Papers by Gennady Markelov
AIP Conference Proceedings, 2005
AIP Conference Proceedings, 2003
The computations of a near-continuum flow with separation were performed using the DSMC method fo... more The computations of a near-continuum flow with separation were performed using the DSMC method for a hollow cylinder flare configuration with the Reynolds number of 15,000 and 26,000. An efficient spatial correlator is developed for the DSMC method to estimate an impact of the statistical dependence between molecules on simulation results. Good agreement between the numerical results and available experimental data is obtained for the least dense case, where the DSMC requirements for cell size and the number of molecules are satisfied. For more dense cases, even 80 million molecules and 20 million cells do not satisfy the DSMC requirements, resulting in the underprediction of the separation zone size.
AIP Conference Proceedings, 2001
A hypersonic monoatomic gas (argon) flow around a hollow cylinder flare was numerically simulated... more 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.
AIP Conference Proceedings, 2003
Statistical simulation of flow around a hollow cylinder flare was performed for LENS Run 9 and Ru... more Statistical simulation of flow around a hollow cylinder flare was performed for LENS Run 9 and Run 11 cases. A comparison with experimental and available numerical results shows that the kinetic approach predicts flow properties rather accurately if all the requirements inherent in the DSMC method (time step, cell size, and the total number of molecules) are satisfied. A recent study of the flow in the LENS wind tunnel shows that the flow is vibrationally non-equilibrium. A computation with corrected flow conditions for Run 11 case predicts lower heat fluxes over the forebody and the aft part of the flare which are in good agreement with experimental data.
Lpi Contributions, Sep 1, 2005
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AIP Conference Proceedings, 2005
Hypersonic chemically reacting flow around a wedge in the near-continuum regime was numerically s... more Hypersonic chemically reacting flow around a wedge in the near-continuum regime was numerically studied by the DSMC method with the main goal of validation of real gas effect models. The influence of vibration-dissociation coupling on the results of numerical simulations was analyzed. To this end, two models of chemical reactions were used in the computations, the total collisional energy model and a vibrationally favored model. The numerical results were compared with the experimental data of Hornung and Smith on the shockwave stand-off distance in a hypersonic flow around the wedge. Sensitivity of simulation results to chemical reaction rate constants was also estimated.
AIP Conference Proceedings, 2001
The SPT-100 thruster plume was simulated using two different methods: the combined particlein-cel... more The SPT-100 thruster plume was simulated using two different methods: the combined particlein-cell technique with direct simulation Monte Carlo method and the particle-in-cell with the addition of Monte Carlo collisions method. The former method offers a more detailed description of the plume, taking into account the effect of ion-neutral collisions on neutral flow. This effect is ignored in the second method, but this method has much lower computational cost. To analyze the influence of uncertainties in plasma parameters at the thruster exit plane, the computations with different boundary conditions were performed. It is shown that the difference in results obtained by the two methods is significantly smaller than that caused by the uncertainty in flow parameters at the thruster exit plane.
ABSTRACT The paper presents a numerical analysis of a molecular flow through purging tubes of Aeo... more ABSTRACT 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.
30th Fluid Dynamics Conference, 1999
40th AIAA Aerospace Sciences Meeting & Exhibit, 2002
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.
Bulletin of the American Astronomical Society, 2004
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" (coherent and spotted) for a non-spherical nucleus at different heliocentric distances. Gas flows from nucleus area containing various morphological formations (such as flat-bottom craters and mesas) with reasonable topographical features are treated. The corresponding boundary conditions at the nucleus surface are determined from a self-consistent thermal model of a cometary nucleus developed by 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 gas density, temperature and velocity are calculated by parallel computer implementation of the kinetic model. The qualitative comparison with the observational data obtained for comet Wild 2 by the Stardust space probe is done. 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 local 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 general nucleus shape as well as nucleus morphology play the major role in interpretation of innermost coma along with physical properties of nucleus.
38th AIAA Thermophysics Conference, 2005
Thermophysics and Aeromechanics
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Papers by Gennady Markelov