Download or read book Simulation of Direct current Surface Plasma Discharges in Air for Supersonic Flow Control written by Shankar Mahadevan and published by . This book was released on 2010 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational simulations of air glow discharge plasma in the presence of supersonic flow are presented. The glow discharge model is based on a self-consistent, multi-species, continuum description of the plasma with finite-rate chemistry effects. The glow discharge model is coupled to a compressible Navier-Stokes solver to study the effect of the plasma on the flow and the counter-effect of the flow on the plasma. A finite-rate air chemistry model is presented and validated against experiments from the literature at a pressure of 600 mTorr. Computational results are compared with experimentally measured V-I characteristics, axial positive ion densities and electron temperature, and reasonably good qualitative and quantitative agreement is observed. The validated air plasma model is then used to study the effect of the surface plasma discharge on M=3 supersonic flow at freestream pressure 18 Torr and the corresponding effects of the flow on the discharge structure in two dimensions. The species concentrations and the gas temperature are examined in the absence and presence of bulk supersonic flow. The peak gas temperature from the computations is found to be 1180 K with the surface plasma alone in the absence of flow, and 830 K in the presence of supersonic flow. Results indicate that O- ions can have comparable densities to electrons in the pressure range 1-20 Torr, and that O2- ion densities are at least two orders of magnitude smaller over the pressure range considered. Different ion species are found to be dominant in the absence and presence of supersonic flow, highlighting the importance of including finite-rate chemistry effects in discharge models for understanding plasma actuator physical phenomena. Electrode polarity effects are investigated, and the cathode upstream actuation is found to be stronger than the actuation strength with the cathode downstream, which is consistent with experimental findings of several groups. A parallel computing implementation of the plasma and flow simulation tools has been developed and is used to study the three-dimensional plasma actuator configuration with circular pin electrodes.
Download or read book A Study of Direct current Surface Discharge Plasma for a Mach 3 Supersonic Flow Control written by Jichul Shin and published by . This book was released on 2007 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: A direct-current, non-equilibrium surface glow discharge plasma in the presence of a Mach 2.85 flow is studied experimentally for flow control applications. The discharge is generated with pin-like electrodes flush mounted on a ceramic plate with sustaining currents from 25 mA to 300 mA. In the presence of a supersonic flow, two distinct discharge modes - diffuse and constricted - are observed depending on the flow and discharge operating conditions. In cathode upstream location, both diffuse and constricted discharges are observed while in cathode downstream location, the discharge mostly exhibits either constricted mode or bistable mixed mode. The effect of the discharge on the flow ("plasma actuation") is characterized by the appearance of a weak shock wave in the vicinity of the discharge. The shock is observed at low powers (~10 W) for the diffuse discharge mode but is absent for the higher power (~100 W) constricted mode. High speed laser schlieren imaging suggests that the diffuse mode plasma actuation is rapid as it occurs on a time scale that is less than 100 [mu]sec. Rotational (gas) and vibrational temperatures within the discharge are estimated by emission spectral line fits of N2 and N2 rovibronic bands near 365-395 nm. The electronic temperatures are estimated by using the Boltzmann plot method for Fe(I) atomic lines. Rotational temperatures are found to be high (~1500 K) in the absence of a flow but drop sharply (~500 K) in the presence of a supersonic flow for both the diffuse and constricted discharge modes. The vibrational and electronic temperatures are measured to be about 3000 K and 1.25 eV (14500 K), respectively, and these temperatures are the same with and without flow. The gas (rotational) temperature spatial profiles above the cathode surface are found to be similar for the diffuse and constricted modes indicating that dilatational effects due to gas heating are similar. However, complete absence of flow actuation for the constricted mode suggests that electrostatic forces may also play an important role in supersonic plasma-flow actuation phenomena. Analytical estimates using cathode sheath theory indicates that ion pressure within the cathode sheath can be significant resulting in gas compression in the sheath and a corresponding expansion above it. The expansion in turn may fully negate the dilatational effect in the constricted case resulting in an apparent absence of forcing in the constricted case. Plasma-induced flow velocity reaches about 1 m/s in stagnant air at the discharge current of order tens of milliamps. This electrostatic forcing in the direction from anode to cathode can play an important role in the boundary layer of supersonic flow.
Download or read book Compressibility Turbulence and High Speed Flow written by Thomas B. Gatski and published by Academic Press. This book was released on 2013-03-05 with total page 343 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compressibility, Turbulence and High Speed Flow introduces the reader to the field of compressible turbulence and compressible turbulent flows across a broad speed range, through a unique complimentary treatment of both the theoretical foundations and the measurement and analysis tools currently used. The book provides the reader with the necessary background and current trends in the theoretical and experimental aspects of compressible turbulent flows and compressible turbulence. Detailed derivations of the pertinent equations describing the motion of such turbulent flows is provided and an extensive discussion of the various approaches used in predicting both free shear and wall bounded flows is presented. Experimental measurement techniques common to the compressible flow regime are introduced with particular emphasis on the unique challenges presented by high speed flows. Both experimental and numerical simulation work is supplied throughout to provide the reader with an overall perspective of current trends. - An introduction to current techniques in compressible turbulent flow analysis - An approach that enables engineers to identify and solve complex compressible flow challenges - Prediction methodologies, including the Reynolds-averaged Navier Stokes (RANS) method, scale filtered methods and direct numerical simulation (DNS) - Current strategies focusing on compressible flow control
Download or read book Simulations of Atmospheric Pressure Plasma Discharges written by Douglas Paul Breden and published by . This book was released on 2013 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt: This document presents a study of the numerical simulation of non-equilibrium plasma discharges in air mixtures in the atmospheric pressure regime. Such plasma is formed by applying a very high electric field over a very short time duration (nano-microsecond) which preferentially heats the electrons to very high temperatures (10 electron Volts or more) while preventing thermalization of the gas. Preferentially heating the electrons to very high temperatures allows the discharge to efficiently and rapidly ionize and dissociate the gas mixture without losing too much energy to thermalization or vibrational excitation. Consequently, two useful characteristics of these discharges are low gas temperatures and rapid electron chemistry. This study focuses on two applications of interest: ignition of fuel-air mixtures and plasma enhanced medicine. For ignition, there are two situations that arise where it is difficult for traditional spark ignition systems to operate. The first is at the supersonic flow regime where the residence time of the flow in the engine is low. The second is high pressure ignition of lean fuel-air mixtures. For plasma medicine and surface treatment, non-equilibrium plasma is an effective means of delivering reactive radical species to the surface while limiting damage due to thermal heating. The problems of interest are characterized by the formation of weakly ionized plasma in the presence of flow fields such as supersonic boundary layers or low speed jets. To simulate the coupled plasma-fluid flow physics of these discharges, two numerical tools are utilized. The first is a two-temperature, multiple species, self-consistent plasma solver with finite rate chemistry which is used to simulate the plasma as it forms in a neutral background gas. The second tool is a multiple-species compressible flow solver which calculates the flow field properties of the background gas mixture.
Download or read book Supersonic Plasma Flow Control Experiments written by and published by . This book was released on 2005 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: A magneto aerodynamic channel was designed and constructed to investigate plasma flow control. Detailed, spatially resolved measurements of dc discharges in the channel freestream were obtained. The flow exaggerated nonuniformities in number density and conductivity. Conductivity was highest near the cathode, and air flow increased conductivity by 2 orders of magnitude near the cathode, compared to a no-flow discharge. There was no significant increase in translational temperature, except near electrode surfaces. There was some limited evidence of vibrational relaxation downstream. Longitudinal dc discharges were created between surface electrodes on a flat plate. Transverse magnetic fields applied parallel to the plate surface created Lorentz forces either into or out of the plate surface. With no applied magnetic field, the discharge increased surface pressure through boundary layer heating and subsequent viscous interaction. A Lorentz force directed into the plate inhibited surface pressure increases, and a Lorentz force in the opposite direction enhanced them. Although this is consistent with a Lorentz force acting on the fluid, joule heating is the dominant effect.
Download or read book Journal of Propulsion and Power written by and published by . This book was released on 2008 with total page 822 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computational Electromagnetic Aerodynamics written by Joseph J. S. Shang and published by John Wiley & Sons. This book was released on 2016-04-11 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents numerical algorithms, procedures, and techniques required to solve engineering problems relating to the interactions between electromagnetic fields and fluid flow and interdisciplinary technology for aerodynamics, electromagnetics, chemical-physic kinetics, and plasmadynamics Integrates interlinking computational model and simulation techniques of aerodynamics and electromagnetics Combines classic plasma drift-diffusion theory and electron impact ionization modeling for electromagnetic-aerodynamic interactions Describes models of internal degrees of freedom for vibration relaxation and electron excitations
Download or read book 43rd AIAA Aerospace Sciences Meeting Exhibit written by and published by . This book was released on 2005 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book U S Government Research Reports written by and published by . This book was released on 1962 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Shock Wave Boundary Layer Interactions written by Holger Babinsky and published by Cambridge University Press. This book was released on 2011-09-12 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shock wave-boundary-layer interaction (SBLI) is a fundamental phenomenon in gas dynamics that is observed in many practical situations, ranging from transonic aircraft wings to hypersonic vehicles and engines. SBLIs have the potential to pose serious problems in a flowfield; hence they often prove to be a critical - or even design limiting - issue for many aerospace applications. This is the first book devoted solely to a comprehensive, state-of-the-art explanation of this phenomenon. It includes a description of the basic fluid mechanics of SBLIs plus contributions from leading international experts who share their insight into their physics and the impact they have in practical flow situations. This book is for practitioners and graduate students in aerodynamics who wish to familiarize themselves with all aspects of SBLI flows. It is a valuable resource for specialists because it compiles experimental, computational and theoretical knowledge in one place.
Download or read book Technical Abstract Bulletin written by Defense Documentation Center (U.S.) and published by . This book was released on 1963 with total page 1032 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book AIAA Journal written by American Institute of Aeronautics and Astronautics and published by . This book was released on 2008 with total page 530 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Multi physics Modeling of Electromagnetically Driven Surface Plasma Discharges written by Yunho Kim and published by . This book was released on 2019 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents the computational modeling of non-equilibrium plasma discharges on an electromagnetically driven surface and its application to plasma assisted combustion. We address challenges often encountered in high pressure plasma discharges such as the non-uniform formation of plasmas due to filamentations and show how they could be handled by using a particular type of metamaterial. A metamaterial in the present context is an artificial composite assembled with periodic elements smaller than an incident wavelength. Metamaterials have drawn significant interest in engineering communities during the past few decades due to their extraordinary electromagnetic (EM) characteristics, e.g., a negative refractive index, that cannot be naturally excited using conventional methods or materials. An interesting electrodynamic phenomenon associated with metamaterials is the possible surface wave excitation on the artificially engineered surfaces. In particular, by carefully designing the assembly of periodic elements consisting of conductors and dielectrics, a strongly localized surface wave mode known as a spoof surface plasmon polariton (SSPP) can be efficiently excited. The extraordinary electromagnetic property of SSPP is its ability to imitate the behaviors of a surface plasmon polariton (SPP) in a wide range of frequencies (GHz -THz) while SPP can exist only in the optical regime (100's THz). In this study, our goal is to provide the in-depth analysis of the electrodynamics of SSPP, transients of surface plasma generation due to SSPP resonances, and to demonstrate the feasibility of using it for plasma assisted combustion. We have used multiple computational models that have been developed by our group and added necessary features to simulate the phenomena more accurately. In the first part of this work, we describe the numerical schemes employed for simulations. The computational tool consists of solvers for three different sets of equations: Maxwell's equations for high frequency (HF) electromagnetics, plasma governing equations for discharge physics, and reactive Navier Stokes equations for combustion. Coupling of these equations must be done carefully due to the multi-scale nature of the high frequency plasma discharges and combustion. The length and time scales range from micrometers to centimeters and nanoseconds to milliseconds, respectively. We provide the details of the coupling of the equations as well as the discretization methods for each set of equations. In this work, one of chief contributions to improving the models is the implementation of an enhanced version of absorbing boundary condition (CFS-PML) for second order Maxwell's equations. CFS-PML is especially suited for electromagnetic wave simulations that involve conductors which we demonstrate by solving a model problem for the verification of the code. In the second part, we present the computational study of argon surface plasma discharges generated by SSPP. The EM surface wave excitation is first analyzed in depth because the electromagnetic power absorption by electrons determines the transients of plasma breakdown. Electrodynamics of the SSPP excitation is investigated using broadband and monochromatic wave simulations. Instead of the infinite array of periodic elements, we have studied the metamaterial with a finite length for practical engineering applications. It is found that over a wide range of length scales from millimeters to centimeters, the EM waves always have a single node structure at resonance frequencies. The surface wave excited on the metasurface is characteristic of coupling between the cavity mode and surface wave mode. We refer to the resonance pertinent to such coupling as hybrid resonance. The shift of the hybrid resonance frequency is investigated in terms of varying dielectric permittivities, distances between perforations, and the whole lengths of the metasurfaces. Using an optimal configuration of the metasurface, the transients of the surface plasma generation due to the field intensification is studied. Interactions among the surface plasma, SSPP and the incident wave are presented. Multiple simulations show that even if the metasurfaces have different lengths, the transients of surface plasma formation are qualitatively identical at the hybrid resonance frequencies. Such scalability is one of the primary features of metamaterials that can be extended to the plasma discharge. In the third part, plasma assisted combustion induced by microwave sources is studied. Previous research in combustion engineering communities have addressed the importance of volumetric formation of flame kernel for successful combustion. Another key point in plasma assisted combustion is the volumetric generation of radical species in nanosecond timescale, which can significantly reduce the ignition delay for lean fuel-air mixtures. Motivated by the need for mechanisms that can generate combustion enhancing radicals over a large area, we have investigated the feasibility of using the SSPP generated surface plasmas for plasma assisted combustion. A kinetic mechanism of H2 - air mixture that was previously established by our group is used for this study. A mixture with the equivalence ratio of 0.3 at the initial pressure and temperature of 1 atm and 1000 K is assumed, respectively. Fully coupled simulations show that the cm-scale plasma kernel can be efficiently transitioned into successful ignition and flame propagation with shortened ignition delay. In the last part, we discuss strategies to parallelize the simulation tools for high performance computing. The governing equations solved in this study are spatially discretized using either finite edge element method or cell-centered finite volume method. They require different approaches to achieve parallel scalability, and in particular, the Maxwell's equations needs a special preconditioning technique to reduce computational time. The technique is known as nodal auxiliary space preconditioning whose theoretical background and performance on a supercomputer are presented. Additionally, the module which solves reactive Navier-Stokes equations is also parallelized to study large scale (centimeters) ignition phenomena. For both plasma-wave coupled solver and combustion solver, we discuss the details of MPI(Message Passing Interface)-based parallelization processes
Download or read book A Selected Listing of NASA Scientific and Technical Reports for 1966 written by United States. National Aeronautics and Space Administration. Scientific and Technical Information Division and published by . This book was released on 1967 with total page 2084 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Kinematics of Mixing written by J. M. Ottino and published by Cambridge University Press. This book was released on 1989 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt: In spite of its universality, mixing is poorly understood and generally speaking, mixing problems are attacked on a case-by-case basis. This is the first book to present a unified treatment of the mixing of fluids from a kinematical viewpoint. The author's aim is to provide a conceptually clear basis from which to launch analysis and to facilitate an understanding of the numerous mixing problems encountered in nature and technology. After presenting the necessary background in kinematics and fluid dynamics, Professor Ottino considers various examples of dealing with necessary background in dynamical systems and chaos. The book assumes little previous knowledge of fluid dynamics and dynamical systems and can be used as a textbook by final-year undergraduates, graduate students and researchers in applied mathematics, engineering science, geophysics and physics who have an interest in fluid dynamics, continuum mechanics and dynamical systems. It is profusely illustrated in colour, with many line diagrams and half-tones. Systems which illustrate the most important concepts, many exercises and examples are included.
Download or read book NASA Patent Abstracts Bibliography written by United States. National Aeronautics and Space Administration. Scientific and Technical Information Office and published by . This book was released on 1978 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt:
