A Method for Predicting Efficiency of Perforated Muzzle Brakes

This paper presents a method for predicting a value of a gasdynamic efficiency coefficient for perforated muzzle brakes. The method is based on the interior ballistics modelling for determining gasdynamic flow parameters at the brake inlet and 2D modelling the processes inside the brake with treating vents as circumferential slots. The modelling provides information about the mass flux time changes at the inlet and at the outlet of the brake. Using this information, the mass partition coefficient values and the gasdynamic efficiency coefficient values are calculated. It has been shown that the mass partition coefficient establishes very quickly and it is determined only by the geometry of the brake. The gasdynamic efficiency coefficient establishes after a relatively long time, what demands carrying out calculations for a relatively long time period. However, it has been shown that this problem can be solved by making use of the established ratio of mass fluxes at the outlet and the inlet. So, flow parameters’ values at the inlet are sufficient for determining the gasdynamic efficiency coefficient to the moment of attaining the final value. It has been shown that this value depends on the ballistics and on the vents inclination angle.

Gasdynamic Flow Control by Ultrafast Local Heating in a Strongly Nonequilibrium Pulsed Plasma

Abstract— The paper presents a review of modern works on gasdynamic flow control using a highly nonequilibrium pulsed plasma. The main attention is paid to the effects based on ultrafast (on the nanosecond time scale for atmospheric pressure) local gas heating, since, at present, the main successes in controlling high-speed flows by means of gas discharges are associated with this thermal mechanism. Attention is paid to the physical mechanisms responsible for the interaction of the discharge with gas flows. The first part of the review outlines the most popular approaches for pulsed energy deposition in plasma aerodynamics: nanosecond surface barrier discharges, pulsed spark discharges, and femto- and nanosecond optical discharges. The mechanisms of ultrafast heating of air at high electric fields realized in these discharges, as well as during the decay of the discharge plasma, are analyzed separately. The second part of the review gives numerous examples of plasma-assisted control of gasdynamic flows. It considers control of the configuration of shock waves in front of a supersonic object, control of its trajectory, control of quasi-stationary separated flows and layers, control of a laminar–turbulent transition, and control of static and dynamic separation of the boundary layer at high angles of attack, as well as issues of the operation of plasma actuators in different weather conditions and the use of plasma for the de-icing of a flying object.

Linear Irreversible Phenomenological Thermodynamics of Polarization Processes in Rigid Unmagnetic Insulators

We show how classical irreversible thermodynamics is used to derive relaxation equations for dielectric polarization processes in insulators. We calculate susceptibilities for multiple polarization processes and show how coupling arises thermodynamically. Furthermore, we derive evolution equations for electromagnetic fields by combining the dielectric relaxation equations with Maxwell’s equations. Analytical solutions for various frequency regimes will be briefly discussed. A complete analogy exists between the dielectric problem, the Kelvin–Voigt viscoelasticity of solid media, and the non-equilibrium (reactive, vibrational) gasdynamic flow. Also, numerical solutions, using the method of characteristics, are given for a generic signal problem in half-space.

Single Pulse Carbon-13 Enrichment of CF3 Under IR MPD in A Short Gas Dynamic Flow

An experimental approach is described for obtaining highly enriched residual gas under IR multiphoton dissociation (MPD) of molecules in one cycle of irradiation. The approach is based on utilization of a pulsed molecular flow of small length (Δxfl≤1cm). The use of a short flow length leads to high values of the dissociation yield of molecules (β≃1) in the whole volume of the flow. Owing to this, high enrichment of the residual gas is achieved in one cycle of irradiation. The isotopically-selective dissociation of CF3I+ in the pulsed gasdynamic flow of a small length was studied. About 400-fold enrichment of the 13C isotope in the residual gas was obtained following irradiation of a molecular flow of CF3I of natural isotope composition by a single laser pulse. The selectivity of dissociation was measured to be α≥10