Plasma Aerodynamics Research Articles

Kinetics of low-temperature plasmas for plasma-assisted combustion and aerodynamics

Kinetic processes in a weakly ionized non-equilibrium plasma are considered under conditions that are typical for plasma-assisted ignition/combustion and flow control. The focus is on the simulation of active species production that leads to ignition delay reduction, flame stabilization and expansion of the flammability limit of combustible mixtures. We discuss the lack of information on electron cross sections for hydrocarbons and the accuracy of widely used approaches to simulate kinetics of active species production in air and combustible mixtures. Fast gas heating after a high-voltage nanosecond discharge is studied for various gas mixtures and reduced electric fields. We analyze the effect of negative ions generated in the afterglow of a high-voltage discharge with regard to plasma-assisted ignition and plasma aerodynamics application.

Electrical Discharge Interaction With Gas Flows in External Magnetic Field

The study of electrical discharges interaction with gas flows of different configurations in external electric and magnetic fields is an important part of plasma aerodynamics. Images of electrical discharge evolution in the external magnetic field in a gas flow are presented in this paper.

Plasma aerodynamics in a supersonic gas flow

We perform an experimental study and numerical simulation of the process of periodic initiation of spark extended discharge in air flow with a Mach number M = 2. Critical parameters of the discharge are measured in a high velocity air flow, and visualization of the gas flow in the presence of the discharge is performed. The influence of the discharge on the flow near the body surface streamlined by the supersonic flow is studied.

Electrical and kinetic model of an atmospheric rf device for plasma aerodynamics applications

The asymmetrically mounted flat plasma actuator is investigated using a self-consistent two-dimensional fluid model at atmospheric pressure. The computational model assumes the drift-diffusion approximation and uses a simple plasma kinetic model. It investigated the electrical and kinetic properties of the plasma, calculated the charged species concentrations, surface charge density, electrohydrodynamic forces, and gas speed. The present computational model contributes to understand the main physical mechanisms, and suggests ways to improve its performance.

Microwave and Direct-Current Discharges in High-Speed Flow: Fundamentals and Application to Ignition

DOI: 10.2514/1.24803 The main parameters and properties of an electrodeless freely localized microwave discharge, a surface microwave discharge, transversal in relation to the gas flow direct-current and pulse-periodic electrode discharges, andacombined microwavedirect-current dischargeareexperimentally investigated.It isshown thatalltypesof the discharges result in a reliable ignition of hydrocarbon fuel. Combustion of a propane–air supersonic stream is realized under condition of the combined surface microwave and direct-current discharge. To find out the influence ofdifferent channels ofenergy transfer onignition ofcombustible mixtures in asupersonic flow,the kinetic modelof ignition of hydrocarbons–air mixtures, and taking into account the influence of electric field on processes of dissociation molecules and creation of the active radicals, excited and charged (electrons, positive and negative ions) particlesunderconditionsofnonequilibriumplasmaofthegasdischargewasdeveloped.Mathematicalmodelinghas revealed a strong influence of the reduced electric field on induction period. The microwave discharges may find applications in different fields of supersonic plasma aerodynamics and in development of new-generation plasma sources for plasma chemistry, nano- and microelectronics purposes (plasma treatment of surfaces, etching, and film deposition), and so on.

Modelling wire-to-wire corona discharge action on aerodynamics and comparison with experiment

The purpose of this paper is to propose a simple model for plasma generation and effect on fluids at atmospheric pressure. Experiments are conducted using a wire-to-wire corona discharge actuator in a subsonic boundary layer flow. Velocity gains of several metres per second are observed. A quasi-2D numerical model of the discharge is proposed and explains the creation of two corona discharges around the electrodes. A one-way approach of the plasma aerodynamics coupling gives access to the ionic wind. It is confirmed that the actuator accelerates the flow from the anode to the cathode. Order of magnitudes of the ionic wind and flow velocity profiles are close to experiments. A first attempt to perform a 2D simulation of the wire-to-wire discharge is presented as the starting point of future works.

Transient Rotating Hydromagnetic Partially-Ionized Heat-Generating Gas Dynamic Flow with Hall/Ion-Slip Current Effects: Finite Element Analysis

A mathematical model is presented for the unsteady magnetohydrodynamic heat-generating free convection flow of a partially-ionized gas past an infinite vertical porous plate in a rotating frame of reference. Hall and ion-slip current effects are incorporated in the model. A finite element solution to the coupled non-linear differential equations is presented under physically realistic boundary conditions. The effects of Hall current parameter, ion-slip current parameter, Prandtl number, heat generation parameter, rotational parameter, Grashof (buoyancy) parameter and also time on the velocity and temperature fields are presented graphically. Primary velocity profile (u) decreases due to an increase in the Hall parameter and the ionslip parameter; however it is boosted with time for positive Grashof numbers (cooling of the plate by free convection currents) and decreases with time for negative Grashof numbers (heating of the plate by free convection currents). Secondary velocity profile (v) is also reduced with rising Hall parameter and ionslip parameter but boosted with time and stronger rotation. The temperature profile (θ) is enhanced with a rise in the heat generating parameter and also increases with time. The flow regime has important applications in MHD energy systems, plasma aerodynamics and induction flow meter technologies.

Theoretical Aerodynamics in Today's Real World: Opportunities and Challenges

*† In spite of the CFD revolution, significant challenges still face aerodynamicists in predicting and controlling various classes of flows. These include three-dimensional separation, boundary layer transition, interaction of separation and transition such as on reentry capsules, multi-element airfoils and wings, UAV low Reynolds number flows and high angle of attack applications. Others include multi-body flows such as those occurring in store and stage separation, “stiff” combustion reacting and unsteady flows as well as plasma aerodynamics and turbulence, to name a few. In many cases, diverse multiple scales are involved and the proper identification and treatment of associated disparate length and time scales is critical in obtaining accurate prediction and effective control. The solution of such multi-scale problems can be a hurdle to effective domain decomposition, even overset, unstructured adaptive gridding and ultimately, solution accuracy. Theoretical insights can help make proper decisions on numerical pre-processing, solution, post-processing and interpretation. Opportunities for a combined theoretical, computational and experimental approach will be discussed. These will be illustrated by examples from the author’s experience. As compared to the limited “pen and paper” theoretical methods of the 50’s, illustrations will be given of the effectiveness of combined asymptotics, similitude, group invariance, approximate physics-based modeling and numerical methods for conceptual vehicle design, flow control innovation, identification of key parameters, leveraging of computational solutions, reducing the parameter space as well as providing added insight into the basic physical processes. These will be related to tradeoffs between accuracy and response speed in typical aerospace environments.

Freely localized microwave discharge in a supersonic gas flow

A discharge produced by a focused microwave beam in a supersonic gas flow has been investigated experimentally. It is shown that the degree of ionization and the gas temperature in the discharge are fairly high and that the main properties of the discharge plasma are only slightly affected by the supersonic air flow. Discharges produced by focused microwave beams can find application in supersonic plasma aerodynamics.

Microwave discharge on the surface of a dielectric antenna

A microwave discharge initiated by a surface wave on a dielectric body placed in a supersonic air flow is studied. The discharge is shown to represent a thin plasma layer that uniformly covers the antenna surface. In experiments, the discharge propagation velocity may be as high as 100 km/s, which is several orders of magnitude higher than the velocity of sound in air. The peak pulse power necessary to excite the discharge in a wide range of air pressures (from 10−3 to 103 Torr) is no higher than 100 kW. It is shown that the gas temperature may rise to 1000–2000 K, rapidly increasing (with a rate of ≈50 K/μs) at the early stage of discharge evolution. The discharge of this type may find applications in super-and hypersonic plasma aerodynamics (such as control of the flow near the surface of a body moving in a dense atmosphere, reduction of surface friction, optimization of ignition and combustion conditions for supersonic flows of gaseous fuel, etc.). It may also be used to advantage in development of new-generation plasma sources for micro-and nanoelectronics purposes (plasma treatment of surfaces, etching, and film deposition).

Advanced Performance Modeling of Experimental Laser Lightcraft

A computational plasma aerodynamics model is developed to study the performance of a laser-propelled lightcraft. The computational methodology is based on a time-accurate, multi-dimensional, finite volume, chemically reacting, unstructured grid pressure-based formulation. The underlying physics are modeled using a building-block approach. The physics modeled include nonequilibrium thermodynamics, nonequilibrium air-plasma finite rate kinetics, specular ray tracing, laser beam energy absorption and refraction by plasma, nonequilibrium plasma radiation, and plasma resonance. A series of transient computations are performed at several laser pulse energy levels and the simulated physics are discussed and compared with those of tests and literatures. The computed impulses and coupling coefficients for the lightcraft compared reasonably well with those of tests conducted on a pendulum apparatus.

極超音速飛行実験（ＨＹＦＬＥＸ）について 飛行結果を中心に ＨＹＦＬＥＸにおける空力加熱及びプラズマ電子密度計測とＣＦＤ解析

極超音速飛行実験（ＨＹＦＬＥＸ）について 飛行結果を中心に ＨＹＦＬＥＸにおける空力加熱及びプラズマ電子密度計測とＣＦＤ解析

A technique for generating strong shock waves at atmospheric pressures

A new technique for generating strong shock waves at atmospheric pressure is reported. The technique has been used for generating Mach 8 shock waves with a capacitively stored energy of 0.612 kJ. The technique is simple to use, particularly for aerodynamic and arc plasma probing applications.