Magnetohydrodynamic (MHD) modelling of solar active phenomena via numerical methods
NASA Technical Reports Server (NTRS)
Wu, S. T.
1988-01-01
Numerical ideal MHD models for the study of solar active phenomena are summarized. Particular attention is given to the following physical phenomena: (1) local heating of a coronal loop in an isothermal and stratified atmosphere, and (2) the coronal dynamic responses due to magnetic field movement. The results suggest that local heating of a magnetic loop will lead to the enhancement of the density of the neighboring loops through MHD wave compression. It is noted that field lines can be pinched off and may form a self-contained magnetized plasma blob that may move outward into interplanetary space.
Chatterjee, Dipankar; Amiroudine, Sakir
2011-02-01
A comprehensive non-isothermal Lattice Boltzmann (LB) algorithm is proposed in this article to simulate the thermofluidic transport phenomena encountered in a direct-current (DC) magnetohydrodynamic (MHD) micropump. Inside the pump, an electrically conducting fluid is transported through the microchannel by the action of an electromagnetic Lorentz force evolved out as a consequence of the interaction between applied electric and magnetic fields. The fluid flow and thermal characteristics of the MHD micropump depend on several factors such as the channel geometry, electromagnetic field strength and electrical property of the conducting fluid. An involved analysis is carried out following the LB technique to understand the significant influences of the aforementioned controlling parameters on the overall transport phenomena. In the LB framework, the hydrodynamics is simulated by a distribution function, which obeys a single scalar kinetic equation associated with an externally imposed electromagnetic force field. The thermal history is monitored by a separate temperature distribution function through another scalar kinetic equation incorporating the Joule heating effect. Agreement with analytical, experimental and other available numerical results is found to be quantitative. PMID:21053082
Magnetohydrodynamic (MHD) channel corner seal
Spurrier, Francis R.
1980-01-01
A corner seal for an MHD duct includes a compressible portion which contacts the duct walls and an insulating portion which contacts the electrodes, sidewall bars and insulators. The compressible portion may be a pneumatic or hydraulic gasket or an open-cell foam rubber. The insulating portion is segmented into a plurality of pieces of the same thickness as the electrodes, insulators and sidewall bars and aligned therewith, the pieces aligned with the insulator being of a different size from the pieces aligned with the electrodes and sidewall bars to create a stepped configuration along the corners of the MHD channel.
Magnetohydrodynamic (MHD) driven droplet mixer
Lee, Abraham P.; Lemoff, Asuncion V.; Miles, Robin R.
2004-05-11
A magnetohydrodynamic fluidic system mixes a first substance and a second substance. A first substrate section includes a first flow channel and a first plurality of pairs of spaced electrodes operatively connected to the first flow channel. A second substrate section includes a second flow channel and a second plurality of pairs of spaced electrodes operatively connected to the second flow channel. A third substrate section includes a third flow channel and a third plurality of pairs of spaced electrodes operatively connected to the third flow channel. A magnetic section and a control section are operatively connected to the spaced electrodes. The first substrate section, the second substrate section, the third substrate section, the first plurality of pairs of spaced electrodes, the second plurality of pairs of spaced electrodes, the third plurality of pairs of spaced electrodes, the magnetic section, and the control section are operated to move the first substance through the first flow channel, the second substance through the second flow channel, and both the first substance and the second substance into the third flow channel where they are mixed.
Application of Magnetohydrodynamics (MHD) and Recent Research Trend
NASA Astrophysics Data System (ADS)
Harada, Nobuhiro
As the applications of Magnetohydrodynamic (MHD) energy conversion, research and development for high-efficiency and low emission electric power generation system, MHD accelerations and/or MHD thrusters, and flow control around hypersonic and re-entry vehicles are introduced. For closed cycle MHD power generation, high-efficiency MHD single system is the most hopeful system and space power system using mixed inert gas (MIG) working medium is proposed. For open cycle MHD, high-efficiency coal fired MHD system with CO2 recovery has been proposed. As inverse process of MHD power generation, MHD accelerators/thrusters are expected as the next generation propulsion system. Heat flux reduction to protect re-entry vehicles is expected by an MHD process for safety return from space missions.
OpenMHD: Godunov-type code for ideal/resistive magnetohydrodynamics (MHD)
NASA Astrophysics Data System (ADS)
Zenitani, Seiji
2016-04-01
OpenMHD is a Godunov-type finite-volume code for ideal/resistive magnetohydrodynamics (MHD). It is written in Fortran 90 and is parallelized by using MPI-2 and OpenMP. The code was originally developed for studying magnetic reconnection problems and has been made publicly available in the hope that others may find it useful.
A kinetic-MHD model for low frequency phenomena
Cheng, C.Z.
1991-07-01
A hybrid kinetic-MHD model for describing low-frequency phenomena in high beta anisotropic plasmas that consist of two components: a low energy core component and an energetic component with low density. The kinetic-MHD model treats the low energy core component by magnetohydrodynamic (MHD) description, the energetic component by kinetic approach such as the gyrokinetic equation, and the coupling between the dynamics of these two components through plasma pressure in the momentum equation. The kinetic-MHD model optimizes both the physics contents and the theoretical efforts in studying low frequency MHD waves and transport phenomena in general magnetic field geometries, and can be easily modified to include the core plasma kinetic effects if necessary. It is applicable to any magnetized collisionless plasma system where the parallel electric field effects are negligibly small. In the linearized limit two coupled eigenmode equations for describing the coupling between the transverse Alfven type and the compressional Alfven type waves are derived. The eigenmode equations are identical to those derived from the full gyrokinetic equation in the low frequency limit and were previously analyzed both analytically nd numerically to obtain the eigenmode structure of the drift mirror instability which explains successfully the multi-satellite observation of antisymmetric field-aligned structure of the compressional magnetic field of Pc 5 waves in the magnetospheric ring current plasma. Finally, a quadratic form is derived to demonstrate the stability of the low-frequency transverse and compressional Alfven type instabilities in terms of the pressure anisotropy parameter {tau} and the magnetic field curvature-pressure gradient parameter. A procedure for determining the stability of a marginally stable MHD wave due to wave-particle resonances is also presented.
MHD (Magnetohydrodynamics) Program Plan, FY 1989
NASA Astrophysics Data System (ADS)
1989-05-01
The essential elements of the current program, which is a continuation of the program outlined in the FY 1988 MHD Program Plan, are to: develop technical and environmental data for the integrated MHD topping cycle system through long-term (1000 hours) proof of concept (POC) testing; develop technical and environmental data for the integrated MHD bottoming cycle subsystem through long-term (4000 hours) POC testing; design and construct a seed regeneration system capable of independent operation, using spent seed materials from the MHD process; prepare a conceptual design for an MHD retrofit plant; and continue system studies and supporting research necessary for system testing. Results of the topping cycle POC tests at the Component Development and Integration Facility (CDIF), coupled with the bottoming cycle POC test results obtained at the Coal Fired Flow Facility (CFFF), and the seed regeneration POC effort will provide the critical engineering data base for the private sector's final decision on proceeding with the design, construction, and operation of an MHD retrofit. The development schedule, decision points, and resource requirements are discussed. As part of the MHD program, international activities of several nations are monitored and evaluated through contact with the international MHD scientific and technical community.
[Nonlinear magnetohydrodynamics]. [Threshold unstable MHD activity
Not Available
1992-01-01
Theoretical predictions were compared with available data from JET on the threshold unstable MHD activity in toroidal confinement devices. In particular, questions arising as to Hartmans number and the selection of a kinematic viscosity are discussed.
Diagnostic development and support of MHD (magnetohydrodynamics) test facilities
Not Available
1989-07-01
Mississippi State University (MSU) is developing diagnostic instruments for Magnetohydrodynamics (MHD) power train data acquisition and for support of MHD component development test facilities. Microprocessor-controlled optical instruments, initially developed for HRSR support, are being refined, and new systems to measure temperatures and gas-seed-slag stream characteristics are being developed. To further data acquisition and analysis capabilities, the diagnostic systems are being interfaced with MHD Energy Center computers. Technical support for the diagnostic needs of the national MHD research effort is being provided. MSU personnel will also cooperate with government agencies and private industries to improve the transformation of research and development results into processes, products and services applicable to their needs.
Explosively-driven magnetohydrodynamic (MHD) generator studies
Agee, F.J.; Lehr, F.M.; Vigil, M.; Kaye, R.; Gaudet, J.; Shiffler, D.
1995-08-01
Plasma jet generators have been designed and tested which used an explosive driver and shocktube with a rectangular cross section that optimize the flow velocity and electrical conductivity. The latest in a series of designs has been tested using a reactive load to diagnose the electrical properties of the MHD generator/electromagnet combination. The results of these tests indicate that the plasma jet/MHD generator design does generate a flow velocity greater than 25 km/s and produces several gigawatts of pulsed power in a very small package size. A larger, new generator design is also presented.
Tesche, F.M.; Barnes, P.R.; Meliopoulos, A.P.S.
1992-02-01
This report discusses the effects of the late-time high-altitude electromagnetic pulse (HEMP) on electrical transmission and distribution (T&D) systems. This environment, known as the magnetohydrodynamic electromagnetic pulse (MHD-EMP), is a very slowly varying electric field induced in the earth`s surface, similar to the field induced by a geomagnetic storm. It can result in the flow of a quasi-dc current in grounded power lines and in the subsequent magnetic saturation of transformers. This saturation, in turn, causes 6-Hz harmonic distortion and an increase in the reactive power required by generation facilities. This report analyzes and discusses these phenomena. The MHD-EMP environment is briefly discussed, and a simplified form of the earth-induced electric field is developed for use in a parametric study of transmission line responses. Various field coupling models are described, and calculated results for the responses of both transmission- and distribution-class power lines are presented. These calculated responses are compared with measurements of transformer operation under dc excitation to infer the MHD-EMP response of these power system components. It is found that the MHD-EMP environment would have a marked effect on a power system by inducing up to several hundreds of amperes of quasi-dc current on power lines. These currents will cause transformers to saturate which could result in excessive harmonic generation, voltage swings, and voltage suppression. The design of critical facilities which are required to operate during and after MHD-EMP events will have to be modified in order to mitigate the effects of these abnormal power system conditions.
Tesche, F.M. , Dallas, TX ); Barnes, P.R. ); Meliopoulos, A.P.S. . Dept. of Electrical Engineering)
1992-02-01
This report discusses the effects of the late-time high-altitude electromagnetic pulse (HEMP) on electrical transmission and distribution (T D) systems. This environment, known as the magnetohydrodynamic electromagnetic pulse (MHD-EMP), is a very slowly varying electric field induced in the earth's surface, similar to the field induced by a geomagnetic storm. It can result in the flow of a quasi-dc current in grounded power lines and in the subsequent magnetic saturation of transformers. This saturation, in turn, causes 6-Hz harmonic distortion and an increase in the reactive power required by generation facilities. This report analyzes and discusses these phenomena. The MHD-EMP environment is briefly discussed, and a simplified form of the earth-induced electric field is developed for use in a parametric study of transmission line responses. Various field coupling models are described, and calculated results for the responses of both transmission- and distribution-class power lines are presented. These calculated responses are compared with measurements of transformer operation under dc excitation to infer the MHD-EMP response of these power system components. It is found that the MHD-EMP environment would have a marked effect on a power system by inducing up to several hundreds of amperes of quasi-dc current on power lines. These currents will cause transformers to saturate which could result in excessive harmonic generation, voltage swings, and voltage suppression. The design of critical facilities which are required to operate during and after MHD-EMP events will have to be modified in order to mitigate the effects of these abnormal power system conditions.
NASA Technical Reports Server (NTRS)
1981-01-01
The reference conceptual design of the magnetohydrodynamic (MHD) Engineering Test Facility (ETF), a prototype 200 MWe coal-fired electric generating plant designed to demonstrate the commercial feasibility of open cycle MHD, is summarized. Main elements of the design, systems, and plant facilities are illustrated. System design descriptions are included for closed cycle cooling water, industrial gas systems, fuel oil, boiler flue gas, coal management, seed management, slag management, plant industrial waste, fire service water, oxidant supply, MHD power ventilating
Analytical investigation of critical MHD phenomena
NASA Technical Reports Server (NTRS)
1981-01-01
Development and analysis of schemes for suppression of the startup overvoltage transient in the AEDC High Performance Demonstration Experiment (HPDE), analysis of performance enhancement due to electrode voltage drop reduction by use of pyrolytic graphites in the HPDE, prediction of optimal loading schemes for the HPDE, prediction of PHDE performance with a diagonal electrical connection, and predictions of the likelihood and effects of axial current leakage between adjacent electrodes in the HPDE are reviewed. Simulations of tests at the AEDC/HPDE with STD Research Corporation multidimensional and time dependent computer codes provided additional validation for the computer codes and shed light on physical mechanisms which govern performance and durability of MHD power generators. The magnetoaerothermal effect was predicted by STD Research Corporation to have a significant effect on the HPDE/MHD generator performance at high interaction.
Isolated Coronal Mass Ejections and Associated Phenomena: MHD Simulations and STEREO Observations
NASA Astrophysics Data System (ADS)
Lugaz, Noé; Roussev, Ilia; Sokolov, Igor; Shibata, Kazunari; Schwadron, Nathan; Downs, Cooper
2012-07-01
Coronal Mass Ejections (CMEs), the most energetic events occurring in our solar system, are associated with a range of other phenomena such as EUV waves, dimming regions and solar energetic particles (SEPs). With the advancement of global numerical simulations and the new fleet of spacecraft observing the Sun and the heliosphere, it is possible to combine simulations with data analyses to gain new insight into the complex Sun-Earth system. In this talk, I will discuss magneto-hydrodynamic (MHD) simulations of CMEs and associated phenomena. In particular, I will focus on the changes in magnetic connectivity and the opening of previously closed field lines during and after an eruption and discuss the consequences for the acceleration and transport of energetic particles. I will also present combined numerical simulations and observations by SDO and STEREO/SECCHI of CMEs and EUV waves, which have led to new insights into CME deflection, expansion and rotation.
Not Available
1987-06-01
This report presents a study of the nuclear weapons magnetohydrodynamic (MHD) effects on submarine communications cables. The study consisted of the analysis and interpretation of currently available data on submarine cable systems TAT-4, TAT-6, and TAT-7. The primary result of the study is that decrease of the effective resistivity with frequency over the available experimental range, coupled with the model results, leads to quite small effective resistivities at the MHD characteristic frequencies, and hence small earth potential differences. Thus, it appears that submarine cable systems are less susceptible to an MHD threat than their land-based counter-parts.
Barnes, P.R. ); Tesche, F.M. , Dallas, TX ); Vance, E.F. , Fort Worth, TX )
1992-03-01
A large nuclear detonation at altitudes of several hundred kilometers above the earth distorts the earth's magnetic field and produces a strong magnetohydrodynamic electromagnetic pulse (MHD-EMP). This can adversely affect electrical power systems. In this report, the effects of this nuclear environment on critical facilities connected to the commercial power system are considered. Methods of mitigating the MHD-EMP impacts are investigated, and recommended protection schemes are presented. Guidelines for testing facilities to determine the effects of MHD-EMP and to validate the mitigation methods also are discussed.
FLIP MHD - A particle-in-cell method for magnetohydrodynamics
NASA Technical Reports Server (NTRS)
Brackbill, J. U.
1991-01-01
The fluid-implicit-particle, or 'FLIP' method presently extended to 2D and 3D MHD flow incorporates a Lagrangian field representation and yields a grid magnetic Reynolds number of up to 16 while preserving contact continuities that retain the Galilean invariance of the MHD flow equations. Analytical arguments and numerical examples demonstrate the conservation of mass, momentum, magnetic flux, and energy; 2D calculation results for the illustrative cases of contact discontinuity convection, Rayleigh-Taylor unstable flow.
Present understanding of MHD and heat transfer phenomena for liquid metal blankets
Kirillov, I.R.; Barleon, L.; Reed, C.B.; Miyazaki, K.
1994-07-01
A review of experimental work on magnetohydrodynamic (MHD) and heat transfer (HT) characteristics of liquid metal flows in fusion relevant conditions is presented. Experimental data on MHD flow pressure drop in straight channels of round and rectangular cross-section with electroconducting walls in a transverse magnetic field show good agreement with theoretical predictions, and simple engineering formulas are confirmed. Less data are available on velocity distribution and HT characteristics, and even less data are available for channels with electroinsulating walls or artificially made self-heating electroinsulating coatings. Some experiments show an interesting phenomena of HT increase in the presence of a transverse or axial magnetic field. For channels of complex geometry -- expansions, contractions, bends, and manifolds -- few experimental data are available. Future efforts should be directed toward investigation of MHD/HT in straight channels with perfect and nonperfect electroinsulated walls, including walls with controlled imperfections, and in channels of complex geometry. International cooperation in manufacturing and operating experimental facilities with magnetic fields at, or even higher than, 5--7 T with comparatively large volumes may be of great help.
NASA Astrophysics Data System (ADS)
Shepard, W. S.
Magnetohydrodynamic is conducted largerly through use of test stand which simulates conditions in the MHD gas stream. Continual modification of the test stand to reflect experimental results produced a test stand capable of test runs of 100 hours; runs of more than 500 hours are planned. The test stand is described, and experimental results are discussed. The design and construction of MHD radiant boiler are described. The radiant furnance serves several functions in a heat recovery and seed recovery system; it cools flue gases to a temperature suitable for entrance to the secondary superheater; it generates steam; it provides for the removal of molten ash at high temperatures; and it provides access for intrusive and nonintrusive instrumentation to the gas-side environment.
Parametric analysis of closed cycle magnetohydrodynamic (MHD) power plants
NASA Technical Reports Server (NTRS)
Owens, W.; Berg, R.; Murthy, R.; Patten, J.
1981-01-01
A parametric analysis of closed cycle MHD power plants was performed which studied the technical feasibility, associated capital cost, and cost of electricity for the direct combustion of coal or coal derived fuel. Three reference plants, differing primarily in the method of coal conversion utilized, were defined. Reference Plant 1 used direct coal fired combustion while Reference Plants 2 and 3 employed on site integrated gasifiers. Reference Plant 2 used a pressurized gasifier while Reference Plant 3 used a ""state of the art' atmospheric gasifier. Thirty plant configurations were considered by using parametric variations from the Reference Plants. Parametric variations include the type of coal (Montana Rosebud or Illinois No. 6), clean up systems (hot or cold gas clean up), on or two stage atmospheric or pressurized direct fired coal combustors, and six different gasifier systems. Plant sizes ranged from 100 to 1000 MWe. Overall plant performance was calculated using two methodologies. In one task, the channel performance was assumed and the MHD topping cycle efficiencies were based on the assumed values. A second task involved rigorous calculations of channel performance (enthalpy extraction, isentropic efficiency and generator output) that verified the original (task one) assumptions. Closed cycle MHD capital costs were estimated for the task one plants; task two cost estimates were made for the channel and magnet only.
NASA Technical Reports Server (NTRS)
Benyo, Theresa L.
2010-01-01
This paper describes the preliminary results of a thermodynamic cycle analysis of a supersonic turbojet engine with a magnetohydrodynamic (MHD) energy bypass system that explores a wide range of MHD enthalpy extraction parameters. Through the analysis described here, it is shown that applying a magnetic field to a flow path in the Mach 2.0 to 3.5 range can increase the specific thrust of the turbojet engine up to as much as 420 N/(kg/s) provided that the magnitude of the magnetic field is in the range of 1 to 5 Tesla. The MHD energy bypass can also increase the operating Mach number range for a supersonic turbojet engine into the hypersonic flight regime. In this case, the Mach number range is shown to be extended to Mach 7.0.
MHD (magnetohydrodynamic) undersea propulsion: A novel concept with renewed interest
Doss, E.D.; Geyer, H.K. ); Roy, G.D. )
1990-01-01
This paper discusses the reasons for the national and international renewed interest in the concept of MHD seawater propulsion. The main advantages of this concept are presented, together with some of the technical challenges that need to be overcome to achieve reliability, performance, and stealth. The paper discusses in more detail some of the technical issues and loss mechanisms influencing the thruster performance in terms of its electrical efficiency. Among the issues discussed are the jet losses and nozzle efficiency. Ohmic losses and frictional losses inside the thruster. Also discussed are the electrical end losses caused by the fringing magnetic field near the end of the electrodes. It has been shown that the frictional and end losses can have strong adverse effects on the thruster performance. Furthermore, a parametric study has been performed to investigate the effects of several parameters on the performance of the MHD thrusters. Those parameters include the magnetic field, thruster diameter, all roughness, flow velocity, and electrical load factor. The results of the parametric study indicate that the thruster efficiency increases with the strength of the magnetic field and thruster diameter, and decreases with the wall roughness and the flow velocity. 8 refs., 8 figs.
WhiskyMHD: Numerical Code for General Relativistic Magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Baiotti, Luca; Giacomazzo, Bruno; Hawke, Ian; et al.
2010-10-01
Whisky is a code to evolve the equations of general relativistic hydrodynamics (GRHD) and magnetohydrodynamics (GRMHD) in 3D Cartesian coordinates on a curved dynamical background. It was originally developed by and for members of the EU Network on Sources of Gravitational Radiation and is based on the Cactus Computational Toolkit. Whisky can also implement adaptive mesh refinement (AMR) if compiled together with Carpet. Whisky has grown from earlier codes such as GR3D and GRAstro_Hydro, but has been rewritten to take advantage of some of the latest research performed here in the EU. The motivation behind Whisky is to compute gravitational radiation waveforms for systems that involve matter. Examples would include the merger of a binary system containing a neutron star, which are expected to be reasonably common in the universe and expected to produce substantial amounts of radiation. Other possible sources are given in the projects list.
Two-dimensional magnetohydrodynamic simulations of poloidal flows in tokamaks and MHD pedestal
Guazzotto, L.; Betti, R.
2011-09-15
Poloidal rotation is routinely observed in present-day tokamak experiments, in particular near the plasma edge and in the high-confinement mode of operation. According to the magnetohydrodynamic (MHD) equilibrium theory [R. Betti and J. P. Freidberg, Phys. Plasmas 7, 2439 (2000)], radial discontinuities form when the poloidal velocity exceeds the poloidal sound speed (or rather, more correctly, the poloidal magneto-slow speed). Two-dimensional compressible magnetohydrodynamic simulations show that the transonic discontinuities develop on a time scale of a plasma poloidal revolution to form an edge density pedestal and a localized velocity shear layer at the pedestal location. While such an MHD pedestal surrounds the entire core, the outboard side of the pedestal is driven by the transonic discontinuity while the inboard side is caused by a poloidal redistribution of the mass. The MHD simulations use a smooth momentum source to drive the poloidal flow. Soon after the flow exceeds the poloidal sound speed, the density pedestal and the velocity shear layer form and persist into a quasi steady state. These results may be relevant to the L-H transition, the early stages of the pedestal and edge transport barrier formation.
NASA Technical Reports Server (NTRS)
Wu, S. T.
1987-01-01
Theoretical and numerical modeling of solar activity and its effects on the solar atmosphere within the context of magnetohydrodynamics were examined. Specifically, the scientific objectives were concerned with the physical mechanisms for the flare energy build-up and subsequent release. In addition, transport of this energy to the corona and solar wind was also investigated. Well-posed, physically self-consistent, numerical simulation models that are based upon magnetohydrodynamics were sought. A systematic investigation of the basic processes that determine the macroscopic dynamic behavior of solar and heliospheric phenomena was conducted. A total of twenty-three articles were accepted and published in major journals. The major achievements are summarized.
Modeling of nonstationary phenomena in the MHD-channel-inverter-substation system
Gusev, Y.P.; Zatelepin, V.N.; Kuznetsova, T.N.; Medin, S.A.; Pishchikov, V.I.
1986-07-01
A method for constructing a mathematical model of nonstationary phenomena in a system consisting of an MHD channel and an inverter substation, operating on a powerful ac grid, is examined. The variants of the realization of the model on a computer are discussed. Results of the solution of model problems with a diagonal MHD channel are presented. It is found that there is a significant coupling between the MHD channel and the inverter substation in transient processes.
Barnes, P.R.; Tesche, F.M.; Vance, E.F.
1992-03-01
A large nuclear detonation at altitudes of several hundred kilometers above the earth distorts the earth`s magnetic field and produces a strong magnetohydrodynamic electromagnetic pulse (MHD-EMP). This can adversely affect electrical power systems. In this report, the effects of this nuclear environment on critical facilities connected to the commercial power system are considered. Methods of mitigating the MHD-EMP impacts are investigated, and recommended protection schemes are presented. Guidelines for testing facilities to determine the effects of MHD-EMP and to validate the mitigation methods also are discussed.
Nonlinear tearing mode study using the almost ideal magnetohydrodynamics (MHD) constraint
Ren, C.; Callen, J.D.; Jensen, T.H.
1998-12-31
The tearing mode is an important resistive magnetohydrodynamics (MHD) mode. It perturbs the initial equilibrium magnetic flux surfaces through magnetic field line reconnection to form new flux surfaces with magnetic islands. In the study of the tearing mode, usually the initial equilibria are one dimensional with two ignorable coordinates and the perturbed equilibria are two dimensional with one ignorable coordinate. The tearing mode can be linearly unstable and its growth saturates at a fine amplitude. The neoclassical tearing mode theory shows that the mode can be nonlinearly driven by the bootstrap current even when it is linearly stable to the classical tearing mode. It is important to study the nonlinear behavior of the tearing mode. As an intrinsically nonlinear approach, the use of the almost ideal MHD constraint is suited to study the nonlinear properties of the tearing mode. In this paper, as a validation of the method, the authors study two characteristics of the tearing mode using the almost ideal MHD constraint: (1) the linear stability condition for the initial one dimensional equilibrium; and (2) the final saturation level for the unstable case. In this work, they only consider the simplest case where no gradient of pressure or current density exists at the mode resonant surface.
Magnetohydrodynamic power generation
NASA Technical Reports Server (NTRS)
Smith, J. L.
1984-01-01
Magnetohydrodynamic (MHD) Power Generation is a concise summary of MHD theory, history, and future trends. Results of the major international MHD research projects are discussed. Data from MHD research is included. Economics of initial and operating costs are considered.
Analytical investigation of critical phenomena in MHD power generators
NASA Technical Reports Server (NTRS)
1980-01-01
Critical phenomena in the Arnold Engineering Development Center (AEDC) High Performance Demonstration Experiment (HPDE) and the U.S. U-25 Experiment, are analyzed. The performance of a NASA specified 500 MW(th) flow train is analyzed. Critical phenomena analyzed include: Hall voltage overshoots; optimal load schedules; parametric dependence of the electrode voltage drops; boundary layer behavior; near electrode phenomena with finite electrode segmentation; current distribution in the end regions; scale up rules; optimum Mach number distribution; and the effects of alternative cross sectional shapes.
Observation of finite-. beta. MHD phenomena in tokamaks
McGuire, K.M.
1984-09-01
Stable high-beta plasmas are required for the tokamak to attain an economical fusion reactor. Recently, intense neutral beam heating experiments in tokamaks have shown new effects on plasma stability and confinement associated with high beta plasmas. The observed spectrum of MHD fluctuations at high beta is clearly dominated by the n = 1 mode when the q = 1 surface is in the plasma. The m/n = 1/1 mode drives other n = 1 modes through toroidal coupling and n > 1 modes through nonlinear coupling. On PDX, with near perpendicular injection, a resonant interaction between the n = 1 internal kink and the trapped fast ions results in loss of beam particles and heating power. Key parameters in the theory are the value of q/sub 0/ and the injection angle. High frequency broadband magnetic fluctuations have been observed on ISX-B and D-III and a correlation with the deterioration of plasma confinement was reported. During enhanced confinement (H-mode) discharges in divertor plasmas, two new edge instabilities were observed, both localized radially near the separatrix. By assembling results from the different tokamak experiments, it is found that the simple theoretical ideal MHD beta limit has not been exceeded. Whether this represents an ultimate tokamak limit or if beta optimized configurations (Dee- or bean-shaped plasmas) can exceed this limit and perhaps enter a second regime of stability remains to be clarified.
NASA Astrophysics Data System (ADS)
Kalteh, M.; Ghorbani, S.; Khademinejad, T.
2016-05-01
An axisymmetric magnetohydrodynamic (MHD) boundary layer flow and heat transfer of a fluid over a slender cylinder are investigated numerically. The effects of viscous dissipation, thermal radiation, and surface transverse curvature are taken into account in the simulations. For this purpose, the governing partial differential equations are transformed to ordinary differential equations by using appropriate similarity transformations. The resultant ordinary differential equations along with appropriate boundary conditions are solved by the fourth-order Runge-Kutta method combined with the shooting technique. The effects of various parameters on the velocity and temperature profiles, local skin friction coefficient, and Nusselt number are analyzed.
NASA Technical Reports Server (NTRS)
1981-01-01
The reference conceptual design of the Magnetohydrodynamic Engineering Test Facility (ETF), a prototype 200 MWe coal-fired electric generating plant designed to demonstrate the commercial feasibility of open cycle MHD is summarized. Main elements of the design are identified and explained, and the rationale behind them is reviewed. Major systems and plant facilities are listed and discussed. Construction cost and schedule estimates, and identification of engineering issues that should be reexamined are also given. The latest (1980-1981) information from the MHD technology program are integrated with the elements of a conventional steam power electric generating plant. Supplementary Engineering Data (Issues, Background, Performance Assurance Plan, Design Details, System Design Descriptions and Related Drawings) is presented.
Bifurcation phenomena and control for magnetohydrodynamic flows in a smooth expanded channel
NASA Astrophysics Data System (ADS)
C. Layek, G.; Mani Shankar, Mandal; A. Khalaf, H.
2014-11-01
This work reports the effects of magnetic field on an electrically conducting fluid with low electrical conductivity flowing in a smooth expanded channel. The governing nonlinear magnetohydrodynamic (MHD) equations in induction-free situations are derived in the framework of MHD approximations and solved numerically using the finite-difference technique. The critical values of Reynolds number (based on upstream mean velocity and channel height) for symmetry breaking bifurcation for a sudden expansion channel (1:4) is about 36, whereas the value in the case of the smooth expansion geometry used in this work is obtained as 298, approximately (non-magnetic case). The flow of an electrically conducting fluid in the presence of an externally applied constant magnetic field perpendicular to the plane of the flow is reduced significantly depending on the magnetic parameter (M). It is found that the critical value of Reynolds number for smooth expansion (1:4) is about 475 for the magnetic parameter M = 2. The separating regions developed behind the smooth symmetric expansion are decreased in length for increasing values of the magnetic parameter. The bifurcation diagram is shown for a symmetric smoothly expanding channel. It is noted that the critical values of Reynolds number increase with increasing magnetic field strength.
Whistler-mode phenomena in electron MHD plasmas
NASA Astrophysics Data System (ADS)
Stenzel, R. L.
2003-12-01
While the linear properties of plane whistler waves are well known, many new phenomena of bounded wavepackets and nonlinear effects are worth to describe. The present talk will review laboratory observations of whistler filaments, whistler vortices, whistler wings, whistler-sound modes in high-beta plasmas, nonlinear whistlers forming magnetic null points, and magnetic reconnection in EMHD plasmas. The time-varying magnetic field of a spatially bounded whistler wave packet consists of 3-D vortices. Each vortex can be decomposed into linked toroidal and poloidal field components. The self-helicity is positive for propagation along the field, negative for opposite propagation. Helicity injection from a suitable source produces unidirectional propagation. Magnetic helicity changes sign, i.e., is not conserved, when the propagation direction along B changes, for example due to reflection or propagation through a magnetic null point. In ideal EMHD the electric and magnetic forces on the electrons are equal, -n e E +J x B=0, i.e., the electron fluid is not compressed. Force-free vortices do not interact during collisions. Vortices are excited with pulsed magnetic antennas or pulsed electrodes. Both transient currents and fields can form vortices that propagate in the whistler mode. Moving dc magnets or dc current systems can also induce whistler modes in a magnetized plasma. These form a Cherenkov-like radiation pattern, a ``whistler wing.'' Nonlinear phenomena arise from wave-induced modifications of the electron temperature, density and magnetic field. In collisional plasmas electrons are heated by strong whistlers. Modifications of the classical conductivity leads to current filamentation. On a slower time scale density modifications arise from ambipolar fields associated with electron heating. In a filamentation instability a strong whistler wave is ducted along a narrow field-aligned density depression. The ion density is also modified by the ac electric field of
NASA Technical Reports Server (NTRS)
Riggins, David W.
2002-01-01
The performance of the MHD energy bypass air-breathing engine for high-speed propulsion is analyzed in this investigation. This engine is a specific type of the general class of inverse cycle engines. In this paper, the general relationship between engine performance (specific impulse and specific thrust) and the overall total pressure ratio through an engine (from inlet plane to exit plane) is first developed and illustrated. Engines with large total pressure decreases, regardless of cause or source, are seen to have exponentially decreasing performance. The ideal inverse cycle engine (of which the MHD engine is a sub-set) is then demonstrated to have a significant total pressure decrease across the engine; this total pressure decrease is cycle-driven, degrades rapidly with energy bypass ratio, and is independent of any irreversibility. The ideal MHD engine (inverse cycle engine with no irreversibility other than that inherent in the MHD work interaction processes) is next examined and is seen to have an additional large total pressure decrease due to MHD-generated irreversibility in the decelerator and the accelerator. This irreversibility mainly occurs in the deceleration process. Both inherent total pressure losses (inverse cycle and MHD irreversibility) result in a significant narrowing of the performance capability of the MHD bypass engine. The fundamental characteristics of MHD flow acceleration and flow deceleration from the standpoint of irreversibility and second-law constraints are next examined in order to clarify issues regarding flow losses and parameter selection in the MM modules. Severe constraints are seen to exist in the decelerator in terms of allowable deceleration Mach numbers and volumetric (length) required for meaningful energy bypass (work interaction). Considerable difficulties are also encountered and discussed due to thermal/work choking phenomena associated with the deceleration process. Lastly, full engine simulations utilizing inlet
Fast Soft X-ray Images of MHD Phenomena in NSTX
C.E. Bush, B.C. Stratton, J. Robinson, L.E. Zakharov, E. D. Fredrickson, D. Stutman, K. Tritz
2008-07-21
A variety of MHD phenomena have been observed on NSTX. Many of these affect fast particle losses, which are of major concern for future burning plasma experiments. Usual diagnostics for studying these phenomena are arrays of Mirnov coils for magnetic oscillations and PIN diode arrays for soft x-ray emission from the plasma core. Data reported here are from an unique fast soft x-ray imaging camera (FSXIC) with a wide-angle (pinhole) tangential view of the entire plasma minor cross section. The camera provides a 64x64 pixel image, on a CCD chip, of light resulting from conversion of soft x-rays incident on a phosphor to the visible. We have acquired plasma images at frame rates of 1-500 kHz (300 frames/shot), and have observed a variety of MHD phenomena: disruptions, sawteeth, fishbones, tearing modes, and ELMs. New data including modes with frequency > 90 kHz are also presented. Data analysis and modeling techniques used to interpret the FSXIC data are described and compared, and FSXIC results are compared to Mirnov and PIN diode array results.
NASA Technical Reports Server (NTRS)
Rigo, H. S.; Bercaw, R. W.; Burkhart, J. A.; Mroz, T. S.; Bents, D. J.; Hatch, A. M.
1981-01-01
A description and the design requirements for the 200 MWe (nominal) net output MHD Engineering Test Facility (ETF) Conceptual Design, are presented. Performance requirements for the plant are identified and process conditions are indicated at interface stations between the major systems comprising the plant. Also included are the description, functions, interfaces and requirements for each of these major systems. The lastest information (1980-1981) from the MHD technology program are integrated with elements of a conventional steam electric power generating plant.
NASA Astrophysics Data System (ADS)
Toth, G.; Daldorff, L. K. S.; Jia, X.; Gombosi, T. I.; Lapenta, G.
2014-12-01
We have recently developed a new modeling capability to embed theimplicit Particle-in-Cell (PIC) model iPIC3D into the BATS-R-USmagnetohydrodynamic model. The PIC domain can cover the regions wherekinetic effects are most important, such as reconnection sites. TheBATS-R-US code, on the other hand, can efficiently handle the rest ofthe computational domain where the MHD or Hall MHD description issufficient. As one of the very first applications of the MHD-EPICalgorithm (Daldorff et al. 2014, JCP, 268, 236) we simulate theinteraction between Jupiter's magnetospheric plasma with Ganymede'smagnetosphere, where the separation of kinetic and global scalesappears less severe than for the Earth's magnetosphere. Because theexternal Jovian magnetic field remains in an anti-parallel orientationwith respect to Ganymede's intrinsic magnetic field, magneticreconnection is believed to be the major process that couples the twomagnetospheres. As the PIC model is able to describe self-consistentlythe electron behavior, our coupled MHD-EPIC model is well suited forinvestigating the nature of magnetic reconnection in thisreconnection-driven mini-magnetosphere. We will compare the MHD-EPICsimulations with pure Hall MHD simulations and compare both modelresults with Galileo plasma and magnetic field measurements to assess therelative importance of ion and electron kinetics in controlling theconfiguration and dynamics of Ganymede's magnetosphere.
MHD Modelling of Flow Phenomena during the Impulse Plasma Deposition Process
NASA Astrophysics Data System (ADS)
Rabiński, M.; Zdunek, K.
2008-03-01
The paper presents recent computational studies of plasma dynamics in a coaxial accelerator used in surface engineering for Impulse Plasma Deposition (IPD). In our earlier studies we proposed a schematic pattern of a discharge region and a physical model of dynamic phenomena in the IPD accelerator with a tubular external electrode. The simplified snow plow code of our previous studies assumes that all the swept up mass is compressed into an infinitely thin layer immediately behind the shock. In the presented work the complete two-dimensional two-fluid magnetohydrodynamic model has been applied to investigate the sweeping of the working gas by the moving layer as well as the details of phenomena that take place behind a current sheet.
NASA Technical Reports Server (NTRS)
1981-01-01
The estimated plant capital cost for a coal fired 200 MWE electric generating plant with open cycle magnetohydrodynamics is divided into principal accounts based on Federal Energy Regulatory Commision account structure. Each principal account is defined and its estimated cost subdivided into identifiable and major equipment systems. The cost data sources for compiling the estimates, cost parameters, allotments, assumptions, and contingencies, are discussed. Uncertainties associated with developing the costs are quantified to show the confidence level acquired. Guidelines established in preparing the estimated costs are included. Based on an overall milestone schedule related to conventional power plant scheduling experience and starting procurement of MHD components during the preliminary design phase there is a 6 1/2-year construction period. The duration of the project from start to commercial operation is 79 months. The engineering phase of the project is 4 1/2 years; the construction duration following the start of the man power block is 37 months.
Lattice Boltzmann model for simulation of magnetohydrodynamics
NASA Technical Reports Server (NTRS)
Chen, Shiyi; Chen, Hudong; Martinez, Daniel; Matthaeus, William
1991-01-01
A numerical method, based on a discrete Boltzmann equation, is presented for solving the equations of magnetohydrodynamics (MHD). The algorithm provides advantages similar to the cellular automaton method in that it is local and easily adapted to parallel computing environments. Because of much lower noise levels and less stringent requirements on lattice size, the method appears to be more competitive with traditional solution methods. Examples show that the model accurately reproduces both linear and nonlinear MHD phenomena.
Two-dimensional non-reacting jet-gas mixing in an MHD (magnetohydrodynamic) second stage combustor
Chang, S.L.; Lottes, S.A.; Berry, G.F.
1990-01-01
Computer simulation is used to aid in the design of a magnetohydrodynamic (MHD) second stage combustor. A two-dimensional steady state computer model, based on mass and momentum conservation laws for multiple gas species, is used to simulate the hydrodynamics of the combustor in which a jet of oxidizer is injected into a confined cross-stream gas flow. The model predicts jet-gas mixing patterns by computing the velocity and species concentration distributions in the combustor. In this paper the effects of parametric variation of jet angle and flow symmetry on the mixing patterns were evaluated. The modeling helps to determine better mixing patterns for the combustor design because improved mixing can increase combustion efficiency and enhance MHD generator performance. A parametric study reveals that (1) non-reacting jet-gas mixing strongly depends on jet angle for coflow injection (jet angle < 90 degrees), (2) counterflow jets have better jet-gas mixing, (3) asymmetry of the inlet gas flow affects the mixing pattern, and (4) exit flow characteristics from two-dimensional simulation can be matched reasonably well with experimental data when experimental jet and simulated slot jet Reynolds numbers are of the same order. 12 refs., 14 figs., 2 tabs.
NASA Technical Reports Server (NTRS)
Wu, S. T.; Song, M. T.; Martens, P. C. H.; Dryer, M.
1991-01-01
A situation wherein a bipolar magnetic field embedded in a stratified solar atmosphere undergoes symmetrical shear motion at the footpoints is investigated via a 2D (nonplanar) MHD simulation. It was found that the vertical plasma flow velocities grow exponentially, leading to a new type of global MHD instability. The growth rate increases almost linearly until it reaches the same order of magnitude as the Alfven speed. Then a nonlinear MHD instability occurs beyond this point. It was found that the central loops are pinched by opposing Lorentz forces, and the outer closed loops stretch upward with the vertically-rising mass flow. The nonlinear dynamical shearing instability is illustrated by a numerical example that is given for three different values of the plasma beta that span several orders of magnitude.
NASA Astrophysics Data System (ADS)
Majid, M. F. M. A.; Apandi, Muhamad Al-Hakim Md; Sabri, M.; Shahril, K.
2016-02-01
As increasing of agricultural and industrial activities each year has led to an increasing in demand for energy. Possibility in the future, the country was not able to offer a lot of energy and power demand. This means that we need to focus on renewable energy to supply the demand for energy. Energy harvesting is among a method that can contribute on the renewable energy. MHD power generator is a new way to harvest the energy especially Ocean wave energy. An experimental investigation was conducted to explore performance of MHD generator. The effect of intensity of NaCl Solution (Sea Water), flow rate of NaCl solution, magnetic strength and magnet position to the current produce was analyzed. The result shows that each factor is give a significant effect to the current produce, because of that each factor need to consider on develop of MHD generator to harvest the wave energy as an alternative way to support the demand for energy.
NASA Astrophysics Data System (ADS)
Winkler, J.; Dahotre, N. B.; Boss, W.
In order to achieve the desired efficiency in the magnetohydrodynamic (MHD) cycle, one of two procedures must be employed. The first is to inject pure oxygen during combustion in order to achieve higher combustion temperatures which will yield better conversion efficiencies. The other is to preheat the combustor air through the use of high temperature air heaters (HTAH). A recuperative air heater heats the combustor air directly by passing it through tubes which are in the exhaust gas flow before sending it into the combustor. The procedure of passing air through the furnace requires a material for the tubes which will withstand the high temperatures and corrosive environment of the furnace and should have a high heat transfer coefficient. All of the necessary properties seem to exist in ceramic materials, so ceramics have begun to be studied for high temperature air heaters as well as other high temperature applications. One such effort to evaluate the performance of a ceramic composite tube in a coal fired MHD facility in order to determine any changes in the tube material after exposure to high temperature and a highly corrosive environment is outlined. A recuperative high temperature air heater (HTAH) would be positioned in the radiant furnace, because the radiant furnace provides conditions comparable to an actual MHD facility and is adequate for testing HTAH materials. The temperature conditions in the furnace range from approximately 1600 C to 1890 C, and velocities of approximately 12 m/s to 100 m/s were measured depending on the location in the furnace. The evaluated tube was placed in the furnace in a reducing environment with approximately 14 m/s velocity, 1650 C gas temperature, and 1230 C tube temperature.
NASA Astrophysics Data System (ADS)
Haiducek, J. D.; Welling, D. T.; Morley, S.; Ozturk, D. S.
2015-12-01
Magnetospheric substorms are events in which energy stored in the magnetotail is released into the auroral zone and into the downstream solar wind. Because of the complex, nonlinear, and possibly chaotic nature of the substorm energy release mechanism, it may be extremely difficult to forecast individual substorms in the near term. However, the inter-substorm timing (the amount of time elapsed between substorms) can be reproduced in a statistical sense, as was demonstrated by Freeman and Morley (2004) using their Minimal Substorm Model (MSM), a simple solar-wind driven model with the only free parameter being a recurrence time. The goal of the present work is to reproduce the observed distribution of inter-substorm timings with a global MHD model. The period of 1-31 January 2005 was simulated using the Space Weather Modeling Framework (SWMF), driven by solar wind observations. Substorms were identified in the model output by synthesizing surface magnetometer data and by looking for tailward-moving plasmoids. Substorms identified in the MHD model are then compared with observational data from the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, Los Alamos National Laboratory (LANL) geostationary satellite energetic particle data, and surface magnetometer data. For each dataset (MHD model and observations), we calculate the substorm occurrence rate, and for the MHD model we additionally calculate the timing error of the substorm onsets relative to the observed substorms. Finally, we calculate distribution functions for the inter-substorm timings in both the observations and the model. The results of this analysis will guide improvements to the MHD-based substorm model, including the use of Hall MHD and embedded particle in cell (EPIC), leading to a better reproduction of the observed inter-substorm timings and an improved understanding of the underlying physical processes. ReferencesM. P. Freeman and S. K. Morley. A minimal substorm model that
Design study of superconducting magnets for a combustion magnetohydrodynamic (MHD) generator
NASA Technical Reports Server (NTRS)
Thome, R. J.; Ayers, J. W.
1977-01-01
Design trade off studies for 13 different superconducting magnet systems were carried out. Based on these results, preliminary design characteristics were prepared for several superconducting magnet systems suitable for use with a combustion driven MHD generator. Each magnet generates a field level of 8 T in a volume 1.524 m (60 in.) long with a cross section 0.254 m x 0.254 m (10 in. x 10 in.) at the inlet and 0.406 m x .406 m (16 in. x 16 in.) at the outlet. The first design involves a racetrack coil geometry intended for operation at 4.2 K; the second design uses a racetrack geometry at 2.0 K; and the third design utilizes a rectangular saddle geometry at 4.2 K. Each case was oriented differently in terms of MHD channel axis and main field direction relative to gravity in order to evaluate fabrication ease. All cases were designed such that the system could be disassembled to allow for alteration of field gradient in the MHD channel by changing the angle between coils. Preliminary design characteristics and assembly drawings were generated for each case.
Experiments in Magnetohydrodynamics
ERIC Educational Resources Information Center
Rayner, J. P.
1970-01-01
Describes three student experiments in magnetohydrodynamics (MHD). In these experiments, it was found that the electrical conductivity of the local water supply was sufficient to demonstrate effectively some of the features of MHD flowmeters, generators, and pumps. (LC)
NASA Technical Reports Server (NTRS)
Leventis, Nicholas; Dass, Amala
2004-01-01
There are three kinds of body forces operating in electrolytic solutions in the magnetic field: the magnetohydrodynamic force F(sub B) (=i x B), the F(sub delB) force (approximately B(raised dot)gradB) and the F(sub delC) force (approximately |B|(sup 2)gradC). These three forces manifest themselves differently, depending on the experimental conditions. Thus, diamagnetic disc millielectrodes (e.g., Au) with their plane parallel to the flux density of the homogeneous magnetic field of an electromagnet yield convective behavior analogous to that observed with rotating electrodes; that response is controlled by F(sub B). The same electrodes placed in the inhomogeneous field of a strong permanent magnet yield also convective behavior that is controlled by both F(sub B) and F(sub delB). Finally, similarly sized millielectrodes made of permanent magnets (e.g., Au-coated Nd-Fe-B discs) yield diffusion-controlled behavior at conditions where a gold disc electrode shows behavior dominated by density gradient driven natural convection; in this case the predominant forces are both F(sub delB) and F(sub delC). Under open circuit conditions, ferromagnetic (i.e., magnetizable) millielectrodes (Co, Fe, Ni) dipped in corrosive solutions and placed in homogeneous magnetic fields yield mass-transfer phenomena that seem to be controlled by magnetophoresis.
Zhu, X. S.; Wang, H. N.; Du, Z. L.; Fan, Y. L.
2013-05-10
We undertake an attempt to reconstruct the Sun's non-force-free magnetic field. The solar corona is often considered to be magnetohydrostatic. We solve the full MHD equations with a semi-realistic atmosphere model to attain this stationary state. Our method is tested with a Sun-like model which simulates the emergence of a magnetic flux rope passing from below the photosphere into the corona. Detailed diagnostics shows that our method can model the forced field more successfully than the optimization and potential method, but it still needs to be applied to real data.
Micro optical fiber display switch based on the magnetohydrodynamic (MHD) principle
NASA Astrophysics Data System (ADS)
Lian, Kun; Heng, Khee-Hang
2001-09-01
This paper reports on a research effort to design, microfabricate and test an optical fiber display switch based on magneto hydrodynamic (MHD) principal. The switch is driven by the Lorentz force and can be used to turn on/off the light. The SU-8 photoresist and UV light source were used for prototype fabrication in order to lower the cost. With a magnetic field supplied by an external permanent magnet, and a plus electrical current supplied across the two inert sidewall electrodes, the distributed body force generated will produce a pressure difference on the fluid mercury in the switch chamber. By change the direction of current flow, the mercury can turn on or cut off the light pass in less than 10 ms. The major advantages of a MHD-based micro-switch are that it does not contain any solid moving parts and power consumption is much smaller comparing to the relay type switches. This switch can be manufactured by molding gin batch production and may have potential applications in extremely bright traffic control,, high intensity advertising display, and communication.
NASA Astrophysics Data System (ADS)
Shimizu, Kazuya; Maeda, Tetsuhiko; Hasegawa, Yasuo
The magnetohydrodynamic flow in a liquid metal MHD generator is investigated with two-dimensional numerical simulation, where the induced magnetic field is considered. Numerical results indicate that the power output becomes the highest at the loading parameter of 0.64, which is higher than the loading parameter of 0.5 giving the highest power output in the theoretical analysis without the induced magnetic field. This results from the strong negative induced magnetic field with the low loading parameter. It is shown that the eddy current exists in the upstream and downstream region of the generator channel. And the induced magnetic flux density is the strongest at the center of the eddy current. This is because x-direction electric field is generated near the upstream and downstream edge of the electrodes. It is observed that the distributions of the x-direction velocity become M-shaped in the generator channel. In the downstream region, the M-shaped Hartmann velocity profile is developed with the high loading parameter. With the low loading parameter, on the contrary, the velocity in the main flow is higher than that near the wall.
Magnetohydrodynamic (MHD) flow of Cu-water nanofluid due to a rotating disk with partial slip
NASA Astrophysics Data System (ADS)
Hayat, Tasawar; Rashid, Madiha; Imtiaz, Maria; Alsaedi, Ahmed
2015-06-01
This paper investigates MHD steady flow of viscous nanofluid due to a rotating disk. Water is treated as a base fluid and copper as nanoparticle. Nanofluid fills the porous medium. Effects of partial slip, viscous dissipation and thermal radiation are also considered. Similarity transformations reduce the nonlinear partial differential equations to ordinary differential equations. Flow and heat transfer characteristics are computed by HAM solutions. Also computations for skin friction coefficient and Nusselt number are presented and examined for pertinent parameters. It is noted that higher velocity slip parameter decreases the radial and azimuthal velocities while temperature decreases for larger values of the thermal slip parameter. Also the rate of heat transfer enhances when the nanoparticle volume fraction increases.
NASA Technical Reports Server (NTRS)
Wang, A. H.; Wu, S. T.; Liu, Yang; Hathaway, D.
2008-01-01
We introduce a numerical simulation method for recovering the photospheric velocity field from the vector magnetograms. The traditional method is local correlation tracking (LCT) which is based on measuring the relative displacements of features in blocks of pixels between successive white-light images or magnetograms. Within this method, there are a variety of implementations. One of recently developed implementations is induction local correlation tracking (ILCT) as described by Welsch et al. (2004). They employ the normal component of magnetic induction equation as a constraint to assure consistent solutions. Our numerical method uses the fully three-dimensional MHD equations to recover the photospheric velocity field with individual vector magnetograms. We compare our method to the ILCT method using NOAA AR8210 as an example. The differences and similarities are discussed in detail.
MAGNETOHYDRODYNAMIC WAVES AND CORONAL HEATING: UNIFYING EMPIRICAL AND MHD TURBULENCE MODELS
Sokolov, Igor V.; Van der Holst, Bart; Oran, Rona; Jin, Meng; Manchester, Ward B. IV; Gombosi, Tamas I.; Downs, Cooper; Roussev, Ilia I.; Evans, Rebekah M.
2013-02-10
We present a new global model of the solar corona, including the low corona, the transition region, and the top of the chromosphere. The realistic three-dimensional magnetic field is simulated using the data from the photospheric magnetic field measurements. The distinctive feature of the new model is incorporating MHD Alfven wave turbulence. We assume this turbulence and its nonlinear dissipation to be the only momentum and energy source for heating the coronal plasma and driving the solar wind. The difference between the turbulence dissipation efficiency in coronal holes and that in closed field regions is because the nonlinear cascade rate degrades in strongly anisotropic (imbalanced) turbulence in coronal holes (no inward propagating wave), thus resulting in colder coronal holes, from which the fast solar wind originates. The detailed presentation of the theoretical model is illustrated with the synthetic images for multi-wavelength EUV emission compared with the observations from SDO AIA and STEREO EUVI instruments for the Carrington rotation 2107.
Magnetohydrodynamic (MHD) flow of Cu-water nanofluid due to a rotating disk with partial slip
Hayat, Tasawar; Rashid, Madiha; Imtiaz, Maria; Alsaedi, Ahmed
2015-06-15
This paper investigates MHD steady flow of viscous nanofluid due to a rotating disk. Water is treated as a base fluid and copper as nanoparticle. Nanofluid fills the porous medium. Effects of partial slip, viscous dissipation and thermal radiation are also considered. Similarity transformations reduce the nonlinear partial differential equations to ordinary differential equations. Flow and heat transfer characteristics are computed by HAM solutions. Also computations for skin friction coefficient and Nusselt number are presented and examined for pertinent parameters. It is noted that higher velocity slip parameter decreases the radial and azimuthal velocities while temperature decreases for larger values of the thermal slip parameter. Also the rate of heat transfer enhances when the nanoparticle volume fraction increases.
An innovative demonstration of high power density in a compact MHD (magnetohydrodynamic) generator
Schmidt, H.J.; Lineberry, J.T.; Chapman, J.N.
1990-06-01
The present program was conducted by the University of Tennessee Space Institute (UTSI). It was by its nature a high risk experimental program to demonstrate the feasibility of high power density operation in a laboratory scale combustion driven MHD generator. Maximization of specific energy was not a consideration for the present program, but the results have implications in this regard by virtue of high energy fuel used. The power density is the ratio of the electrical energy output to the internal volume of the generator channel. The MHD process is a volumetric process and the power density is therefore a direct measure of the compactness of the system. Specific energy, is the ratio of the electrical energy output to consumable energy used for its production. The two parameters are conceptually interrelated. To achieve high power density and implied commensurate low system volume and weight, it was necessary to use an energetic fuel. The high energy fuel of choice was a mixture of powdered aluminum and carbon seeded with potassium carbonate and burned with gaseous oxygen. The solid fuel was burned in a hybrid combustion scheme wherein the fuel was cast within a cylindrical combustor in analogy with a solid propellant rocket motor. Experimental data is limited to gross channel output current and voltage, magnetic field strength, fuel and oxidizer flow rates, flow train external temperatures and combustor pressure. Similarly, while instantaneous oxidizer flow rates were measured, only average fuel consumption based on pre and post test component weights and dimensions was possible. 4 refs., 60 figs., 9 tabs.
ERIC Educational Resources Information Center
Kantrowitz, Arthur; Rosa, Richard J.
1975-01-01
Explains the operation of the Magnetohydrodynamic (MHD) generator and advantages of the system over coal, oil or nuclear powered generators. Details the development of MHD generators in the United States and Soviet Union. (CP)
NASA Astrophysics Data System (ADS)
Hua, T. A.; Picologlou, B. F.; Reed, C. B.; Walker, J. S.
1988-02-01
Magnetohydrodynamic flows of liquid metals in thin conducting ducts of various geometries in the presence of strong nonuniform transverse magnetic fields are examined. The interaction parameter and Hartmann number are assumed to be large, whereas the magnetic Reynolds number is assumed to be small. Under these assumptions, viscous and inertial effects are confined in very thin boundary layers adjacent to the walls. At walls parallel to the magnetic field lines, as at the side walls of a rectangular duct, the boundary layers (side layers) carry a significant fraction of the volumetric flow rate in the form of high velocity jets. The presence of these jets strongly enhances heat transfer performance. In addition, heat transfer can be further improved by guiding the flow toward a heated wall by proper variation of wall thicknesses, duct cross sectional dimensions and/or shape. Flows in nonconducting circular ducts are also examined. Experimental results obtained from the ALEX experiments at the Argonne National Laboratory are used to validate the numerical predictions.
Hua, T.A.; Picologlou, B.F.; Reed, C.B.; Walker, J.S.
1988-02-01
Magnetohydrodynamic flows of liquid metals in thin conducting ducts of various geometries in the presence of strong nonuniform transverse magnetic fields are examined. The interaction parameter and Hartmann number are assumed to be large, whereas the magnetic Reynolds number is assumed to be small. Under these assumptions, viscous and inertial effects are confined in very thin boundary layers adjacent to the walls. At walls parallel to the magnetic field lines, as at the side walls of a rectangular duct, the boundary layers (side layers) carry a significant fraction of the volumetric flow rate in the form of high velocity jets. The presence of these jets strongly enhances heat transfer performance. In addition, heat transfer can be further improved by guiding the flow toward a heated wall by proper variation of wall thicknesses, duct cross sectional dimensions and/or shape. Flows in nonconducting circular ducts are also examined. Experimental results obtained from the ALEX experiments at the Argonne National Laboratory are used to validate the numerical predictions. 6 refs., 7 figs.
MHD (magnetohydrodynamics) channel development: Quarterly report for January 1987-March 1987
Not Available
1987-04-01
During the report period several slag doping tests were performed. Four of these tests are described in this report. The results were generally encouraging. Four dopants were investigated: Fe/sub 2/O/sub 3/, Fe/sub 3/O/sub 4/, MnO, and CrO/sub 2/. All but the CrO/sub 2/ proved effective within some range of dopant flow rate. At flow rates above or below this range none of the dopants were desirable. The proper ranges for each of the dopants was coarsely mapped in these experiments. When the dopants were injected directly on the anode wall a power increase was observed. This indicates a possible reduction in the voltage drop due to the presence of the dopant. No power gain or loss was observed when the dopant was injected on the cathode wall. However, inter-cathode voltages were observed to spread more uniformly along the wall. High voltages decreased and low voltages increased. This result should help to reduce wear on the cathodes and their neighboring wall elements by reducing the local electrical field. Current control circuits were tested on both MK VI and MK VII type generators and components for consolidation circuits ordered. Solutions to waste disposal problems created by the implementation of new environmental regulations are being investigated. The MHD generator data from the CDIF 87-SEED-1, 87-SEED-2, and 87-SEED-3 tests have been analyzed and the results are presented in this report. The results of the SIDA model presented in this quarterly report are obtained by assuming a constant boundary layer voltage drop. Variations in the boundary layer voltage drop as a result of diagonal loading changes, iron oxide addition, or seeding rates changes were not considered. Corrections for the effects of ..delta..V/sub b1/ will be made to the results of SIDA when the voltage drop measurements become available.
The Magnetohydrodynamics of Supersonic Gas Clouds: MHD Cosmic Bullets and Wind-swept Clumps
NASA Astrophysics Data System (ADS)
Jones, T. W.; Ryu, Dongsu; Tregillis, I. L.
1996-12-01
We report an extensive set of two-dimensional MHD simulations exploring the role and evolution of magnetic fields in the dynamics of supersonic plasma clumps. We examine the influence of both ambient field strength and orientation on the problem. Of those two characteristics, field orientation is far more important in the cases we have considered with β0 = Pg/Pb ≥ 1. That is due to the geometry-sensitivity of field stretching/amplification from large-scale shearing motions around the bullet When the ambient magnetic field is transverse to the bullet motion, even a very modest field, well below equipartition strength, can be amplified by field line stretching around the bullet within a couple of bullet crushing times so that Maxwell stresses become comparable to the ram pressure associated with the bullet motion. The possibility is discussed that those situations might lead to large, induced electric potentials capable of accelerating charged particles. When the ambient field is aligned to the bullet motion, on the other hand, reconnection-prone topologies develop that shorten the stretched field and release much of the excess energy it contains. In this geometry, the Maxwell stresses on the bullet never approach the ram pressure level. In both cases, however, the presence of a field with even moderate initial strength acts to help the flow realign itself around the bullet into a smoother, more laminar form. That reduces bullet fragmentation tendencies caused by destructive instabilities. Eddies seem less effective at field amplification than flows around the bullet, because fields within eddies tend to be expelled to the eddy perimeters. Similar effects cause the magnetic field within the bullet itself to be reduced below its initial value over time. For oblique fields, we expect that the transverse field cases modeled here are more generally relevant What counts is whether field lines threading the face of the bullet are swept around it in a fashion that folds
NASA Astrophysics Data System (ADS)
Benyo, Theresa Louise
Historically, the National Aeronautics and Space Administration (NASA) has used rocket-powered vehicles as launch vehicles for access to space. A familiar example is the Space Shuttle launch system. These vehicles carry both fuel and oxidizer onboard. If an external oxidizer (such as the Earth's atmosphere) is utilized, the need to carry an onboard oxidizer is eliminated, and future launch vehicles could carry a larger payload into orbit at a fraction of the total fuel expenditure. For this reason, NASA is currently researching the use of air-breathing engines to power the first stage of two-stage-to-orbit hypersonic launch systems. Removing the need to carry an onboard oxidizer leads also to reductions in total vehicle weight at liftoff. This in turn reduces the total mass of propellant required, and thus decreases the cost of carrying a specific payload into orbit or beyond. However, achieving hypersonic flight with air-breathing jet engines has several technical challenges. These challenges, such as the mode transition from supersonic to hypersonic engine operation, are under study in NASA's Fundamental Aeronautics Program. One propulsion concept that is being explored is a magnetohydrodynamic (MHD) energy- bypass generator coupled with an off-the-shelf turbojet/turbofan. It is anticipated that this engine will be capable of operation from takeoff to Mach 7 in a single flowpath without mode transition. The MHD energy bypass consists of an MHD generator placed directly upstream of the engine, and converts a portion of the enthalpy of the inlet flow through the engine into electrical current. This reduction in flow enthalpy corresponds to a reduced Mach number at the turbojet inlet so that the engine stays within its design constraints. Furthermore, the generated electrical current may then be used to power aircraft systems or an MHD accelerator positioned downstream of the turbojet. The MHD accelerator operates in reverse of the MHD generator, re-accelerating the
NASA Astrophysics Data System (ADS)
Benyo, Theresa Louise
Historically, the National Aeronautics and Space Administration (NASA) has used rocket-powered vehicles as launch vehicles for access to space. A familiar example is the Space Shuttle launch system. These vehicles carry both fuel and oxidizer onboard. If an external oxidizer (such as the Earth's atmosphere) is utilized, the need to carry an onboard oxidizer is eliminated, and future launch vehicles could carry a larger payload into orbit at a fraction of the total fuel expenditure. For this reason, NASA is currently researching the use of air-breathing engines to power the first stage of two-stage-to-orbit hypersonic launch systems. Removing the need to carry an onboard oxidizer leads also to reductions in total vehicle weight at liftoff. This in turn reduces the total mass of propellant required, and thus decreases the cost of carrying a specific payload into orbit or beyond. However, achieving hypersonic flight with air-breathing jet engines has several technical challenges. These challenges, such as the mode transition from supersonic to hypersonic engine operation, are under study in NASA's Fundamental Aeronautics Program. One propulsion concept that is being explored is a magnetohydrodynamic (MHD) energy- bypass generator coupled with an off-the-shelf turbojet/turbofan. It is anticipated that this engine will be capable of operation from takeoff to Mach 7 in a single flowpath without mode transition. The MHD energy bypass consists of an MHD generator placed directly upstream of the engine, and converts a portion of the enthalpy of the inlet flow through the engine into electrical current. This reduction in flow enthalpy corresponds to a reduced Mach number at the turbojet inlet so that the engine stays within its design constraints. Furthermore, the generated electrical current may then be used to power aircraft systems or an MHD accelerator positioned downstream of the turbojet. The MHD accelerator operates in reverse of the MHD generator, re-accelerating the
Gyroscopic analog for magnetohydrodynamics
Holm, D.D.
1981-01-01
The gross features of plasma equilibrium and dynamics in the ideal magnetohydrodynamics (MHD) model can be understood in terms of a dynamical system which closely resembles the equations for a deformable gyroscope.
Boquist, Carl W.; Marchant, David D.
1978-01-01
A ceramic-metal composite suitable for use in a high-temperature environment consists of a refractory ceramic matrix containing 10 to 50 volume percent of a continuous high-temperature metal reinforcement. In a specific application of the composite, as an electrode in a magnetohydrodynamic generator, the one surface of the electrode which contacts the MHD fluid may have a layer of varying thickness of nonreinforced refractory ceramic for electrode temperature control. The side walls of the electrode may be coated with a refractory ceramic insulator. Also described is an electrode-insulator system for a MHD channel.
MHD Effect of Liquid Metal Film Flows as Plasma-Facing Components
NASA Astrophysics Data System (ADS)
Zhang, Xiujie; Xu, Zengyu; Pan, Chuanjie
2008-12-01
Stability of liquid metal film flow under gradient magnetic field is investigated. Three dimensional numerical simulations on magnetohydrodynamics (MHD) effect of free surface film flow were carried out, with emphasis on the film thickness variation and its surface stability. Three different MHD phenomena of film flow were observed in the experiment, namely, retardant, rivulet and flat film flow. From our experiment and numerical simulation it can be concluded that flat film flow is a good choice for plasma-facing components (PFCs)
NASA Astrophysics Data System (ADS)
Wang, Qiang; Li, Baokuan; He, Zhu; Feng, Naixiang
2013-12-01
A three-dimensional (3D) transient mathematical model has been developed to understand the effect of innovative cathode on molten cryolite (bath)/molten aluminum (metal) interface fluctuation as well as energy-saving mechanism in aluminum electrolytic cell with innovative cathode. Based on the finite element method, the steady charge conservation law, Ohm's law, and steady-state Maxwell's equations were solved in order to investigate electric current field, magnetic field, and electromagnetic force (EMF) field. Then, an inhomogeneous multiphase flow model of three phases including bath, metal, and gas bubbles, based on the finite volume method, was implemented using the Euler/Euler approach to investigate melt motion and bath/metal interface fluctuation. EMF was incorporated into the momentum equations of bath and metal as a source term. Additionally, the interphase drag force was employed to consider different phase interactions. Thus, present work owns three main features: (1) magnetohydrodynamic multiphase flow are demonstrated in detail both in aluminum electrolytic cell with traditional cathode and innovative cathode; (2) bath/metal interface fluctuation due to different driving forces of gas bubbles, EMF, and the combined effect of the two driving forces is investigated, which is critical to the energy saving; and (3) the effect of innovative cathode on melt flow and motion of gas bubbles. A good agreement between the predicated results and measurement is obtained. The velocity difference leading to the melt oscillation decreases due to more uniform flow field. The average velocity of metal in the cell with innovative cathode decreases by approximately 33.98 pct. The gas bubbles in the cell with innovative cathode releases more quickly under the effect of protrusion on the cathode. The average bubble release frequency increases from 1.1 to 1.98 Hz. Hence, the voltage drop caused by gas bubbles would decrease significantly. In addition, the two large vortices
Not Available
1988-03-15
This progress report of the Space Power MHD System project presents the accomplishments during 1 November 1987 through 31 January 1988. The scope of work covered encompasses the definition of an MHD power system conceptual design and development plan (Task 1). Progress included the following: Subcontracts were issued to the MIT Plasma Fusion Center and the Westinghouse R and D Center. The performance of the 100 MW 500 sec. power system was optimized and the design concept finalized, including mass and energy balances. Mass and cost estimates were prepared. A design review was held at DOE/PETC. This also included the review of the technical issues definition and of the R and D Plan. Following the review, a final iteration on the conceptual design was initiated. Formulation of the R and D Plan was continued. Preparation of the Task 1 R and D Report was initiated. 12 figs.
NASA Technical Reports Server (NTRS)
1981-01-01
Main elements of the design are identified and explained, and the rationale behind them was reviewed. Major systems and plant facilities are listed and discussed. Construction cost and schedule estimates are presented, and the engineering issues that should be reexamined are identified. The latest (1980-1981) information from the MHD technology program is integrated with the elements of a conventional steam power electric generating plant.
Anghaie, S.; Saraph, G.
1995-12-31
A nuclear driven magnetohydrodynamic (MHD) generator system is proposed for the space nuclear applications of few hundreds of megawatts. The MHD generator is coupled to a vapor-droplet core reactor that delivers partially ionized fissioning plasma at temperatures in range of 3,000 to 4,000 K. A detailed MHD model is developed to analyze the basic electrodynamics phenomena and to perform the design analysis of the nuclear driven MHD generator. An incompressible quasi one dimensional model is also developed to perform parametric analyses.
Weller, A.; Anton, M.; Geiger, J.; Goerner, C.; Jaenicke, R.; Konrad, C.; Penningsfeld, F.P.; Rust, N.; Teo, C.Y.; Spong, D.A.
1997-12-31
Energy and particle transport in W7-AS exhibits a resonance like dependence on the edge rotational transform (iota) as long as the magnetic shear is relatively weak (low beta, no significant net toroidal currents). MHD modes at resonant surfaces may cause enhanced radial transport depending on the magnitude and radial extent of the magnetic perturbations. In many cases discharges in W7-AS are very quiescent, or in case of mode activity, often no influence on energy and particle confinement is found. In the high beta regime ((beta)
Winkler, J; Dahotre, N B; Boss, W
1993-02-01
In order to achieve the desired efficiency in the MHD cycle, one of two procedures must be employed. The first is to inject pure oxygen during combustion in order to achieve higher combustion temperatures which will yield better conversion efficiencies. The other is to preheat the combustor air through the use of high temperature air heaters (HTAH). A recuperative air heater heats the combustor air directly by passing it through tubes which are in the exhaust gas flow before sending it into the combustor. The procedure of passing air through the furnace requires a material for the tubes which will withstand the high temperatures and corrosive environment of the furnace and should have a high heat transfer coefficient. All of the necessary properties seem to exist in ceramic materials, so ceramics have begun to be studied for high temperature air heaters as well as other high temperature applications. The present project outlines one such effort to evaluate the performance of a ceramic composite tube in a coal fired MHD facility in order to determine any changes in the tube material after exposure to high temperature and a highly corrosive environment. A recuperative high temperature air heater (HTAH) would be positioned in the radiant furnace, because the radiant furnace provides conditions comparable to an actual MHD facility and is adequate for testing HTAH materials. The temperature conditions in the furnace range from approximately 1600{degree}C to 1890{degree}C, and velocities of approximately 12 m/s to 100 m/s have been measured depending on the location in the furnace. The evaluated tube was placed in the furnace in a reducing environment with approximately 14 m/s velocity, 1650{degree}C gas temperature, and 1230{degree}C tube temperature.
NASA Technical Reports Server (NTRS)
Wu, S. T.; Guo, W. P.
1997-01-01
We present results for an investigation of the interaction of a helmet streamer arcade and a helical flux-rope emerging from the sub-photosphere. These results are obtained by using a three-dimensional axisymmetric, time-dependent ideal magnetohydrodynamic (MHD) model. Because of the physical nature of the flux-rope, we investigate two types of flux-ropes; (1) high density flux-rope (i.e. flux-rope without cavity), and (2) low density flux rope (i.e. flux-rope with cavity). When the streamer is disrupted by the flux-rope, it will evolve into a configuration resembling the typical observed loop-like Coronal Mass Ejection (CMES) for both cases. The streamer-flux rope system with cavity is easier to be disrupted and the propagation speed of the CME is faster than the streamer-flux rope system without cavity. Our results demonstrate that magnetic buoyancy force plays an important role in disrupting the streamer.
Magnetohydrodynamic Turbulence
NASA Astrophysics Data System (ADS)
Montgomery, David C.
2004-01-01
Magnetohydrodynamic (MHD) turbulence theory is modeled on neutral fluid (Navier-Stokes) turbulence theory, but with some important differences. There have been essentially no repeatable laboratory MHD experiments wherein the boundary conditions could be controlled or varied and a full set of diagnostics implemented. The equations of MHD are convincingly derivable only in the limit of small ratio of collision mean-free-paths to macroscopic length scales, an inequality that often goes the other way for magnetofluids of interest. Finally, accurate information on the MHD transport coefficients-and thus, the Reynolds-like numbers that order magnetofluid behavior-is largely lacking; indeed, the algebraic expressions used for such ingredients as the viscous stress tensor are often little more than wishful borrowing from fluid mechanics. The one accurate thing that has been done extensively and well is to solve the (strongly nonlinear) MHD equations numerically, usually in the presence of rectangular periodic boundary conditions, and then hope for the best when drawing inferences from the computations for those astrophysical and geophysical MHD systems for which some indisputably turbulent detailed data are available, such as the solar wind or solar prominences. This has led to what is perhaps the first field of physics for which computer simulations are regarded as more central to validating conclusions than is any kind of measurement. Things have evolved in this way due to a mixture of the inevitable and the bureaucratic, but that is the way it is, and those of us who want to work on the subject have to live with it. It is the only game in town, and theories that have promised more-often on the basis of some alleged ``instability''-have turned out to be illusory.
NASA Astrophysics Data System (ADS)
Chaplin, Vernon H.
This thesis describes investigations of two classes of laboratory plasmas with rather different properties: partially ionized low pressure radiofrequency (RF) discharges, and fully ionized high density magnetohydrodynamically (MHD)-driven jets. An RF pre-ionization system was developed to enable neutral gas breakdown at lower pressures and create hotter, faster jets in the Caltech MHD-Driven Jet Experiment. The RF plasma source used a custom pulsed 3 kW 13.56 MHz RF power amplifier that was powered by AA batteries, allowing it to safely float at 4-6 kV with the cathode of the jet experiment. The argon RF discharge equilibrium and transport properties were analyzed, and novel jet dynamics were observed. Although the RF plasma source was conceived as a wave-heated helicon source, scaling measurements and numerical modeling showed that inductive coupling was the dominant energy input mechanism. A one-dimensional time-dependent fluid model was developed to quantitatively explain the expansion of the pre-ionized plasma into the jet experiment chamber. The plasma transitioned from an ionizing phase with depressed neutral emission to a recombining phase with enhanced emission during the course of the experiment, causing fast camera images to be a poor indicator of the density distribution. Under certain conditions, the total visible and infrared brightness and the downstream ion density both increased after the RF power was turned off. The time-dependent emission patterns were used for an indirect measurement of the neutral gas pressure. The low-mass jets formed with the aid of the pre-ionization system were extremely narrow and collimated near the electrodes, with peak density exceeding that of jets created without pre-ionization. The initial neutral gas distribution prior to plasma breakdown was found to be critical in determining the ultimate jet structure. The visible radius of the dense central jet column was several times narrower than the axial current channel
Magnetohydrodynamic fluidic system
Lee, Abraham P.; Bachman, Mark G.
2004-08-24
A magnetohydrodynamic fluidic system includes a reagent source containing a reagent fluid and a sample source containing a sample fluid that includes a constituent. A reactor is operatively connected to the supply reagent source and the sample source. MHD pumps utilize a magnetohydrodynamic drive to move the reagent fluid and the sample fluid in a flow such that the reagent fluid and the sample fluid form an interface causing the constituent to be separated from the sample fluid.
AC magnetohydrodynamic microfluidic switch
Lemoff, A V; Lee, A P
2000-03-02
A microfluidic switch has been demonstrated using an AC Magnetohydrodynamic (MHD) pumping mechanism in which the Lorentz force is used to pump an electrolytic solution. By integrating two AC MHD pumps into different arms of a Y-shaped fluidic circuit, flow can be switched between the two arms. This type of switch can be used to produce complex fluidic routing, which may have multiple applications in {micro}TAS.
NASA Technical Reports Server (NTRS)
Kabin, K.; Hansen, K. C.; Gombosi, T. I.; Combi, M. R.; Linde, T. J.; DeZeeuw, D. L.; Groth, C. P. T.; Powell, K. G.; Nagy, A. F.
2000-01-01
Magnetohydrodynamics (MHD) provides an approximate description of a great variety of processes in space physics. Accurate numerical solutions of the MHD equations are still a challenge, but in the past decade a number of robust methods have appeared. Once these techniques made the direct solution of MHD equations feasible, a number of global three-dimensional models were designed and applied to many space physics objects. The range of these objects is truly astonishing, including active galactic nuclei, the heliosphere, the solar corona, and the solar wind interaction with planets, satellites, and comets. Outside the realm of space physics, MHD theory has been applied to such diverse problems as laboratory plasmas and electromagnetic casting of liquid metals. In this paper we present a broad spectrum of models of different phenomena in space science developed in the recent years at the University of Michigan. Although the physical systems addressed by these models are different, they all use the MHD equations as a unifying basis.
Commercialization of MHD power technology
Aleman, D.J.; Jensen, A.D.; Probert, P.B.
1984-08-01
This paper presents an approach to the commercialization of Magnetohydrodynamics (MHD) technology from the perspective of an equipment manufacturer. It discusses and recommends actions to be taken in solving technical problems and mitigating risk for the first commercial MHD power plant.
Marchant, David D.; Killpatrick, Don H.
1978-01-01
An electrode capable of withstanding high temperatures and suitable for use as a current collector in the channel of a magnetohydrodynamic (MHD) generator consists of a sintered powdered metal base portion, the upper surface of the base being coated with a first layer of nickel aluminide, an intermediate layer of a mixture of nickel aluminide - refractory ceramic on the first layer and a third or outer layer of a refractory ceramic material on the intermediate layer. The sintered powdered metal base resists spalling by the ceramic coatings and permits greater electrode compliance to thermal shock. The density of the powdered metal base can be varied to allow optimization of the thermal conductivity of the electrode and prevent excess heat loss from the channel.
Tripathi, Dharmendra; Anwar Bég, O
2013-11-01
Magnetic fields are increasingly being utilized in endoscopy and gastric transport control. In this regard, the present study investigates the influence of a transverse magnetic field in the transient peristaltic rheological transport. An electrically-conducting couple stress non-Newtonian model is employed to accurately simulate physiological fluids in peristaltic flow through a sinusoidally contracting channel of finite length. This model is designed for computing the intra-bolus oesophageal and intestinal pressures during the movement of food bolus in the digestive system under magneto-hydro-dynamic effects. Long wavelength and low Reynolds number approximations have been employed to reduce the governing equations from nonlinear to linear form, this being a valid approach for creeping flows which characterizes physiological dynamics. Analytical approximate solutions for axial velocity, transverse velocity, pressure gradient, local wall shear stress and volumetric flow rate are obtained for the non-dimensional conservation equations subject to appropriate boundary conditions. The effects of couple stress parameter and transverse magnetic field on the velocity profile, pressure distribution, local wall shear stress and the averaged flow rate are discussed with the aid of computational results. The comparative study of non-integral and integral number of waves propagating along the finite length channel is also presented. Magnetic field and non-Newtonian properties are found to strongly influence peristaltic transport. PMID:23911695
MHD Effects on Surface Stability and Turbulence in Liquid Metal
NASA Astrophysics Data System (ADS)
Bell, Lauren; Ji, Hantau; Zweben, Stewart
2000-10-01
Magnetohydrodynamic (MHD) turbulence is a significant element in understanding many phenomena observed in space and laboratory plasmas. MHD models also appropriately describe behaviors of liquid metals. Currently, there are many interests in the utilization of liquid metal in fusion devices; therefore an understanding of MHD physics in liquid metals is imperative. A small experiment has been built to study the MHD effects on turbulence and surface waves in liquid metal. To fully examine the MHD properties, a reference case in hydrodynamics is established using water or Gallium without the presence of the magnetic field or electrical current. An external wave driver with varying frequency and amplitude excites surface waves on the liquid metal. The experimental case using Gallium is run with the presence of the magnetic field and/ or electric pulses. The magnetic field is induced using two magnetic field coils on either side of the liquid metal and the electrical current is induced using electrodes. The measured dispersion relations of the two cases are then compared to the theoretical predictions. Several diagnostics are used in concert to accurately measure the wave characteristics. The surface waves will be recorded visually through a camera and the amplitude and frequency of the waves will be measured using a laser and fiber-optic system. This successful experiment will significantly enhance knowledge of liquid metal wave behavior and therefore aid in the applications of MHD in fusion plasmas. This worked was conducted as part of the DOE-sponsored National Undergraduate Fellowship Program in Plasma Physics
The infinite interface limit of multiple-region relaxed magnetohydrodynamics
Dennis, G. R.; Dewar, R. L.; Hole, M. J.; Hudson, S. R.
2013-03-15
We show the stepped-pressure equilibria that are obtained from a generalization of Taylor relaxation known as multi-region, relaxed magnetohydrodynamics (MRXMHD) are also generalizations of ideal magnetohydrodynamics (ideal MHD). We show this by proving that as the number of plasma regions becomes infinite, MRXMHD reduces to ideal MHD. Numerical convergence studies illustrating this limit are presented.
NASA Astrophysics Data System (ADS)
1981-09-01
Engineering design details for the principal systems, system operating modes, site facilities, and structures of an engineering test facility (ETF) of a 200 MWE power plant are presented. The ETF resembles a coal-fired steam power plant in many ways. It is analogous to a conventional plant which has had the coal combustor replaced with the MHD power train. Most of the ETF components are conventional. They can, however, be sized or configured differently or perform additional functions from those in a conventional coal power plant. The boiler not only generates steam, but also performs the functions of heating the MHD oxidant, recovering seed, and controlling emissions.
NASA Technical Reports Server (NTRS)
1981-01-01
Engineering design details for the principal systems, system operating modes, site facilities, and structures of an engineering test facility (ETF) of a 200 MWE power plant are presented. The ETF resembles a coal-fired steam power plant in many ways. It is analogous to a conventional plant which has had the coal combustor replaced with the MHD power train. Most of the ETF components are conventional. They can, however, be sized or configured differently or perform additional functions from those in a conventional coal power plant. The boiler not only generates steam, but also performs the functions of heating the MHD oxidant, recovering seed, and controlling emissions.
Feasibility of MHD submarine propulsion
Doss, E.D. ); Sikes, W.C. )
1992-09-01
This report describes the work performed during Phase 1 and Phase 2 of the collaborative research program established between Argonne National Laboratory (ANL) and Newport News Shipbuilding and Dry Dock Company (NNS). Phase I of the program focused on the development of computer models for Magnetohydrodynamic (MHD) propulsion. Phase 2 focused on the experimental validation of the thruster performance models and the identification, through testing, of any phenomena which may impact the attractiveness of this propulsion system for shipboard applications. The report discusses in detail the work performed in Phase 2 of the program. In Phase 2, a two Tesla test facility was designed, built, and operated. The facility test loop, its components, and their design are presented. The test matrix and its rationale are discussed. Representative experimental results of the test program are presented, and are compared to computer model predictions. In general, the results of the tests and their comparison with the predictions indicate that thephenomena affecting the performance of MHD seawater thrusters are well understood and can be accurately predicted with the developed thruster computer models.
Temporal intermittency of energy dissipation in magnetohydrodynamic turbulence.
Zhdankin, Vladimir; Uzdensky, Dmitri A; Boldyrev, Stanislav
2015-02-13
Energy dissipation in magnetohydrodynamic (MHD) turbulence is known to be highly intermittent in space, being concentrated in sheetlike coherent structures. Much less is known about intermittency in time, another fundamental aspect of turbulence which has great importance for observations of solar flares and other space or astrophysical phenomena. In this Letter, we investigate the temporal intermittency of energy dissipation in numerical simulations of MHD turbulence. We consider four-dimensional spatiotemporal structures, "flare events," responsible for a large fraction of the energy dissipation. We find that although the flare events are often highly complex, they exhibit robust power-law distributions and scaling relations. We find that the probability distribution of dissipated energy has a power-law index close to α≈1.75, similar to observations of solar flares, indicating that intense dissipative events dominate the heating of the system. We also discuss the temporal asymmetry of flare events as a signature of the turbulent cascade. PMID:25723225
Multi-region relaxed magnetohydrodynamics with flow
Dennis, G. R. Dewar, R. L.; Hole, M. J.; Hudson, S. R.
2014-04-15
We present an extension of the multi-region relaxed magnetohydrodynamics (MRxMHD) equilibrium model that includes plasma flow. This new model is a generalization of Woltjer's model of relaxed magnetohydrodynamics equilibria with flow. We prove that as the number of plasma regions becomes infinite, our extension of MRxMHD reduces to ideal MHD with flow. We also prove that some solutions to MRxMHD with flow are not time-independent in the laboratory frame, and instead have 3D structure which rotates in the toroidal direction with fixed angular velocity. This capability gives MRxMHD potential application to describing rotating 3D MHD structures such as 'snakes' and long-lived modes.
Potential vorticity in magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Webb, G. M.; Mace, R. L.
2015-01-01
A version of Noether's second theorem using Lagrange multipliers is used to investigate fluid relabelling symmetries conservation laws in magnetohydrodynamics (MHD). We obtain a new generalized potential vorticity type conservation equation for MHD which takes into account entropy gradients and the J × B force on the plasma due to the current J and magnetic induction B. This new conservation law for MHD is derived by using Noether's second theorem in conjunction with a class of fluid relabelling symmetries in which the symmetry generator for the Lagrange label transformations is non-parallel to the magnetic field induction in Lagrange label space. This is associated with an Abelian Lie pseudo algebra and a foliated phase space in Lagrange label space. It contains as a special case Ertel's theorem in ideal fluid mechanics. An independent derivation shows that the new conservation law is also valid for more general physical situations.
Magneto-Hydrodynamics Based Microfluidics
Qian, Shizhi; Bau, Haim H.
2009-01-01
In microfluidic devices, it is necessary to propel samples and reagents from one part of the device to another, stir fluids, and detect the presence of chemical and biological targets. Given the small size of these devices, the above tasks are far from trivial. Magnetohydrodynamics (MHD) offers an elegant means to control fluid flow in microdevices without a need for mechanical components. In this paper, we review the theory of MHD for low conductivity fluids and describe various applications of MHD such as fluid pumping, flow control in fluidic networks, fluid stirring and mixing, circular liquid chromatography, thermal reactors, and microcoolers. PMID:20046890
Coal-burning magnetohydrodynamic power generation
Kessler, R.; Hals, F. )
1992-01-01
In this paper, coal-burning magnetohydrodynamic (MHD) electric power generation technology is described, and its economic and environmental advantages are discussed. advanced MHD/steam plants can achieve efficiencies of 55%-60% with less environmental intrusion than form conventional coal-burning steam plants. The national program for development of MHD power generation is outlined and the development status of individual components and subsystems is presented.
NASA Technical Reports Server (NTRS)
Tsu, T. C.
1976-01-01
A closed-cycle MHD system for an electric power plant was studied. It consists of 3 interlocking loops, an external heating loop, a closed-cycle cesium seeded argon nonequilibrium ionization MHD loop, and a steam bottomer. A MHD duct maximum temperature of 2366 K (3800 F), a pressure of 0.939 MPa (9.27 atm) and a Mach number of 0.9 are found to give a topping cycle efficiency of 59.3%; however when combined with an integrated gasifier and optimistic steam bottomer the coal to bus bar efficiency drops to 45.5%. A 1978 K (3100 F) cycle has an efficiency of 55.1% and a power plant efficiency of 42.2%. The high cost of the external heating loop components results in a cost of electricity of 21.41 mills/MJ (77.07 mills/kWh) for the high temperature system and 19.0 mills/MJ (68.5 mills/kWh) for the lower temperature system. It is, therefore, thought that this cycle may be more applicable to internally heated systems such as some futuristic high temperature gas cooled reactor.
NASA Astrophysics Data System (ADS)
Erdélyi, R.
2007-07-01
The heating of solar atmosphere from chromosphere to corona is one of the key fundamental and yet unresolved questions of modern space and plasma physics. In spite of the multi-fold efforts spanning over half a century including the many superb technological advances and theoretical developments (both analytical and computational) the unveiling of the subtle of coronal heating still remains an exciting job for the 21st century! In the present paper I review the various popular heating mechanisms put forward in the existing extensive literature. The heating processes are, somewhat arbitrarily, classified as hydrodynamic (HD), magnetohydrodynamic (MHD) or kinetic based on the model medium. These mechanisms are further divided based on the time scales of the ultimate dissipation involved (i.e. AC and DC heating, turbulent heating). In particular, attention is paid to discuss shock dissipation, Landau damping, mode coupling, resonant absorption, phase mixing, and, reconnection. Finally, I briefly review the various observational consequences of the many proposed heating mechanisms and confront them with high-resolution ground-based and satellite data currently available.
Liquid metal MHD research and development in Israel
NASA Astrophysics Data System (ADS)
Branover, H.
1991-05-01
The study and development of liquid-metal magnetohydrodynamics (MHD) in Israel, from 1973 to the present, are reviewed. Following extensive research and evaluation, it was established that the most promising concept for a relatively short development time was the gravitational system, using lead or lead alloys as the magnetohydrodynamic fluid and steam or gases as the working fluid. The Etgar Program, set up to investigate such systems, is comprised of seven segments, of which the first six have been completed; work on the last segment has been started. The segments are as follows: studies of the physical phenomena; development of a universal numerical code for parametric studies and optimization and design of the system; materials studies; development of engineering components; construction and testing of small-scale Etgar-type systems; economic evaluation and comparison with conventional technologies; and development of an industrial demonstration plant.
Solar Flares: Magnetohydrodynamic Processes
NASA Astrophysics Data System (ADS)
Shibata, Kazunari; Magara, Tetsuya
2011-12-01
This paper outlines the current understanding of solar flares, mainly focused on magnetohydrodynamic (MHD) processes responsible for producing a flare. Observations show that flares are one of the most explosive phenomena in the atmosphere of the Sun, releasing a huge amount of energy up to about 10^32 erg on the timescale of hours. Flares involve the heating of plasma, mass ejection, and particle acceleration that generates high-energy particles. The key physical processes for producing a flare are: the emergence of magnetic field from the solar interior to the solar atmosphere (flux emergence), local enhancement of electric current in the corona (formation of a current sheet), and rapid dissipation of electric current (magnetic reconnection) that causes shock heating, mass ejection, and particle acceleration. The evolution toward the onset of a flare is rather quasi-static when free energy is accumulated in the form of coronal electric current (field-aligned current, more precisely), while the dissipation of coronal current proceeds rapidly, producing various dynamic events that affect lower atmospheres such as the chromosphere and photosphere. Flares manifest such rapid dissipation of coronal current, and their theoretical modeling has been developed in accordance with observations, in which numerical simulations proved to be a strong tool reproducing the time-dependent, nonlinear evolution of a flare. We review the models proposed to explain the physical mechanism of flares, giving an comprehensive explanation of the key processes mentioned above. We start with basic properties of flares, then go into the details of energy build-up, release and transport in flares where magnetic reconnection works as the central engine to produce a flare.
Parabolized Navier-Stokes Code for Computing Magneto-Hydrodynamic Flowfields
NASA Technical Reports Server (NTRS)
Mehta, Unmeel B. (Technical Monitor); Tannehill, J. C.
2003-01-01
This report consists of two published papers, 'Computation of Magnetohydrodynamic Flows Using an Iterative PNS Algorithm' and 'Numerical Simulation of Turbulent MHD Flows Using an Iterative PNS Algorithm'.
NASA Technical Reports Server (NTRS)
Hoover, D. Q.
1976-01-01
Electric power plant costs and efficiencies are presented for three basic open-cycle MHD systems: (1) direct coal fired system, (2) a system with a separately fired air heater, and (3) a system burning low-Btu gas from an integrated gasifier. Power plant designs were developed corresponding to the basic cases with variation of major parameters for which major system components were sized and costed. Flow diagrams describing each design are presented. A discussion of the limitations of each design is made within the framework of the assumptions made.
Newtonian CAFE: a new ideal MHD code to study the solar atmosphere
NASA Astrophysics Data System (ADS)
González, J. J.; Guzmán, F.
2015-12-01
In this work we present a new independent code designed to solve the equations of classical ideal magnetohydrodynamics (MHD) in three dimensions, submitted to a constant gravitational field. The purpose of the code centers on the analysis of solar phenomena within the photosphere-corona region. In special the code is capable to simulate the propagation of impulsively generated linear and non-linear MHD waves in the non-isothermal solar atmosphere. We present 1D and 2D standard tests to demonstrate the quality of the numerical results obtained with our code. As 3D tests we present the propagation of MHD-gravity waves and vortices in the solar atmosphere. The code is based on high-resolution shock-capturing methods, uses the HLLE flux formula combined with Minmod, MC and WENO5 reconstructors. The divergence free magnetic field constraint is controlled using the Flux Constrained Transport method.
Magneto-hydrodynamics Simulation in Astrophysics
NASA Astrophysics Data System (ADS)
Pang, Bijia
2011-08-01
Magnetohydrodynamics (MHD) studies the dynamics of an electrically conducting fluid under the influence of a magnetic field. Many astrophysical phenomena are related to MHD, and computer simulations are used to model these dynamics. In this thesis, we conduct MHD simulations of non-radiative black hole accretion as well as fast magnetic reconnection. By performing large scale three dimensional parallel MHD simulations on supercomputers and using a deformed-mesh algorithm, we were able to conduct very high dynamical range simulations of black hole accretion of Sgr A* at the Galactic Center. We find a generic set of solutions, and make specific predictions for currently feasible observations of rotation measure (RM). The magnetized accretion flow is subsonic and lacks outward convection flux, making the accretion rate very small and having a density slope of around -1. There is no tendency for the flows to become rotationally supported, and the slow time variability of th! e RM is a key quantitative signature of this accretion flow. We also provide a constructive numerical example of fast magnetic reconnection in a three-dimensional periodic box. Reconnection is initiated by a strong, localized perturbation to the field lines and the solution is intrinsically three-dimensional. Approximately 30% of the magnetic energy is released in an event which lasts about one Alfvén time, but only after a delay during which the field lines evolve into a critical configuration. In the co-moving frame of the reconnection regions, reconnection occurs through an X-like point, analogous to the Petschek reconnection. The dynamics appear to be driven by global flows rather than local processes. In addition to issues pertaining to physics, we present results on the acceleration of MHD simulations using heterogeneous computing systems te{shan2006heterogeneous}. We have implemented the MHD code on a variety of heterogeneous and multi-core architectures (multi-core x86, Cell, Nvidia and
Plasma relaxation and topological aspects in Hall magnetohydrodynamics
Shivamoggi, B. K.
2012-07-15
Parker's formulation of isotopological plasma relaxation process in magnetohydrodynamics (MHD) is extended to Hall MHD. The torsion coefficient {alpha} in the Hall MHD Beltrami condition turns out now to be proportional to the potential vorticity. The Hall MHD Beltrami condition becomes equivalent to the potential vorticity conservation equation in two-dimensional (2D) hydrodynamics if the Hall MHD Lagrange multiplier {beta} is taken to be proportional to the potential vorticity as well. The winding pattern of the magnetic field lines in Hall MHD then appears to evolve in the same way as potential vorticity lines in 2D hydrodynamics.
Modeling eruptive coronal magnetohydrodynamic systems with FLUX
NASA Astrophysics Data System (ADS)
Rachmeler, L. A.
In this dissertation I explore solar coronal energetic eruptions in the context of magnetic reconnection, which is commonly thought to be a required trigger mechanism for solar eruptions. Reconnection is difficult to directly observe in the corona, and current numerical methods cannot model reconnectionless control cases. Thus, it is not possible to determine if reconnection is a necessary component of these eruptions. I have executed multiple controlled simulations to determine the importance of reconnection for initiation and evolution of several eruptive systems using FLUX, a numerical model that uses the comparatively new fluxon technique. I describe two types of eruptions modeled with FLUX: a metastable confined flux rope theory for coronal mass ejection (CME) initiation, and symmetrically twisted coronal jets in a uniform vertical background field. In the former, I identified an ideal magnetohydrodynamic (MHD) instability that allows metastable twisted flux rope systems to suddenly lose stability and erupt even in the absence of reconnection, contradicting previous conjecture. The CME result is in contrast to the azimuthally symmetric coronal jet initiation model, where jet-like behavior does not manifest without reconnection. My work has demonstrated that some of the observed eruptive phenomena may be triggered by non-reconnective means such as ideal MHD instabilities, and that magnetic reconnection is not a required element in all coronal eruptions.
Multiple time scale methods in tokamak magnetohydrodynamics
Jardin, S.C.
1984-01-01
Several methods are discussed for integrating the magnetohydrodynamic (MHD) equations in tokamak systems on other than the fastest time scale. The dynamical grid method for simulating ideal MHD instabilities utilizes a natural nonorthogonal time-dependent coordinate transformation based on the magnetic field lines. The coordinate transformation is chosen to be free of the fast time scale motion itself, and to yield a relatively simple scalar equation for the total pressure, P = p + B/sup 2//2..mu../sub 0/, which can be integrated implicitly to average over the fast time scale oscillations. Two methods are described for the resistive time scale. The zero-mass method uses a reduced set of two-fluid transport equations obtained by expanding in the inverse magnetic Reynolds number, and in the small ratio of perpendicular to parallel mobilities and thermal conductivities. The momentum equation becomes a constraint equation that forces the pressure and magnetic fields and currents to remain in force balance equilibrium as they evolve. The large mass method artificially scales up the ion mass and viscosity, thereby reducing the severe time scale disparity between wavelike and diffusionlike phenomena, but not changing the resistive time scale behavior. Other methods addressing the intermediate time scales are discussed.
Variational principle with singular perturbation of Hall magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Ohsaki, Shuichi; Yoshida, Zensho
2005-06-01
The Hall magnetohydrodynamics (H-MHD) model can describe an intrinsic small scale (ion skin depth ℓi) introduced by the Hall effect. The Hall term appears as a singular perturbation to the conventional magnetohydrodynamics (MHD) model, and hence, the MHD limit (ℓi→0) may be singular. The H-MHD system has three constants of motion, the energy, the magnetic (electron) and ion helicities. The ion helicity is known to be "fragile" with respect to the energy norm of the magnetic and flow fields [Z. Yoshida and S. M. Mahajan, Phys. Rev. Lett. 88, 095001 (2002)]. Under an appropriate ordering of scales, the ion helicity translates as the cross helicity that is a constant of motion of the MHD system. Conservation of the cross helicity is an essential condition to recover the macroscopic MHD picture from the H-MHD framework.
Generalized reduced magnetohydrodynamic equations
Kruger, S.E.
1999-02-01
A new derivation of reduced magnetohydrodynamic (MHD) equations is presented. A multiple-time-scale expansion is employed. It has the advantage of clearly separating the three time scales of the problem associated with (1) MHD equilibrium, (2) fluctuations whose wave vector is aligned perpendicular to the magnetic field, and (3) those aligned parallel to the magnetic field. The derivation is carried out without relying on a large aspect ratio assumption; therefore this model can be applied to any general configuration. By accounting for the MHD equilibrium and constraints to eliminate the fast perpendicular waves, equations are derived to evolve scalar potential quantities on a time scale associated with the parallel wave vector (shear-Alfven wave time scale), which is the time scale of interest for MHD instability studies. Careful attention is given in the derivation to satisfy energy conservation and to have manifestly divergence-free magnetic fields to all orders in the expansion parameter. Additionally, neoclassical closures and equilibrium shear flow effects are easily accounted for in this model. Equations for the inner resistive layer are derived which reproduce the linear ideal and resistive stability criterion of Glasser, Greene, and Johnson. The equations have been programmed into a spectral initial value code and run with shear flow that is consistent with the equilibrium input into the code. Linear results of tearing modes with shear flow are presented which differentiate the effects of shear flow gradients in the layer with the effects of the shear flow decoupling multiple harmonics.
Viscosity and Vorticity in Reduced Magneto-Hydrodynamics
Joseph, Ilon
2015-08-12
Magneto-hydrodynamics (MHD) critically relies on viscous forces in order for an accurate determination of the electric eld. For each charged particle species, the Braginskii viscous tensor for a magnetized plasma has the decomposition into matrices with special symmetries.
Channel-wall limitations in the magnetohydrodynamic induction generator
NASA Technical Reports Server (NTRS)
Jackson, W. D.; Pierson, E. S.
1969-01-01
Discussion of magnetohydrodynamic induction generator examines the machine in detail and materials problems influencing its design. The higher upper-temperature limit of the MHD system promises to be more efficient than present turbine systems for generating electricity.
Relative timing of substorm features in MHD simulations
NASA Technical Reports Server (NTRS)
Hesse, Michael; Birn, Joachim
1992-01-01
An investigation of the temporal sequence of substorm phenomena based on three dimensional MHD (magnetohydrodynamic) simulations of magnetic reconnection and plasmoid formation is presented. The investigation utilizes a spatially localized resistivity model which leads to a significantly faster evolution than found in previous investigations. The analysis of the results concentrates on substorm features that have received considerable attention in the past. The formation of magnetic neutral lines, the occurrence of fast flows directed both earthward and tailward, and the magnetic field changes leading to the formation of the substorm current wedge, and to the depolarization of the magnetic field earthward of the reconnection region and its dependence on the spatial distribution of resistivity, are discussed. These phenomena are seen as an integral part of the nonlinear evolution of the three dimensional tearing instability.
Method for manufacturing magnetohydrodynamic electrodes
Killpatrick, D.H.; Thresh, H.R.
1980-06-24
A method of manufacturing electrodes for use in a magnetohydrodynamic (MHD) generator is described comprising the steps of preparing a billet having a core of a first metal, a tubular sleeve of a second metal, and an outer sheath of an extrusile metal; evacuating the space between the parts of the assembled billet; extruding the billet; and removing the outer jacket. The extruded bar may be made into electrodes by cutting and bending to the shape required for an MHD channel frame. The method forms a bond between the first metal of the core and the second metal of the sleeve strong enough to withstand a hot and corrosive environment.
An AC magnetohydrodynamic micropump: towards a true integrated microfluidic system
Lee, A P; Lemoff, A V; McConaghy, C F; Miles, R R
1999-03-01
An AC Magnetohydrodynamic (MHD) micropump has been demonstrated in which the Lorentz force is used to propel an electrolytic solution along a microchannel etched in silicon. This micropump has no moving parts, produces a continuous (not pulsatile) flow, and is compatible with solutions containing biological specimens. micropump, using the Lorentz force as the pumping mechanism for biological analysis. The AC Magnetohydrodynamic (MHD) micropump investigated produces a continuous flow and allows for complex microchannel design.
Remarkable connections between extended magnetohydrodynamics models
Lingam, M. Morrison, P. J. Miloshevich, G.
2015-07-15
Through the use of suitable variable transformations, the commonality of all extended magnetohydrodynamics (MHD) models is established. Remarkable correspondences between the Poisson brackets of inertialess Hall MHD and inertial MHD (which has electron inertia, but not the Hall drift) and extended MHD (which has both effects) are established. The helicities (two in all) for each of these models are obtained through these correspondences. The commonality of all the extended MHD models is traced to the existence of two Lie-dragged 2-forms, which are closely associated with the canonical momenta of the two underlying species. The Lie-dragging of these 2-forms by suitable velocities also leads to the correct equations of motion. The Hall MHD Poisson bracket is analyzed in detail, the Jacobi identity is verified through a detailed proof, and this proof ensures the Jacobi identity for the Poisson brackets of all the models.
Magnetohydrodynamically generated velocities in confined plasma
Morales, Jorge A. Bos, Wouter J. T.; Schneider, Kai; Montgomery, David C.
2015-04-15
We investigate by numerical simulation the rotational flows in a toroid confining a conducting magnetofluid in which a current is driven by the application of externally supported electric and magnetic fields. The computation involves no microscopic instabilities and is purely magnetohydrodynamic (MHD). We show how the properties and intensity of the rotations are regulated by dimensionless numbers (Lundquist and viscous Lundquist) that contain the resistivity and viscosity of the magnetofluid. At the magnetohydrodynamic level (uniform mass density and incompressible magnetofluids), rotational flows appear in toroidal, driven MHD. The evolution of these flows with the transport coefficients, geometry, and safety factor are described.
Conservation of circulation in magnetohydrodynamics
Bekenstein; Oron
2000-10-01
We demonstrate at both the Newtonian and (general) relativistic levels the existence of a generalization of Kelvin's circulation theorem (for pure fluids) that is applicable to perfect magnetohydrodynamics. The argument is based on the least action principle for magnetohydrodynamic flow. Examples of the new conservation law are furnished. The new theorem should be helpful in identifying new kinds of vortex phenomena distinct from magnetic ropes or fluid vortices. PMID:11089118
The Classification of Magnetohydrodynamic Regimes of Thermonuclear Combustion
NASA Astrophysics Data System (ADS)
Remming, Ian S.; Khokhlov, Alexei M.
2014-10-01
Physical properties of magnetohydrodynamic (MHD) reaction fronts are studied as functions of the thermodynamic conditions, and the strength and orientation of the magnetic field in the unburned matter through which the fronts propagate. We determine the conditions for the existence of the various types of MHD reaction fronts and the character of the changes in physical quantities across these reaction fronts. The analysis is carried out in general for a perfect gas equation of state and a constant energy release, and then extended to thermonuclear reaction fronts in degenerate carbon-oxygen mixtures and degenerate helium in conditions typical of Type Ia supernova explosions. We find that as unburned matter enters perpendicular to a reaction front, the release of energy through burning generates shear velocity in the reacting gas that, depending on the type of reaction front, strengthens or weakens the magnetic field. In addition, we find that the steady-state propagation of a reaction front is impossible for certain ranges of magnetic field direction. Our results provide insight into the phenomena of MHD thermonuclear combustion that is relevant to the interpretation of future simulations of SN Ia explosions that have magnetic fields systematically incorporated.
The classification of magnetohydrodynamic regimes of thermonuclear combustion
Remming, Ian S.; Khokhlov, Alexei M.
2014-10-10
Physical properties of magnetohydrodynamic (MHD) reaction fronts are studied as functions of the thermodynamic conditions, and the strength and orientation of the magnetic field in the unburned matter through which the fronts propagate. We determine the conditions for the existence of the various types of MHD reaction fronts and the character of the changes in physical quantities across these reaction fronts. The analysis is carried out in general for a perfect gas equation of state and a constant energy release, and then extended to thermonuclear reaction fronts in degenerate carbon-oxygen mixtures and degenerate helium in conditions typical of Type Ia supernova explosions. We find that as unburned matter enters perpendicular to a reaction front, the release of energy through burning generates shear velocity in the reacting gas that, depending on the type of reaction front, strengthens or weakens the magnetic field. In addition, we find that the steady-state propagation of a reaction front is impossible for certain ranges of magnetic field direction. Our results provide insight into the phenomena of MHD thermonuclear combustion that is relevant to the interpretation of future simulations of SN Ia explosions that have magnetic fields systematically incorporated.
Compressible magnetohydrodynamic sawtooth crash
NASA Astrophysics Data System (ADS)
Sugiyama, Linda E.
2014-02-01
In a toroidal magnetically confined plasma at low resistivity, compressible magnetohydrodynamic (MHD) predicts that an m = 1/n = 1 sawtooth has a fast, explosive crash phase with abrupt onset, rate nearly independent of resistivity, and localized temperature redistribution similar to experimental observations. Large scale numerical simulations show that the 1/1 MHD internal kink grows exponentially at a resistive rate until a critical amplitude, when the plasma motion accelerates rapidly, culminating in fast loss of the temperature and magnetic structure inside q < 1, with somewhat slower density redistribution. Nonlinearly, for small effective growth rate the perpendicular momentum rate of change remains small compared to its individual terms ∇p and J × B until the fast crash, so that the compressible growth rate is determined by higher order terms in a large aspect ratio expansion, as in the linear eigenmode. Reduced MHD fails completely to describe the toroidal mode; no Sweet-Parker-like reconnection layer develops. Important differences result from toroidal mode coupling effects. A set of large aspect ratio compressible MHD equations shows that the large aspect ratio expansion also breaks down in typical tokamaks with rq =1/Ro≃1/10 and a /Ro≃1/3. In the large aspect ratio limit, failure extends down to much smaller inverse aspect ratio, at growth rate scalings γ =O(ɛ2). Higher order aspect ratio terms, including B˜ϕ, become important. Nonlinearly, higher toroidal harmonics develop faster and to a greater degree than for large aspect ratio and help to accelerate the fast crash. The perpendicular momentum property applies to other transverse MHD instabilities, including m ≥ 2 magnetic islands and the plasma edge.
MHD technology in aluminum casting
Kalinichenko, I.
1984-08-01
The use of MHD technology in aluminum casting is discussed. Associates of the Latvian Academy of Sciences Institute of Physics developed magnetohydrodynamic units for the Siberian plant. A MHD unit made it possible to free five persons from heavy work at the plant. Labor productivity doubled in this section. With the aid of the magnetic field, the alloy silumin is obtained in only three hours. Specialists of the Irkutsk affiliate of the All-Union Scientific Research and Design Institute of the Aluminum, Magnesium and Electrode Industry are convinced that MHD technology has a bright future. However, this will necessitate the development of new MHD technology for different types of casting facilities, with their specific features taken into account.
Dynamo onset as a first-order transition: lessons from a shell model for magnetohydrodynamics.
Sahoo, Ganapati; Mitra, Dhrubaditya; Pandit, Rahul
2010-03-01
We carry out systematic and high-resolution studies of dynamo action in a shell model for magnetohydrodynamic (MHD) turbulence over wide ranges of the magnetic Prandtl number PrM and the magnetic Reynolds number ReM. Our study suggests that it is natural to think of dynamo onset as a nonequilibrium first-order phase transition between two different turbulent, but statistically steady, states. The ratio of the magnetic and kinetic energies is a convenient order parameter for this transition. By using this order parameter, we obtain the stability diagram (or nonequilibrium phase diagram) for dynamo formation in our MHD shell model in the (PrM-1,ReM) plane. The dynamo boundary, which separates dynamo and no-dynamo regions, appears to have a fractal character. We obtain a hysteretic behavior of the order parameter across this boundary and suggestions of nucleation-type phenomena. PMID:20365864
Self-organisation and non-linear dynamics in driven magnetohydrodynamic turbulent flows
NASA Astrophysics Data System (ADS)
Dallas, V.; Alexakis, A.
2015-04-01
Magnetohydrodynamic (MHD) turbulent flows driven by random, large-scale, mechanical and electromagnetic external forces of zero helicities are investigated by means of direct numerical simulations. It is shown that despite the absence of helicities in the forcing, the system is attracted to helical states of large scale condensates that exhibit laminar behaviour despite the large value of the Reynolds numbers examined. We demonstrate that the correlation time of the external forces controls the time spent on these states, i.e., for short correlation times, the system remains in the turbulent state while as the correlation time is increased, the system spends more and more time in the helical states. As a result, time averaged statistics are significantly affected by the time spent on these states. These results have important implications for MHD and turbulence theory and they provide insight into various physical phenomena where condensates transpire.
Magnetohydrodynamic generators using two-phase liquid-metal flows
NASA Technical Reports Server (NTRS)
Petrick, M.
1969-01-01
Two-phase flow generator cycle of a magnetohydrodynamic /MHD/ generator uses a working fluid which is compressible and treated as an expanding gas. The two-phase mixture passes from the heat source through the MHD generator, where the expansion process takes place and the electrical energy is extracted.
Multi-symplectic magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Webb, G. M.; McKenzie, J. F.; Zank, G. P.; Zank
2014-10-01
A multi-symplectic formulation of ideal magnetohydrodynamics (MHD) is developed based on the Clebsch variable variational principle in which the Lagrangian consists of the kinetic minus the potential energy of the MHD fluid modified by constraints using Lagrange multipliers that ensure mass conservation, entropy advection with the flow, the Lin constraint, and Faraday's equation (i.e. the magnetic flux is Lie dragged with the flow). The analysis is also carried out using the magnetic vector potential Ã where α=Ã. d x is Lie dragged with the flow, and B=∇×Ã. The multi-symplectic conservation laws give rise to the Eulerian momentum and energy conservation laws. The symplecticity or structural conservation laws for the multi-symplectic system corresponds to the conservation of phase space. It corresponds to taking derivatives of the momentum and energy conservation laws and combining them to produce n(n-1)/2 extra conservation laws, where n is the number of independent variables. Noether's theorem for the multi-symplectic MHD system is derived, including the case of non-Cartesian space coordinates, where the metric plays a role in the equations.
Magnetohydrodynamic turbulence: Observation and experiment
Brown, M. R.; Schaffner, D. A.; Weck, P. J.
2015-05-15
We provide a tutorial on the paradigms and tools of magnetohydrodynamic (MHD) turbulence. The principal paradigm is that of a turbulent cascade from large scales to small, resulting in power law behavior for the frequency power spectrum for magnetic fluctuations E{sub B}(f). We will describe five useful statistical tools for MHD turbulence in the time domain: the temporal autocorrelation function, the frequency power spectrum, the probability distribution function of temporal increments, the temporal structure function, and the permutation entropy. Each of these tools will be illustrated with an example taken from MHD fluctuations in the solar wind. A single dataset from the Wind satellite will be used to illustrate all five temporal statistical tools.
Magnetohydrodynamic Turbulence and the Geodynamo
NASA Technical Reports Server (NTRS)
Shebalin, John V.
2014-01-01
The ARES Directorate at JSC has researched the physical processes that create planetary magnetic fields through dynamo action since 2007. The "dynamo problem" has existed since 1600, when William Gilbert, physician to Queen Elizabeth I, recognized that the Earth was a giant magnet. In 1919, Joseph Larmor proposed that solar (and by implication, planetary) magnetism was due to magnetohydrodynamics (MHD), but full acceptance did not occur until Glatzmaier and Roberts solved the MHD equations numerically and simulated a geomagnetic reversal in 1995. JSC research produced a unique theoretical model in 2012 that provided a novel explanation of these physical observations and computational results as an essential manifestation of broken ergodicity in MHD turbulence. Research is ongoing, and future work is aimed at understanding quantitative details of magnetic dipole alignment in the Earth as well as in Mercury, Jupiter and its moon Ganymede, Saturn, Uranus, Neptune, and the Sun and other stars.
Generalized reduced MHD equations
Kruger, S.E.; Hegna, C.C.; Callen, J.D.
1998-07-01
A new derivation of reduced magnetohydrodynamic (MHD) equations is presented. A multiple-time-scale expansion is employed. It has the advantage of clearly separating the three time scales of the problem associated with (1) MHD equilibrium, (2) fluctuations whose wave vector is aligned perpendicular to the magnetic field, and (3) those aligned parallel to the magnetic field. The derivation is carried out without relying on a large aspect ratio assumption; therefore this model can be applied to any general toroidal configuration. By accounting for the MHD equilibrium and constraints to eliminate the fast perpendicular waves, equations are derived to evolve scalar potential quantities on a time scale associated with the parallel wave vector (shear-alfven wave time scale), which is the time scale of interest for MHD instability studies. Careful attention is given in the derivation to satisfy energy conservation and to have manifestly divergence-free magnetic fields to all orders in the expansion parameter. Additionally, neoclassical closures and equilibrium shear flow effects are easily accounted for in this model. Equations for the inner resistive layer are derived which reproduce the linear ideal and resistive stability criterion of Glasser, Greene, and Johnson.
MHD Energy Bypass Scramjet Engine
NASA Technical Reports Server (NTRS)
Mehta, Unmeel B.; Bogdanoff, David W.; Park, Chul; Arnold, Jim (Technical Monitor)
2001-01-01
Revolutionary rather than evolutionary changes in propulsion systems are most likely to decrease cost of space transportation and to provide a global range capability. Hypersonic air-breathing propulsion is a revolutionary propulsion system. The performance of scramjet engines can be improved by the AJAX energy management concept. A magneto-hydro-dynamics (MHD) generator controls the flow and extracts flow energy in the engine inlet and a MHD accelerator downstream of the combustor accelerates the nozzle flow. A progress report toward developing the MHD technology is presented herein. Recent theoretical efforts are reviewed and ongoing experimental efforts are discussed. The latter efforts also include an ongoing collaboration between NASA, the US Air Force Research Laboratory, US industry, and Russian scientific organizations. Two of the critical technologies, the ionization of the air and the MHD accelerator, are briefly discussed. Examples of limiting the combustor entrance Mach number to a low supersonic value with a MHD energy bypass scheme are presented, demonstrating an improvement in scramjet performance. The results for a simplified design of an aerospace plane show that the specific impulse of the MHD-bypass system is better than the non-MHD system and typical rocket over a narrow region of flight speeds and design parameters. Equilibrium ionization and non-equilibrium ionization are discussed. The thermodynamic condition of air at the entrance of the engine inlet determines the method of ionization. The required external power for non-equilibrium ionization is computed. There have been many experiments in which electrical power generation has successfully been achieved by magneto-hydrodynamic (MHD) means. However, relatively few experiments have been made to date for the reverse case of achieving gas acceleration by the MHD means. An experiment in a shock tunnel is described in which MHD acceleration is investigated experimentally. MHD has several
MHD simple waves and the divergence wave
Webb, G. M.; Pogorelov, N. V.; Zank, G. P.
2010-03-25
In this paper we investigate magnetohydrodynamic (MHD) simple divergence waves in MHD, for models in which nablacentre dotBnot =0. These models are related to the eight wave Riemann solvers in numerical MHD, in which the eighth wave is the divergence wave associated with nablacentre dotBnot =0. For simple wave solutions, all physical variables (the gas density, pressure, fluid velocity, entropy, and magnetic field induction in the MHD case) depend on a single phase function phi. We consider the form of the MHD equations used by both Powell et al. and Janhunen. It is shown that the Janhunen version of the equations possesses fully nonlinear, exact simple wave solutions for the divergence wave, but no physically meaningful simple divergence wave solution exists for the Powell et al. system. We suggest that the 1D simple, divergence wave solution for the Janhunen system, may be useful for the testing and validation of numerical MHD codes.
Global Magnetohydrodynamic Modeling of the Solar Corona
NASA Technical Reports Server (NTRS)
Linker, Jon A.
2001-01-01
This report describes the progress made in the investigation of the solar corona using magnetohydrodynamic (MHD) simulations. Coronal mass ejections (CME) are believed to be the primary cause of nonrecurrent geomagnetic storms and these have been investigated through the use of three-dimensional computer simulation.
Newtonian CAFE: a new ideal MHD code to study the solar atmosphere
NASA Astrophysics Data System (ADS)
González-Avilés, J. J.; Cruz-Osorio, A.; Lora-Clavijo, F. D.; Guzmán, F. S.
2015-12-01
We present a new code designed to solve the equations of classical ideal magnetohydrodynamics (MHD) in three dimensions, submitted to a constant gravitational field. The purpose of the code centres on the analysis of solar phenomena within the photosphere-corona region. We present 1D and 2D standard tests to demonstrate the quality of the numerical results obtained with our code. As solar tests we present the transverse oscillations of Alfvénic pulses in coronal loops using a 2.5D model, and as 3D tests we present the propagation of impulsively generated MHD-gravity waves and vortices in the solar atmosphere. The code is based on high-resolution shock-capturing methods, uses the Harten-Lax-van Leer-Einfeldt (HLLE) flux formula combined with Minmod, MC, and WENO5 reconstructors. The divergence free magnetic field constraint is controlled using the Flux Constrained Transport method.
Symmetry transforms for ideal magnetohydrodynamics equilibria.
Bogoyavlenskij, Oleg I
2002-11-01
A method for constructing ideal magnetohydrodynamics (MHD) equilibria is introduced. The method consists of the application of symmetry transforms to any known MHD equilibrium [ O. I. Bogoyavlenskij, Phys. Rev. E. 62, 8616, (2000)]. The transforms break the geometrical symmetries of the field-aligned solutions and produce continuous families of the nonsymmetric MHD equilibria. The method of symmetry transforms also allows to obtain MHD equilibria with current sheets and exact solutions with noncollinear vector fields B and V. A model of the nonsymmetric astrophysical jets outside of their accretion disks is developed. The total magnetic and kinetic energy of the jet is finite in any layer c(1)
BOOK REVIEW: Nonlinear Magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Shafranov, V.
1998-08-01
Nonlinear magnetohydrodynamics by Dieter Biskamp is a thorough introduction to the physics of the most impressive non-linear phenomena that occur in conducting magnetoplasmas. The basic systems, in which non-trivial dynamic processes are observed, accompanied by changes of geometry of the magnetic field and the effects of energy transformation (magnetic energy into kinetic energy or the opposite effect in magnetic dynamos), are the plasma magnetic confinement systems for nuclear fusion and space plasmas, mainly the solar plasma. A significant number of the examples of the dynamic processes considered are taken from laboratory plasmas, for which an experimental check of the theory is possible. Therefore, though the book is intended for researchers and students interested in both laboratory, including nuclear fusion, and astrophysical plasmas, it is most probably closer to the first category of reader. In the Introduction the author notes that unlike the hydrodynamics of non-conducting fluids, where the phenomena caused by rapid fluid motions are the most interesting, for plasmas in a strong magnetic field the quasi-static configurations inside which the local dynamic processes occur are often the most important. Therefore, the reader will also find in this book rather traditional material on the theory of plasma equilibrium and stability in magnetic fields. In addition, it is notable that, as opposed to a linear theory, the non-linear theory, as a rule, cannot give quite definite explanations or predictions of phenomena, and consequently there are in the book many results obtained by consideration of numerical models with the use of supercomputers. The treatment of non-linear dynamics is preceded by Chapters 2 to 4, in which the basics of MHD theory are presented with an emphasis on the role of integral invariants of the magnetic helicity type, a derivation of the reduced MHD equations is given, together with examples of the exact solutions of the equilibrium
Doss, E.D.; Sikes, W.C.
1992-09-01
This report describes the work performed during Phase 1 and Phase 2 of the collaborative research program established between Argonne National Laboratory (ANL) and Newport News Shipbuilding and Dry Dock Company (NNS). Phase I of the program focused on the development of computer models for Magnetohydrodynamic (MHD) propulsion. Phase 2 focused on the experimental validation of the thruster performance models and the identification, through testing, of any phenomena which may impact the attractiveness of this propulsion system for shipboard applications. The report discusses in detail the work performed in Phase 2 of the program. In Phase 2, a two Tesla test facility was designed, built, and operated. The facility test loop, its components, and their design are presented. The test matrix and its rationale are discussed. Representative experimental results of the test program are presented, and are compared to computer model predictions. In general, the results of the tests and their comparison with the predictions indicate that thephenomena affecting the performance of MHD seawater thrusters are well understood and can be accurately predicted with the developed thruster computer models.
[Nonlinear magnetohydrodynamics
Not Available
1992-11-01
Theoretical predictions were compared with available data from JET on the threshold unstable MHD activity in toroidal confinement devices. In particular, questions arising as to Hartmans number and the selection of a kinematic viscosity are discussed.
Free boundary skin current MHD (magnetohydrodynamic) equilibria
Reusch, M.F.
1988-02-01
Function theoretic methods in the complex plane are used to develop simple parametric hodograph formulae which generate sharp boundary equilibria of arbitrary shape. The related method of Gorenflo and Merkel is discussed. A numerical technique for the construction of solutions, based on one of the methods is presented. A study is made of the bifurcations of an equilibrium of general form. 28 refs., 9 figs.
Magnetohydrodynamic Simulations of Current-Sheet Formation and Reconnection at a Magnetic X Line
NASA Astrophysics Data System (ADS)
DeVore, C. R.; Antiochos, S. K.; Karpen, J. T.; Black, C.
2011-12-01
Phenomena ranging from the quiescent heating of the ambient plasma to the highly explosive release of energy and acceleration of particles in flares are conjectured to result from magnetic reconnection at electric current sheets in the Sun's corona. We are investigating numerically, using a macroscopic magnetohydrodynamic (MHD) model with adaptive mesh refinement, the formation and reconnection of a current sheet in an initially potential 2D magnetic field containing a null. Subjecting this simple configuration to unequal stresses in the four quadrants bounded by the X-line separatrix distorts the potential null into a double-Y-line current sheet. We find that even small distortions of the magnetic field induce the formation of a tangential discontinuity in the high-beta region around the null. A continuously applied stress eventually leads to the onset of fast magnetic reconnection across the sheet, with copious production, merging, and ejection of magnetic islands. We compare the current-sheet development and evolution for three cases: quasi-ideal MHD with numerical resistivity only; uniformly resistive MHD; and MHD with an embedded kinetic reconnection model. Analogous kinetic simulations using particle-in-cell (PIC) methods to investigate the small-scale dynamics of the system also are being pursued (C. Black et al., this meeting). Our progress toward understanding this simple system will be reported, as will the implications of our results for the dynamic activity associated with coronal current sheets and for general multiscale modeling of magnetized plasmas in the Heliosphere. Our research was supported by NASA.
NASA Astrophysics Data System (ADS)
de Sterck, H.; Low, B. C.; Poedts, S.
1998-11-01
Two-dimensional ideal magnetohydrodynamic (MHD) simulations are presented that demonstrate several novel phenomena in MHD shock formation. The stationary symmetrical flow of a uniform, planar, field-aligned, low-β and superfast magnetized plasma around a perfectly conducting cylinder is calculated. The velocity of the incoming flow is chosen such that the formation of fast switch-on shocks is possible. Using a time marching procedure, a stationary bow shock is obtained, composed of two consecutive interacting shock fronts. The leading shock front has a dimpled shape and is composed of fast, intermediate and hydrodynamic shock parts. A second shock front follows the leading front. Additional intermediate shocks and tangential discontinuities are present in the downstream part of the flow. The intermediate shocks are of the 1-3, 1-4, 2-4 and 1=2-3=4 types. This is a confirmation in two dimensions of recent results on the admissibility of these types of shocks. Recently it has also been shown that the 1=2-3=4 shock, embedded in a double compound wave, is present in the analytical solution of some planar one-dimensional MHD Riemann problems. This MHD flow with interacting shocks may have applications for some observed features of fast solar Coronal Mass Ejections and other phenomena in low-β space plasmas.
Alfven Wave Tomography for Cold MHD Plasmas
I.Y. Dodin; N.J. Fisch
2001-09-07
Alfven waves propagation in slightly nonuniform cold plasmas is studied by means of ideal magnetohydrodynamics (MHD) nonlinear equations. The evolution of the MHD spectrum is shown to be governed by a matrix linear differential equation with constant coefficients determined by the spectrum of quasi-static plasma density perturbations. The Alfven waves are shown not to affect the plasma density inhomogeneities, as they scatter off of them. The application of the MHD spectrum evolution equation to the inverse scattering problem allows tomographic measurements of the plasma density profile by scanning the plasma volume with Alfven radiation.
Multirail electromagnetic launcher powered from a pulsed magnetohydrodynamic generator
NASA Astrophysics Data System (ADS)
Afonin, A. G.; Butov, V. G.; Panchenko, V. P.; Sinyaev, S. V.; Solonenko, V. A.; Shvetsov, G. A.; Yakushev, A. A.
2015-09-01
The operation of an electromagnetic multirail launcher of solids powered from a pulsed magnetohydrodynamic (MHD) generator is studied. The plasma flow in the channel of the pulsed MHD generator and the possibility of launching solids in a rapid-fire mode of launcher operation are considered. It is shown that this mode of launcher operation can be implemented by matching the plasma flow dynamics in the channel of the pulsed MHD generator and the launching conditions. It is also shown that powerful pulsed MHD generators can be used as a source of electrical energy for rapid-fire electromagnetic rail launchers operating in a burst mode.
Magnetohydrodynamic Augmented Propulsion Experiment
NASA Technical Reports Server (NTRS)
Litchford, Ron J.; Cole, John; Lineberry, John; Chapman, Jim; Schmidt, Harold; Cook, Stephen (Technical Monitor)
2002-01-01
A fundamental obstacle to routine space access is the specific energy limitations associated with chemical fuels. In the case of vertical take-off, the high thrust needed for vertical liftoff and acceleration to orbit translates into power levels in the 10 GW range. Furthermore, useful payload mass fractions are possible only if the exhaust particle energy (i.e., exhaust velocity) is much greater than that available with traditional chemical propulsion. The electronic binding energy released by the best chemical reactions (e.g., LOX/LH2 for example, is less than 2 eV per product molecule (approx. 1.8 eV per H2O molecule), which translates into particle velocities less than 5 km/s. Useful payload fractions, however, will require exhaust velocities exceeding 15 km/s (i.e., particle energies greater than 20 eV). As an added challenge, the envisioned hypothetical RLV (reusable launch vehicle) should accomplish these amazing performance feats while providing relatively low acceleration levels to orbit (2-3g maximum). From such fundamental considerations, it is painfully obvious that planned and current RLV solutions based on chemical fuels alone represent only a temporary solution and can only result in minor gains, at best. What is truly needed is a revolutionary approach that will dramatically reduce the amount of fuel and size of the launch vehicle. This implies the need for new compact high-power energy sources as well as advanced accelerator technologies for increasing engine exhaust velocity. Electromagnetic acceleration techniques are of immense interest since they can be used to circumvent the thermal limits associated with conventional propulsion systems. This paper describes the Magnetohydrodynamic Augmented Propulsion Experiment (MAPX) being undertaken at NASA Marshall Space Flight Center (MSFC). In this experiment, a 1-MW arc heater is being used as a feeder for a 1-MW magnetohydrodynamic (MHD) accelerator. The purpose of the experiment is to demonstrate
A photolithographic fabrication technique for magnetohydrodynamic micropumps
NASA Astrophysics Data System (ADS)
Kuenstner, Stephen; Baylor, Martha-Elizabeth
2014-03-01
Magnetohydrodynamic (MHD) devices use perpendicular electric and magnetic fields to exert a Lorentz body force on a conducting fluid. Miniaturized MHD devices have been used to create pumps, stirrers, heat exchangers, and microfluidic networks. Compared to mechanical micropumps, MHD micropumps are appealing because they require no moving parts, which simplifies fabrication, and because they are amenable to electronic control. This abstract reports the fabrication and testing of a centimeter-scale MHD pump using a thiol-ene/methacrylate-based photopolymer and mask-based photolithographic technique. Pumps like this one could simplify the fabrication of sophisticated optofluidic devices, including liquid-core, liquid cladding (L2) waveguides, which are usually created with PDMS using stamps, or etched into silicon wafers. The photolithographic technique demonstrated here requires only one masking step to create fluid channels with complex geometries.
Magnetohydrodynamics of chiral relativistic fluids
NASA Astrophysics Data System (ADS)
Boyarsky, Alexey; Fröhlich, Jürg; Ruchayskiy, Oleg
2015-08-01
We study the dynamics of a plasma of charged relativistic fermions at very high temperature T ≫m , where m is the fermion mass, coupled to the electromagnetic field. In particular, we derive a magnetohydrodynamical description of the evolution of such a plasma. We show that, compared to conventional magnetohydronamics (MHD) for a plasma of nonrelativistic particles, the hydrodynamical description of the relativistic plasma involves new degrees of freedom described by a pseudoscalar field originating in a local asymmetry in the densities of left-handed and right-handed fermions. This field can be interpreted as an effective axion field. Taking into account the chiral anomaly we present dynamical equations for the evolution of this field, as well as of other fields appearing in the MHD description of the plasma. Due to its nonlinear coupling to helical magnetic fields, the axion field significantly affects the dynamics of a magnetized plasma and can give rise to a novel type of inverse cascade.
Scaling laws in magnetohydrodynamic turbulence
Campanelli, Leonardo
2004-10-15
We analyze the decay laws of the kinetic and magnetic energies and the evolution of correlation lengths in freely decaying incompressible magnetohydrodynamic (MHD) turbulence. Scale invariance of MHD equations assures that, in the case of constant dissipation parameters (i.e., kinematic viscosity and resistivity) and null magnetic helicity, the kinetic and magnetic energies decay in time as E{approx}t{sup -1}, and the correlation lengths evolve as {xi}{approx}t{sup 1/2}. In the helical case, assuming that the magnetic field evolves towards a force-free state, we show that (in the limit of large magnetic Reynolds number) the magnetic helicity remains constant, and the kinetic and magnetic energies decay as E{sub v}{approx}t{sup -1} and E{sub B}{approx}t{sup -1/2} respectively, while both the kinetic and magnetic correlation lengths grow as {xi}{approx}t{sup 1/2}.
Micromachined magnetohydrodynamic actuators and sensors
Lee, Abraham P.; Lemoff, Asuncion V.
2000-01-01
A magnetohydrodynamic (MHD) micropump and microsensor which utilizes micromachining to integrate the electrodes with microchannels and includes a magnet for producing magnetic fields perpendicular to both the electrical current direction and the fluid flow direction. The magnet can also be micromachined and integrated with the micropump using existing technology. The MHD micropump, for example, can generate continuous, reversible flow, with readily controllable flow rates. The flow can be reversed by either reversing the electrical current flow or reversing the magnetic field. By mismatching the electrodes, a swirling vortex flow can be generated for potential mixing applications. No moving parts are necessary and the dead volume is minimal. The micropumps can be placed at any position in a fluidic circuit and a combination of micropumps can generate fluidic plugs and valves.
MHD Integrated Topping Cycle Project
Not Available
1992-03-01
The Magnetohydrodynamics (MHD) Integrated Topping Cycle (ITC) Project represents the culmination of the proof-of-concept (POC) development stage in the US Department of Energy (DOE) program to advance MHD technology to early commercial development stage utility power applications. The project is a joint effort, combining the skills of three topping cycle component developers: TRW, Avco/TDS, and Westinghouse. TRW, the prime contractor and system integrator, is responsible for the 50 thermal megawatt (50 MW{sub t}) slagging coal combustion subsystem. Avco/TDS is responsible for the MHD channel subsystem (nozzle, channel, diffuser, and power conditioning circuits), and Westinghouse is responsible for the current consolidation subsystem. The ITC Project will advance the state-of-the-art in MHD power systems with the design, construction, and integrated testing of 50 MW{sub t} power train components which are prototypical of the equipment that will be used in an early commercial scale MHD utility retrofit. Long duration testing of the integrated power train at the Component Development and Integration Facility (CDIF) in Butte, Montana will be performed, so that by the early 1990's, an engineering data base on the reliability, availability, maintainability and performance of the system will be available to allow scaleup of the prototypical designs to the next development level. This Sixteenth Quarterly Technical Progress Report covers the period May 1, 1991 to July 31, 1991.
NASA Astrophysics Data System (ADS)
Freidberg, Jeffrey P.
2014-06-01
1. Introduction; 2. The ideal MHD model; 3. General properties of ideal MHD; 5. Equilibrium: one-dimensional configurations; 6. Equilibrium: two-dimensional configurations; 7. Equilibrium: three-dimensional configurations; 8. Stability: general considerations; 9. Alternate MHD models; 10. MHD stability comparison theorems; 11. Stability: one-dimensional configurations; 12. Stability: multi-dimensional configurations; Appendix A. Heuristic derivation of the kinetic equation; Appendix B. The Braginskii transport coefficients; Appendix C. Time derivatives in moving plasmas; Appendix D. The curvature vector; Appendix E. Overlap limit of the high b and Greene-Johnson stellarator models; Appendix F. General form for q(y); Appendix G. Natural boundary conditions; Appendix H. Upper and lower bounds on dQKIN.
Magnetohydrodynamic turbulence in the solar wind
NASA Technical Reports Server (NTRS)
Goldstein, Melvyn L.
1995-01-01
The fluctuations in magnetic field and plasma velocity in solar wind, which possess many features of fully developed magnetohydrodynamic (MHD) turbulence, are discussed. Direct spacecraft observations from 0.3 to over 20 AU, remote sensing radio scintillation observations, numerical simulations, and various models provide complementary methods that show that the fluctuations in the wind parameters undergo significant dynamical evolution independent of whatever turbulence might exist in the solar photosphere and corona. The Cluster mission, with high time resolution particle and field measurements and its variable separation strategies, should be able to provide data for answering many questions on MHD turbulence.
Magnetohydrodynamic modelling of exploding foil initiators
NASA Astrophysics Data System (ADS)
Neal, William
2015-06-01
Magnetohydrodynamic (MHD) codes are currently being developed, and used, to predict the behaviour of electrically-driven flyer-plates. These codes are of particular interest to the design of exploding foil initiator (EFI) detonators but there is a distinct lack of comparison with high-fidelity experimental data. This study aims to compare a MHD code with a collection of temporally and spatially resolved diagnostics including PDV, dual-axis imaging and streak imaging. The results show the code's excellent representation of the flyer-plate launch and highlight features within the experiment that the model fails to capture.
NASA Astrophysics Data System (ADS)
Sych, Robert
2016-02-01
The study of magnetohydrodynamic (MHD) waves and oscillations in the solar atmosphere is one of the fastest developing fields in solar physics, and lies in the mainstream of using solar instrumentation data. This chapter first addresses the spatial frequency morphology of sources of sunspot oscillations and waves, including their localization, size, oscillation periods, and height localization with the mechanism of cutoff frequency that forms the observed emission variability. Then, it presents a review dynamic of sunspot wave processes, provides the information about the structure of wave fronts and their time variations, and investigates the oscillation frequency transformation depending on the wave energy. The chapter also addresses the initializing solar flares caused by trigger agents like magnetoacoustic waves, accelerated particle beams, and shocks. Special attention is paid to the relation between the flare reconnection periodic initialization and the dynamics of sunspot slow magnetoacoustic waves.
Lacey, James J.; Kurtzrock, Roy C.; Bienstock, Daniel
1976-08-24
A hot gaseous fluid of low ash content, suitable for use in open-cycle MHD (magnetohydrodynamic) power generation, is produced by means of a three-stage process comprising (1) partial combustion of a fossil fuel to produce a hot gaseous product comprising CO.sub.2 CO, and H.sub.2 O, (2) reformation of the gaseous product from stage (1) by means of a fluidized char bed, whereby CO.sub.2 and H.sub.2 O are converted to CO and H.sub.2, and (3) combustion of CO and H.sub.2 from stage (2) to produce a low ash-content fluid (flue gas) comprising CO.sub.2 and H.sub.2 O and having a temperature of about 4000.degree. to 5000.degree.F.
Direct comparisons of compressible magnetohydrodynamics and reduced magnetohydrodynamics turbulence
NASA Astrophysics Data System (ADS)
Dmitruk, Pablo; Matthaeus, William H.; Oughton, Sean
2005-11-01
Direct numerical simulations of low Mach number compressible three-dimensional magnetohydrodynamic (CMHD3D) turbulence in the presence of a strong mean magnetic field are compared with simulations of reduced magnetohydrodynamics (RMHD). Periodic boundary conditions in the three spatial coordinates are considered. Different sets of initial conditions are chosen to explore the applicability of RMHD and to study how close the solution remains to the full compressible MHD solution as both freely evolve in time. In a first set, the initial state is prepared to satisfy the conditions assumed in the derivation of RMHD, namely, a strong mean magnetic field and plane-polarized fluctuations, varying weakly along the mean magnetic field. In those circumstances, simulations show that RMHD and CMHD3D evolve almost indistinguishably from one another. When some of the conditions are relaxed the agreement worsens but RMHD remains fairly close to CMHD3D, especially when the mean magnetic field is large enough. Moreover, the well-known spectral anisotropy effect promotes the dynamical attainment of the conditions for RMHD applicability. Global quantities (mean energies, mean-square current, and vorticity) and energy spectra from the two solutions are compared and point-to-point separation estimations are computed. The specific results shown here give support to the use of RMHD as a valid approximation of compressible MHD with a mean magnetic field under certain but quite practical conditions.
Investigation of a liquid-metal magnetohydrodynamic power system.
NASA Technical Reports Server (NTRS)
Elliott, D. G.; Hays, L. G.; Cerini, D. J.; Bogdanoff, D. W.
1972-01-01
Liquid-metal magnetohydrodynamic power conversion is being investigated for nuclear-electric propulsion. A liquid-metal MHD converter has no moving mechanical parts and requires a heat source temperature of only 1300 K. Cycle efficiencies of 5% to 8% for single-stage converters and 10% for multistage converters appear attainable. The specific weight of a 240 kWe MHD power plant has been estimated as 30 kg/kWe with shielding for unmanned science missions.
Exact solutions of the incompressible dissipative Hall magnetohydrodynamics
Xia, Zhenwei; Yang, Weihong
2015-03-15
By using analytical method, the exact solutions of the incompressible dissipative Hall magnetohydrodynamics (MHD) equations are derived. It is found that a phase difference may occur between the velocity and magnetic field fluctuations when the kinetic and magnetic Reynolds numbers are both very large. Since velocity and magnetic field fluctuations are both circular polarized, the phase difference makes them no longer parallel or anti-parallel like that in the incompressible ideal Hall MHD.
Magnetohydrodynamic energy conversion by using convexly divergent channel
Murakami, Tomoyuki; Okuno, Yoshihiro
2009-12-21
We describe a magnetohydrodynamic (MHD) electrical power generator equipped with a convexly divergent channel, as determined through shock-tunnel-based experiments. The quality of MHD power-generating plasma and the energy conversion efficiency in the convexly divergent channel are compared with those from previous linearly divergent channel. The divergence enhancement in the channel upstream is effective for suppressing an excessive increase in static pressure, whereby notably high isentropic efficiency is achieved.
Magnetohydrodynamic instability
NASA Technical Reports Server (NTRS)
Priest, E. R.; Cargill, P.; Forbes, T. G.; Hood, A. W.; Steinolfson, R. S.
1986-01-01
There have been major advances in the theory of magnetic reconnection and of magnetic instability, with important implications for the observations, as follows: (1) Fast and slow magnetic shock waves are produced by the magnetohydrodynamics of reconnection and are potential particle accelerators. (2) The impulsive bursty regime of reconnection gives a rapid release of magnetic energy in a series of bursts. (3) The radiative tearing mode creates cool filamentary structures in the reconnection process. (4) The stability analyses imply that an arcade can become unstable when either its height or twist of plasma pressure become too great.
MHD turbulence model for global simulations of the solar wind and SEP acceleration
Sokolov, Igor V.; Roussev, Ilia I.
2008-08-25
The aim of the present work is to unify the various transport equations for turbulent waves that are used in different areas of space physics. We mostly focus on the magnetohydrodynamic (MHD) turbulence, in particular the Alfvenic turbulence.
MHD coal-fired flow facility. Annual technical progress report, October 1979-September 1980
Alstatt, M.C.; Attig, R.C.; Brosnan, D.A.
1981-03-01
The University of Tennessee Space Institute (UTSI) reports on significant activity, task status, planned research, testing, development, and conclusions for the Magnetohydrodynamics (MHD) Coal-Fired Flow Faclity (CFFF) and the Energy Conversion Facility (ECF).
NASA Astrophysics Data System (ADS)
Vlahakis, Nektarios
2010-03-01
Outflows emanating from the environment of stellar or galactic objects are a widespread phenomenon in astrophysics. Their morphology ranges from nearly spherically symmetric winds to highly collimated jets. In some cases, e.g., in jets associated with young stellar objects, the bulk outflow speeds are nonrelativistic, while in others, e.g., in jets associated with active galactic nuclei or gamma-ray bursts, it can even be highly relativistic. The main driving mechanism of collimated outflows is likely related to magnetic fields. These fields are able to tap the rotational energy of the compact object or disk, accelerate, and collimate matter ejecta. To zeroth order these outflows can be described by the highly intractable theory of magnetohydrodynamics (MHD). Even in systems where the assumptions of zero resistivity (ideal MHD), steady state, axisymmetry, one fluid description, and polytropic equation of state are applicable, the problem remains difficult. In this case the problem reduces to only two equations, corresponding to the two components of the momentum equation along the flow and in the direction perpendicular to the magnetic field (transfield direction). The latter equation is the most difficult to solve, but also the most important. It answers the question on the degree of the collimation, but also crucially affects the solution of the first, the acceleration efficiency and the bulk velocity of the flow. The first and second parts of this chapter refer to nonrelativistic and relativistic flows, respectively. These Parts can be read independently. In each one, the governing equations are presented and discussed, focusing on the case of flows that are magnetically dominated near the central source. The general characteristics of the solutions in relation to the acceleration and collimation mechanisms are analyzed. As specific examples of exact solutions of the full system of the MHD equations that satisfy all the analyzed general characteristics, self
Broken Ergodicity in MHD Turbulence
NASA Technical Reports Server (NTRS)
Shebalin, John V.
2010-01-01
Ideal magnetohydrodynamic (MHD) turbulence may be represented by finite Fourier series, where the inherent periodic box serves as a surrogate for a bounded astrophysical plasma. Independent Fourier coefficients form a canonical ensemble described by a Gaussian probability density function containing a Hermitian covariance matrix with positive eigenvalues. The eigenvalues at lowest wave number can be very small, resulting in a large-scale coherent structure: a turbulent dynamo. This is seen in computations and a theoretical explanation in terms of 'broken ergodicity' contains Taylor s theory of force-free states. An important problem for future work is the case of real, i.e., dissipative flows. In real flows, broken ergodicity and coherent structure are still expected to occur in MHD turbulence at the largest scale, as suggested by low resolution simulations. One challenge is to incorporate coherent structure at the largest scale into the theory of turbulent fluctuations at smaller scales.
[Nonlinear magnetohydrodynamics
Not Available
1994-01-01
Resistive MHD equilibrium, even for small resistivity, differs greatly from ideal equilibrium, as do the dynamical consequences of its instabilities. The requirement, imposed by Faraday`s law, that time independent magnetic fields imply curl-free electric fields, greatly restricts the electric fields allowed inside a finite-resistivity plasma. If there is no flow and the implications of the Ohm`s law are taken into account (and they need not be, for ideal equilibria), the electric field must equal the resistivity times the current density. The vanishing of the divergence of the current density then provides a partial differential equation which, together with boundary conditions, uniquely determines the scalar potential, the electric field, and the current density, for any given resistivity profile. The situation parallels closely that of driven shear flows in hydrodynamics, in that while dissipative steady states are somewhat more complex than ideal ones, there are vastly fewer of them to consider. Seen in this light, the vast majority of ideal MHD equilibria are just irrelevant, incapable of being set up in the first place. The steady state whose stability thresholds and nonlinear behavior needs to be investigated ceases to be an arbitrary ad hoc exercise dependent upon the whim of the investigator, but is determined by boundary conditions and choice of resistivity profile.
Global magnetohydrodynamic simulations on multiple GPUs
NASA Astrophysics Data System (ADS)
Wong, Un-Hong; Wong, Hon-Cheng; Ma, Yonghui
2014-01-01
Global magnetohydrodynamic (MHD) models play the major role in investigating the solar wind-magnetosphere interaction. However, the huge computation requirement in global MHD simulations is also the main problem that needs to be solved. With the recent development of modern graphics processing units (GPUs) and the Compute Unified Device Architecture (CUDA), it is possible to perform global MHD simulations in a more efficient manner. In this paper, we present a global magnetohydrodynamic (MHD) simulator on multiple GPUs using CUDA 4.0 with GPUDirect 2.0. Our implementation is based on the modified leapfrog scheme, which is a combination of the leapfrog scheme and the two-step Lax-Wendroff scheme. GPUDirect 2.0 is used in our implementation to drive multiple GPUs. All data transferring and kernel processing are managed with CUDA 4.0 API instead of using MPI or OpenMP. Performance measurements are made on a multi-GPU system with eight NVIDIA Tesla M2050 (Fermi architecture) graphics cards. These measurements show that our multi-GPU implementation achieves a peak performance of 97.36 GFLOPS in double precision.
Global Magnetohydrodynamic Modeling of the Solar Corona
NASA Technical Reports Server (NTRS)
Linker, Jon A.
1997-01-01
Under this contract, we have continued our investigations of the large scale structure of the solar corona and inner heliosphere using global magnetohydrodynamic (MHD) simulations. These computations have also formed the basis for studies of coronal mass ejections (CMES) using realistic coronal configurations. We have developed a technique for computing realistic magnetohydrodynamic (MHD) computations of the solar corona and inner heliosphere. To perform computations that can be compared with specific observations, it is necessary to incorporate solar observations into the boundary conditions. We have used the Wilcox Solar Observatory synoptic maps (collected during a solar rotation by daily measurements of the line-of-sight magnetic field at central meridian) to specify the radial magnetic field (B,) at the photosphere. For the initial condition, we use a potential magnetic field consistent with the specified distribution of B, at the lower boundary, and a wind solution consistent with the specified plasma density and temperature at the solar surface. Together this initial condition forms a (non-equilibrium) approximation of the state of the solar corona for the time-dependent MHD computation. The MHD equations are then integrated in time to steady state. Here we describe solutions relevant to a recent solar eclipse, as well as Ulysses observations. We have also developed a model configuration of solar minimum, useful for studying CME initiation and propagation.
Selective decay and dynamic alignment in the MHD turbulence: The role of the rugged invariants
NASA Astrophysics Data System (ADS)
Telloni, Daniele; Perri, Silvia; Carbone, Vincenzo; Bruno, Roberto
2016-03-01
In the evolving MagnetoHydroDynamic (MHD) turbulence a key role is played by the relaxation processes, which drive a magnetized fluid towards self-organized, stable configurations, like a force-free state (resulting from a selective decay) or a dynamic alignment (anti-alignment) between the plasma flow velocity and magnetic field. The evolution of the three MHD rugged invariants, namely of the magnetic helicity Hm, the cross-helicity Hc and the total energy E, is of particular importance in interpreting the asymptotic solutions of the MHD decay. It is thus prominent to investigate the magnetic and cross-helicity content carried by the solar wind and by magnetic structures advected by the flowing plasma, and particularly their radial evolution throughout the inner heliosphere, in order to offer a rather complete picture of the phenomenological aspect of the relaxation phenomena occurring in the solar wind turbulence. The results presented in this paper show that within some solar wind streams, the ideal MHD decays towards a state with maximal cross-helicity, where the magnetic and velocity fluctuations are (anti-)aligned with a high correlation degree. The maximal magnetic helicity state, say the force-free configuration, is instead observed in interplanetary flux ropes, a particular class of magnetic objects advected by the solar wind. However, it is worth noting that in some peculiar flux ropes, the competitive action of both rugged invariants drives the MHD configuration of these structures to intermediate states, where both the magnetic and cross-helicity significantly deviate from zero, without, however, reaching a maximum value.
Action principles for extended magnetohydrodynamic models
Keramidas Charidakos, I.; Lingam, M.; Morrison, P. J.; White, R. L.; Wurm, A.
2014-09-15
The general, non-dissipative, two-fluid model in plasma physics is Hamiltonian, but this property is sometimes lost or obscured in the process of deriving simplified (or reduced) two-fluid or one-fluid models from the two-fluid equations of motion. To ensure that the reduced models are Hamiltonian, we start with the general two-fluid action functional, and make all the approximations, changes of variables, and expansions directly within the action context. The resulting equations are then mapped to the Eulerian fluid variables using a novel nonlocal Lagrange-Euler map. Using this method, we recover Lüst's general two-fluid model, extended magnetohydrodynamic (MHD), Hall MHD, and electron MHD from a unified framework. The variational formulation allows us to use Noether's theorem to derive conserved quantities for each symmetry of the action.
Entropy generation analysis of magnetohydrodynamic induction devices
NASA Astrophysics Data System (ADS)
Salas, Hugo; Cuevas, Sergio; López de Haro, Mariano
1999-10-01
Magnetohydrodynamic (MHD) induction devices such as electromagnetic pumps or electric generators are analysed within the approach of entropy generation. The flow of an electrically-conducting incompressible fluid in an MHD induction machine is described through the well known Hartmann model. Irreversibilities in the system due to ohmic dissipation, flow friction and heat flow are included in the entropy-generation rate. This quantity is used to define an overall efficiency for the induction machine that considers the total loss caused by process irreversibility. For an MHD generator working at maximum power output with walls at constant temperature, an optimum magnetic field strength (i.e. Hartmann number) is found based on the maximum overall efficiency.
Nuclear magnetohydrodynamic EMP, solar storms, and substorms
Rabinowitz, M. ); Meliopoulous, A.P.S.; Glytsis, E.N. . School of Electrical Engineering); Cokkinides, G.J. )
1992-10-20
In addition to a fast electromagnetic pulse (EMP), a high altitude nuclear burst produces a relatively slow magnetohydrodynamic EMP (MHD EMP), whose effects are like those from solar storm geomagnetically induced currents (SS-GIC). The MHD EMP electric field E [approx lt] 10[sup [minus] 1] V/m and lasts [approx lt] 10[sup 2] sec, whereas for solar storms E [approx gt] 10[sup [minus] 2] V/m and lasts [approx gt] 10[sup 3] sec. Although the solar storm electric field is lower than MHD EMP, the solar storm effects are generally greater due to their much longer duration. Substorms produce much smaller effects than SS-GIC, but occur much more frequently. This paper describes the physics of such geomagnetic disturbances and analyzes their effects.
Nearly incompressible fluids. II - Magnetohydrodynamics, turbulence, and waves
NASA Technical Reports Server (NTRS)
Zank, G. P.; Matthaeus, W. H.
1993-01-01
The theory of nearly incompressible (NI) fluid dynamics developed previously for hydrodynamics is extended to magnetohydrodynamics (MHD). Based on a singular expansion technique, modified systems of fluid equations are obtained for which the effects of compressibility are admitted only weakly in terms of the different possible incompressible solutions. NI MHD represents the interface between the compressible and incompressible magnetofluid descriptions in the subsonic regime. It is shown that three distinct NI descriptions exist corresponding to each of the three possible plasma beta regimes. The detailed theory of weakly compressible corrections to the various incompressible MHD descriptions is presented, and the implications for the solar wind are discussed.
Computation of Multi-region Relaxed Magnetohydrodynamic Equilibria
Hudson, S. R.; Dewar, R. L.; Dennis, G.; Hole, M. J.; McGann, M.; von Nessi, G.; Lazerson, S.
2013-03-29
We describe the construction of stepped-pressure equilibria as extrema of a multi-region, relaxed magnetohydrodynamic (MHD) energy functional that combines elements of ideal MHD and Taylor relaxation, and which we call MRXMHD. The model is compatible with Hamiltonian chaos theory and allows the three-dimensional MHD equilibrium problem to be formulated in a well-posed manner suitable for computation. The energy-functional is discretized using a mixed finite-element, Fourier representation for the magnetic vector potential and the equilibrium geometry; and numerical solutions are constructed using the stepped-pressure equilibrium code, SPEC. Convergence studies with respect to radial and Fourier resolution are presented.
Magnetohydrodynamic flow at microelectrodes
NASA Astrophysics Data System (ADS)
Ragsdale, Steven Ronald
1998-12-01
Voltammetric reduction of nitrobenzene (NB) at a 12.5 μm-radius Pt microdisk electrode in acetonitrile solutions containing 0.001/le x NB/le 0.999 is reported (x NB is the mole fraction of NB). The voltammetric response displays a reversible, sigmoidalshape wave, corresponding to the one-electron reduction of NB. The maximum limiting current occurs in solutions containing intermediate redox concentrations, x NB/le0.2. Voltammetric currents are analyzed using the Cullinan-Vignes model to describe the interdiffusion of the redox species and solvent. Mutual diffusivities are corrected for activity effects using isothermal liquid-vapor equilibrium data. Application of the activity-corrected diffusivities in the Cullinan- Vignes model yields reasonably accurate predictions of the dependence of the voltammetric current on solution composition. The influence of an external magnetic field (0-1 Tesla) on the voltammetric response of Pt and Au microdisk electrodes (0.1, 6.4, 12.5 and 25 μm radius) is described. Magnetohydrodynamic (MHD) flow within a microscopic volume element adjacent to the microdisk surface results from the magnetic force generated by the flux of electrogenerated ions through the magnetic field. An analytic expression is presented for the magnetic force generated during steady-state voltammetry at a hemispherical microelectrode immersed in a uniform magnetic field. The magnetic volume force, F/bf mag (N/m3), is shown to decrease as r-2 (where r is the distance from the center of the electrode). The dependence of F/bf mag on r-2 confines the MHD flow to small volumes very close to the electrode surface (e.g., ~2×10-9 L for a 12.5 μm-radius electrode). Scanning electrochemical microscopy (SECM) is used to map MHD flows at a 25 μm-radius Pt microdisk electrode during the one-electron reduction of NB. Unidirectional lateral flow is observed when the magnetic field is aligned parallel to the electrode surface; rotational or cyclotron flow is observed when
NASA Astrophysics Data System (ADS)
Daldorff, L. K. S.; Toth, G.; Borovikov, D.; Gombosi, T. I.; Lapenta, G.
2014-12-01
With the new modeling capability in the Space Weather Modeling Framework (SWMF) of embedding an implicit Particle-in-Cell (PIC) model iPIC3D into the BATS-R-US magnetohydrodynamics model (Daldorff et al. 2014, JCP, 268, 236) we are ready to locally handle the full physics of the reconnection and its implications on the full system where globally, away from the reconnection region, a magnetohydrodynamic description is satisfactory. As magnetic reconnection is one of the main drivers in magnetospheric and heliospheric plasma dynamics, the self-consistent description of the electron dynamics in the coupled MHD-EPIC model is well suited for investigating the nature of these systems. We will compare the new embedded MHD-EPIC model with pure MHD and Hall MHD simulations of the Earth's magnetosphere.
Regular shock refraction in planar ideal MHD
NASA Astrophysics Data System (ADS)
Delmont, P.; Keppens, R.
2010-03-01
We study the classical problem of planar shock refraction at an oblique density discontinuity, separating two gases at rest, in planar ideal (magneto)hydrodynamics. In the hydrodynamical case, 3 signals arise and the interface becomes Richtmyer-Meshkov unstable due to vorticity deposition on the shocked contact. In the magnetohydrodynamical case, on the other hand, when the normal component of the magnetic field does not vanish, 5 signals will arise. The interface then typically remains stable, since the Rankine-Hugoniot jump conditions in ideal MHD do not allow for vorticity deposition on a contact discontinuity. We present an exact Riemann solver based solution strategy to describe the initial self similar refraction phase. Using grid-adaptive MHD simulations, we show that after reflection from the top wall, the interface remains stable.
Flow of Magnetohydrodynamic Micropolar Fluid Induced by Radially Stretching Sheets
NASA Astrophysics Data System (ADS)
Hayat, Tasawar; Nawaz, Muhammad; Hendi, Awatif A.
2011-02-01
We investigate the flow of a micropolar fluid between radial stretching sheets. The magnetohydrodynamic (MHD) nonlinear problem is treated using the homotopy analysis method (HAM) and the velocity profiles are predicted for the pertinent parameters. The values of skin friction and couple shear stress coefficients are obtained for various values of Reynolds number, Hartman number, and micropolar fluid parameter.
NASA Astrophysics Data System (ADS)
Dewar, R. L.; Mills, R.; Hole, M. J.
2009-05-01
The celebration of Allan Kaufman's 80th birthday was an occasion to reflect on a career that has stimulated the mutual exchange of ideas (or memes in the terminology of Richard Dawkins) between many researchers. This paper will revisit a meme Allan encountered in his early career in magnetohydrodynamics, the continuation of a magnetohydrodynamic mode through a singularity, and will also mention other problems where Allan's work has had a powerful cross-fertilizing effect in plasma physics and other areas of physics and mathematics. To resolve the continuation problem we regularize the Newcomb equation, solve it in terms of Legendre functions of imaginary argument, and define the small weak solutions of the Newcomb equation as generalized functions in the manner of Lighthill, i.e. via a limiting sequence of analytic functions that connect smoothly across the singularity.
Note: Tangential x-ray diagnosis for investigating fast MHD events in EAST tokamak.
Li, Erzhong; Hu, Liqun; Chen, Kaiyun; Zhang, Jizong; Chen, Yiebin; Zhou, Ruijie; Gan, Kaifu; Liu, Yong
2010-10-01
A tangential x-ray diagnosis has been installed in the experimental advanced superconducting tokamakvacuum vessel for the study of fast magnetohydrodynamics (MHD) events. This system is based on absolute x-ray ultraviolet detectors with a collimator which is processed by laser machine. The first experimental results have proved its ability to measure the small-scale and transient MHD perturbations. PMID:21034130
The optimization air separation plants for combined cycle MHD-power plant applications
NASA Technical Reports Server (NTRS)
Juhasz, A. J.; Springmann, H.; Greenberg, R.
1980-01-01
Some of the design approaches being employed during a current supported study directed at developing an improved air separation process for the production of oxygen enriched air for magnetohydrodynamics (MHD) combustion are outlined. The ultimate objective is to arrive at conceptual designs of air separation plants, optimized for minimum specific power consumption and capital investment costs, for integration with MHD combined cycle power plants.
Accurate, meshless methods for magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Hopkins, Philip F.; Raives, Matthias J.
2016-01-01
Recently, we explored new meshless finite-volume Lagrangian methods for hydrodynamics: the `meshless finite mass' (MFM) and `meshless finite volume' (MFV) methods; these capture advantages of both smoothed particle hydrodynamics (SPH) and adaptive mesh refinement (AMR) schemes. We extend these to include ideal magnetohydrodynamics (MHD). The MHD equations are second-order consistent and conservative. We augment these with a divergence-cleaning scheme, which maintains nabla \\cdot B≈ 0. We implement these in the code GIZMO, together with state-of-the-art SPH MHD. We consider a large test suite, and show that on all problems the new methods are competitive with AMR using constrained transport (CT) to ensure nabla \\cdot B=0. They correctly capture the growth/structure of the magnetorotational instability, MHD turbulence, and launching of magnetic jets, in some cases converging more rapidly than state-of-the-art AMR. Compared to SPH, the MFM/MFV methods exhibit convergence at fixed neighbour number, sharp shock-capturing, and dramatically reduced noise, divergence errors, and diffusion. Still, `modern' SPH can handle most test problems, at the cost of larger kernels and `by hand' adjustment of artificial diffusion. Compared to non-moving meshes, the new methods exhibit enhanced `grid noise' but reduced advection errors and diffusion, easily include self-gravity, and feature velocity-independent errors and superior angular momentum conservation. They converge more slowly on some problems (smooth, slow-moving flows), but more rapidly on others (involving advection/rotation). In all cases, we show divergence control beyond the Powell 8-wave approach is necessary, or all methods can converge to unphysical answers even at high resolution.
Thermal radiation and slip effects on MHD stagnation point flow of nanofluid over a stretching sheet
NASA Astrophysics Data System (ADS)
Ul Haq, Rizwan; Nadeem, Sohail; Hayat Khan, Zafar; Sher Akbar, Noreen
2015-01-01
Present model is devoted for the stagnation point flow of nanofluid with magneto-hydrodynamics (MHD) and thermal radiation effects passed over a stretching sheet. Moreover, we have considered the combined effects of velocity and thermal slip. Condition of zero normal flux of nanoparticles at the wall for the stretched flow phenomena is yet to be explored in the literature. Convinced partial differential equations of the model are transformed into the system of coupled nonlinear differential equations and then solved numerically. Graphical results are plotted for velocity, temperature and nanoparticle concentration for various values of emerging parameters. Variation of stream lines, skin friction coefficient, local Nusselt and Sherwood number are displayed along with the effective parameters. Final conclusion has been drawn on the basis of both numerical and graphs results.
BOOK REVIEW: Magnetohydrodynamics of Plasma Relaxation
NASA Astrophysics Data System (ADS)
Connor, J. W.
1998-06-01
This monograph on magnetohydrodynamic (MHD) relaxation in plasmas by Ortolani and Schnack occupies a fascinating niche in the plasma physics literature. It is rare in the complex and often technically sophisticated subject of plasma physics to be able to isolate a topic and deal with it comprehensively in a mere 180 pages. Furthermore, it brings a refreshingly original and personal approach to the treatment of plasma relaxation, synthesizing the experiences of the two authors to produce a very readable account of phenomena appearing in such diverse situations as laboratory reversed field pinches (RFPs) and the solar corona. Its novelty lies in that, while it does acknowledge the seminal Taylor theory of relaxation as a general guide, it emphasizes the role of large scale numerical MHD simulations in developing a picture for the relaxation phenomena observed in experiment and nature. Nevertheless, the volume has some minor shortcomings: a tendency to repetitiveness and some omissions that prevent it being entirely self-contained. The monograph is divided into nine chapters, with the first a readable, `chatty', introduction to the physics and phenomena of relaxation discussed in the later chapters. Chapter 2 develops the tools for describing relaxation processes, namely the resistive MHD model, leading to a discussion of resistive instabilities and the stability properties of RFPs. This chapter demonstrates the authors' confessed desire to avoid mathematical detail with a rather simplified discussion of Δ' and magnetic islands; it also sets the stage for their own belief, or thesis, that numerical simulation of the non-linear consequences of the MHD model is the best approach to explaining the physics of relaxation. Nevertheless, in Chapter 3 they provide a reasonably good account and critique of one analytic approach that is available, and which is the commonly accepted picture for relaxation in pinches - the Taylor relaxation theory based on the conservation of
Flow development and analysis of MHD generators and seawater thrusters
Doss, E.D. ); Roy, G.D. )
1992-03-01
In this paper, the flow characteristics inside magnetohydrodynamic (MHD) plasma generators and seawater thrusters are analyzed and are compared using a three-dimensional computer model that solves the governing partial differential equations for fluid flow and electrical fields. Calculations have been performed for a Faraday plasma generator and for a continuous electrode seawater thruster. The results of the calculations show that the effects caused by the interaction of the MHD forces with the fluid flow are strongly manifested in the case of the MHD generator as compared to the flow development in the MHD thruster. The existence of velocity overshoots over the sidewalls confirm previously published results for MHD generators with strong MHD interaction. For MHD thrusters, the velocity profile is found to be slightly flatter over the sidewall as compared to that over the electrode wall. As a result, distinct enhancement of the skin friction exists over the sidewalls of MHD generators in comparison to that of MHD thrusters. Plots of velocity profiles and skin friction distributions are presented to illustrate and compare the flow development in MHD generators and thrusters.
Magnetohydrodynamics Accelerator Research into Advanced Hypersonics (MARIAH). Part 2
NASA Technical Reports Server (NTRS)
Baughman, Jack A.; Micheletti, David A.; Nelson, Gordon L.; Simmons, Gloyd A.
1997-01-01
This report documents the activities, results, conclusions and recommendations of the Magnetohydrodynamics Accelerator Research Into Advanced Hypersonics (MARIAH) Project in which the use of magnetohydrodynamics (MHD) technology is investigated for its applicability to augment hypersonic wind tunnels. The long range objective of this investigation is to advance the development of ground test facilities to support the development of hypervelocity flight vehicles. The MHD accelerator adds kinetic energy directly to the wind tunnel working fluid, thereby increasing its Mach number to hypervelocity levels. Several techniques for MHD augmentation, as well as other physical characteristics of the process are studied to enhance the overall performance of hypersonic wind tunnel design. Specific recommendations are presented to improve the effectiveness of ground test facilities. The work contained herein builds on nearly four decades of research and experimentation by the aeronautics ground test and evaluation community, both foreign and domestic.
Magnetohydrodynamics Accelerator Research Into Advanced Hypersonics (MARIAH). Part 1
NASA Technical Reports Server (NTRS)
Micheletti, David A.; Baughman, Jack A.; Nelson, Gordon L.; Simmons, Gloyd A.
1997-01-01
This report documents the activities, results, conclusions and recommendations of the Magnetohydrodynamics Accelerator Research Into Advanced Hypersonics (MARIAH) Project in which the use of magnetohydrodynamics (MHD) technology is investigated for its applicability to augment hypersonic wind tunnels. The long range objective of this investigation is to advance the development of ground test facilities to support the development of hypervelocity flight vehicles. The MHD accelerator adds kinetic energy directly to the wind tunnel working fluid, thereby increasing its Mach number to hypervelocity levels. Several techniques for MHD augmentation, as well as other physical characteristics of the process are studied to enhance the overall performance of hypersonic wind tunnel design. Specific recommendations are presented to improve the effectiveness of ground test facilities. The work contained herein builds on nearly four decades of research and experimentation by the aeronautics ground test and evaluation community, both foreign and domestic.
NASA Astrophysics Data System (ADS)
Vlaykov, Dimitar G.; Grete, Philipp; Schmidt, Wolfram; Schleicher, Dominik R. G.
2016-06-01
Compressible magnetohydrodynamic (MHD) turbulence is ubiquitous in astrophysical phenomena ranging from the intergalactic to the stellar scales. In studying them, numerical simulations are nearly inescapable, due to the large degree of nonlinearity involved. However, the dynamical ranges of these phenomena are much larger than what is computationally accessible. In large eddy simulations (LESs), the resulting limited resolution effects are addressed explicitly by introducing to the equations of motion additional terms associated with the unresolved, subgrid-scale dynamics. This renders the system unclosed. We derive a set of nonlinear structural closures for the ideal MHD LES equations with particular emphasis on the effects of compressibility. The closures are based on a gradient expansion of the finite-resolution operator [W. K. Yeo (CUP, 1993)] and require no assumptions about the nature of the flow or magnetic field. Thus, the scope of their applicability ranges from the sub- to the hyper-sonic and -Alfvénic regimes. The closures support spectral energy cascades both up and down-scale, as well as direct transfer between kinetic and magnetic resolved and unresolved energy budgets. They implicitly take into account the local geometry, and in particular, the anisotropy of the flow. Their properties are a priori validated in Paper II [P. Grete et al., Phys. Plasmas 23, 062317 (2016)] against alternative closures available in the literature with respect to a wide range of simulation data of homogeneous and isotropic turbulence.
MHD augmented chemical rocket propulsion for space applications
NASA Astrophysics Data System (ADS)
Schulz, R. J.; Chapman, J. N.; Rhodes, R. P.
1992-07-01
A performance analysis is carried out of a magnetohydrodynamic (MHD) augmented chemical thruster (based on a gaseous hydrogen-oxygen system) for space applications such as orbit transfer. The mathematical model used in the analysis is a one-dimensional flow model using equilibrium chemistry for the combustor, choked nozzle, and MHD channel portions of the system, and chemical nonequilibrium kinetics for the high area-ratio gas dynamic nozzle portion of the system. The performance of the chemical-MHD-augmented thruster is compared with that of a pure electric thruster of the same specific impulse level.
Broken Symmetry and Coherent Structure in MHD Turbulence
NASA Technical Reports Server (NTRS)
Shebalin, John V.
2007-01-01
Absolute equilibrium ensemble theory for ideal homogeneous magnetohydrodynamic (MHD) turbulence is fairly well developed. Theory and Simulation indicate that ideal MHD turbulence non-ergodic and contains coherent structure. The question of applicability real (i.e., dissipative) MHD turbulence is examined. Results from several very long time numerical simulations on a 64(exp 3) grid are presented. It is seen that coherent structure begins to form before decay dominates over nonlinearity. The connection with inverse spectral cascades and selective decay will also be discussed.
MHD technology transfer, integration, and review committee
NASA Astrophysics Data System (ADS)
1990-05-01
As part of Task 8 of the magnetohydrodynamic (MHD) Integrated Topping Cycle (ITC) project, TRW was given the responsibility to organize, charter and co-chair, with the Department of Energy (DOE), an MHD Technology Transfer, Integration and Review Committee (TTIRC). The TTIRC consists of an Executive Committee (EC) which acts as the governing body, and a General Committee (GC), also referred to as the main or full committee, consisting of representatives from the various POC contractors, participating universities and national laboratories, utilities, equipment suppliers, and other potential MHD users or investors. The purpose of the TTIRC is to: (1) review all Proof-of-Concept (POC) projects and schedules in the national MHD program; to assess their compatibility with each other and the first commercial MHD retrofit plant; (2) establish and implement technology transfer formats for users of this technology; (3) identify interfaces, issues, and funding structures directly impacting the success of the commercial retrofit; (4) investigate and identify the manner in which, and by whom, the above should be resolved; and (5) investigate and assess other participation (foreign and domestic) in the U.S. MHD Program. There are seven sections: introduction; Executive Committee and General Committee activity; Committee activities related to technology transfer; ongoing POC integration activities being performed under the auspices of the Executive Committee; recommendations passed on to the DOE by the Executive Committee; Planned activities for the next six months.
Perfect magnetohydrodynamics as a field theory
Bekenstein, Jacob D.; Betschart, Gerold
2006-10-15
We propose the generally covariant action for the theory of a self-coupled complex scalar field and electromagnetism which by virtue of constraints is equivalent, in the regime of long wavelengths, to perfect magnetohydrodynamics (MHD). We recover from it the Euler equation with Lorentz force, and the thermodynamic relations for a prefect fluid. The equation of state of the latter is related to the scalar field's self potential. We introduce 1+3 notation to elucidate the relation between MHD and field variables. In our approach the requirement that the scalar field be single valued leads to the quantization of a certain circulation in steps of ({Dirac_h}/2{pi}); this feature leads, in the classical limit, to the conservation of that circulation. The circulation is identical to that in Oron's generalization of Kelvin's circulation theorem to perfect MHD; we here characterize the new conserved helicity associated with it. We also demonstrate the existence for MHD of two Bernoulli-like theorems for each spacetime symmetry of the flow and geometry; one of these is pertinent to suitably defined potential flow. We exhibit the conserved quantities explicitly in the case that two symmetries are simultaneously present, and give examples. Also in this case we exhibit a new conserved MHD circulation distinct from Oron's, and provide an example.
Method for manufacturing magnetohydrodynamic electrodes
Killpatrick, Don H.; Thresh, Henry R.
1982-01-01
A method of manufacturing electrodes for use in a magnetohydrodynamic (MHD) generator comprising the steps of preparing a billet having a core 10 of a first metal, a tubular sleeve 12 of a second metal, and an outer sheath 14, 16, 18 of an extrusile metal; evacuating the space between the parts of the assembled billet; extruding the billet; and removing the outer jacket 14. The extruded bar may be made into electrodes by cutting and bending to the shape required for an MDH channel frame. The method forms a bond between the first metal of the core 10 and the second metal of the sleeve 12 strong enough to withstand a hot and corrosive environment.
MHD Oscillations in the Earth's Magnetotail
NASA Astrophysics Data System (ADS)
Leonovich, A. S.; Mazur, V. A.; Kozlov, D. A.
2016-02-01
In studies of hydromagnetic oscillations of the Earth's magnetosphere, it is often considered as a giant resonator for magnetohydrodynamic (MHD) waves. A shear flow instability on the magnetopause has long been regarded as a possible source of MHD oscillations in the Earth's magnetosphere. A most interesting phenomenon investigated for the past two decades are ultra-low-frequency oscillations with a discrete spectrum. Such oscillations are recorded usually in the midnight-morning sector of the magnetosphere at 60° to 80° latitudes. Another type of MHD oscillations typical of the magnetotail is the coupled Alfvén and slow magnetosonic waves on stretched magnetic field lines passing through the current sheet. Each of these modes can propagate along paths that almost coincide with the magnetic field lines. The recently discovered kink-like oscillations are oscillations of the current sheet itself, similar to a piece of fabric fluttering in the wind. In this regard they are called flapping modes.
NASA Astrophysics Data System (ADS)
Griton, Léa; Pantellini, Filippo; Moncuquet, Michel
2016-04-01
We present 3D simulations of the interaction of the solar wind with Mercury's magnetosphere using the magnetohydrodynamic code AMRVAC. A procedure for the identification of standing MHD modes has been applied to these simulations showing that large scale standing slow mode structures may exist in Mercury's magnetosheath. The identification is mostly based on relatively simple approximate analytical solutions to the old problem of determining the family of all standing linear plane MHD waves in a flowing plasma. The question of the identification of standing slow mode structures using in situ measurements such as the future BepiColombo MMO mission to Mercury will be discussed as well.
Pulsar Magnetohydrodynamic Winds
NASA Astrophysics Data System (ADS)
Okamoto, Isao; Sigalo, Friday B.
2006-12-01
The acceleration and collimation/decollimation of relativistic magnetocentrifugal winds are discussed concerning a cold plasma from a strongly magnetized, rapidly rotating neutron star in a steady axisymmetric state based on ideal magnetohydrodynamics. There exist unipolar inductors associated with the field line angular frequency, α, at the magnetospheric base surface, SB, with a huge potential difference between the poles and the equator, which drive electric current through the pulsar magnetosphere. Any ``current line'' must emanate from one terminal of the unipolar inductor and return to the other, converting the Poynting flux to the kinetic flux of the wind at finite distances. In a plausible field structure satisfying the transfield force-balance equation, the fast surface, SF, must exist somewhere between the subasymptotic and asymptotic domains, i.e., at the innermost point along each field line of the asymptotic domain of \\varpaA2/\\varpi2 ≪ 1, where \\varpiA is the Alfvénic axial distance. The criticality condition at SF yields the Lorentz factor, γF = μ\\varepsilon1/3, and the angular momentum flux, β, as the eigenvalues in terms of the field line angular velocity, α, the mass flux per unit flux tube, η, and one of the Bernoulli integrals, μδ, which are assumed to be specifiable as the boundary conditions at SB. The other Bernoulli integral, μɛ, is related to μδ as μɛ = μδ[1-(α2\\varpiA2/c2)]-1, and both μɛ and \\varpiA2 are eigenvalues to be determined by the criticality condition at SF. Ongoing MHD acceleration is possible in the superfast domain. This fact may be helpful in resolving a discrepancy between the wind theory and the Crab-nebula model. It is argued that the ``anti-collimation theorem'' holds for relativistic winds, based on the curvature of field streamlines determined by the transfield force balance. The ``theorem'' combines with the ``current-closure condition'' as a global condition in the wind zone to produce a
Seyler, C. E.; Martin, M. R.
2011-01-15
It is shown that the two-fluid model under a generalized Ohm's law formulation and the resistive magnetohydrodynamics (MHD) can both be described as relaxation systems. In the relaxation model, the under-resolved stiff source terms constrain the dynamics of a set of hyperbolic equations to give the correct asymptotic solution. When applied to the collisional two-fluid model, the relaxation of fast time scales associated with displacement current and finite electron mass allows for a natural transition from a system where Ohm's law determines the current density to a system where Ohm's law determines the electric field. This result is used to derive novel algorithms, which allow for multiscale simulation of low and high frequency extended-MHD physics. This relaxation formulation offers an efficient way to implicitly advance the Hall term and naturally simulate a plasma-vacuum interface without invoking phenomenological models. The relaxation model is implemented as an extended-MHD code, which is used to analyze pulsed power loads such as wire arrays and ablating foils. Two-dimensional simulations of pulsed power loads are compared for extended-MHD and MHD. For these simulations, it is also shown that the relaxation model properly recovers the resistive-MHD limit.
MHD--Developing New Technology to Meet the Energy Crisis
ERIC Educational Resources Information Center
Fitch, Sandra S.
1978-01-01
Magnetohydrodynamics is a technology that could utilize the nation's most abundant fossil fuel and produce electrical energy more efficiently and cleanly than present-day turbines. A national research and development program is ongoing in Butte, Montana at the Montana Energy and MHD Research and Development Institute (MERDI). (Author/RK)
Double-duct liquid metal magnetohydrodynamic engine
Haaland, Carsten M.
1995-01-01
An internal combustion, liquid metal (LM) magnetohydrodynamic (MHD) engine and an alternating current (AC) magnetohydrodynamic generator, are used in combination to provide useful AC electric energy output. The engine design has-four pistons and a double duct configuration, with each duct containing sodium potassium liquid metal confined between free pistons located at either end of the duct. The liquid metal is forced to flow back and forth in the duct by the movement of the pistons, which are alternatively driven by an internal combustion process. In the MHD generator, the two LM-MHD ducts pass in close proximity through a Hartmann duct with output transformer. AC power is produced by operating the engine with the liquid metal in the two generator ducts always flowing in counter directions. The amount of liquid metal maintained in the ducts may be varied. This provides a variable stroke length for the pistons. The engine/generator provides variable AC power at variable frequencies that correspond to the power demands of the vehicular propulsion. Also the engine should maintain nearly constant efficiency throughout the range of power usage. Automobiles and trucks could be powered by the invention, with no transmission or power converter devices being required.
Double-duct liquid metal magnetohydrodynamic engine
Haaland, Carsten M.
1997-01-01
An internal combustion, liquid metal (LM) magnetohydrodynamic (MHD) engine and an alternating current (AC) magnetohydrodynamic generator, are used in combination to provide useful AC electric energy output. The engine design has four pistons and a double duct configuration, with each duct containing sodium potassium liquid metal confined between free pistons located at either end of the duct. The liquid metal is forced to flow back and forth in the duct by the movement of the pistons, which are alternatively driven by an internal combustion process. In the MHD generator, the two LM-MHD ducts pass in close proximity through a Hartmann duct with output transformer. AC power is produced by operating the engine with the liquid metal in the two generator ducts always flowing in counter directions. The amount of liquid metal maintained in the ducts may be varied. This provides a variable stroke length for the pistons. The engine/generator provides variable AC power at variable frequencies that correspond to the power demands of the vehicular propulsion. Also the engine should maintain nearly constant efficiency throughout the range of power usage. Automobiles and trucks could be powered by the invention, with no transmission or power converter devices being required.
Notes on Magnetohydrodynamics of Magnetic Reconnection in Turbulent Media
NASA Astrophysics Data System (ADS)
Browning, Philippa; Lazarian, Alex
2013-10-01
Astrophysical fluids have very large Reynolds numbers and therefore turbulence is their natural state. Magnetic reconnection is an important process in many astrophysical plasmas, which allows restructuring of magnetic fields and conversion of stored magnetic energy into heat and kinetic energy. Turbulence is known to dramatically change different transport processes and therefore it is not unexpected that turbulence can alter the dynamics of magnetic field lines within the reconnection process. We shall review the interaction between turbulence and reconnection at different scales, showing how a state of turbulent reconnection is natural in astrophysical plasmas, with implications for a range of phenomena across astrophysics. We consider the process of magnetic reconnection that is fast in magnetohydrodynamic (MHD) limit and discuss how turbulence—both externally driven and generated in the reconnecting system—can make reconnection independent on the microphysical properties of plasmas. We will also show how relaxation theory can be used to calculate the energy dissipated in turbulent reconnecting fields. As well as heating the plasma, the energy dissipated by turbulent reconnection may cause acceleration of non-thermal particles, which is briefly discussed here.
Notes on Magnetohydrodynamics of Magnetic Reconnection in Turbulent Media
NASA Astrophysics Data System (ADS)
Browning, Philippa; Lazarian, Alex
Astrophysical fluids have very large Reynolds numbers and therefore turbulence is their natural state. Magnetic reconnection is an important process in many astrophysical plasmas, which allows restructuring of magnetic fields and conversion of stored magnetic energy into heat and kinetic energy. Turbulence is known to dramatically change different transport processes and therefore it is not unexpected that turbulence can alter the dynamics of magnetic field lines within the reconnection process. We shall review the interaction between turbulence and reconnection at different scales, showing how a state of turbulent reconnection is natural in astrophysical plasmas, with implications for a range of phenomena across astrophysics. We consider the process of magnetic reconnection that is fast in magnetohydrodynamic (MHD) limit and discuss how turbulence—both externally driven and generated in the reconnecting system—can make reconnection independent on the microphysical properties of plasmas. We will also show how relaxation theory can be used to calculate the energy dissipated in turbulent reconnecting fields. As well as heating the plasma, the energy dissipated by turbulent reconnection may cause acceleration of non-thermal particles, which is briefly discussed here.
Magnetohydrodynamic Propulsion for the Classroom
NASA Astrophysics Data System (ADS)
Font, Gabriel I.; Dudley, Scott C.
2004-10-01
The cinema industry can sometimes prove to be an ally when searching for material with which to motivate students to learn physics. Consider, for example, the electromagnetic force on a current in the presence of a magnetic field. This phenomenon is at the heart of magnetohydrodynamic (MHD) propulsion systems. A submarine employing this type of propulsion was immortalized in the movie Hunt for Red October. While mentioning this to students certainly gets their attention, it often elicits comments that it is only fiction and not physically possible. Imagine their surprise when a working system is demonstrated! It is neither difficult nor expensive to construct a working system that can be demonstrated in the front of a classroom.2 In addition, all aspects of the engineering hurdles that must be surmounted and myths concerning this "silent propulsion" system are borne out in a simple apparatus. This paper details how to construct an inexpensive MHD propulsion boat that can be demonstrated for students in the classroom.
Properties of mass-loading shocks. II - Magnetohydrodynamics. [of Giacobini-Zinner and Halley comets
NASA Technical Reports Server (NTRS)
Zank, G. P.; Oughton, S.; Neubauer, F. M.; Webb, G. M.
1992-01-01
The one-dimensional magnetohydrodynamics of mass-loading shocks is examined. These shocks, which are distinct from MHD shocks of classical nonreacting fluid dynamics and of combustion theory and which are characterized by the addition of mass within the shock transition, are to be found at comets and, depending upon circumstances, at nonmagnetized and weakly magnetized planets such as Venus and Mars. A completely general mass-loading form of the Hugoniot equation is derived, and some of the most important differences between mass-loading and nonreacting classical MHD shocks are identified. Two new types of MHD shocks are described which have no classical MHD analogues.
ANALYTIC APPROXIMATE SEISMOLOGY OF PROPAGATING MAGNETOHYDRODYNAMIC WAVES IN THE SOLAR CORONA
Goossens, M.; Soler, R.; Arregui, I.
2012-12-01
Observations show that propagating magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere. The technique of MHD seismology uses the wave observations combined with MHD wave theory to indirectly infer physical parameters of the solar atmospheric plasma and magnetic field. Here, we present an analytical seismological inversion scheme for propagating MHD waves. This scheme uses the observational information on wavelengths and damping lengths in a consistent manner, along with observed values of periods or phase velocities, and is based on approximate asymptotic expressions for the theoretical values of wavelengths and damping lengths. The applicability of the inversion scheme is discussed and an example is given.
Ji, H.; Almagri, A.F.; Prager, S.C.; Sarff, J.S. )
1994-08-01
We report the first experimental verification of the magnetohydrodynamic (MHD) dynamo in the reversed-field pinch (RFP). A burst of MHD dynamo electric field is observed during the sawtooth crash, followed by an increase in the local parallel current in the Madison Symmetric Totus RFP edge. By measuring each term, the parallel MHD mean-field Ohm's law is observed to hold within experimental error bars both between and during sawtooth crashes.
Theory and Simulation Basis for Magnetohydrodynamic Stability in DIII-D
Turnbull, A.D.; Brennan, D.P.; Chu, M.S.; Lao, L.L.; Snyder, P.B.
2005-10-15
Theory and simulation have provided one of the critical foundations for many of the significant achievements in magnetohydrodynamic (MHD) stability in DIII-D over the past two decades. Early signature achievements included the validation of tokamak MHD stability limits, beta and performance optimization through cross-section shaping and profiles, and the development of new operational regimes. More recent accomplishments encompass the realization and sustainment of wall stabilization using plasma rotation and active feedback, a new understanding of edge stability and its relation to edge-localized modes, and recent successes in predicting resistive tearing and interchange instabilities. The key to success has been the synergistic tie between the theory effort and the experiment made possible by the detailed equilibrium reconstruction data available in DIII-D and the corresponding attention to the measured details in the modeling. This interaction fosters an emphasis on the important phenomena and leads to testable theoretical predictions. Also important is the application of a range of analytic and simulation techniques, coupled with a program of numerical tool development. The result is a comprehensive integrated approach to fusion science and improving the tokamak approach to burning plasmas.
Magnetohydrodynamics for collisionless plasmas from the gyrokinetic perspective
NASA Astrophysics Data System (ADS)
Lee, W. W.
2016-07-01
The effort to obtain a set of MagnetoHydroDynamic (MHD) equations for a magnetized collisionless plasma was started nearly 60 years ago by Chew et al. [Proc. R. Soc. London, Ser. A 236(1204), 112-118 (1956)]. Many attempts have been made ever since. Here, we will show the derivation of a set of these equations from the gyrokinetic perspective, which we call it gyrokinetic MHD, and it is different from the conventional ideal MHD. However, this new set of equations still has conservation properties and, in the absence of fluctuations, recovers the usual MHD equilibrium. Furthermore, the resulting equations allow for the plasma pressure balance to be further modified by finite-Larmor-radius effects in regions with steep pressure gradients. The present work is an outgrowth of the paper on "Alfven Waves in Gyrokinetic Plasmas" by Lee and Qin [Phys. Plasmas 10, 3196 (2003)].
Toward textbook multigrid efficiency for fully implicit resistive magnetohydrodynamics
Adams, Mark F.; Samtaney, Ravi; Brandt, Achi
2010-09-01
Multigrid methods can solve some classes of elliptic and parabolic equations to accuracy below the truncation error with a work-cost equivalent to a few residual calculations – so-called ‘‘textbook” multigrid efficiency. We investigate methods to solve the system of equations that arise in time dependent magnetohydrodynamics (MHD) simulations with textbook multigrid efficiency. We apply multigrid techniques such as geometric interpolation, full approximate storage, Gauss–Seidel smoothers, and defect correction for fully implicit, nonlinear, second-order finite volume discretizations of MHD. We apply these methods to a standard resistive MHD benchmark problem, the GEM reconnection problem, and add a strong magnetic guide field, which is a critical characteristic of magnetically confined fusion plasmas. We show that our multigrid methods can achieve near textbook efficiency on fully implicit resistive MHD simulations.
Toward textbook multigrid efficiency for fully implicit resistive magnetohydrodynamics
Adams, Mark F.; Samtaney, Ravi; Brandt, Achi
2010-09-01
Multigrid methods can solve some classes of elliptic and parabolic equations to accuracy below the truncation error with a work-cost equivalent to a few residual calculations - so-called 'textbook' multigrid efficiency. We investigate methods to solve the system of equations that arise in time dependent magnetohydrodynamics (MHD) simulations with textbook multigrid efficiency. We apply multigrid techniques such as geometric interpolation, full approximate storage, Gauss-Seidel smoothers, and defect correction for fully implicit, nonlinear, second-order finite volume discretizations of MHD. We apply these methods to a standard resistive MHD benchmark problem, the GEM reconnection problem, and add a strong magnetic guide field, which is a critical characteristic of magnetically confined fusion plasmas. We show that our multigrid methods can achieve near textbook efficiency on fully implicit resistive MHD simulations.
Spontaneous chiral symmetry breaking of Hall magnetohydrodynamic turbulence.
Meyrand, Romain; Galtier, Sébastien
2012-11-01
Hall magnetohydrodynamics (MHD) is investigated through three-dimensional direct numerical simulations. We show that the Hall effect induces a spontaneous chiral symmetry breaking of the turbulent dynamics. The normalized magnetic polarization is introduced to separate the right- (R) and left-handed (L) fluctuations. A classical k(-7/3) spectrum is found at small scales for R magnetic fluctuations which corresponds to the electron MHD prediction. A spectrum compatible with k(-11/3) is obtained at large-scales for the L magnetic fluctuations; we call this regime the ion MHD. These results are explained heuristically by rewriting the Hall MHD equations in a succinct vortex dynamical form. Applications to solar wind turbulence are discussed. PMID:23215387
Multi-region relaxed Hall magnetohydrodynamics with flow
NASA Astrophysics Data System (ADS)
Lingam, Manasvi; Abdelhamid, Hamdi M.; Hudson, Stuart R.
2016-08-01
The recent formulations of multi-region relaxed magnetohydrodynamics (MRxMHD) have generalized the famous Woltjer-Taylor states by incorporating a collection of "ideal barriers" that prevent global relaxation and flow. In this paper, we generalize MRxMHD with flow to include Hall effects, and thereby obtain the partially relaxed counterparts of the famous double Beltrami states as a special subset. The physical and mathematical consequences arising from the introduction of the Hall term are also presented. We demonstrate that our results (in the ideal MHD limit) constitute an important subset of ideal MHD equilibria, and we compare our approach against other variational principles proposed for deriving the partially relaxed states.
Toward textbook multigrid efficiency for fully implicit resistive magnetohydrodynamics
Adams, Mark F.; Samtaney, Ravi; Brandt, Achi
2013-12-14
Multigrid methods can solve some classes of elliptic and parabolic equations to accuracy below the truncation error with a work-cost equivalent to a few residual calculations – so-called “textbook” multigrid efficiency. We investigate methods to solve the system of equations that arise in time dependent magnetohydrodynamics (MHD) simulations with textbook multigrid efficiency. We apply multigrid techniques such as geometric interpolation, full approximate storage, Gauss-Seidel smoothers, and defect correction for fully implicit, nonlinear, second-order finite volume discretizations of MHD. We apply these methods to a standard resistive MHD benchmark problem, the GEM reconnection problem, and add a strong magnetic guide field, which is a critical characteristic of magnetically confined fusion plasmas. We show that our multigrid methods can achieve near textbook efficiency on fully implicit resistive MHD simulations.
Toward textbook multigrid efficiency for fully implicit resistive magnetohydrodynamics
Adams, Mark F.; Samtaney, Ravi; Brandt, Achi
2010-09-01
Multigrid methods can solve some classes of elliptic and parabolic equations to accuracy below the truncation error with a work-cost equivalent to a few residual calculations – so-called ‘‘textbook” multigrid efficiency. We investigate methods to solve the system of equations that arise in time dependent magnetohydrodynamics (MHD) simulations with textbook multigrid efficiency. We apply multigrid techniques such as geometric interpolation, full approximate storage, Gauss–Seidel smoothers, and defect correction for fully implicit, nonlinear, second-order finite volume discretizations of MHD. We apply these methods to a standard resistive MHD benchmark problem, the GEM reconnection problem, and add a strong magnetic guide field,more » which is a critical characteristic of magnetically confined fusion plasmas. We show that our multigrid methods can achieve near textbook efficiency on fully implicit resistive MHD simulations.« less
Nonlinear magnetohydrodynamic simulation of Tore Supra hollow current profile discharges
NASA Astrophysics Data System (ADS)
Maget, P.; Huysmans, G. T. A.; Garbet, X.; Ottaviani, M.; Lütjens, H.; Luciani, J.-F.
2007-05-01
Magnetohydrodynamic (MHD) activity often undermines the realization of fully noninductive plasma discharges in the Tore Supra tokamak [J. Jacquinot, Nucl. Fusion 45, S118 (2005)], by producing large degradation of electron energy confinement in the plasma core and the bifurcation to a regime with permanent MHD activity. The nonlinear evolution of MHD modes in these hollow current density profile discharges is studied with the full-scale three-dimensional MHD code XTOR [K. Lerbinger and J.-F. Luciani, J. Comput. Phys. 97, 444 (1991)] and compared with experimental features. Large confinement degradation is predicted when q(0) is close to 2. This derives either from the full reconnection of an unstable double-tearing mode, or from the coupling between a single tearing mode and adjacent stable modes in a region with reduced magnetic shear.
Ballooning mode stability in the Hall-magnetohydrodynamics model
Torasso, R.; Hameiri, Eliezer
2005-03-01
The governing equations of the ballooning modes are derived within the Hall-magneto-hydrodynamics (HMHD) model and given a standard Hamiltonian form, which is then used to derive sufficient conditions for stability. In most cases, ideal magnetohydrodynamics (MHD) stability implies HMHD stability, as is the case for tokamak configurations if the pressure is a monotone increasing function of density and the entropy is monotone decreasing. The same result holds for general MHD plasmas with constant entropy and for incompressible plasmas. However, in the case of (compressible) closed-line systems such as the field-reversed configuration, or in a typical magnetospheric magnetic field, MHD ballooning stability does not guarantee HMHD stability. For the explicitly solvable configuration of the Z pinch it is in fact shown that the plasma can be MHD stable but HMHD unstable.
Magnetohydrodynamic Modeling of the Jovian Magnetosphere
NASA Technical Reports Server (NTRS)
Walker, Raymond
2005-01-01
Under this grant we have undertaken a series of magnetohydrodynamic (MHD) simulation and data analysis studies to help better understand the configuration and dynamics of Jupiter's magnetosphere. We approached our studies of Jupiter's magnetosphere in two ways. First we carried out a number of studies using our existing MHD code. We carried out simulation studies of Jupiter s magnetospheric boundaries and their dependence on solar wind parameters, we studied the current systems which give the Jovian magnetosphere its unique configuration and we modeled the dynamics of Jupiter s magnetosphere following a northward turning of the interplanetary magnetic field (IMF). Second we worked to develop a new simulation code for studies of outer planet magnetospheres.
Numerical Methods for Radiation Magnetohydrodynamics in Astrophysics
Klein, R I; Stone, J M
2007-11-20
We describe numerical methods for solving the equations of radiation magnetohydrodynamics (MHD) for astrophysical fluid flow. Such methods are essential for the investigation of the time-dependent and multidimensional dynamics of a variety of astrophysical systems, although our particular interest is motivated by problems in star formation. Over the past few years, the authors have been members of two parallel code development efforts, and this review reflects that organization. In particular, we discuss numerical methods for MHD as implemented in the Athena code, and numerical methods for radiation hydrodynamics as implemented in the Orion code. We discuss the challenges introduced by the use of adaptive mesh refinement in both codes, as well as the most promising directions for future developments.
Scale-locality of magnetohydrodynamic turbulence
Aluie, Hussein; Eyink, Gregory L
2009-01-01
We investigate the scale-locality of cascades of conserved invariants at high kinetic and magnetic Reynolds numbers in the 'inertial-inductive range' of magnetohydrodynamic (MHD) turbulence, where velocity and magnetic field increments exhibit suitable power-law scaling. We prove that fluxes of total energy and cross-helicity - or, equivalently, fluxes of Elsaesser energies - are dominated by the contributions of local triads. Corresponding spectral transfers are also scale-local when defined using octave wavenumber bands. Flux and transfer of magnetic helicity may be dominated by nonlocal triads. The magnetic stretching term also may be dominated by non-local triads but we prove that it can convert energy only between velocity and magnetic modes at comparable scales. We explain the disagreement with numerical studies that have claimed conversion non locally between disparate scales. We present supporting data from a 1024{sup 3} simulation of forced MHD turbulence.
Dipole Alignment in Rotating MHD Turbulence
NASA Technical Reports Server (NTRS)
Shebalin, John V.; Fu, Terry; Morin, Lee
2012-01-01
We present numerical results from long-term CPU and GPU simulations of rotating, homogeneous, magnetohydrodynamic (MHD) turbulence, and discuss their connection to the spherically bounded case. We compare our numerical results with a statistical theory of geodynamo action that has evolved from the absolute equilibrium ensemble theory of ideal MHD turbulence, which is based on the ideal MHD invariants are energy, cross helicity and magnetic helicity. However, for rotating MHD turbulence, the cross helicity is no longer an exact invariant, although rms cross helicity becomes quasistationary during an ideal MHD simulation. This and the anisotropy imposed by rotation suggests an ansatz in which an effective, nonzero value of cross helicity is assigned to axisymmetric modes and zero cross helicity to non-axisymmetric modes. This hybrid statistics predicts a large-scale quasistationary magnetic field due to broken ergodicity , as well as dipole vector alignment with the rotation axis, both of which are observed numerically. We find that only a relatively small value of effective cross helicity leads to the prediction of a dipole moment vector that is closely aligned (less than 10 degrees) with the rotation axis. We also discuss the effect of initial conditions, dissipation and grid size on the numerical simulations and statistical theory.
Corrosion and arc erosion in MHD channels
NASA Astrophysics Data System (ADS)
Rosa, Richard J.; Pollina, Richard J.
1990-04-01
The objective of this task is to study the corrosion and arc erosion of magnetohydrodynamic (MHD) materials in a cooperative effort with, and to support, the MHD topping cycle program. Materials tested in the Avco Research Laboratory/Textron facility, or materials which have significant MHD importance, will be analyzed to document their physical deterioration. Conclusions shall be drawn about their wear mechanisms and lifetime in the MHD environment with respect to the following issues: sulfur corrosion, electrochemical corrosion, and arc erosion. The impact of any materials or slag conditions on the level of power output and on the level of leakage current in the MHD channel will also be noted, where appropriate. The detailed correlation and analysis of data obtained from nearly all of the tests performed since 1986 has shown that the apparent leakage current flowing through the slag on the channel walls depends upon channel operating parameters in an unexpected way. A comprehensive report of the results obtained to date and a first attempt at their interpretation has been prepared and a copy is attached. The second activity has concerned the examination of electrodes (platinum anodes/tungsten cathodes) by scanning electron microscopy and energy dispersive x ray spectroscopy of the surface degradation. Results of these examinations are reported.
MHD Wave Modes Resolved in Fine-Scale Chromospheric Magnetic Structures
NASA Astrophysics Data System (ADS)
Verth, G.; Jess, D. B.
2016-02-01
Due to its complex and dynamic fine-scale structure, the chromosphere is a particularly challenging region of the Sun's atmosphere to understand. It is now widely accepted that to model chromospheric dynamics, even on a magnetohydrodynamic (MHD) scale, while also calculating spectral line emission, one must realistically include the effects of partial ionization and radiative transfer in a multi-fluid plasma under non-LTE conditions. Accurate quantification of MHD wave energetics must be founded on a precise identification of the actual wave mode being observed. This chapter focuses on MHD kink-mode identification, MHD sausage mode identification, and MHD torsional Alfvén wave identification. It then reviews progress in determining more accurate energy flux estimations of specific MHD wave modes observed in the chromosphere. The chapter finally examines how the discovery of these MHD wave modes has helped us advance the field of chromospheric magnetoseismology.
Lattice Boltzmann model for resistive relativistic magnetohydrodynamics.
Mohseni, F; Mendoza, M; Succi, S; Herrmann, H J
2015-08-01
In this paper, we develop a lattice Boltzmann model for relativistic magnetohydrodynamics (MHD). Even though the model is derived for resistive MHD, it is shown that it is numerically robust even in the high conductivity (ideal MHD) limit. In order to validate the numerical method, test simulations are carried out for both ideal and resistive limits, namely the propagation of Alfvén waves in the ideal MHD and the evolution of current sheets in the resistive regime, where very good agreement is observed comparing to the analytical results. Additionally, two-dimensional magnetic reconnection driven by Kelvin-Helmholtz instability is studied and the effects of different parameters on the reconnection rate are investigated. It is shown that the density ratio has a negligible effect on the magnetic reconnection rate, while an increase in shear velocity decreases the reconnection rate. Additionally, it is found that the reconnection rate is proportional to σ-1/2, σ being the conductivity, which is in agreement with the scaling law of the Sweet-Parker model. Finally, the numerical model is used to study the magnetic reconnection in a stellar flare. Three-dimensional simulation suggests that the reconnection between the background and flux rope magnetic lines in a stellar flare can take place as a result of a shear velocity in the photosphere. PMID:26382548
Lattice Boltzmann model for resistive relativistic magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Mohseni, F.; Mendoza, M.; Succi, S.; Herrmann, H. J.
2015-08-01
In this paper, we develop a lattice Boltzmann model for relativistic magnetohydrodynamics (MHD). Even though the model is derived for resistive MHD, it is shown that it is numerically robust even in the high conductivity (ideal MHD) limit. In order to validate the numerical method, test simulations are carried out for both ideal and resistive limits, namely the propagation of Alfvén waves in the ideal MHD and the evolution of current sheets in the resistive regime, where very good agreement is observed comparing to the analytical results. Additionally, two-dimensional magnetic reconnection driven by Kelvin-Helmholtz instability is studied and the effects of different parameters on the reconnection rate are investigated. It is shown that the density ratio has a negligible effect on the magnetic reconnection rate, while an increase in shear velocity decreases the reconnection rate. Additionally, it is found that the reconnection rate is proportional to σ-1 / 2, σ being the conductivity, which is in agreement with the scaling law of the Sweet-Parker model. Finally, the numerical model is used to study the magnetic reconnection in a stellar flare. Three-dimensional simulation suggests that the reconnection between the background and flux rope magnetic lines in a stellar flare can take place as a result of a shear velocity in the photosphere.
Preliminary Analysis of Liquid Metal MHD Pressure Drop in the Blanket for the FDS
NASA Astrophysics Data System (ADS)
Wang, Hong-yan; Wu, Yi-can; He, Xiao-xong
2002-10-01
Preliminary analysis and calculation of liquid metal Li17Pb83 magnetohydrodynamic (MHD) pressure drop in the blanket for the FDS have been presented to evaluate the significance of MHD effects on the thermal-hydraulic design of the blanket. To decrease the liquid metal MHD pressure drop, Al2O3 is applied as an electronically insulated coating onto the inner surface of the ducts. The requirement for the insulated coating to reduce the additional leakage pressure drop caused by coating imperfections has been analyzed. Finally, the total liquid metal MHD pressure drop and magnetic pump power in the FDS blanket have been given.
Development and Application of a Parallel MHD code
NASA Astrophysics Data System (ADS)
Peterkin, , Jr.
1997-08-01
Over the past few years, we (In collaboration with S. Colella, M. H. Frese, D. E. Lileikis and U. Shumlak.) have built a general purpose, portable, scalable three-dimensional finite volume magnetohydrodynamic code, called uc(mach3,) based on an arbitrary Lagrangian-Eulerian fluid algorithm to simulate time-dependent MHD phenomena for real materials. The physical domain of integration on which uc(mach3) works is decomposed into a patchwork of rectangular logical blocks that represent hexadedral physical subdomains. This block domain decomposition technique gives us a natural framework in which to implement coarse parallelization via message passing with the single program, multiple data (SPMD) model. Portability is achieved by using a parallel library that is separate from the physics code. At present, we are using the Message Passing Interface (MPI) because it is one of the industry standards, and because its Derived Data Type supports the sending and receiving of data with an arbitrary stride in memory. This feature is consistent with the manner in which boundary data is exchanged between connected block domains via ghost cells in the serial version of uc(mach3.) In this talk, we discuss the details of the uc(mach3) algorithm. In addition, we present results from some simple test problems as well as from complex 3-D time-dependent simulations including magnetoplasmadynamic thrusters, fast z-pinches, and magnetic flux compression generators.
Cooling of Moving Wavy Surface through MHD Nanofluid
NASA Astrophysics Data System (ADS)
Mehmood, Ahmer; Iqbal, Muhammad Saleem; Mustafa, Irfan
2016-07-01
Heat transfer analysis has been carried out in the Magnetohydrodynamic (MHD) boundary layer formed near the wavy rough plate moving in x-direction. Due to the presence of metallic nanoparticle in the fluid and enhanced surface area of the plate as a consequence of surface texture, an increase in heat transfer rates is expected. However, the calculation of these enhanced rates of heat transfer is not straightforward because the convection phenomena become more complicated due to the motion of nanoparticle in the base fluid and also the waviness of the plate surface. The contribution of nanoparticle toward convective heat transfer is manifold which requires a suitable model in order to capture the correct physics. Famous Tiwari and Das model has been utilised in the current study. Percent increase in the rate of heat transfer is calculated for the nanoparticle of different metals, such as MWCNT, SWCNT, Al2O3, TiO2 and Ag. Appreciable increase in the rate of heat transfer is observed, which is 24% at the most for Al2O3 nanoparticle. The effect of applied magnetic field on the velocity profile, skin friction coefficient, and Nusselt number has also been presented through graphs. The concentration of the nanoparticle has been limited up to 10%.
Nuclear-electric magnetohydrodynamic propulsion for submarine. Master's thesis
Bednarczyk, A.A.
1989-05-01
The thesis analyzes the superconducting technology for a shipboard magnetohydrodynamic propulsion system. Based on the the principles of magnetohydrodynamics (MHD), the concept of open-water efficiency was used to optimize the preliminary design of the MHD thruster. After the baseline submarine hull modeled after the Los Angeles class submarine was selected, propulsive efficiency and the top speed for four variant MHD submarines were evaluated. The design criteria were set at a 100-MWt nuclear reactor power upper limit and a requirement of 30 knots for the top speed. This required advanced reactor plants and advanced energy conversion systems. The selection of High Temperature Gas Reactor (HTGR) and Liquid-Metal Fast Breeder Reactor (LMFBR) was based on the combined merits of safety, environmental impact, high source temperature and maximum-volume power density (KW/L). With the reactor outlet temperatures of 2000 K, direct-cycle energy conversion-systems gave the best results in terms of thermal efficiency and propulsion plant power density. Two energy conversion systems selected were closed-cycle gas turbine geared to a superconducting generator, and closed-cycle liquid-metal MHD generator. Based on submarine reliability and safety, the option of using an intermediate heat exchanger was also considered. Finally, non-nuclear support systems affected by the advanced power plant and MHD propulsion, stressing submarine safety, are proposed.
Filamentary magnetohydrodynamic plasmas
Kinney, R.; Tajima, T. ); McWilliams, J.C. ); Petviashvili, N. )
1994-02-01
A filamentary construct of magnetohydrodynamical plasma dynamics based on the Elsaesser variables is developed. This approach is modeled after discrete vortex models of hydrodynamical turbulence, which cannot be expected in general to produce results identical to those based on a Fourier decomposition of the fields. In a highly intermittent plasma, the induction force is small compared to the convective motion, and when this force is neglected, the plasma vortex system is described by a Hamiltonian. A statistical treatment of a collection of discrete current-vorticity concentrations is given. Canonical and microcanonical statistical calculations show that both the vorticity and the current spectra are peaked at long wavelengths, and the expected states revert to known hydrodynamical states as the magnetic field vanishes. These results differ from previous Fourier-based statistical theories, but it is found that when the filament calculation is expanded to include the inductive force, the results approach the Fourier equilibria in the low-temperature limit, and the previous Hamiltonian plasma vortex results in the high-temperature limit. Numerical simulations of a large number of filaments are carried out and support the theory. A three-dimensional vortex model is presented as well, which is also Hamiltonian when the inductive force is neglected. A statistical calculation in the canonical ensemble and numerical simulations show that a nonzero large-scale magnetic field is statistically favored, and that the preferred shape of this field is a long, thin tube of flux. Possible applications to a variety of physical phenomena are suggested.
Magnetohydrodynamic waves and coronal seismology: an overview of recent results.
De Moortel, Ineke; Nakariakov, Valery M
2012-07-13
Recent observations have revealed that magnetohydrodynamic (MHD) waves and oscillations are ubiquitous in the solar atmosphere, with a wide range of periods. We give a brief review of some aspects of MHD waves and coronal seismology that have recently been the focus of intense debate or are newly emerging. In particular, we focus on four topics: (i) the current controversy surrounding propagating intensity perturbations along coronal loops, (ii) the interpretation of propagating transverse loop oscillations, (iii) the ongoing search for coronal (torsional) Alfvén waves, and (iv) the rapidly developing topic of quasi-periodic pulsations in solar flares. PMID:22665899
Time-resolved observation of discrete and continuous MHD dynamo in the reversed-field pinch edge
Ji, H.; Almagri, A.F.; Prager, S.C.; Sarff, J.S.
1994-01-06
We report the first experimental verification of the MHD dynamo in the RFP. A burst of magnetohydrodynamic (MHD) dynamo electric field is observed during the sawtooth crash, followed by an increase in the local parallel current in the MST RFP edge. By measuring each term, the parallel MHD mean-field Ohm`s law is observed to hold within experimental error bars both between and during sawtooth crashes.
MHD Turbulence and Magnetic Dynamos
NASA Technical Reports Server (NTRS)
Shebalin, John V
2014-01-01
Incompressible magnetohydrodynamic (MHD) turbulence and magnetic dynamos, which occur in magnetofluids with large fluid and magnetic Reynolds numbers, will be discussed. When Reynolds numbers are large and energy decays slowly, the distribution of energy with respect to length scale becomes quasi-stationary and MHD turbulence can be described statistically. In the limit of infinite Reynolds numbers, viscosity and resistivity become zero and if these values are used in the MHD equations ab initio, a model system called ideal MHD turbulence results. This model system is typically confined in simple geometries with some form of homogeneous boundary conditions, allowing for velocity and magnetic field to be represented by orthogonal function expansions. One advantage to this is that the coefficients of the expansions form a set of nonlinearly interacting variables whose behavior can be described by equilibrium statistical mechanics, i.e., by a canonical ensemble theory based on the global invariants (energy, cross helicity and magnetic helicity) of ideal MHD turbulence. Another advantage is that truncated expansions provide a finite dynamical system whose time evolution can be numerically simulated to test the predictions of the associated statistical mechanics. If ensemble predictions are the same as time averages, then the system is said to be ergodic; if not, the system is nonergodic. Although it had been implicitly assumed in the early days of ideal MHD statistical theory development that these finite dynamical systems were ergodic, numerical simulations provided sufficient evidence that they were, in fact, nonergodic. Specifically, while canonical ensemble theory predicted that expansion coefficients would be (i) zero-mean random variables with (ii) energy that decreased with length scale, it was found that although (ii) was correct, (i) was not and the expected ergodicity was broken. The exact cause of this broken ergodicity was explained, after much
Phenomenology treatment of magnetohydrodynamic turbulence with nonequipartition and anisotropya)
NASA Astrophysics Data System (ADS)
Zhou, Ye; Matthaeus, W. H.
2005-05-01
Magnetohydrodynamics (MHD) turbulence theory, often employed satisfactorily in astrophysical applications, has often focused on parameter ranges that imply nearly equal values of kinetic and magnetic energies and length scales. However, MHD flow may have disparity magnetic Prandtl number, dissimilar kinetic and magnetic Reynolds number, different kinetic and magnetic outer length scales, and strong anisotropy. Here a phenomenology for such "nonequipartitioned" MHD flow is discussed. Two conditions are proposed for a MHD flow to transition to strong turbulent flow, which are extensions of (i) Taylor's constant flux in an inertial range and (ii) Kolmogorov's scale separation between the large and small scale boundaries of an inertial range. For this analysis, the detailed information on turbulence structure is not needed. These two conditions for MHD transition are expected to provide consistent predictions and should be applicable to anisotropic MHD flows, after the length scales are replaced by their corresponding perpendicular components. Second, it is stressed that the dynamics and anisotropy of MHD fluctuations are controlled by the relative strength between the straining effects between eddies of similar size and the sweeping action by the large eddies, or propagation effect of the large-scale magnetic fields, on the small scales, and analysis of this balance, in principle, also requires consideration of nonequipartition effects.
Thermodynamic Cycle Analysis of Magnetohydrodynamic-Bypass Hypersonic Airbreathing Engines
NASA Technical Reports Server (NTRS)
Litchford, R. J.; Cole, J. W.; Bityurin, V. A.; Lineberry, J. T.
2000-01-01
The prospects for realizing a magnetohydrodynamic (MHD) bypass hypersonic airbreathing engine are examined from the standpoint of fundamental thermodynamic feasibility. The MHD-bypass engine, first proposed as part of the Russian AJAX vehicle concept, is based on the idea of redistributing energy between various stages of the propulsion system flow train. The system uses an MHD generator to extract a portion of the aerodynamic heating energy from the inlet and an MHD accelerator to reintroduce this power as kinetic energy in the exhaust stream. In this way, the combustor entrance Mach number can be limited to a specified value even as the flight Mach number increases. Thus, the fuel and air can be efficiently mixed and burned within a practical combustor length, and the flight Mach number operating envelope can be extended. In this paper, we quantitatively assess the performance potential and scientific feasibility of MHD-bypass engines using a simplified thermodynamic analysis. This cycle analysis, based on a thermally and calorically perfect gas, incorporates a coupled MHD generator-accelerator system and accounts for aerodynamic losses and thermodynamic process efficiencies in the various engin components. It is found that the flight Mach number range can be significantly extended; however, overall performance is hampered by non-isentropic losses in the MHD devices.
MHD SIMULATIONS OF ACCRETION ONTO Sgr A*: QUIESCENT FLUCTUATIONS, OUTBURSTS, AND QUASIPERIODICITY
Chan Chikwan; Liu Siming; Fryer, Christopher L.; Psaltis, Dimitrios; Oezel, Feryal; Melia, Fulvio; Rockefeller, Gabriel
2009-08-10
High-resolution observations of Sgr A* have revealed a wide variety of phenomena, ranging from intense rapid flares to quasi-periodic oscillations (QPOs), making this object an ideal system to study the properties of low luminosity accreting black holes. In this paper, we use a pseudospectral algorithm to construct and evolve a three-dimensional magnetohydrodynamic (MHD) model of the accretion disk in Sgr A*. Assuming a hybrid thermal-nonthermal emission scheme and calibrating the parameters by observations, we show that the MHD turbulence in the environment of Sgr A* can by itself only produce factor two fluctuations in luminosity. These fluctuations cannot explain the magnitude of flares observed in this system. However, we also demonstrate that external forcing of the accretion disk, which may be generated by the 'clumpy material' raining down onto the disk from the large-scale flow, do produce outbursts qualitatively similar to those observed by XMM-Newton in X-rays and by ground-based facilities in the near infrared. Strong, but short-term QPOs emerge naturally in the simulated light curves. We attribute these to nonaxisymmetric density perturbations that emerge as the disk evolves back toward its quiescent state.
Consequences of magnetohydrodynamic processes for large scale flow in the magnetosheath
NASA Technical Reports Server (NTRS)
Kivelson, M. G.; Chen, S.-H.; Southwood, D. J.
1994-01-01
The remarkable success with which gas dynamic models characterize the plasma properties in the magnetosheath has to some degree diverted attention from certain inherently magnetohydrodynamic effects that are expected to introduce important modifications. Three recent aspects of magnetosheath observations: a slow mode structure near the subsolar point, flows at speeds in excess of the solar wind speed, and the shape of the internal boundary, i.e., the magnetopause, provide examples of inherently magnetohydrodynamic (MHD) effects.
Corrosion and arc erosion in MHD channels
NASA Astrophysics Data System (ADS)
Rosa, R. J.; Pollina, R. J.
1991-04-01
The objective of this task is to study the corrosion and arc erosion of MHD materials in a cooperative effort with, and to support, the MHD topping cycle program. Materials tested in the Avco Research Laboratory/Textron facility, or materials which have significant MHD importance, will be analyzed to document their physical deterioration. Conclusions shall be drawn about their wear mechanisms and lifetime in the MHD environment with respect to the following issues; sulfur corrosion, electrochemical corrosion, and arc erosion. The impact of any materials or slag conditions on the level of power output and on the level of leakage current in the MHD channel will also be noted, where appropriate. Two phenomena that can effect the analysis of slag leakage current have been investigated and found significant. These are: (1) transverse current along the slag layer in the insulator walls of an MHD duct, and (2) electrode surface voltage drops. Both tend to reduce the value inferred for average plasma conductivity and increase the value inferred for axial leakage current. These two effects in combination are potentially capable of explaining the high leakage inferred. Corrosion on the water side of metal MHD duct wall elements has been examined in CDIF and Mark 7 generators. It appears to be controllable by adjusting the pH of the water and/or by controlling the dissolved oxygen content.
Heeter, R F; Fasoli, A; Testa, D; Sharapov, S; Berk, H L; Breizman, B; Gondhalekar, A; Mantsinen, M
2004-03-23
Experiments are conducted on the JET tokamak to assess the diagnostic potential of MHD active and passive spectroscopy, for the plasma bulk and its suprathermal components, using Alfv{acute e}n Eigenmodes (AEs) excited by external antennas and by energetic particles. The measurements of AE frequencies and mode numbers give information on the bulk plasma. Improved equilibrium reconstruction, in particular in terms of radial profiles of density and safety factor, is possible from the comparison between the antenna driven spectrum and that calculated theoretically. Details of the time evolution of the non-monotonic safety factor profile in advanced scenarios can be reconstructed from the frequency of ICRH-driven energetic particle modes. The plasma effective mass can be inferred from the resonant frequency of externally driven AEs in discharges with similar equilibrium profiles. The stability thresholds and the nonlinear development of the instabilities can give clues on energy and spatial distribution of the fast particle population. The presence of unstable AEs provides lower limits in the energy of ICRH generated fast ion tails. Fast ion pressure gradients and their evolution can be inferred from the stability of AEs at different plasma radial positions. Finally, the details of the AE spectrum in the nonlinear stage can be used to obtain information about the fast particle velocity space diffusion.
Development and validation of a magneto-hydrodynamic solver for blood flow analysis
NASA Astrophysics Data System (ADS)
Kainz, W.; Guag, J.; Benkler, S.; Szczerba, D.; Neufeld, E.; Krauthamer, V.; Myklebust, J.; Bassen, H.; Chang, I.; Chavannes, N.; Kim, J. H.; Sarntinoranont, M.; Kuster, N.
2010-12-01
The objective of this study was to develop a numerical solver to calculate the magneto-hydrodynamic (MHD) signal produced by a moving conductive liquid, i.e. blood flow in the great vessels of the heart, in a static magnetic field. We believe that this MHD signal is able to non-invasively characterize cardiac blood flow in order to supplement the present non-invasive techniques for the assessment of heart failure conditions. The MHD signal can be recorded on the electrocardiogram (ECG) while the subject is exposed to a strong static magnetic field. The MHD signal can only be measured indirectly as a combination of the heart's electrical signal and the MHD signal. The MHD signal itself is caused by induced electrical currents in the blood due to the moving of the blood in the magnetic field. To characterize and eventually optimize MHD measurements, we developed a MHD solver based on a finite element code. This code was validated against literature, experimental and analytical data. The validation of the MHD solver shows good agreement with all three reference values. Future studies will include the calculation of the MHD signals for anatomical models. We will vary the orientation of the static magnetic field to determine an optimized location for the measurement of the MHD blood flow signal.
A study of a commercial MHD power plant scheme
NASA Astrophysics Data System (ADS)
Pashkov, S. A.; Shishkov, E. V.
1980-07-01
Power engineering specialists are currently interested in electrical power stations with magnetohydrodynamic generators. This paper is devoted to an investigation of one of the possible process flow diagrams of MHD electrical power plants. The structure of MHD electrical power plants, the interrelation between the aggregates, issues concerning the starting of the plant and the working of the power unit under various partial load conditions are discussed. With the availability of new theoretical and experimental data, the process flow diagrams of industrial MHD electrical power plants will naturally undergo changes. However, the methodical approach and the investigation described in this paper should retain their validity for all process flow diagrams of electrical power plants with MHD generators.
Three Dimensional Simulations of Compressible Hall MHD Plasmas
Shaikh, Dastgeer; Shukla, P. K.
2008-10-15
We have developed three dimensional, time dependent, compressible, non-adiabatic, driven and massively parallelized Hall magnetohydrodynamic (MHD) simulations to investigate turbulent spectral cascades in a regime where characteristic lengthscales associated with plasma fluctuations are smaller than ion gyro radii. Such regime is ubiquitously present in solar wind and many other collisionless space plasmas. Particularly in the solar wind, the high time resolution databases identify a spectral break at the end of MHD inertial range spectrum that corresponds to a high frequency regime. In the regime, turbulent cascades cannot be explained by the usual MHD models. With the help of our 3D Hall MHD code, we find that characteristic turbulent interactions in the high frequency regime evolve typically on kinetic Alfven time scales. The turbulent fluctuation associated with kinetic Alfven interactions are compressive and anisotropic and possess equipartition of kinetic and magnetic energies.
Laser-powered MHD generators for space application
NASA Technical Reports Server (NTRS)
Jalufka, N. W.
1986-01-01
Magnetohydrodynamic (MHD) energy conversion systems of the pulsed laser-supported detonation (LSD) wave, plasma MHD, and liquid-metal MHD (LMMHD) types are assessed for their potential as space-based laser-to-electrical power converters. These systems offer several advantages as energy converters relative to the present chemical, nuclear, and solar devices, including high conversion efficiency, simple design, high-temperature operation, high power density, and high reliability. Of these systems, the Brayton cycle liquid-metal MHD system appears to be the most attractive. The LMMHD technology base is well established for terrestrial applications, particularly with regard to the generator, mixer, and other system components. However, further research is required to extend this technology base to space applications and to establish the technology required to couple the laser energy into the system most efficiently. Continued research on each of the three system types is recommended.
Investigation on Plasma Jet Flow Phenomena During DC Air Arc Motion in Bridge-Type Contacts
NASA Astrophysics Data System (ADS)
Zhai, Guofu; Bo, Kai; Chen, Mo; Zhou, Xue; Qiao, Xinlei
2016-05-01
Arc plasma jet flow in the air was investigated under a bridge-type contacts in a DC 270 V resistive circuit. We characterized the arc plasma jet flow appearance at different currents by using high-speed photography, and two polished contacts were used to search for the relationship between roughness and plasma jet flow. Then, to make the nature of arc plasma jet flow phenomena clear, a simplified model based on magnetohydrodynamic (MHD) theory was established and calculated. The simulated DC arc plasma was presented with the temperature distribution and the current density distribution. Furthermore, the calculated arc flow velocity field showed that the circular vortex was an embodiment of the arc plasma jet flow progress. The combined action of volume force and contact surface was the main reason of the arc jet flow. supported by National Natural Science Foundation of China (Nos. 51307030, 51277038)
Multimegawatt NEP with vapor core reactor MHD
NASA Astrophysics Data System (ADS)
Smith, Blair; Knight, Travis; Anghaie, Samim
2002-01-01
Efforts at the Innovative Nuclear Space Power and Propulsion Institute have assessed the feasibility of combining gaseous or vapor core reactors with magnetohydrodynamic power generators to provide extremely high quality, high density, and low specific mass electrical power for space applications. Innovative shielding strategies are employed to maintain an effective but relatively low mass shield, which is the most dominating part of multi-megawatt space power systems. The fission driven magnetohydrodynamic generator produces tens of kilowatt DC power at specific mass of less than 0.5 kg/kW for the total power system. The MHD output with minor conditioning is coupled to magnetoplasmadynamic thruster to achieve an overall NEP system specific mass of less than 1.0 kg/kW for power levels above 20 MWe. Few other concepts would allow comparable ensuing payload savings and flexible mission abort options for manned flights to Mars for example. .
Experimental investigation of the magnetohydrodynamic parachute effect in a hypersonic air flow
NASA Astrophysics Data System (ADS)
Fomichev, V. P.; Yadrenkin, M. A.
2013-01-01
New data on experimental implementation of the magnetohydrodynamic (MHD) parachute configuration in an air flow with Mach number M = 6 about a flat plate are considered. It is shown that MHD interaction near a flat plate may transform an attached oblique shock wave into a normal detached one, which considerably extends the area of body-incoming flow interaction. This effect can be employed in optimizing return space vehicle deceleration conditions in the upper atmosphere.
Efficient acceleration of relativistic magnetohydrodynamic jets
NASA Astrophysics Data System (ADS)
Toma, Kenji; Takahara, Fumio
2013-08-01
Relativistic jets in active galactic nuclei, galactic microquasars, and gamma-ray bursts are widely considered to be magnetohydrodynamically driven by black hole accretion systems, although the conversion mechanism from the Poynting into the particle kinetic energy flux is still open. Recent detailed numerical and analytical studies of global structures of steady, axisymmetric magnetohydrodynamic (MHD) flows with specific boundary conditions have not reproduced as rapid an energy conversion as required by observations. In order to find more suitable boundary conditions, we focus on the flow along a poloidal magnetic field line just inside the external boundary, without treating the transfield force balance in detail. We find some examples of the poloidal field structure and corresponding external pressure profile for an efficient and rapid energy conversion as required by observations, and that the rapid acceleration requires a rapid decrease of the external pressure above the accretion disk. We also clarify the differences between the fast magnetosonic point of the MHD flow and the sonic point of the de Laval nozzle.
Pankratov, I. M. E-mail: rjzhou@ipp.ac.cn; Zhou, R. J. E-mail: rjzhou@ipp.ac.cn; Hu, L. Q.
2015-07-15
Peculiar phenomena were observed during experiments with runaway electrons: rapid changes in the synchrotron spot and its intensity that coincided with stepwise increases in the electron cyclotron emission (ECE) signal (cyclotron radiation of suprathermal electrons). These phenomena were initially observed in TEXTOR (Tokamak Experiment for Technology Oriented Research), where these events only occurred in the current decay phase or in discharges with thin stable runaway beams at a q = 1 drift surface. These rapid changes in the synchrotron spot were interpreted by the TEXTOR team as a fast pitch angle scattering event. Recently, similar rapid changes in the synchrotron spot and its intensity that coincided with stepwise increases in the non-thermal ECE signal were observed in the EAST (Experimental Advanced Superconducting Tokamak) runaway discharge. Runaway electrons were located around the q = 2 rational magnetic surface (ring-like runaway electron beam). During the EAST runaway discharge, stepwise ECE signal increases coincided with enhanced magnetohydrodynamic (MHD) activity. This behavior was peculiar to this shot. In this paper, we show that these non-thermal ECE step-like jumps were related to the abrupt growth of suprathermal electrons induced by bursting electric fields at reconnection events during this MHD plasma activity. Enhancement of the secondary runaway electron generation also occurred simultaneously. Local changes in the current-density gradient appeared because of local enhancement of the runaway electron generation process. These current-density gradient changes are considered to be a possible trigger for enhancement of the MHD plasma activity and the rapid changes in runaway beam behavior.
NASA Astrophysics Data System (ADS)
Wu, S. T.; Zhou, Yufen; Jiang, Chaowei; Feng, Xueshang; Wu, Chin-Chun; Hu, Qiang
2016-02-01
In this study, we present a three-dimensional magnetohydrodynamic model based on an observed eruptive twisted flux rope (sigmoid) deduced from solar vector magnetograms. This model is a combination of our two very well tested MHD models: (i) data-driven 3-D magnetohydrodynamic (MHD) active region evolution (MHD-DARE) model for the reconstruction of the observed flux rope and (ii) 3-D MHD global coronal-heliosphere evolution (MHD-GCHE) model to track the propagation of the observed flux rope. The 6 September 2011, AR11283, event is used to test this model. First, the formation of the flux rope (sigmoid) from AR11283 is reproduced by the MHD-DARE model with input from the measured vector magnetograms given by Solar Dynamics Observatory/Helioseismic and Magnetic Imager. Second, these results are used as the initial boundary condition for our MHD-GCHE model for the initiation of a coronal mass ejection (CME) as observed. The model output indicates that the flux rope resulting from MHD-DARE produces the physical properties of a CME, and the morphology resembles the observations made by STEREO/COR-1.
Hyperbolic Divergence Cleaning Method for Godunov Smoothed Particle Magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Iwasaki, K.; Inutsuka, S.-I.
2013-04-01
In this paper, we implement a divergence cleaning method into Godunov smoothed particle magnetohydrodynamics (GSPM). In the GSPM, to describe MHD shocks accurately, a Riemann solver is applied to the SPH method instead of artificial viscosity and resistivity that have been used in previous works. We confirmed that the divergence cleaning method reduces divergence errors significantly. The performance of the method is demonstrated in the numerical simulations of a strongly magnetized gas and bipolar outflow from the first core.
Computational Methods for Ideal Magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Kercher, Andrew D.
Numerical schemes for the ideal magnetohydrodynamics (MHD) are widely used for modeling space weather and astrophysical flows. They are designed to resolve the different waves that propagate through a magnetohydro fluid, namely, the fast, Alfven, slow, and entropy waves. Numerical schemes for ideal magnetohydrodynamics that are based on the standard finite volume (FV) discretization exhibit pseudo-convergence in which non-regular waves no longer exist only after heavy grid refinement. A method is described for obtaining solutions for coplanar and near coplanar cases that consist of only regular waves, independent of grid refinement. The method, referred to as Compound Wave Modification (CWM), involves removing the flux associated with non-regular structures and can be used for simulations in two- and three-dimensions because it does not require explicitly tracking an Alfven wave. For a near coplanar case, and for grids with 213 points or less, we find root-mean-square-errors (RMSEs) that are as much as 6 times smaller. For the coplanar case, in which non-regular structures will exist at all levels of grid refinement for standard FV schemes, the RMSE is as much as 25 times smaller. A multidimensional ideal MHD code has been implemented for simulations on graphics processing units (GPUs). Performance measurements were conducted for both the NVIDIA GeForce GTX Titan and Intel Xeon E5645 processor. The GPU is shown to perform one to two orders of magnitude greater than the CPU when using a single core, and two to three times greater than when run in parallel with OpenMP. Performance comparisons are made for two methods of storing data on the GPU. The first approach stores data as an Array of Structures (AoS), e.g., a point coordinate array of size 3 x n is iterated over. The second approach stores data as a Structure of Arrays (SoA), e.g. three separate arrays of size n are iterated over simultaneously. For an AoS, coalescing does not occur, reducing memory efficiency
Hyperbolic Divergence Cleaning for the MHD Equations
NASA Astrophysics Data System (ADS)
Dedner, A.; Kemm, F.; Kröner, D.; Munz, C.-D.; Schnitzer, T.; Wesenberg, M.
2002-01-01
In simulations of magnetohydrodynamic (MHD) processes the violation of the divergence constraint causes severe stability problems. In this paper we develop and test a new approach to the stabilization of numerical schemes. Our technique can be easily implemented in any existing code since there is no need to modify the solver for the MHD equations. It is based on a modified system in which the divergence constraint is coupled with the conservation laws by introducing a generalized Lagrange multiplier. We suggest a formulation in which the divergence errors are transported to the domain boundaries with the maximal admissible speed and are damped at the same time. This corrected system is hyperbolic and the density, momentum, magnetic induction, and total energy density are still conserved. In comparison to results obtained without correction or with the standard “divergence source terms,” our approach seems to yield more robust schemes with significantly smaller divergence errors.
MHD shocks in coronal mass ejections
NASA Technical Reports Server (NTRS)
Steinolfson, R. S.
1991-01-01
The primary objective of this research program is the study of the magnetohydrodynamic (MHD) shocks and nonlinear simple waves produced as a result of the interaction of ejected lower coronal plasma with the ambient corona. The types of shocks and nonlinear simple waves produced for representative coronal conditions and disturbance velocities were determined. The wave system and the interactions between the ejecta and ambient corona were studied using both analytic theory and numerical solutions of the time-dependent, nonlinear MHD equations. Observations from the SMM coronagraph/polarimeter provided both guidance and motivation and are used extensively in evaluating the results. As a natural consequence of the comparisons with the data, the simulations assisted in better understanding the physical interactions in coronal mass ejections (CME's).
Numerical MHD codes for modeling astrophysical flows
NASA Astrophysics Data System (ADS)
Koldoba, A. V.; Ustyugova, G. V.; Lii, P. S.; Comins, M. L.; Dyda, S.; Romanova, M. M.; Lovelace, R. V. E.
2016-05-01
We describe a Godunov-type magnetohydrodynamic (MHD) code based on the Miyoshi and Kusano (2005) solver which can be used to solve various astrophysical hydrodynamic and MHD problems. The energy equation is in the form of entropy conservation. The code has been implemented on several different coordinate systems: 2.5D axisymmetric cylindrical coordinates, 2D Cartesian coordinates, 2D plane polar coordinates, and fully 3D cylindrical coordinates. Viscosity and diffusivity are implemented in the code to control the accretion rate in the disk and the rate of penetration of the disk matter through the magnetic field lines. The code has been utilized for the numerical investigations of a number of different astrophysical problems, several examples of which are shown.
NASA Astrophysics Data System (ADS)
Ofman, L.
2016-02-01
This chapter focuses on reviewing several observational aspects of magnetohydrodynamic (MHD) waves in the solar wind, in particular on Alfvén waves, Alfvénic turbulent spectrum, and their role in heating and accelerating the solar wind. It also reviews computational models that incorporate Alfvén waves as the driving source of the wind in the lower corona (coronal holes) and in the inner heliosphere, with emphasis on multi-dimensional models. Evidence for MHD waves in the solar wind is obtained from interplanetary scintillation (IPS) observations using Earth-based radio telescope observations of distant (galactic) radio sources. The solar wind electron density variability in the line of sight affects the received radio signal. The propagating fluctuations and their correlations are used to estimate the solar wind velocity and the wave amplitude in the parallel and the perpendicular directions in line of sight.
H2OTSTUF: Appropriate Operating Regimes for Magnetohydrodynamic Augmentation
NASA Technical Reports Server (NTRS)
Jones, Jonathan E.; Hawk, Clark W.
1998-01-01
A trade study of magnetohydrodynamic (MHD) augmented propulsion reveals a unique operating regime at lower thrust levels. Substantial mass savings are realized over conventional chemical, solar, and electrical propulsion concepts when MHD augmentation is used to obtain optimal I(sub sp). However, trip times for the most conservative estimates of power plant specific impulse and accelerator efficiency may be prohibitively long. Quasi-one-dimensional calculations show that a solar or nuclear thermal system augmented by MHD can provide competitive performance while utilizing a diverse range of propellants including water, which is available from the Space Shuttle, the Moon, asteroids, and various moons and planets within our solar system. The use of in-situ propellants will reduce costs of space operations as well as enable human exploration of our Solar System. The following conclusions can be drawn from the results of the mission trade study: (1) There exists a maximum thrust or mass flow rate above which MHD augmentation increases the initial mass in low earth orbit (LEO); (2) Mass saving of over 50% can be realized for unique combination of solar/MHD systems; (3) Trip times for systems utilizing current power supply technology may be prohibitively long. Theoretical predictions of MHD performance for in space propulsion systems show that improved efficiencies can reduce trip times to acceptable levels; (4) Long trip times indicative of low thrust systems can be shortened by an increase in the MHD accelerator efficiency or a decrease in the specific mass of the power supply and power processing unit; and (5) As for all propulsion concepts, missions with larger (Delta)v's benefit more from the increased specific impulse resulting from MHD augmentation. Using a quasi-one-dimensional analysis, the required operating conditions for a MHD accelerator to reach acceptable efficiencies are outlined. This analysis shows that substantial non-equilibrium ionization is