Mario R. Carraro

Electrohydrodynamic interaction induced by a dielectric barrier discharge

In the present work an experimental investigation on the electrohydrodynamic (EHD) interaction effect, induced by means of a dielectric barrier discharge on a 1atm subsonic air flow, is described. The air flow is obtained in an open circuit blowing wind tunnel at different air speeds. A plane plasma panel equipped with a dielectric discharge barrier system is immersed in the flow. A single phase sinusoidal power supply system, a superposition of a single phase sinusoidal system with a dc voltage supply, and a three phase symmetrical power supply configuration are considered. Electric, fluid dynamic, and spectroscopic diagnostic techniques are utilized. Pitot probe measurements are performed in the boundary layer on the plasma panel surface. Schlieren imaging is done to visualize the plasma sheath. Vibrational and rotational temperatures are evaluated by means of spectroscopic techniques. The force induced on the flow by the dielectric barrier discharge acts on the ions of the non-neutral sheath ahead of t...

Magnetohydrodynamic Interaction in the Shock Layer of a Wedge in a Hypersonic Flow

This paper describes the results of an experimental investigation on the effect of magnetohydrodynamic (MHD) interaction with the plasma of the shock layer at a test body in a hypersonic argon flow. The hypersonic flow is obtained from the high-enthalpy arc-heated wind tunnel of Alta, Pisa, Italy, on Mach 6. Tests are carried out at heating chamber stagnation pressures of 0.65, 0.85, and 1 bar and magnetic fields of 0.15-0.35 T. The experimental observations are done by means of a set of electrical probes, an optical multichannel analyzer, and a fast shutter charge-coupled device camera. In order to maximize the effect of MHD interaction, the Faraday field is shorted, and a magnetic field perpendicular to the test body surface is used. An increase of the distance between the shock front and the body, owing to the MHD interaction, is observed. The MHD interaction effect is reduced by the low conductivity of the plasma in the boundary layer at the test body surface

Numerical modeling of MHD interaction in the boundary layer of hypersonic flows

A model for the analysis of the magnetoplasmadynamic regime, devoted to magnetohydrodynamics (MHD) systems in a hypersonic flight vehicle, is presented. In the model, the discrete formulation of fluid dynamics and electrodynamics are coupled. The Navier-Stokes equations are discretized by means of a finite volume formulation. The electrodynamics is discretized by means of a finite-element method. The model has been utilized for the analysis of MHD interaction for the fluid control over a hypersonic body. Calculations have shown that MHD interaction can strongly affect the boundary layer fluid dynamic regime.

Hypersonic MHD Interaction on a Conical Test Body With a Hall Electrical Connection

The MHD interaction around a conical test body in a hypersonic argon flow was experimentally investigated. The aim of the experiment was to produce a database to be used for the validation of numerical codes for the analysis and simulation of the magnetofluid dynamics in hypersonic flows. In these experiments, the flow was obtained in the High-Enthalpy Arc-heated hypersonic wind Tunnel of Alta, Pisa, Italy. Speeds at Mach 6 were reached. In this experiment, the flow and plasma characteristics have been determined. The MHD interaction was obtained in the shock layer of a conical test body placed at the exit of the hypersonic nozzle. The realized electrical configuration allowed the enhancement of the effect of the MHD interaction on the plasma parameters. This was done by utilizing the Hall field to generate the MHD interaction and by short-circuiting the Faraday current inside the plasma of the shock layer. The magnetic-flux density was produced by an array of three magnets located in the test body. Test runs were performed at three different stagnation pressures. Fluid-dynamic, electrical, and optical observations have been done. The experiment showed a large effect of the MHD interaction on the values of the measured quantities. In order to have a test body that is entirely contained in the region where a uniform hypersonic flow has been measured, a test body of smaller size has been constructed and tested. The results obtained in this case confirm the results of the tests with the larger body.

Analysis of Magnetoplasmadynamic Interaction in the Boundary Layer of a Hypersonic Vehicle

A model for the analysis of the magnetoplasmadynamic regime, devoted to magnetohydrodynamic (MHD) systems in a hypersonic flight, is presented. In the assumption of a low-magnetic-Reynolds-number regime, the model couplesa time-dependent formulation of fluid dynamics with steady-state electrodynamics. The Navier-Stokes equations are discretized by means of a finite volume formulation. The electrodynamics is discretized by means of a finite element method. The model has been utilized for the analysis of the MHD interaction in the boundary layer of a test body in a wind tunnel. The activity is aimed to design the experimental activity in the frame of an Italian Space Agency research project on the MHD interaction in hypersonic flows. Calculations have shown that MHD interaction can be greatly weakened by the effect of the Hall current.

An Analysis of a Three Phase Flat Panel Uniform Barrier Discharge at Atmospheric Pressure

In this work, the properties of a one atmosphere uniform three phase barrier discharge panel in a subsonic wind tunnel have been investigated. The power supply system has been specifically designed for this application by means of a PIC generated signal reference and audio MOSFET amplifiers. Electric, fluid-dynamic and spectroscopic diagnostic techniques were utilized to characterize the plasma. The discharge panel had been tested inside an open circuit blowing wind tunnel, at different power supply conditions and air flow speeds. Moreover, a phase transposition has been performed in order to investigate the influence of the three phase translating wave on the fluid acceleration. All diagnostics were applied to the different electrode connection schemes. Vibrational and rotational temperatures were evaluated by means of spectroscopic techniques. Active and reactive power have been monitored by means of voltage and current probes. The flow velocity on the board surface was measured by means of a Pitot probe.

Plasma and Flow Characterization in a Flat Panel One Atmosphere Uniform Barrier Discharge

The properties of a one atmosphere uniform barrier discharge panel in a subsonic wind tunnel, have been investigate. Electric, fluid-dynamic and spectroscopic diagnostic techniques have been utilized. The discharge panel was tested inside an open circuit blowing wind tunnel, at different power supply conditions and air speeds. The characteristic of the boundary layer on the plasma panel, have been investigated by means of a Pitot probe. Vibrational and rotational temperatures have been evaluated by means of spectroscopic techniques. The measured electric properties were correlated to spectroscopic data. Flow visualization was also performed by means of a Schlieren setup. In order to raise the thrust efficiency, the set up of the plasma panel has been varied. For each electrode pair, a high voltage DC electrode was added. This leads to a DC discharge on the plasma sustained by the AC barrier discharge. This discharge causes an aerodynamic effect originated by the associated ionic wind.

MHD Interaction over an Axial Symmetric Body in a Hypersonic Flow

The MHD interaction around a conical test body in a hypersonic argon flow is experimentally investigated. The hypersonic flow is realized in the high-enthalpy arc-heated wind tunnel of Alta (Pisa-Italy) at Mach 6. The aim of the experiment is to produce a data base to be used for the validation of numerical codes which are utilized to analyze the magneto-fluid dynamics in hypersonic flows. In the present experiment the MHD interaction is obtained in the shock layer of a conical test body placed at the exit of the hypersonic nozzle. The electrical configuration realized, allows to enhance the effect of the MHD interaction on the plasma parameters. This is done by utilizing the Hall field to generate the MHD interaction and by short-circuiting the Faraday current inside the plasma of the shock layer. The magnetic flux density is produced by an array of three magnets located in the test body. Test runs are performed at three different stagnation pressures. Fluid-dynamic, electrical and optical observations have been done. The experiment showed a large effect of the MHD interaction on the values of the measured quantities.

Numerical solution of the nonlinear electrodynamics in MHD regimes with magnetic Reynolds number near one

In magnetohydrodynamic (MHD) regimes of plasmas with magnetic Reynolds number comparable to one, electrodynamics exhibits a nonlinear characteristic. In the present paper, the electrodynamics has been discretized utilizing a finite-element method. The problem unknown is the electric scalar potential. Nonlinearity is caused by the dependence of the electric transport parameters and of the source terms on the magnetic flux density. Different approaches are evaluated to deal with the nonlinearity. The model has been coupled with a solver of the Navier-Stokes equations. The MHD interaction in the boundary layer of an hypersonic flight has been analyzed.

Non-Intrusive Characterization of the Ionized Flow Produced by Nozzle of an Hypersonic Wind Tunnel

The supersonic expansion of an ionized gas through a converging-diverging nozzle is characterized by strong departure from equilibrium conditions. In this work, a complete plasma characterization has been carried out on the Alta High-Enthalpy Arc-Heated Tunnel (HEAT), as a preliminary activity of a test campaign focused on the effect of the MHD interaction with the plasma of the shock layer. After a standard aerothermodynamic characterization of the hypersonic flow carried out through pressure and heat flux measurements, two different plasmas diagnostic systems have been utilised to characterize the system: emission spectroscopy in the HEAT plenum chamber and microwaves at the exit of the nozzle. The plasma in the arc heater plenum chamber has been investigated by means of optical emission spectroscopy techniques relying on the high pressure and, thus, on the PLTE conditions before the expansion in the nozzle. Electron excitation temperature has been evaluated from continuum and Boltzmann plots; electron number density has been derived from H-alpha Stark broadening and continuum. Conversely, the plasma cools down throughout the expansion in the nozzle and electrons develop non equilibrium distribution, as demonstrated by the calculations done in order to simulate the process. Microwaves absorption diagnostic technique shows a very weak dependence on electron energy distribution, and therefore was chosen to probe the electron number density at the end of the nozzle. Probing the plasma at the same time both at the beginning and at the end of the nozzle leads to the correlation of the measures to the results of a quasi one-dimensional model of the plasma expansion code based on the state-to-state kinetics, that consider a kinetic equation for each internal state of the heavy particles, self consistently coupled with the Boltzmann equation of free electrons.