Instability of Front Separation Regions Initiated by Energy Deposition of Various Geometrical Configurations

Abstract

†Regimes of wave drag reduction for various energy deposition geometrical configurations are studied focusing on the efficiency and stability aspects. Some regimes were examined previously but now all numerical experiments were repeated for more accuracy. Also the new regime – the flow past blunt and streamlined bodies in the presence of the energy deposition in the toroidal-type region was examined. The typical peculiarity of this regime is Mach reflection of the shock near the symmetry axes. The regime appears as perspective – the considerable wave drag reduction is obtained and in addition the body surface is isolated from the temperature wake by the high enthalpy cold stream. I. Introduction During the past 20 years the localized energy deposition in particular was considered as the method for an improvement of aerodynamic characteristics of different bodies in the supersonic flow. Surveys of the theoretical and experimental investigations for using of the energy deposition for flow control and the aerodynamic drag reduction for different historical period are presented by respectable authors in Ref. 1–4. Wide range of related problems is discussed during regular conferences such as International Workshop on Magneto-Plasma Aerodynamics in Moscow, Russia or Weakly Ionized Gases Workshop in USA. Many physical ideas basing on the plasma physics techniques are proposed for realization of the localized energy deposition in the supersonic flow: electric discharges of different type, or microwave discharges, or laser-spark optical breakdown, or combined technique of laser-pulse controlled microwave discharges. In the last few years the guidelines of the future research activities for the control of the flow past bodies are the subject of discussion. Very complicated numerical simulations for conditions of specific physical experiments are carried out. In Ref. 5 sophisticated mathematical model of the electric discharge was used for numerical simulation of the viscous supersonic flow past the sphere. In Ref. 6 the results of parametrical numerical researches of flows over blunt and streamlined axisymmetrical bodies with the pulse-periodic energy deposition for conditions of P. Tretyakov et al. physical experiments with laser sparks were presented. In Ref. 7 the interaction of the microwave filament with the shock layer ahead of blunt bodies was examined. Very complicated kinetic for the microwave discharge in the supersonic flow in application for a flow control past blunt bodies was analyzed in Ref. 8. In our opinion the investigation of classical gasdynamics problems of the supersonic flow past bodies in the presence of the localized energy deposition is also very important for understanding the perspectives of plasma techniques application for flow control. The theoretical possibility of wave drag reduction for blunt bodies by the localized energy deposition was shown in early works Ref. 9–10. The idea of the effective flow control for wave drag reduction was associated with the formation of front separation regions ahead of a fore surface of both blunt and streamlined bodies in Ref. 11. Term “effective” means, that the saved power is higher than the power input. Appearing of front separation regions is resulted from the interaction of the high temperature wake, which is formed downstream the energy deposition region, with the shock structure and the shock layer ahead of the body. According to Ref. 12 steady isobaric front separation regions are acceptable for the wake-type upstream flow of any nature (in particular for temperature wakes of any thickness). So for the infinitely small energy deposition region