows are formed. Therefore the nucleus and the innermost coma of an active comet constitute an interacting physical system.
A Direct Simulation Monte Carlo (DSMC) method is used to model low density axisymmetric gas flows... more A Direct Simulation Monte Carlo (DSMC) method is used to model low density axisymmetric gas flows in the innermost coma region. We consider various types of "activity" (and spotted) both for a spherical and non-spherical nucleus at different heliocentric distances. The corresponding boundary conditions at the nucleus surface are determined from a self-consistent thermal model of a cometary nucleus developed by the authors (Davidsson and Skorov, Icarus, 2002). New model features are the absorption of the irradiation within the uppermost layers of the pores, kinetic treatment of gas transport into porous ice, the return gas fluxes from the coma, and temperature dependent condensation and sublimation coefficients. Fields of density, different types of temperature and velocity are calculated by parallel computer implementation of the kinetic model. The comparison with the results of fluid dynamics simulation is done where it is possible. We show that the innermost coma is sensitive to the nucleus shape as well as to the variations of local gas production rates. At the same time, small topography features produce only small coma "disturbances". In general spatial structures of the innermost coma (both gas and dust) are a result of interactions of gas flows sublimated from different surface regions. We conclude that the nucleus shape plays the major role in interpretation of innermost coma along with physical properties of nucleus.
The paper presents a numerical analysis of a molecular flow through purging tubes of Aeolus space... more The paper presents a numerical analysis of a molecular flow through purging tubes of Aeolus spacecraft. The tubes have complex three-dimensional shapes and connect power laser head devices with the surface of the spacecraft. The flow around the spacecraft is nearly free-molecular and it is formed due to material outgassing and erosion, thruster firing, ambient atmosphere at low Earth orbit etc. Due to low pressure intermolecular collisions do not affect the results and the tube transmission probabilities were computed mainly using the test particle Monte Carlo method. The correspondent software was developed out of the well-known code, SMILE that is used to model rarefied gas flows. Effects of sticking of molecules on the tube wall and incomplete accommodation of tangential momentum on the transmission probability were studied. The obtained results were used to estimate pressure build-up inside the power laser head device and contamination of the equipment there.
Future descent of space station ``Mir'' requires the choice of an... more 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
Lecture Notes in Computer Science, 2008
ABSTRACT
Proceedings of 10th World Congress on Computational Mechanics, 2014
Vacuum, 2012
The paper presents a numerical analysis of plume exhausted from the 10N bipropellant thruster. Th... more The paper presents a numerical analysis of plume exhausted from the 10N bipropellant thruster. The computations have been performed for steady state and pulse mode firing of the thruster. The plume impinges a multi-layer insulation (MLI) that covers a satellite surface, where plume effects have been computed for ideal and bulged shapes of the MLI. The ideal shape is a circular cylinder surface, where the bulge is a deflection of the MLI due to satellite spin. Plume effects, pressure and heat flux, are almost doubled for the bulged MLI. An engineering model based on experimental data has been applied. It was shown that it is conservative against the numerical modeling in the plume backflow. An application of the pulse mode leads to a formation of droplets. One of the sources of the droplets is a rupture of liquid film at the nozzle lip. A parametric study with different droplet sizes and initial velocities has been performed for thrusters firing along and against the satellite spin. The thruster that fires against the satellite spin contaminates the MLI more than the other thruster. Droplets with an initial velocity smaller than 6m/s cannot contaminate the MLI.
Journal of Spacecraft and Rockets, 2007
ABSTRACT
Journal of Physics: Conference Series, 2008
ABSTRACT ALADIN is the very first space-based lidar that will provide global wind profile and a s... more ABSTRACT ALADIN is the very first space-based lidar that will provide global wind profile and a special attention has been paid to contamination of ALADIN optics. The paper presents a numerical approach, which is based on the direct simulation Monte Carlo method. The method allows one to accurately compute collisions between various species, in the case under consideration, free-stream flow and outgassing from solar array materials. The collisions create a contamination flux onto the optics despite there is no line-of-sight from the solar arrays to the optics. Comparison of obtained results with a simple analytical model prediction shows that the analytical model underpredicts mass fluxes.
Solar System Research - SOLAR SYST RES, 2004
The key to the explanation of the variety of processes associated with the activity of comets lie... more The key to the explanation of the variety of processes associated with the activity of comets lies in a more profound understanding of the events that occur in the near-surface layer of the cometary nucleus and in the inner part of the cometary atmosphere, which is formed under the action of solar radiation. A complete description of the mass- and energy-transfer processes inside and outside the cometary nucleus, which can be presented as a body with a complex morphology and high porosity and which is composed of mineral, organic, and volatile components, is an extremely complicated problem of space physics. The nucleus and the inner part of the coma are closely related to each other as physical subsystems, and physical processes in these regions are in close symbiosis because of the permanent exchange of both energy and mass. The thermophysical model of the circumnuclear coma cannot be confined only to the consideration of the processes in the nucleus---the entire system should be ...
IEEE Transactions on Plasma Science, 2000
SMART-1 is the first European spacecraft that uses electric propulsion as the main propulsion sys... more SMART-1 is the first European spacecraft that uses electric propulsion as the main propulsion system. The thruster characteristics and plasma measurements performed during SMART-1 mission lay a good foundation for understanding spacecraft/plasma interactions. This paper discusses the applications and modifications of spacecraft plasma interaction system software, which originally was developed to simulate an interaction of the space plasma with the spacecraft-surface materials and to compute a plasma-induced charging. The particle-in-cell and Monte Carlo collision (PIC-MCC) method and a simplified and fast approach that tracks only slow ion motion are implemented to model the plasma flow around the spacecraft with electric propulsion. The simplified approach consists of a consecutive application of a direct simulation MC (DSMC)-based software for neutral flow, axisymmetric PIC-MCC for plume flow, and three-dimensional (3-D) PIC software for plasma flow around the spacecraft. Three-dimensional computations are performed to analyze the effects of single- and double-charged Xenon ions, constant and spatially variable electron temperature, an application of quasi-neutral assumption or Poisson solver, and low Earth orbit environment on plasma flow around SMART-1. It was shown that a spatially variable electron temperature has the most significant effect on the plasma-flow properties
Shock Waves, 2001
New numerical and experimental results on the transition between regular and Mach reflections of ... more New numerical and experimental results on the transition between regular and Mach reflections of steady shock waves are presented. The influence of flow three-dimensionality on transition between steady regular and Mach reflection has been studied in detail both numerically and experimentally. Characteristic features of 3D shock wave configuration, such as peripheral Mach reflection, non-monotonous Mach stem variation in transverse direction, the existence of combined Mach-regular-peripheral Mach shock wave configuration, have been found in the numerical simulations. The application of laser sheet imaging technique in streamwise direction allowed us to confirm all the details of shock wave configuration in the experiments. Close agreement of the numerical and experimental data on Mach stem heights is shown.
9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, 2006
This paper presents the software system SMILE for 2D/3D direct statistical simulation of rarefied... more This paper presents the software system SMILE for 2D/3D direct statistical simulation of rarefied flows. The system is designed for parallel computations on multiprocessor computers, is equipped by a user-friendly graphical interface, and includes sophisticated models of real gas effects. A generic description of the system structure and approaches implemented is given. Results illustrating the possibilities of the SMILE code are presented.
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Papers by Gennady Markelov