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.
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
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.
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.
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.
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)
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.
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.
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 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.
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.
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.
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.
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.
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.
Magnetohydrodynamic (MHD) stretched flow of nanofluid with power-law velocity and chemical reaction
NASA Astrophysics Data System (ADS)
Hayat, Tasawar; Rashid, Madiha; Imtiaz, Maria; Alsaedi, Ahmed
2015-11-01
This paper deals with the boundary layer flow of nanofluid over power-law stretched surface. Analysis has been carried out in the presence of applied magnetic field and chemical reaction. Heat and mass transfer characteristics are studied using heat and mass convective conditions. The governing partial differential equations are transferred to the nonlinear ordinary differential equations. Convergent series solutions are obtained for fluid velocity, temperature and concentrations fields. Influences of pertinent parameters including Hartman number, thermal and concentration Biot numbers and chemical reaction parameters are discussed on the velocity, temperature and concentration profiles. Graphical result are presented and discussed. Computations for local Nusselt and Sherwood numbers are carried out. It is observed that the heat transfer rate is enhanced by increasing power-law index, thermal Biot number and chemical reaction parameter while mass transfer rate increases for power-law index and chemical reaction parameter.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
NASA Technical Reports Server (NTRS)
1981-01-01
The results of magnet system special investigations listed below are summarized: 4 Tesla Magnet Alternate Design Study; 6 Tesla Magnet Manufacturability Study. The conceptual design for a 4 Tesla superconducting magnet system for use with an alternate (supersonic) ETF power train is described, and estimated schedule and cost are identified. The magnet design is scaled from the ETF 6 T Tesla design. Results of a manufacturability study and a revised schedule and cost estimate for the ETF 6 T magnet are reported. Both investigations are extensions of the conceptual design of a 6 T magnet system performed earlier as a part of the overall MED-ETF conceptual design described in Conceptual Design Engineering Report (CDER) Vol. V, System Design Description (SDD) 503 dated September, 1981, DOE/NASA/0224-1; NASA CR-165/52.
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.
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 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.
Pulse Detonation Rocket Magnetohydrodynamic Power Experiment
NASA Technical Reports Server (NTRS)
Litchford, R. J.; Jones, J. E.; Dobson, C. C.; Cole, J. W.; Thompson, B. R.; Plemmons, D. H.; Turner, M. W.
2003-01-01
The production of onboard electrical power by pulse detonation engines is problematic in that they generate no shaft power; however, pulse detonation driven magnetohydrodynamic (MHD) power generation represents one intriguing possibility for attaining self-sustained engine operation and generating large quantities of burst power for onboard electrical systems. To examine this possibility further, a simple heat-sink apparatus was developed for experimentally investigating pulse detonation driven MHD generator concepts. The hydrogen oxygen fired driver was a 90 cm long stainless steel tube having a 4.5 cm square internal cross section and a short Schelkin spiral near the head end to promote rapid formation of a detonation wave. The tube was intermittently filled to atmospheric pressure and seeded with a CsOH/methanol prior to ignition by electrical spark. The driver exhausted through an aluminum nozzle having an area contraction ratio of A*/A(sub zeta) = 1/10 and an area expansion ratio of A(sub zeta)/A* = 3.2 (as limited by available magnet bore size). The nozzle exhausted through a 24-electrode segmented Faraday channel (30.5 cm active length), which was inserted into a 0.6 T permanent magnet assembly. Initial experiments verified proper drive operation with and without the nozzle attachment, and head end pressure and time resolved thrust measurements were acquired. The exhaust jet from the nozzle was interrogated using a polychromatic microwave interferometer yielding an electron number density on the order of 10(exp 12)/cm at the generator entrance. In this case, MHD power generation experiments suffered from severe near-electrode voltage drops and low MHD interaction; i.e., low flow velocity, due to an inherent physical constraint on expansion with the available magnet. Increased scaling, improved seeding techniques, higher magnetic fields, and higher expansion ratios are expected to greatly improve performance.
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.
Litchford, R.J.; Thompson, B.R.; Lineberry, J.T.
1998-07-01
A series of laboratory scale experiments were conducted to investigate the basic engineering performance characteristics of a pulse detonation driven magnetohydrodynamic electric power generator. In these experiments, stoichiometric oxy-acetylene mixtures seeded with a cesium-hydroxide/ methanol spray were detonated at atmospheric pressure in a 1 m long tube having an inside diameter of 2.54 cm. Experiments with a plasma diagnostic channel attached to the end of the tube confirmed the attainment of detonation conditions (p{sub 2}/p{sub 1} {approximately} 34 and D {approximately} 2400 m/s) and enabled the measurement of current density ({approximately} 2 A/cm{sup 2}) and electrical conductivity ({approximately} 6 mho/m) behind the detonation wave front. In a second set of experiments, a 30 cm long continuous electrode Faraday channel having a height of 2.54 cm and a width of 2.0 cm was attached to the end of the tube using an area transition duct. The Faraday channel was placed inside a permanent magnet assembly having a nominal magnetic induction of 0.6 Tesla, and the electrodes were connected to an active loading circuit in order to characterize power extraction dependence on load impedance while also simulating higher effective magnetic induction. In these single-shot experiments, the near-electrode potential drop was found to consume approximately 60% of the effective u x B induced potential. For B = 0.6 Tesla, the authors obtained a peak open circuit voltage of V{sub O}C = Bh {approximately} 10 volts implying an effective burned gas velocity relative to the tube of {approximately} 660 m/s which may be compared with the theoretical equilibrium value for the idealized case (1100 m/s). The experiments indicated peak power extraction at a load impedance between 5 and 10 Ohms. The measured peak electrical energy density ranged from 10 to 10{sup 3} J/m{sup 3} when the effective magnetic induction was varied from 0.6 to 4.2 Tesla. These results
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.
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.
Magnetohydrodynamic Power Generation in the Laboratory Simulated Martian Entry Plasma
NASA Technical Reports Server (NTRS)
Vuskovic, L.; Popovic, S.; Drake, J.; Moses, R. W.
2005-01-01
This paper addresses the magnetohydrodynamic (MHD) conversion of the energy released during the planetary entry phase of an interplanetary vehicle trajectory. The effect of MHD conversion is multi-fold. It reduces and redirects heat transferred to the vehicle, and regenerates the dissipated energy in reusable and transportable form. A vehicle on an interplanetary mission carries about 10,000 kWh of kinetic energy per ton of its mass. This energy is dissipated into heat during the planetary atmospheric entry phase. For instance, the kinetic energy of Mars Pathfinder was about 4220 kWh. Based on the loss in velocity, Mars Pathfinder lost about 92.5% of that energy during the plasma-sustaining entry phase that is approximately 3900 kWh. An ideal MHD generator, distributed over the probe surface of Mars Pathfinder could convert more than 2000 kWh of this energy loss into electrical energy, which correspond to more than 50% of the kinetic energy loss. That means that the heat transferred to the probe surface can be reduced by at least 50% if the converted energy is adequately stored, or re-radiated, or directly used. Therefore, MHD conversion could act not only as the power generating, but also as the cooling process. In this paper we describe results of preliminary experiments with light and microwave emitters powered by model magnetohydrodynamic generators and discuss method for direct use of converted energy.
Integrated Pulse Detonation Propulsion and Magnetohydrodynamic Power
NASA Technical Reports Server (NTRS)
Litchford, R. J.; Lyles, Garry M. (Technical Monitor)
2001-01-01
The prospects for realizing an integrated pulse detonation propulsion and magnetohydrodynamic (MHD) power system are examined. First, energy requirements for direct detonation initiation of various fuel-oxygen and fuel-air mixtures are deduced from available experimental data and theoretical models. Second, the pumping power requirements for effective chamber scavenging are examined through the introduction of a scavenging ratio parameter and a scavenging efficiency parameter. A series of laboratory experiments were carried out to investigate the basic engineering performance characteristics of a pulse detonation-driven MHD electric power generator. In these experiments, stoichiometric oxy-acetylene mixtures seeded with a cesium hydroxide/methanol spray were detonated at atmospheric pressure in a 1-m-long tube having an i.d. of 2.54 cm. Experiments with a plasma diagnostic channel attached to the end of the tube confirmed the attainment of detonation conditions (p(sub 2)/p(sub 1) approx. 34 and D approx. 2,400 m/sec) and enabled the direct measurement of current density and electrical conductivity (=6 S/m) behind the detonation wave front. In a second set of experiments, a 30-cm-long continuous electrode Faraday channel, having a height of 2.54 cm and a width of 2 cm, was attached to the end of the tube using an area transition duct. The Faraday channel was inserted in applied magnetic fields of 0.6 and 0.95 T. and the electrodes were connected to an active loading circuit to characterize power extraction dependence on load impedance while also simulating higher effective magnetic induction. The experiments indicated peak power extraction at a load impedance between 5 and 10 Ohm. The measured power density was in reasonable agreement with a simple electrodynamic model incorporating a correction for near-electrode potential losses. The time-resolved thrust characteristics of the system were also measured, and it was found that the MHD interaction exerted a
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.
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.
Integrated Pulse Detonation Propulsion and Magnetohydrodynamic Power
NASA Technical Reports Server (NTRS)
Litchford, Ron J.
2001-01-01
The prospects for realizing an integrated pulse detonation propulsion and magnetohydrodynamic (MHD) power system are examined. First, energy requirements for direct detonation initiation of various fuel-oxygen and fuel-air mixtures are deduced from available experimental data and theoretical models. Second, the pumping power requirements for effective chamber scavenging are examined through the introduction of a scavenging ratio parameter and a scavenging efficiency parameter. A series of laboratory experiments were carried out to investigate the basic engineering performance characteristics of a pulse detonation-driven MHD electric power generator. In these experiments, stoichiometric oxy-acetylene mixtures seeded with a cesium hydroxide/methanol spray were detonated at atmospheric pressure in a 1-m-long tube having an i.d. of 2.54 cm. Experiments with a plasma diagnostic channel attached to the end of the tube confirmed the attainment of detonation conditions (p2/p1 approximately 34 and D approximately 2,400 m/sec) and enabled the direct measurement of current density and electrical conductivity (approximately = 6 S/m) behind the detonation wave front, In a second set of experiments, a 30-cm-long continuous electrode Faraday channel, having a height of 2.54 cm and a width of 2 cm, was attached to the end of the tube using an area transition duct. The Faraday channel was inserted in applied magnetic fields of 0.6 and 0.95 T, and the electrodes were connected to an active loading circuit to characterize power extraction dependence on load impedance while also simulating higher effective magnetic induction. The experiments indicated peak power extraction at a load impedance between 5 and 10 Omega. The measured power density was in reasonable agreement with a simple electrodynamic model incorporating a correction for near-electrode potential losses. The time-resolved thrust characteristics of the system were also measured, and it was found that the NM interaction
Open cycle gas fired MHD power plants
Medin, S.A. ); Negrini, F. )
1991-01-01
In this paper, the main objectives for the present development of gas fired MHD power generation are considered. The state of the world-wide natural gas consumption and its utilization for electricity production is analyzed. The experimental efforts in gas-fired MHD studies are briefly described. The essential features of the two major world gas-fired MHD project - the Ryazan MHDES-580 (U-500) power plant and the Italian 230 MWt retrofit are presented. New suggestions for improving the efficiency of MHD systems and the theoretical and experimental aspects of MHD development are discussed.
NASA Technical Reports Server (NTRS)
Holman, R. R.; Lippert, T. E.
1976-01-01
Electric Power Plant costs and efficiencies are presented for two basic liquid-metal cycles corresponding to 922 and 1089 K (1200 and 1500 F) for a commercial applications using direct coal firing. Sixteen plant designs are considered for which major component equipment were sized and costed. The design basis for each major component is discussed. Also described is the overall systems computer model that was developed to analyze the thermodynamics of the various cycle configurations that were considered.
MHD channel performance for potential early commercial MHD power plants
NASA Technical Reports Server (NTRS)
Swallom, D. W.
1981-01-01
The commercial viability of full and part load early commercial MHD power plants is examined. The load conditions comprise a mass flow of 472 kg/sec in the channel, Rosebud coal, 34% by volume oxygen in the oxidizer preheated to 922 K, and a one percent by mass seeding with K. The full load condition is discussed in terms of a combined cycle plant with optimized electrical output by the MHD channel. Various electrical load parameters, pressure ratios, and magnetic field profiles are considered for a baseload MHD generator, with a finding that a decelerating flow rate yields slightly higher electrical output than a constant flow rate. Nominal and part load conditions are explored, with a reduced gas mass flow rate and an enriched oxygen content. An enthalpy extraction of 24.6% and an isentropic efficiency of 74.2% is predicted for nominal operation of a 526 MWe MHD generator, with higher efficiencies for part load operation.
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.
Power Requirement for Nonequilibrium MHD-Bypass Scramjet
NASA Technical Reports Server (NTRS)
Park, Chul; Bogdanoff, David W.; Mehta, Unmeel
2000-01-01
It has been suggested previously that the performance of scramjet propulsion system may be improved by the use of magnetohydrodynamic (MHD) energy bypass: an MHD generator could be made to decelerate the flow entering the combustor, thereby improving combustion efficiency, and the electrical power generated could be made to accelerate the flow exiting from the combustor prior to expanding through the nozzle. In one of such proposed schemes, the MHD generator is proposed to be operated at a low temperature and ionization is to be achieved under nonequilibrium by the application of an external power. In the present work, the required power of such an external source is calculated assuming a 100%-efficient nonequilibrium ionization scheme. The power required is that needed to prevent the degree of ionization from reaching equilibrium with the low gas temperature. The flow is seeded with potassium or cesium. Specific impulse is calculated with and without turbulent friction. The results show that, for typical intended flight conditions, the specific impulse obtained is substantially higher than that of a typical scramjet, but the required external-power is several times that of the power generated in the MHD generator.
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.
Overview of nuclear MHD power conversion for multi-megawatt electric propulsion
NASA Astrophysics Data System (ADS)
Smith, Blair M.; Knight, Travis W.; Anghaie, Samim
2001-02-01
An overview of recent research findings on space applications of nuclear magnetohydrodynamic (MHD) power for generation of multi klbf electric thrust at thousands of seconds of specific impulse is presented. The high operating temperatures of the nuclear MHD system and potential for direct coupling of the output power to the electric thruster system are characterizing features that allow for design of ultracompact and ultralight nuclear electric propulsion systems. Order of magnitude figures for some mission-critical parameters are collated from various engineering analyses. Specific mass and specific impulse values highlight the inherent benefits of further research and development investment in MHD power. .
Pulse Detonation Rocket MHD Power Experiment
NASA Technical Reports Server (NTRS)
Litchford, Ron J.; Cook, Stephen (Technical Monitor)
2002-01-01
A pulse detonation research engine (MSFC (Marshall Space Flight Center) Model PDRE (Pulse Detonation Rocket Engine) G-2) has been developed for the purpose of examining integrated propulsion and magnetohydrodynamic power generation applications. The engine is based on a rectangular cross-section tube coupled to a converging-diverging nozzle, which is in turn attached to a segmented Faraday channel. As part of the shakedown testing activity, the pressure wave was interrogated along the length of the engine while running on hydrogen/oxygen propellants. Rapid transition to detonation wave propagation was insured through the use of a short Schelkin spiral near the head of the engine. The measured detonation wave velocities were in excess of 2500 m/s in agreement with the theoretical C-J velocity. The engine was first tested in a straight tube configuration without a nozzle, and the time resolved thrust was measured simultaneously with the head-end pressure. Similar measurements were made with the converging-diverging nozzle attached. The time correlation of the thrust and head-end pressure data was found to be excellent. The major purpose of the converging-diverging nozzle was to configure the engine for driving an MHD generator for the direct production of electrical power. Additional tests were therefore necessary in which seed (cesium-hydroxide dissolved in methanol) was directly injected into the engine as a spray. The exhaust plume was then interrogated with a microwave interferometer in an attempt to characterize the plasma conditions, and emission spectroscopy measurements were also acquired. Data reduction efforts indicate that the plasma exhaust is very highly ionized, although there is some uncertainty at this time as to the relative abundance of negative OH ions. The emission spectroscopy data provided some indication of the species in the exhaust as well as a measurement of temperature. A 24-electrode-pair segmented Faraday channel and 0.6 Tesla permanent
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.
Rapporteur report: MHD electric power plants
NASA Technical Reports Server (NTRS)
Seikel, G. R.
1980-01-01
Five US papers from the Proceedings of the Seventh International Conference on MHD Electrical Power Generation at the Massachusetts Institute of Technology are summarized. Results of the initial parametric phase of the US effort on the study of potential early commercial MHD plants are reported and aspects of the smaller commercial prototype plant termed the Engineering Test Facility are discussed. The alternative of using a disk geometry generator rather than a linear generator in baseload MHD plants is examined. Closed-cycle as well as open-cycle MHD plants are considered.
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.
Coal-gasification/MHD/steam-turbine combined-cycle (GMS) power generation
Lytle, J.M.; Marchant, D.D.
1980-11-01
The coal-gasification/MHD/steam-turbine combined cycle (GMS) refers to magnetohydrodynamic (MHD) systems in which coal gasification is used to supply a clean fuel (free of mineral matter and sulfur) for combustion in an MHD electrical power plant. Advantages of a clean-fuel system include the elimination of mineral matter or slag from all components other than the coal gasifier and gas cleanup system; reduced wear and corrosion on components; and increased seed recovery resulting from reduced exposure of seed to mineral matter or slag. Efficiencies in some specific GMS power plants are shown to be higher than for a comparably sized coal-burning MHD power plant. The use of energy from the MHD exhaust gas to gasify coal (rather than the typical approach of burning part of the coal) results in these higher efficiencies.
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.
Solar driven liquid metal MHD power generator
NASA Astrophysics Data System (ADS)
Lee, J. H.; Hohl, F.
1983-06-01
A solar energy collector focuses solar energy onto a solar oven which is attached to a mixer which in turn is attached to the channel of a MHD generator. Gas enters the oven and a liquid metal enters the mixer. The gas/liquid metal mixture is heated by the collected solar energy and moves through the MHD generator thereby generating electrical power. The mixture is then separated and recycled.
Solar driven liquid metal MHD power generator
NASA Technical Reports Server (NTRS)
Lee, J. H.; Hohl, F. (Inventor)
1983-01-01
A solar energy collector focuses solar energy onto a solar oven which is attached to a mixer which in turn is attached to the channel of a MHD generator. Gas enters the oven and a liquid metal enters the mixer. The gas/liquid metal mixture is heated by the collected solar energy and moves through the MHD generator thereby generating electrical power. The mixture is then separated and recycled.
Gas Core Reactor-MHD Power System with Cascading Power Cycle
Smith, Blair M.; Anghaie, Samim; Knight, Travis W.
2002-07-01
The US Department of Energy initiative Gen-IV aim is to produce an entire nuclear energy production system with next generation features for certification before 2030. A Generation 4 capable system must have superior sustainability, safety and reliability, and economic cost advantages in comparison with third generation light water reactors. A gas core reactor (GCR) with magnetohydrodynamic (MHD) power converter and cascading power cycle forms the basis for a Generation IV concept that is expected to set the upper performance limits in sustainability and power conversion efficiency among all existing and proposed fission powered systems. A gaseous core reactor delivering 1000's MW fission power acts as the heat source for a high temperature magnetohydrodynamic power converter. A uranium tetrafluoride fuel mix, with {approx}95% mole fraction helium gas, provides a stable working fluid for the primary MHD-Brayton cycle. A helium Brayton cycle extracts waste heat from the MHD generator with about 20% energy efficiency, but the low temperature side is still hot enough ({approx}1600 K) to drive a second conventional helium Brayton cycle with about 35% efficiency. There is enough heat at the low temperature side of the He-Brayton cycle to generate steam, and so another heat recovery cycle can be added, this time a Rankine steam cycle with up to 40% efficiency. The proof of concept does not require a tremendously efficient (first law) MHD cycle, the high temperature direct energy conversion capability of an MHD dynamo, combined with already sophisticated steam powered turbine industry knowledge base allows the cascading cycle design to achieve break-through first law energy efficiencies previously unheard of in the nuclear power industry. Although simple in concept, the gas core reactor design has not achieved the state of technological maturity that, say, molten salt or high-temperature gas-cooled reactors have pioneered. However, even on paper the GCR-MHD concept holds
Gas Core Reactor with Magnetohydrodynamic Power System and Cascading Power Cycle
Smith, Blair M.; Anghaie, Samim
2004-03-15
The U.S. Department of Energy initiative Generation IV aim is to produce an entire nuclear energy production system with next-generation features for certification before 2030. A Generation IV-capable system must have superior sustainability, safety and reliability, and economic cost advantages in comparison with third generation light water reactors (LWRs). A gas core reactor (GCR) with magnetohydrodynamic (MHD) power converter and cascading power cycle forms the basis for a Generation IV concept that is expected to set the upper performance limits in sustainability and power conversion efficiency among all existing and proposed fission powered systems. A gaseous core reactor delivering thousands of megawatt fission power acts as the heat source for a high-temperature MHD power converter. A uranium tetrafluoride fuel mix, with {approx}95% mol fraction helium gas, provides a stable working fluid for the primary MHD Brayton cycle. The hot working fluid exiting a topping cycle MHD generator has sufficient heat to drive a conventional helium Brayton cycle with 35% thermal efficiency as well as a superheated steam Rankine cycle, with up to 40% efficiency, which recovers the waste heat from the intermediate Brayton cycle. A combined cycle efficiency of close to 70% can be achieved with only a modest MHD topping cycle efficiency. The high-temperature direct-energy conversion capability of an MHD dynamo combined with an already sophisticated steam-powered turbine industry knowledge base allows the cascading cycle design to achieve breakthrough first-law energy efficiencies previously unheard of in the nuclear power industry. Although simple in concept, the gas core reactor design has not achieved the state of technological maturity that established high-temperature gas-cooled reactors and high-temperature molten salt core reactors have pioneered. However, the GCR-MHD concept has considerable promise; for example, like molten salt reactors the fuel is continuously cycled
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.
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)
Murakami, Tomoyuki; Okuno, Yoshihiro
2011-05-01
We describe shock-tunnel-based experiments carried out to evaluate a magnetohydrodynamic electrical power generator equipped with a convexly divergent supersonic channel. Two-dimensional structure of the streaming MHD plasma and the temporal behaviour of electron temperature are examined. The spatial profile of MHD power-generating plasma and the energy-conversion efficiency in the convexly divergent channel are compared with those from a linearly divergent channel. For an understanding of the basic scaling of the channel geometry modification effect, a convexity parameter is proposed. With this simple and fundamental scaling parameter, the dependence of plasma-fluid properties and energy-conversion efficiency on the channel convexity is quantitatively examined. The quality of MHD plasma and the generator performance are improved at the convexity parameter of 0.35 (a slight enhancement of the channel convexity) rather than at the convexity parameter of zero (no convexity or concavity). This paper is the first part of a duology.
High-temperature coal-syngas plasma characteristics for advanced MHD power generation
Mikheev, A.V.; Kayukawa, N.; Okinaka, N.; Kamada, Y.; Yatsu, S.
2006-03-15
Properties of magnetohydrodynamic (MHD) plasma based on syngas (CO, H{sub 2}) combustion products were investigated experimentally with shock tube facility. The experiments were carried out under various MHD generator load and shock tube operation conditions. Important characteristics of syngas plasma such as temperature, electric field, conductivity, and total output power were directly measured and evaluated. Special attention was paid to the influence of syngas composition (CO : H{sub 2} : O{sub 2} ratio). The results show that syngas combustion can provide high plasma ionization and attainable plasma electrical conductivity has an order of 60-80 S/m at gas temperature 3100-3300 K.
Off-design study of an open cycle MHD power plant with oxygen enrichment
NASA Astrophysics Data System (ADS)
Geyer, H. K.; Berry, G. F.
1981-01-01
Some of the more important aspects of off-design operation for a magnetohydrodynamic (MHD) power plant are discussed. It is noted that the plant must be designed to meet part-load and overload conditions and that the optimal design should be subject to a specified load demand curve. An analysis is made for off-design regimes to determine the compatible joint operating conditions for an MHD topping cycle, a steam bottoming plant, a turbine train, a compressor, and an oxygen separation plant. The analysis is subject to such constraints as metal temperatures, second law violations, component performance requirements, and environmental considerations.
Lithium-sulfur hexafluoride magnetohydrodynamic power system
Dobran, F.
1987-02-24
A method is described to operate a two-phase flow magnetohydrodynamic electric power generation system with liquid lithium and gaseous sulfur-hexafluoride flowing through a diverging channel, with side electrodes to remove the electric current generated in the flowing liquid lithium, across the applied magnetic field that is perpendicular to both the flow velocity and electrodes. Sulfur-hexafluoride is dispersed in the form of small bubbles and reacts with liquid lithium that forms a continuous phase to conduct the current between the electrodes so as to produce a near isothermal two-phase flow mixture and provides for an expansion of lithium across the magnetic field in the generator.
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
Numerical simulation of the operation of a MHD generator in transient regimes in MHD power stations
Bityurin, V.A.; Ivanov, P.P.; Koryagina, G.M.; Lyubimov, G.A.; Medin, S.A.; Morozov, G.N.; Prokop, A.S.
1982-09-01
Transient regimes of a MHD generator operating in combination with equipment in a MHD power station are analzyed with the help of a numerical model. The MHD generator, whose flow-through part consists of a nozzle, a channel, and a diffuser, is regulated by changing the flow rate and the load. Three types of MHD channels are studied: Faraday supersonic and subsonic, and diagonal supersonic. Their characteristics are presented and the efficiency of the MHD power station under nonrated regimes is determined. It is established that a MHD generator and the MHD power station as a whole admit quite efficient and deep regulation of the change in the flow rate of the working body.
Ideal MHD Stability Prediction and Required Power for EAST Advanced Scenario
NASA Astrophysics Data System (ADS)
Chen, Junjie; Li, Guoqiang; Qian, Jinping; Liu, Zixi
2012-11-01
The Experimental Advanced Superconducting Tokamak (EAST) is the first fully superconducting tokamak with a D-shaped cross-sectional plasma presently in operation. The ideal magnetohydrodynamic (MHD) stability and required power for the EAST advanced tokamak (AT) scenario with negative central shear and double transport barrier (DTB) are investigated. With the equilibrium code TOQ and stability code GATO, the ideal MHD stability is analyzed. It is shown that a moderate ratio of edge transport barriers' (ETB) height to internal transport barriers' (ITBs) height is beneficial to ideal MHD stability. The normalized beta βN limit is about 2.20 (without wall) and 3.70 (with ideal wall). With the scaling law of energy confinement time, the required heating power for EAST AT scenario is calculated. The total heating power Pt increases as the toroidal magnetic field BT or the normalized beta βN is increased.
Power generator design for the billings MHD demonstration project
Pian, C.C.P.; Kessler, R.; Schmitt, E.W.; Morrison, D.J.
1993-12-31
The proposed design of the MHD Power generator for the Billings MHD Demonstration Project is presented. The Billings MHD Demonstration Project, proposed by the MHD Development Corporation (MDC) for the U.S. Department of Energy`s Clean Coal Technology V Program, will demonstrate the significant environmental advantages and efficiency potential of MHD electric power generation. A diagonally-loaded, supersonic MHD generator channel is proposed. The generator channel has a thermal input of 250 MW, is 11 meters long and produces 28.5 MW gross power output at the nominal design operating condition. The gasdynamic, gas-side, and mechanical designs of the proposed generator are derived from the design of the 50 MW{sub t} proof-of-concept MHD generator, currently undergoing long duration testing at the CDIF test facility. The design and operation of the proposed generator will be typical of those anticipated in future commercial MHD generator channels.
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.
Chang, S.L.; Lottes, S.A.; Bouillard, J.X.; Petrick, M.
1997-11-01
This report covers application of Argonne National Laboratory`s (ANL`s) computer codes to simulation and analysis of components of the magnetohydrodynamic (MHD) power train system at the Component Development and Integration Facility (CDIF). Major components of the system include a 50-MWt coal-fired, two-stage combustor and an MHD channel. The combustor, designed and built by TRW, includes a deswirl section between the first and the second-stage combustor and a converging nozzle following the second-stage combustor, which connects to the MHD channel. ANL used computer codes to simulate and analyze flow characteristics in various components of the MHD system. The first-stage swirl combustor was deemed a mature technology and, therefore, was not included in the computer simulation. Several versions of the ICOMFLO computer code were used for the deswirl section and second-stage combustor. The MGMHD code, upgraded with a slag current leakage submodel, was used for the MHD channel. Whenever possible data from the test facilities were used to aid in calibrating parameters in the computer code, to validate the computer code, or to set base-case operating conditions for computations with the computer code. Extensive sensitivity and parametric studies were done on cold-flow mixing in the second-stage combustor, reacting flow in the second-stage combustor and converging nozzle, and particle-laden flow in the deswirl zone of the first-stage combustor, the second-stage combustor, and the converging nozzle. These simulations with subsequent analysis were able to show clearly in flow patterns and various computable measures of performance a number of sensitive and problematical areas in the design of the power train. The simulations of upstream components also provided inlet parameter profiles for simulation of the MHD power generating channel. 86 figs., 18 tabs.
Power facility with a built-in multipolar MHD generator
Kovalev, K.L.; Markina, T.A.
1995-05-01
The scheme of a power facility with a built-in multipolar MHD generator is discussed. In most papers devoted to airborne high-power MHD generators (self-contained or built into the nozzle of the propulsion unit), MHD channels are discussed that are based on a two-pole scheme. The processes of energy conversion in these MHD generators are usually accompanied by disturbances of flow in the entire channel volume, which, in many cases, is undesirable for the operation of power facilities. Depending on the number of pairs of poles, the proposed facility makes it possible to accomplish MHD conversion both in the nozzle peripheral zone and in the central part of the flow. An analysis of the methods and results of calculations of volume MHD effects for finite Hall parameters {beta} and MHD-interaction s, as well as of the output characteristics of multipolar MHD generators equipped with electrode modules of different types are given. A comparison of the theoretical and experimental data is made. A scheme involving an advanced propulsion unit fired with cryogenic fuel H{sub 2}+O{sub 2} and a built-in multipolar MHD generator is considered. The problems of using built-in multipolar MHD generators in propulsion units utilizing other fuel pairs are discussed.
NASA Astrophysics Data System (ADS)
Murakami, Tomoyuki; Okuno, Yoshihiro
2011-05-01
We describe quasi-three-dimensional numerical calculations based on large eddy simulation model for magnetohydrodynamic (MHD) electrical power generators equipped with modified wall configurations. The wall profile of the MHD channel is finely tuned in four types of geometry, that is, a concavely divergent channel, a linearly divergent channel, a convexly divergent channel and a highly convexed channel. The plasma-fluid properties and energy conversion efficiency are examined in detail. Although the deterioration in the plasma-fluid behaviour is not completely overcome, the advantages of the convexly divergent channel are notable. The convexly divergent channel exhibits the highest energy conversion performance, which is followed by the highly convexed, linearly and concavely divergent channels in order. The effect of the channel geometry modification on the generator performance is clearly quantified using a convexity parameter. This paper is the second part of a duology.
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.
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)
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
Power, J.W.
1986-11-01
This investigation examined the possibility of using a rocket-powered magnetohydrodynamic generator for pulse power in space of 300 megawatts (MW). The result is a preliminary design of an MHD generator using an open cycle disk channel and a single superconducting solenoid coil. The disk channel acts as a thrust deflector, and internal vanes counteract induced vorticity. The use of a solid-fuel-wafer grain design rocket motor is proposed for increased electrical conductivity and pulse operation of the generator. Using conservative parameters, a generator design capable of being carried on one or two space-shuttle launches is developed with estimated mass of 24,450 kg and estimated power output of 1346 MW. The nominal operation time before refurbishment is 115 seconds; the restriction operation time is deterioration of the channel throat. This design exceeds present nuclear and solar-cell power systems in power output per unit mass.
Oxygen-enriched air for MHD power plants
NASA Technical Reports Server (NTRS)
Ebeling, R. W., Jr.; Cutting, J. C.; Burkhart, J. A.
1979-01-01
Cryogenic air-separation process cycle variations and compression schemes are examined. They are designed to minimize net system power required to supply pressurized, oxygen-enriched air to the combustor of an MHD power plant with a coal input of 2000 MWt. Power requirements and capital costs for oxygen production and enriched air compression for enrichment levels from 13 to 50% are determined. The results are presented as curves from which total compression power requirements can be estimated for any desired enrichment level at any delivery pressure. It is found that oxygen enrichment and recuperative heating of MHD combustor air to 1400 F yields near-term power plant efficiencies in excess of 45%. A minimum power compression system requires 167 MW to supply 330 lb of oxygen per second and costs roughly 100 million dollars. Preliminary studies show MHD/steam power plants to be competitive with plants using high-temperature air preheaters burning gas.
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 (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.
NASA Astrophysics Data System (ADS)
Murakami, Tomoyuki; Okuno, Yoshihiro
2008-06-01
We describe experiments carried out to evaluate a newly developed high-performance nonequilibrium-plasma magnetohydrodynamic (MHD) electrical power generator equipped with a slightly divergent supersonic channel. The slightly divergent generator and a similar-scale highly divergent generator are evaluated in shock-tube experiments. The effects of electrical conductivity control and magnetic flux density control on the generator operation are investigated, and Hall voltage-Hall current characteristics, plasma-fluid behaviour and plasma structures are described. The slightly divergent channel configuration and the application of high- and uniform-density magnetic flux overcome the disadvantages of the generator due to its compactness, and markedly improves its performance. The ratio of isentropic efficiency to enthalpy extraction ratio and the power output density are outstanding compared with previous MHD power generators. The experimental results are supported by the numerically simulated results. This paper is the second part of a duology.
Evaluation of the ECAS open cycle MHD power plant design
NASA Technical Reports Server (NTRS)
Seikel, G. R.; Staiger, P. J.; Pian, C. C. P.
1978-01-01
The Energy Conversion Alternatives Study (ECAS) MHD/steam power plant is described. The NASA critical evaluation of the design is summarized. Performance of the MHD plant is compared to that of the other type ECAS plant designs on the basis of efficiency and the 30-year levelized cost of electricity. Techniques to improve the plant design and the potential performance of lower technology plants requiring shorter development time and lower development cost are then discussed.
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.
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.
Supplemental information on a conceptual design of a space-based multimegawatt MHD power system
Pierce, B.L.; Holman, R.R.; Lance, J.R.
1988-02-01
The objective of this project is to perform a feasibility assessment of space-based multimegawatt (MMW) magnetohydrodynamic (MHD) power systems for Strategic Defense Initiative Organization (SDIO) mission applications and to resolve technical uncertainties that may impact their future implementation. The ultimate goal of the SDIO is to provide security for the United States and Its allies. The near term objective of the SDIO is to conduct research on those technologies for defensive systems that might be capable of intercepting ballistic missiles after launch and preventing them from hitting their targets. System concepts currently being considered for space-based weapons applications will, if implemented, require specially tailored power systems. These power systems may possess characteristics and specifications lying considerably outside the design range of conventional devices. Their development may require major advances in existing technology and the accelerated development of entirely new approaches.
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.
Multi-MW Closed Cycle MHD Nuclear Space Power Via Nonequilibrium He/Xe Working Plasma
NASA Technical Reports Server (NTRS)
Litchford, Ron J.; Harada, Nobuhiro
2011-01-01
Prospects for a low specific mass multi-megawatt nuclear space power plant were examined assuming closed cycle coupling of a high-temperature fission reactor with magnetohydrodynamic (MHD) energy conversion and utilization of a nonequilibrium helium/xenon frozen inert plasma (FIP). Critical evaluation of performance attributes and specific mass characteristics was based on a comprehensive systems analysis assuming a reactor operating temperature of 1800 K for a range of subsystem mass properties. Total plant efficiency was expected to be 55.2% including plasma pre-ionization power, and the effects of compressor stage number, regenerator efficiency and radiation cooler temperature on plant efficiency were assessed. Optimal specific mass characteristics were found to be dependent on overall power plant scale with 3 kg/kWe being potentially achievable at a net electrical power output of 1-MWe. This figure drops to less than 2 kg/kWe when power output exceeds 3 MWe. Key technical issues include identification of effective methods for non-equilibrium pre-ionization and achievement of frozen inert plasma conditions within the MHD generator channel. A three-phase research and development strategy is proposed encompassing Phase-I Proof of Principle Experiments, a Phase-II Subscale Power Generation Experiment, and a Phase-III Closed-Loop Prototypical Laboratory Demonstration Test.
MHD conversion of solar energy. [space electric power system
NASA Technical Reports Server (NTRS)
Lau, C. V.; Decher, R.
1978-01-01
Low temperature plasmas wherein an alkali metal vapor is a component are uniquely suited to simultaneously absorb solar radiation by coupling to the resonance lines and produce electrical power by the MHD interaction. This work is an examination of the possibility of developing space power systems which take advantage of concentrated solar power to produce electricity. It is shown that efficient cycles in which expansion work takes place at nearly constant top cycle temperature can be devised. The power density of the solar MHD generator is lower than that of conventional MHD generators because of the relatively high seed concentration required for radiation absorption and the lower flow velocity permitted to avoid total pressure losses due to heating.
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)
Berry, G.F.; Minkov, V.; Petrick, M.
1981-11-02
A magnetohydrodynamic (MHD) power generating system is described in which ionized combustion gases with slag and seed are discharged from an MHD combustor and pressurized high temperature inlet air is introduced into the combustor for supporting fuel combustion at high temperatures necessary to ionize the combustion gases, and including a heat exchanger in the form of a continuous loop with a circulating heat transfer liquid such as copper oxide. The heat exchanger has an upper horizontal channel for providing direct contact between the heat transfer liquid and the combustion gases to cool the gases and condense the slag which thereupon floats on the heat transfer liquid and can be removed from the channel, and a lower horizontal channel for providing direct contact between the heat transfer liquid and pressurized air for preheating the inlet air. The system further includes a seed separator downstream of the heat exchanger.
Berry, Gregory F.; Minkov, Vladimir; Petrick, Michael
1988-01-01
A magnetohydrodynamic (MHD) power generating system in which ionized combustion gases with slag and seed are discharged from an MHD combustor and pressurized high temperature inlet air is introduced into the combustor for supporting fuel combustion at high temperatures necessary to ionize the combustion gases, and including a heat exchanger in the form of a continuous loop with a circulating heat transfer liquid such as copper oxide. The heat exchanger has an upper horizontal channel for providing direct contact between the heat transfer liquid and the combustion gases to cool the gases and condense the slag which thereupon floats on the heat transfer liquid and can be removed from the channel, and a lower horizontal channel for providing direct contact between the heat transfer liquid and pressurized air for preheating the inlet air. The system further includes a seed separator downstream of the heat exchanger.
Berry, Gregory F.; Minkov, Vladimir; Petrick, Michael
1988-01-05
A magnetohydrodynamic (MHD) power generating system in which ionized combustion gases with slag and seed are discharged from an MHD combustor and pressurized high temperature inlet air is introduced into the combustor for supporting fuel combustion at high temperatures necessary to ionize the combustion gases, and including a heat exchanger in the form of a continuous loop with a circulating heat transfer liquid such as copper oxide. The heat exchanger has an upper horizontal channel for providing direct contact between the heat transfer liquid and the combustion gases to cool the gases and condense the slag which thereupon floats on the heat transfer liquid and can be removed from the channel, and a lower horizontal channel for providing direct contact between the heat transfer liquid and pressurized air for preheating the inlet air. The system further includes a seed separator downstream of the heat exchanger.
NASA Astrophysics Data System (ADS)
Lorzel, Heath
The time-dependent, 2½-dimensional, axisymmetric, magnetohydrodynamics (MHD) solver MACH2 has been upgraded to include the effects of non-equilibrium air chemistry using the well-established reaction model developed by Park. Several validation cases are presented based on comparisons to the experimentally deduced shock stand-off distance of nitrogen flow over spheres, the shock stand-off distance of spheres fired into air in a ballistic test facility, and the electron number density on the surface of the Ram-C re-entry experiment. In addition, the magnetic induction equation has been upgraded with new verified models that compute the effects of the Hall and ion slip terms. The upgraded code is utilized to model an annular, Hall-type MHD generator that can be employed upstream of a turbojet engine for freestream conditions corresponding to Mach 5 flight at an altitude of 20km. The simulations demonstrate the feasibility of convening inlet kinetic power to storable electric power. Using ionization provided by electron-beam guns and a radial magnetic field B=3T, the generator is shown to produce a maximum of 4.8MW of electric power while reducing the total kinetic power of the flow by 31%. Optimizing the loading parameter, K*Load, across the electrodes demonstrates that the generator could produce 1.54MW of excess electric power that can be stored and used for on-board power requirements. Further, the reduction in flow kinetic power results in an increase in static pressure of 30% and a reduction in stagnation temperature of 3% at the turbojet's compressor inlet that aids the subsequent process of combustion.
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.
NASA Astrophysics Data System (ADS)
Aini Mat, Nor Azian; Arifin, Norihan Md.; Nazar, Roslinda; Ismail, Fudziah; Bachok, Norfifah
2013-09-01
A similarity solution of the steady magnetohydrodynamic (MHD) mixed convection boundary layer flow due to a stretching vertical heated sheet in a power law nanofluid with thermal radiation effect is theoretically studied. The governing system of partial differential equations is first transformed into a system of ordinary differential equations. The transformed equations are solved numerically using the shooting method. The influence of pertinent parameters such as the nanoparticle volume fraction parameter, the magnetic parameter, the buoyancy or mixed convection parameter and the radiation parameter on the flow and heat transfer characteristics is discussed. Comparisons with published results are also presented.
H2-O2 combustion powered steam-MHD central power systems
NASA Technical Reports Server (NTRS)
Seikel, G. R.; Smith, J. M.; Nichols, L. D.
1974-01-01
Estimates are made for both the performance and the power costs of H2-O2 combustion powered steam-MHD central power systems. Hydrogen gas is assumed to be transmitted by pipe from a remote coal gasifier into the city and converted to electricity in a steam MHD plant having an integral gaseous oxygen plant. These steam MHD systems appear to offer an attractive alternative to both in-city clean fueled conventional steam power plants and to remote coal fired power plants with underground electric transmission into the city.
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 (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.
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.
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.
Pamir-3U pulsed portable MHD power system
Zeigarnik, V.A.; Swallom, D.W.; Gibbs, J.S.
1994-12-31
The results of the development of a portable, pulsed MHD power system, called the Pamir-3U, are presented. The maximum operating parameters of the Pamir-3U MHD power system are a net power output of 15 MW and a maximum duration of the electrical pulse at the load of 10 seconds. The work is being performed by the {open_quotes}IVTAN - Association{close_quotes} of the Russian Academy of Sciences (Russia) and Textron Defense Systems (USA). Major subcontractors also participating in this effort are Nizhny Novgorod Machine Building Plant (Russia), Lubertsy Scientific and Production Association (Russia) and Aerojet Corporation (USA). Textron Defense Systems is the prime contractor with overall management and systems integration of the project. Aerojet Corporation will provide the test site and perform the acceptance test program. The Russian subcontract team is led by IVTAN, who is responsible for the overall design and integration of the Pamir-3U System and the electrical control and data acquisition. The two subcontractors working for IVTAN are responsible for the magnets, channels, and electrical equipment (Nizhny Novgorod) and the plasma generators (Lubertsy). The Pamir-3U MHD system is a portable power system that can be transported to various operational locations. The power system is self-contained and does not require extensive support equipment to generate the design power.
Performance calculations for 1000 MWe MHD/steam power plants
NASA Technical Reports Server (NTRS)
Pian, C. C. P.
1981-01-01
The effects of MHD generator operating conditions and constraints on the performance of MHD/steam power plants are investigated. Power plants using high temperature combustion air preheat (2500 F) and plants using intermediate temperature preheat (1100 F) with oxygen enrichment are considered. Variations of these two types of power plants are compared on the basis of fixed total electrical output (1000 MWe). Results are presented to show the effects of generator plant length and level of oxygen enrichment on the plant thermodynamic efficiency and on the required generator mass flow rate. Factors affecting the optimum levels of oxygen enrichment are analyzed. It is shown that oxygen enrichment can reduce magnet stored energy requirement.
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.
NASA Astrophysics Data System (ADS)
Murakami, Tomoyuki; Okuno, Yoshihiro
2008-06-01
We describe quasi-three-dimensional numerical simulations of a high-performance nonequilibrium-plasma magnetohydrodynamic (MHD) electrical power generator using a slightly divergent configuration. The slightly divergent generator provides greater isentropic efficiency (IE) than a highly divergent generator when an identical enthalpy extraction ratio (EER) is obtained. The inherent feature of a small divergent geometry is clarified; MHD energy conversion is accompanied by less entropy production as well as less gas expansion. The orientation of the performance improvement on an IE-EER map is consistent with the theoretically predicted orientation, which is formulated using an algebraic method based on classical thermodynamic results for supersonic compressible fluid dynamics. The power-generating performance indicators, IE and EER, are clearly determined by modified magnetic flux density, that is, the square of magnetic flux density divided by total inflow pressure. A virtual operating condition for a practical closed-cycle MHD system is proposed considering the relationships between the applied magnetic flux density, the total inflow pressure and the total pressure gradient throughout the generator. This paper is the first part of a duology.
MHD Advanced Power Train Phase I, Final Report, Volume 7
A. R. Jones
1985-08-01
This appendix provides additional data in support of the MHD/Steam Power Plant Analyses reported in report Volume 5. The data is in the form of 3PA/SUMARY computer code printouts. The order of presentation in all four cases is as follows: (1) Overall Performance; (2) Component/Subsystem Information; (3) Plant Cost Accounts Summary; and (4) Plant Costing Details and Cost of Electricity.
Towards Integrated Pulse Detonation Propulsion and MHD Power
NASA Technical Reports Server (NTRS)
Litchford, Ron J.; Thompson, Bryan R.; Lineberry, John T.
1999-01-01
with PDEs for integrated aerospace propulsion and MHD power. An effort is made to estimate the energy requirements for direct detonation initiation of potential fuel/oxidizer mixtures and to determine the electrical power requirements. This requirement is evaluated in terms of the possibility for MHD power generation using the combustion detonation wave. Small scale laboratory experiments were conducted using stoichiometric mixtures of acetylene and oxygen with an atomized spray of cesium hydroxide dissolved in alcohol as an ionization seed in the active MHD region. Time resolved thrust and MHD power generation measurements were performed. These results show that PDEs yield higher I(sub sp) levels than a comparable rocket engine and that MHD power generation is viable candidate for achieving self-excited engine operation.
Plasma plume MHD power generator and method
Hammer, J.H.
1993-08-10
A method is described of generating power at a situs exposed to the solar wind which comprises creating at separate sources at the situs discrete plasma plumes extending in opposed directions, providing electrical communication between the plumes at their source and interposing a desired electrical load in the said electrical communication between the plumes.
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)
Jiao, Chengru; Zheng, Liancun; Ma, Lianxi
2015-08-01
This paper studies the magnetohydrodynamic (MHD) thermosolutal Marangoni convection heat and mass transfer of power-law fluids driven by a power law temperature and a power law concentration which is assumed that the surface tension varies linearly with both the temperature and concentration. Heat and mass transfer constitutive equation is proposed based on N-diffusion proposed by Philip and the abnormal convection-diffusion model proposed by Pascal in which we assume that the heat diffusion depends non-linearly on both the temperature and the temperature gradient and the mass diffusion depends non-linearly on both the concentration and the concentration gradient with modified Fourier heat conduction for power law fluid. The governing equations are reduced to nonlinear ordinary differential equations by using suitable similarity transformations. Approximate analytical solution is obtained using homotopy analytical method (HAM). The transport characteristics of velocity, temperature and concentration fields are analyzed in detail.
Comparative analysis of CCMHD power plants. [Closed Cycle MHD
NASA Technical Reports Server (NTRS)
Alyea, F. N.; Marston, C. H.; Mantri, V. B.; Geisendorfer, B. G.; Doss, H.
1981-01-01
A study of Closed Cycle MHD (CCMHD) power generation systems has been conducted which emphasizes both advances in component conceptual design and overall system performance. New design data are presented for the high temperature, regenerative argon heaters (HTRH) and the heat recovery/seed recovery (HRSR) subsystem. Contamination of the argon by flue gas adsorbed in the HTRH is examined and a model for estimation of contamination effects in operating systems is developed. System performance and cost data have been developed for the standard CCMHD/steam cycle as powered by both direct fired cyclone combustors and selected coal gasifiers. In addition, a new CCMHD thermodynamic cycle has been identified.
System studies of coal fired-closed cycle MHD for central station power plants
NASA Technical Reports Server (NTRS)
Zauderer, B.
1976-01-01
This paper presents a discussion of the closed-cycle MHD results obtained in a recent study of various advanced energy-conversion power systems. The direct coal-fired MHD topping-steam bottoming cycle was established as the current choice for central station power generation. Emphasis is placed on the background assumptions and the conclusions that can be drawn from the closed-cycle MHD analysis. It is concluded that closed-cycle MHD has efficiencies comparable to that of open-cycle MHD. Its cost will possibly be slightly higher than that of the open-cycle MHD system. Also, with reasonable fuel escalation assumptions, both systems can produce lower-cost electricity than conventional steam power plants. Suggestions for further work in closed-cycle MHD components and systems are made.
Experiments on H2-O2MHD power generation
NASA Technical Reports Server (NTRS)
Smith, J. M.
1980-01-01
Magnetohydrodynamic power generation experiments utilizing a cesium-seeded H2-O2 working fluid were carried out using a diverging area Hall duct having an entrance Mach number of 2. The experiments were conducted in a high-field strength cryomagnet facility at field strengths up to 5 tesla. The effects of power takeoff location, axial duct location within the magnetic field, generator loading, B-field strength, and electrode breakdown voltage were investigated. For the operating conditions of these experiments, it is found that the power output increases with the square of the B-field and can be limited by choking of the channel or interelectrode voltage breakdown which occurs at Hall fields greater than 50 volts/insulator. Peak power densities of greater than 100 MW/cu M were achieved.
Impinging jet separators for liquid metal magnetohydrodynamic power cycles
NASA Technical Reports Server (NTRS)
Bogdanoff, D. W.
1973-01-01
In many liquid metal MHD power, cycles, it is necessary to separate the phases of a high-speed liquid-gas flow. The usual method is to impinge the jet at a glancing angle against a solid surface. These surface separators achieve good separation of the two phases at a cost of a large velocity loss due to friction at the separator surface. This report deals with attempts to greatly reduce the friction loss by impinging two jets against each other. In the crude impinging jet separators tested to date, friction losses were greatly reduced, but the separation of the two phases was found to be much poorer than that achievable with surface separators. Analyses are presented which show many lines of attack (mainly changes in separator geometry) which should yield much better separation for impinging jet separators).
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.
MHD micropumping of power-law fluids: A numerical solution
NASA Astrophysics Data System (ADS)
Moghaddam, Saied
2013-02-01
The performance of MHD micropumps is studied numerically assuming that the viscosity of the fluid is shear-dependent. Using power-law model to represent the fluid of interest, the effect of power-law exponent, N, is investigated on the volumetric flow rate in a rectangular channel. Assuming that the flow is laminar, incompressible, two-dimensional, but (approximately) unidirectional, finite difference method (FDM) is used to solve the governing equations. It is found that shear-thinning fluids provide a larger flow rate as compared to Newtonian fluids provided that the Hartmann number is above a critical value. There exists also an optimum Hartmann number (which is larger than the critical Hartmann number) at which the flow rate is maximum. The power-law exponent, N, strongly affects the optimum geometry depending on the Hartmann number being smaller or larger than the critical Hartmann number.
Experiments on H2-O2 MHD power generation
NASA Astrophysics Data System (ADS)
Smith, J. M.
1980-06-01
MHD power generation experiments utilizing a cesium-seeded H2-O2 working fluid have been carried out using a diverging area Hall duct having an entrance Mach number of 2. The experiments are conducted in a high-field strength cryomagnet facility at field strengths up to 5 tesla. The effects of power takeoff location, axial duct location within the magnetic field, generator loading, B-field strength, and electrode breakdown voltage were investigated. For the operating conditions of these experiments it is found that the power output increases with the square of the B-field and can be limited by choking of the channel or interelectrode voltage breakdown which occurs at Hall fields greater than 50 volts/insulator.
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 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.
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
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.
Downstream component corrosion in coal-fired MHD power plants
White, M. K.
1980-06-01
Results are given to date of corrosion probe studies conducted to evaluate the nature and severity of degradation of oiler and superheater materials in coal-fired MHD power generation systems. Tests were conducted with two air or nitrogen cooled probes in Cell III of the UTSI MHD facility. One probe had carbon steel samples subjected to metal temperatures of from 547K to 719K and reducing (SR = 0.85) gas conditions to simulate boiler tube conditions. The exposure time to date on these samples is 240 minutes. The other probe had samples of carbon steel, chromium-molybdenum steels and stainless steels subjected to temperatures ranging from 811K to 914K with oxidizing (SR = 1.15) gas conditions. The total run time on these samples was 70 minutes. The boiler probe samples were found to undergo predominantly pitted type corrosion beneath a deposit of ash/seed material having approximately 34% K/sub 2/SO/sub 4/. Weight loss rates varied from about 1.5 x 10/sup -4/ gm/hr-cm/sup 2/ at the cool end of the probe to about 5.5 x 10/sup -4/ gm/hr-cm/sup 2/ at the hot end. This loss is attributed primarily to sulfidation by hydrogen sulfide. Resistance to scaling of superheater materials increased progressively with the degree of alloying. Attack appeared to be in the form of surface scales containing mixtures of oxides and is attributed to either gaseous oxidation or to the presence of complex potassium trisulfates.
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
Parametric study of potential early commercial MHD power plants
NASA Technical Reports Server (NTRS)
Hals, F. A.
1979-01-01
Three different reference power plant configurations were considered with parametric variations of the various design parameters for each plant. Two of the reference plant designs were based on the use of high temperature regenerative air preheaters separately fired by a low Btu gas produced from a coal gasifier which was integrated with the power plant. The third reference plant design was based on the use of oxygen enriched combustion air preheated to a more moderate temperature in a tubular type metallic recuperative heat exchanger which is part of the bottoming plant heat recovery system. Comparative information was developed on plant performance and economics. The highest net plant efficiency of about 45 percent was attained by the reference plant design with the use of a high temperature air preheater separately fired with the advanced entrained bed gasifier. The use of oxygen enrichment of the combustion air yielded the lowest cost of generating electricity at a slightly lower plant efficiency. Both of these two reference plant designs are identified as potentially attractive for early MHD power plant applications.
System studies of coal fired-closed cycle MHD for central station power plants
NASA Technical Reports Server (NTRS)
Zauderer, B.
1976-01-01
This paper presents a discussion of the closed cycle MHD results obtained in a recent study of various advanced energy conversion (ECAS) power systems. The study was part of the first phase of this ECAS study. Since this was the first opportunity to evaluate the coal fired closed cycle MHD system, a number of iterations were required to partially optimize the system. The present paper deals with the latter part of the study in which the direct coal fired, MHD topping-steam bottoming cycle was established as the current choice for central station power generation. The emphasis of the paper is on the background assumptions and the conclusions that can be drawn from the closed cycle MHD analysis. The author concludes that closed cycle MHD has efficiencies comparable to that of open cycle MHD and that both systems are considerably more efficient than the other system studies in Phase 1 of the GE ECAS. Its cost will possibly be slightly higher than that of the open cycle MHD system. Also, with reasonable fuel escalation assumptions, both systems can produce lower cost electricity than conventional steam power plants. Suggestions for further work in closed cycle MHD components and systems is made.
Liquid metal magnetohydrodynamic (LMMHD) converter for space power system
NASA Astrophysics Data System (ADS)
Alemany, A.; Marty, Ph.; Thibault, J. P.
The liquid metal MHD or (Faraday) Converter is a conversion system which allows the production of electricity from thermal energy without any moving solid part. Then, such a system is very attractive in space where a long lifetime is required. The basic principle of the process is the expansion of a gas to accelerate a high-temperature liquid metal in an MHD generator where this liquid metal interacts with a magnetic field to produce electricity. By using an inductive generator the electric current can be delivered directly on the alternative form with adjustable voltage and frequency.
Engineering support for magnetohydrodynamic power plant analysis and design studies
NASA Technical Reports Server (NTRS)
Carlson, A. W.; Chait, I. L.; Marchmont, G.; Rogali, R.; Shikar, D.
1980-01-01
The major factors which influence the economic engineering selection of stack inlet temperatures in combined cycle MHD powerplants are identified and the range of suitable stack inlet temperatures under typical operating conditions is indicated. Engineering data and cost estimates are provided for four separately fired high temperature air heater (HTAH) system designs for HTAH system thermal capacity levels of 100, 250, 500 and 1000 MWt. An engineering survey of coal drying and pulverizing equipment for MHD powerplant application is presented as well as capital and operating cost estimates for varying degrees of coal pulverization.
Engineering support for magnetohydrodynamic power plant analysis and design studies
NASA Astrophysics Data System (ADS)
Carlson, A. W.; Chait, I. L.; Marchmont, G.; Rogali, R.; Shikar, D.
1980-08-01
The major factors which influence the economic engineering selection of stack inlet temperatures in combined cycle MHD powerplants are identified and the range of suitable stack inlet temperatures under typical operating conditions is indicated. Engineering data and cost estimates are provided for four separately fired high temperature air heater (HTAH) system designs for HTAH system thermal capacity levels of 100, 250, 500 and 1000 MWt. An engineering survey of coal drying and pulverizing equipment for MHD powerplant application is presented as well as capital and operating cost estimates for varying degrees of coal pulverization.
NASA Technical Reports Server (NTRS)
Dellinger, T. C.; Hnat, J. G.; Marston, C. H.
1979-01-01
A parametric study of the performance of the MHD generator and combustor components of potential early commercial open-cycle MHD/steam power plants is presented. Consideration is given to the effects of air heater system concept, MHD combustor type, coal type, thermal input power, oxygen enrichment of the combustion, subsonic and supersonic generator flow and magnetic field strength on coupled generator and combustor performance. The best performance is found to be attained with a 3000 F, indirectly fired air heater, no oxygen enrichment, Illinois no. 6 coal, a two-stage cyclone combustor with 85% slag rejection, a subsonic generator, and a magnetic field configuration yielding a constant transverse electric field of 4 kV/m. Results indicate that optimum net MHD generator power is generally compressor-power-limited rather than electric-stress-limited, with optimum net power a relatively weak function of operating pressure.
Conceptual design of a space-based multimegawatt MHD power system. Topical report
Barton, J.R.; Bernard, F.E.; Carrington, R.A.; Hanson, L.P.; Holman, R.R.
1988-01-01
This report presents the system requirements and design guidelines for the space based multimegawatt MHD power system conceptual design, and comprises Volume 2 of the topical report describing the Task 1 MHD Power System Conceptual Design and Development Plan. In the interest of completeness, this report includes a summary description of the MHD power system concept with the functional requirements, design scope and design objectives. Then subsequent sections present the system requirements including operational requirements, space platform/weapon system interfaces, subsystem interfaces, and design guidelines. The analytical methods used for system analysis and parametric studies are also included. A description of the MHD power system, in the standard data table format for multimegawatt space power systems, is included in the Appendices.
NASA Astrophysics Data System (ADS)
Wang, Qiang; Rong, Wenjie; Li, Baokuan
2015-11-01
A transient three-dimensional (3D) coupled mathematical model of electroslag remelting (ESR) furnace has been developed to investigate the impact of power control function on the heat transfer and magnetohydrodynamic (MHD) two-phase flow. Maxwell's equations are solved by electrical potential method. The volume of fluid (VOF) approach is implemented to describe the two phase flow. The Lorentz force and the Joule heating are updated at each iteration as a function of phase distribution. The solidification is modeled by enthalpy-porosity formulation. A reasonable agreement between the experiment and simulation is obtained. The melt rate increases 15.83% in the remelting process with a constant current of 1600 A. With the power control function, the current would be reduced if the melt rate is 1.05 times larger than its initial value. The fluctuation range of the melt rate therefore decreases to 7.23%. Moreover, the fluctuation is limited within 5.12% if we start the power control program when the melt rate is 1.03 times higher than its initial value. Not only the metal pool depth but also the input power decreases under the effect of the current control function.
Radio-frequency power-assisted performance improvement of a magnetohydrodynamic power generator
Murakami, Tomoyuki; Okuno, Yoshihiro; Yamasaki, Hiroyuki
2005-12-01
We describe a radio-frequency (rf) electromagnetic-field-assisted magnetohydrodynamic power generation experiment, where an inductively coupled rf field (13.56 MHz, 5.2 kW) is continuously supplied to the disk generator. The rf power assists the precise plasma ignition, by which the otherwise irregular plasma behavior was stabilized. The rf heating suppresses the ionization instability in the plasma behavior and homogenizes the nonuniformity of the plasma structures. The power-generating performance is significantly improved with the aid of the rf power under wide seeding conditions: insufficient, optimum, and excessive seed fractions. The increment of the enthalpy extraction ratio of around 2% is significantly greater than the fraction of the net rf power, that is, 0.16%, to the thermal input.
A summary of the ECAS MHD power plant results
NASA Technical Reports Server (NTRS)
Seikel, G. R.; Harris, L. P.
1976-01-01
The performance and the cost of electricity (COE) for MHD systems utilizing coal or coal derived fuels are summarized along with a conceptual open cycle MHD plant design. The results show that open cycle coal fired recuperatively preheated MHD systems have potentially one of the highest coal-pile-to-bus bar efficiencies (48.3%) and also one of the lowest COE of the systems studied. Closed cycle, inert gas systems do not appear to have the potential of exceeding the efficiency of or competing with the COE of advanced steam plants.
Parametric study of potential early commercial power plants Task 3-A MHD cost analysis
NASA Technical Reports Server (NTRS)
1983-01-01
The development of costs for an MHD Power Plant and the comparison of these costs to a conventional coal fired power plant are reported. The program is divided into three activities: (1) code of accounts review; (2) MHD pulverized coal power plant cost comparison; (3) operating and maintenance cost estimates. The scope of each NASA code of account item was defined to assure that the recently completed Task 3 capital cost estimates are consistent with the code of account scope. Improvement confidence in MHD plant capital cost estimates by identifying comparability with conventional pulverized coal fired (PCF) power plant systems is undertaken. The basis for estimating the MHD plant operating and maintenance costs of electricity is verified.
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.
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.
Results from the Pamir-3U pulsed portable MHD power system program
Swallom, D.W.; Goldfarb, V.M.; Gibbs, J.S.
1996-12-31
The Pamir-3U MHD Power System Acceptance Test Program was successfully performed in the United States in 1995. The Pamir-3U MHD system is a portable power system that can be transported to various operational locations. The power system is self-contained and does not require extensive support equipment to generate the design power. The work was performed by the IVTAN-Association of the Russian Academy of Sciences (Russia) and Textron Systems Division (US). Major subcontractors that participated in this effort are Nizhny Novgorod Machine Building Plant (Russia), Federal Center of Dual Technologies Soyuz (Russia) and Aerojet Corporation (US). A preliminary acceptance test program, consisting of five power tests and several preliminary tests, was conducted during August 1994 at Geodesiya Research and Development Institute, Krasnoarmejsk, Russia. During this test program, power levels as high as 15 MW(e) were obtained. Operation of the facility in various operating modes was demonstrated, and several tests were conducted where the resistance was varied during the hot-fire test run. For the final Pamir-3U MHD Power System Acceptance Test Program, eight hot-fire tests were performed. The performance levels of the Pamir-3U MHD Power System were confirmed during these tests. As a result of the experiments performed, the operational ability of the Pamir-3U MHD power system to operate in a variety of performance modes and under a variety of operating conditions was confirmed.
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.
Studies of cycles for liquid-metal magnetohydrodynamic generation of power
NASA Technical Reports Server (NTRS)
Lee, K.; Petrick, M.
1969-01-01
Studies of liquid-metal magnetohydrodynamic power cycles indicate that the overall efficiency of a binary cycle, employing a liquid-metal topping cycle and a bottoming steam cycle, may reach 60 percent. Details of analyses and data on cycles are presented, and the commercial potential of the binary cycle is discussed.
Ultrahigh temperature vapor core reactor-MHD system for space nuclear electric power
NASA Technical Reports Server (NTRS)
Maya, Isaac; Anghaie, Samim; Diaz, Nils J.; Dugan, Edward T.
1991-01-01
The conceptual design of a nuclear space power system based on the ultrahigh temperature vapor core reactor with MHD energy conversion is presented. This UF4 fueled gas core cavity reactor operates at 4000 K maximum core temperature and 40 atm. Materials experiments, conducted with UF4 up to 2200 K, demonstrate acceptable compatibility with tungsten-molybdenum-, and carbon-based materials. The supporting nuclear, heat transfer, fluid flow and MHD analysis, and fissioning plasma physics experiments are also discussed.
The first experiments with Pamir-3U pulsed portable MHD power system
Zeigarnik, V.A.; Aitov, N.A.; Okunev, V.I.
1995-12-31
The results of the first experiments with a portable, pulsed MHD Power System, called the Pamir-3U, performed in Russia in 1994 are presented and discussed. The Pamir-3U MHD system is a portable power system that can be transported to various operational locations. The power system is self-contained and does not require extensive support equipment to generate the design power. The work is being performed by the IVTAN-Association of the Russian Academy of Sciences (Russia) and Textron Defense Systems (USA). Major subcontractors also participating in this effort are Nizhny Novgorod Machine Building Plant (Russia), Lubertsy Scientific and Production Association Soyuz (Russia) and Aerojet Corporation (USA). Five hot-fire tests were performed for the adjustment of the components of the Pamir-3U MHD Power System and for the demonstration of the Pamir-3U MM Power System operating parameters. Correspondence of the operating performance to the requirements of the technical assignment document was also demonstrated. The following output parameters of the Pamir-3U MHD power system were obtained during the hot-fire tests: (1) nominal output power - 10-15 MW{sub e}; (2) maximal output power - 15.1 MW{sub e}; and (3) maximal current pulse duration in the load - 7.15 s. The performance output of the Pamir-3U Power System satisfied the primary requirements of the technical assignment document.
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.
Wall surface leakage effects on MHD power generator performance
Pian, C.C.P.; Schmitt, E.W.
1994-12-31
Internal surface leakage effects on the MHD generator performance were studied using a combined experimental and analytical approach. A method to determine the wall resistances and slag layer conductivities from seed shut-off test data is introduced. These measured resistance values are then utilized in generator performance analyses. Calculated results were compared with measured data from MHD generator tests to verify the modeling approach. Finally, these calculated results were used to investigate the distribution of internal leakage currents as a function of generator size, generator operating conditions, and iron oxide injection rates. An advantage of this analysis methodology is the ability to differentiate between wall leakage and apparent leakage effects in the measured test data.
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)
Rabbi, Khan Md.; Rakib, Tawfiqur; Das, Sourav; Mojumder, Satyajit; Saha, Sourav
2016-07-01
This paper demonstrates magneto-hydrodynamic (MHD) mixed convection flow through a channel with a rectangular obstacle at the entrance region using non-Newtonian power law fluid. The obstacle is kept at uniformly high temperature whereas the inlet and top wall of the channel are maintained at a temperature lower than obstacle temperature. Poiseuille flow is implemented as the inlet velocity boundary condition. Grid independency test and code validation are performed to justify the computational accuracy before solving the present problem. Galerkin weighted residual method has been appointed to solve the continuity, momentum and energy equations. The problem has been solved for wide range of pertinent parameters like Richardson number (Ri = 0.1 - 10) at a constant Reynolds number (Re = 100), Hartmann number (Ha = 0 - 100), power index (n = 0.6 - 1.6). The flow and thermal field have been thoroughly discussed through streamline and isothermal lines respectively. The heat transfer performance of the given study has been illustrated by average Nusselt number plots. It is observed that increment of Hartmann number (Ha) tends to decrease the heat transfer rate up to a critical value (Ha = 20) and then let increase the heat transfer performance. Thus maximum heat transfer rate has been recorded for higher Hartmann number and Rayleigh number in case of pseudo-plastic (n = 0.6) non-Newtonian fluid flow.
Exploratory study of several advanced nuclear-MHD power plant systems.
NASA Technical Reports Server (NTRS)
Williams, J. R.; Clement, J. D.; Rosa, R. J.; Yang, Y. Y.
1973-01-01
In order for efficient multimegawatt closed cycle nuclear-MHD systems to become practical, long-life gas cooled reactors with exit temperatures of about 2500 K or higher must be developed. Four types of nuclear reactors which have the potential of achieving this goal are the NERVA-type solid core reactor, the colloid core (rotating fluidized bed) reactor, the 'light bulb' gas core reactor, and the 'coaxial flow' gas core reactor. Research programs aimed at developing these reactors have progressed rapidly in recent years so that prototype power reactors could be operating by 1980. Three types of power plant systems which use these reactors have been analyzed to determine the operating characteristics, critical parameters and performance of these power plants. Overall thermal efficiencies as high as 80% are projected, using an MHD turbine-compressor cycle with steam bottoming, and slightly lower efficiencies are projected for an MHD motor-compressor cycle.
Samim Anghaie; Blair Smith; Travis Knight
2002-11-12
This report focuses on the power conversion cycle and efficiency. The technical issues involving the ionization mechanisms, the power management and distribution and radiation shielding and safety will be discussed in future reports.
MHD generators as pulse power sources for arc-driven railguns
Esposito, N.; Raugi, M.; Tellini, A.
1995-01-01
In this paper the performances of an electromagnetic launch system constituted by an arc driven railgun powered by a MHD generator are investigated. A small bore plasma driven railgun for fusion fuel pellet injection is examined considering as pulse power source a MHD generator having characteristics taken from operating devices. The analysis of the railgun and generator has been carried out by means of a lumped parameter equivalent network model that takes into account drag force and ablation effects and allowing the evaluation of the main electrical and thermodynamic quantity distributions of the plasma arc.
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.
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.
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. .
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.
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.
Solar-Driven Liquid-Metal MHD Generator
NASA Technical Reports Server (NTRS)
Hohl, F.; Lee, J. H.
1982-01-01
Liquid-metal magnetohydrodynamic (MHD) power generator with solar oven as its heat source has potential to produce electric power in space and on Earth at high efficiency. Generator focuses radiation from Sun to heat driving gas that pushes liquid metal past magnetic coil. Power is extracted directly from electric currents set up in conducting liquid. Using solar energy as fuel can save considerable costs and payload weight, compared to previous systems.
Not Available
1981-11-01
Program accomplishments in a continuing effort to demonstrate the feasibility of direct coal fired, closed cycle, magnetohydrodynamic power generation are detailed. These accomplishments relate to all system aspects of a CCMHD power generation system including coal combustion, heat transfer to the MHD working fluid, MHD power generation, heat and cesium seed recovery and overall systems analysis. Direct coal firing of the combined cycle has been under laboratory development in the form of a high slag rejection, regeneratively air cooled cyclone coal combustor concept, originated within this program. A hot bottom ceramic regenerative heat exchanger system was assembled and test fired with coal for the purposes of evaluating the catalytic effect of alumina on NO/sub x/ emission reduction and operability of the refractory dome support system. Design, procurement, fabrication and partial installation of a heat and seed recovery flow apparatus was accomplished and was based on a stream tube model of the full scale system using full scale temperatures, tube sizes, rates of temperature change and tube geometry. Systems analysis capability was substantially upgraded by the incorporation of a revised systems code, with emphasis on ease of operator interaction as well as separability of component subroutines. The updated code was used in the development of a new plant configuration, the Feedwater Cooled (FCB) Brayton Cycle, which is superior to the CCMHD/Steam cycle both in performance and cost. (WHK)
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.
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
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.
Closed Cycle Magnetohydrodynamic Nuclear Space Power Generation Using Helium/Xenon Working Plasma
NASA Technical Reports Server (NTRS)
Litchford, R. J.; Harada, N.
2005-01-01
A multimegawatt-class nuclear fission powered closed cycle magnetohydrodynamic space power plant using a helium/xenon working gas has been studied, to include a comprehensive system analysis. Total plant efficiency was expected to be 55.2 percent including pre-ionization power. The effects of compressor stage number, regenerator efficiency, and radiation cooler temperature on plant efficiency were investigated. The specific mass of the power generation plant was also examined. System specific mass was estimated to be 3 kg/kWe for a net electrical output power of 1 MWe, 2-3 kg/kWe at 2 MWe, and approx.2 kg/KWe at >3 MWe. Three phases of research and development plan were proposed: (1) Phase I-proof of principle, (2) Phase II-demonstration of power generation, and (3) Phase III-prototypical closed loop test.
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.
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.
Performance calculations for 200-1000 MWe MHD/steam power plants
NASA Technical Reports Server (NTRS)
Staiger, P. J.
1981-01-01
The effects of MHD generator length, level of oxygen enrichment, and oxygen production power on the performance of MHD/steam power plants ranging from 200 to 1000 MW in electrical output are investigated. The plants considered use oxygen enriched combustion air preheated to 1100 F. Both plants in which the MHD generator is cooled with low temperature and pressure boiler feedwater and plants in which the generator is cooled with high temperature and pressure boiler feedwater are considered. For plants using low temperature boiler feedwater for generator cooling the maximum thermodynamic efficiency is obtained with shorter generators and a lower level of oxygen enrichment compared to plants using high temperature boiler feedwater for generator cooling. The generator length at which the maximum plant efficiency occurs increases with power plant size for plants with a generator cooled by low temperature feedwater. Also shown is the relationship of the magnet stored energy requirement of the generator length and the power plant performance. Possible cost/performance tradeoffs between magnet cost and plant performance are indicated.
Optimization of the oxidant supply system for combined cycle MHD power plants
NASA Technical Reports Server (NTRS)
Juhasz, A. J.
1982-01-01
An in-depth study was conducted to determine what, if any, improvements could be made on the oxidant supply system for combined cycle MHD power plants which could be reflected in higher thermal efficiency and a reduction in the cost of electricity, COE. A systematic analysis of air separation process varitions which showed that the specific energy consumption could be minimized when the product stream oxygen concentration is about 70 mole percent was conducted. The use of advanced air compressors, having variable speed and guide vane position control, results in additional power savings. The study also led to the conceptual design of a new air separation process, sized for a 500 MW sub e MHD plant, referred to a internal compression is discussed. In addition to its lower overall energy consumption, potential capital cost savings were identified for air separation plants using this process when constructed in a single large air separation train rather than multiple parallel trains, typical of conventional practice.
Results from conceptual design study of potential early commercial MHD/steam power plants
NASA Technical Reports Server (NTRS)
Hals, F.; Kessler, R.; Swallom, D.; Westra, L.; Zar, J.; Morgan, W.; Bozzuto, C.
1981-01-01
This paper presents conceptual design information for a potential early MHD power plant developed in the second phase of a joint study of such plants. Conceptual designs of plant components and equipment with performance, operational characteristics and costs are reported on. Plant economics and overall performance including full and part load operation are reviewed. Environmental aspects and the methods incorporated in plant design for emission control of sulfur and nitrogen oxides are reviewed. Results from reliability/availability analysis conducted are also included.
Results from conceptual design study of potential early commercial MHD/steam power plants
NASA Astrophysics Data System (ADS)
Hals, F.; Kessler, R.; Swallom, D.; Westra, L.; Zar, J.; Morgan, W.; Bozzuto, C.
1981-06-01
This paper presents conceptual design information for a potential early MHD power plant developed in the second phase of a joint study of such plants. Conceptual designs of plant components and equipment with performance, operational characteristics and costs are reported on. Plant economics and overall performance including full and part load operation are reviewed. Environmental aspects and the methods incorporated in plant design for emission control of sulfur and nitrogen oxides are reviewed. Results from reliability/availability analysis conducted are also included.
MHD performance demonstration experiment, FY 1974 to FY 1984
NASA Astrophysics Data System (ADS)
Whitehead, G. L.; Christensen, L. S.; Felderman, R. J.
1984-06-01
A national program for the development of commercial, open-cycle, magnetohydrodynamic (MHD) power generation is described. The emphasis of that national program was, and is, on establishing the engineering feasibilty of using coal to fuel the MHD power system. In order to establish feasibility it was necessary to experimentally demonstrate that an MHD generator system simulating a commercial-sized device can convert 16 to 18% of the available thermal energy into electric power at an isentropic efficiency of 60 to 70%. A presidential decree encouraged any government agency which might possess an organic MHD capability to assist ERDA in formulating and executing the national program. Since the largest MHD facility in the United States was located at the Arnold Engineering Development Center (AEDC), it was selected to be the national program element to demonstrate performance. As a result, the AEDC has been under contract since December 1973 (first to ERDA, later to its successor, the department of Energy, DOE) to modify existing equipment and to design, fabricate, and install new hardware to perform the MHD Performance Demonstration Experiment. The MHD facility is described and all results achieved to date are summarized.
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
Closed cycle MHD power generation experiments in the NASA Lewis Facility
NASA Technical Reports Server (NTRS)
Sovie, R. J.; Nichols, L. D.
1974-01-01
Many modifications were made in the MHD facility. These include a redesign of the MHD duct interior, addition of mixing bars, increased electrical isolation of all the high temperature components from each other and from ground, and experimentation with various cesium seed vaporization and injection techniques. With the exception of the cesium system which needs further improvement the above modifications were quite successful and resulted in improvements in generator performance. The facility was run for a total of 400 hours in the past year, with 70 hours of this operation at temperatures of 2000 K or more with hot generator walls. With the exception of replacing one cracked brick in the MHD channel no repairs were required in the high temperature loop components for the duration of these tests. Uniform Faraday and Hall voltage profiles were obtained and the Faraday open circuit voltage varied from 90 to 100 percent of the ideal uBh. The magnitudes of the measured parameters are: Faraday open circuit voltage approximately 70 V, total Faraday current approximately 20 A, Hall voltage approximately 250 V, power output approximately 300 W, and power density .036 W/cu cm.
Performance capabilities of a space-power liquid metal MHD converter
NASA Astrophysics Data System (ADS)
Laborde, R.; Alemany, A.; Werkoff, F.
In a Liquid Metal MHD (or Faraday) converter, thermal energy is converted into electrical energy by the expansion of a condensable fluid, the acceleration of a liquid metal and its circulation through a MHD generator. The performance capabilities of such a converter appear to be very attractive for a utilization in space with lithium and caesium as liquid metal and condensable fluid respectively. A code based on balance equations has been developed to estimate the masses, sizes and efficiencies of all parts of the converters. Iterative methods are used for each part, while the caesium mass flow rate acts as a control parameter in an external loop. Lastly we present results typical of a 200 kW electrical power station.
Methods of reducing energy consumption of the oxidant supply system for MHD/steam power plants
NASA Technical Reports Server (NTRS)
Juhasz, A. J.
1983-01-01
An in-depth study was conducted to identify possible improvements to the oxidant supply system for combined cycle MHD power plants which would lead to higher thermal efficiency and reduction in the cost of electricity, COE. Results showed that the oxidant system energy consumption could be minimized when the process was designed to deliver a product O2 concentration of 70 mole percent. The study also led to the development of a new air separation process, referred to as liquid pumping and internal compression. MHD system performance calculations show that the new process would permit an increase in plant thermal efficiency of 0.6 percent while allowing more favorable tradeoffs between magnetic energy and oxidant system capacity requirements.
Methods of reducing energy consumption of the oxidant supply system for MHD/steam power plants
NASA Technical Reports Server (NTRS)
Juhasz, A. J.
1983-01-01
An in-depth study was conducted to identify possible improvements to the oxidant supply system for combined cycle MHD power plants which would lead to higher thermal efficiency and reduction in the cost of electricity, COE. Results showed that the oxidant system energy consumption could be minimized when the process was designed to deliver a product O2 concentration of 70 mole percent. The study also led to the development of a new air separation process, referred to as 'liquid pumping and internal compression'. MHD system performance calculations show that the new process would permit an increase in plant thermal efficiency of 0.6 percent while allowing more favorable tradeoffs between magnetic energy and oxidant system capacity requirements.
Advanced fusion MHD power conversion using the CFAR (compact fusion advanced Rankine) cycle concept
Hoffman, M.A.; Campbell, R.; Logan, B.G.; Lawrence Livermore National Lab., CA )
1988-10-01
The CFAR (compact fusion advanced Rankine) cycle concept for a tokamak reactor involves the use of a high-temperature Rankine cycle in combination with microwave superheaters and nonequilibrium MHD disk generators to obtain a compact, low-capital-cost power conversion system which fits almost entirely within the reactor vault. The significant savings in the balance-of-plant costs are expected to result in much lower costs of electricity than previous concepts. This paper describes the unique features of the CFAR cycle and a high- temperature blanket designed to take advantage of it as well as the predicted performance of the MHD disk generators using mercury seeded with cesium. 40 refs., 8 figs., 3 tabs.
NASA Technical Reports Server (NTRS)
Smith, J. M.; Nichols, L. D.
1977-01-01
The value of percent seed, oxygen to fuel ratio, combustion pressure, Mach number, and magnetic field strength which maximize either the electrical conductivity or power density at the entrance of an MHD power generator was obtained. The working fluid is the combustion product of H2 and O2 seeded with CsOH. The ideal theoretical segmented Faraday generator along with an empirical form found from correlating the data of many experimenters working with generators of different sizes, electrode configurations, and working fluids, are investigated. The conductivity and power densities optimize at a seed fraction of 3.5 mole percent and an oxygen to hydrogen weight ratio of 7.5. The optimum values of combustion pressure and Mach number depend on the operating magnetic field strength.
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.
NASA Astrophysics Data System (ADS)
Riley, Pete; Linker, Jon A.; Lionello, R.; Mikic, Z.
2012-07-01
The declining phase of solar activity cycle 23 has provided an unprecedented opportunity to study the evolution and properties of corotating interaction regions (CIRs) during unique and relatively steady conditions. The absence of significant transient activity has allowed modelers to test ambient solar wind models, but has also challenged them to reproduce structure that was qualitatively different than had been observed previously (at least within the space era). In this study, we present and analyze global magnetohydrodynamic (MHD) solutions of the inner heliosphere (from 1RS to 1 AU) for several intervals defined as part of a Center for Integrated Space weather Modeling (CISM) interdisciplinary campaign study, and, in particular, Carrington rotation 2060. We compare in situ measurements from ACE and STEREO A and B with the model results to illustrate both the capabilities and limitations of current numerical techniques. We show that, overall, the models do capture the essential structural features of the solar wind for specific time periods; however, there are times when the models and observations diverge. We describe, and, to some extent assess the sources of error in the modeling chain from the input photospheric magnetograms to the numerical schemes used to propagate structure through the heliosphere, and speculate on how they may be resolved, or at least mitigated in the future.
Extended magnetohydrodynamics with embedded particle-in-cell simulation of Ganymede's magnetosphere
NASA Astrophysics Data System (ADS)
Tóth, Gábor; Jia, Xianzhe; Markidis, Stefano; Peng, Ivy Bo; Chen, Yuxi; Daldorff, Lars K. S.; Tenishev, Valeriy M.; Borovikov, Dmitry; Haiducek, John D.; Gombosi, Tamas I.; Glocer, Alex; Dorelli, John C.
2016-02-01
We have recently developed a new modeling capability to embed the implicit particle-in-cell (PIC) model iPIC3D into the Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme magnetohydrodynamic (MHD) model. The MHD with embedded PIC domains (MHD-EPIC) algorithm is a two-way coupled kinetic-fluid model. As one of the very first applications of the MHD-EPIC algorithm, we simulate the interaction between Jupiter's magnetospheric plasma and Ganymede's magnetosphere. We compare the MHD-EPIC simulations with pure Hall MHD simulations and compare both model results with Galileo observations to assess the importance of kinetic effects in controlling the configuration and dynamics of Ganymede's magnetosphere. We find that the Hall MHD and MHD-EPIC solutions are qualitatively similar, but there are significant quantitative differences. In particular, the density and pressure inside the magnetosphere show different distributions. For our baseline grid resolution the PIC solution is more dynamic than the Hall MHD simulation and it compares significantly better with the Galileo magnetic measurements than the Hall MHD solution. The power spectra of the observed and simulated magnetic field fluctuations agree extremely well for the MHD-EPIC model. The MHD-EPIC simulation also produced a few flux transfer events (FTEs) that have magnetic signatures very similar to an observed event. The simulation shows that the FTEs often exhibit complex 3-D structures with their orientations changing substantially between the equatorial plane and the Galileo trajectory, which explains the magnetic signatures observed during the magnetopause crossings. The computational cost of the MHD-EPIC simulation was only about 4 times more than that of the Hall MHD simulation.
Experimental studies on closed cycle MHD power generation with Fuji-1 facility
Okuno, Yoshihiro; Kabashima, Shigeharu; Okamura, Tetsuji; Yoshikawa, Kunio; Tsuji, Kiyoshi; Suekane, Tetsuya; Shioda, Susumu; Yamasaki, Hiroyuki; Hasegawa, Yasuo
1996-12-31
Experimental studies on closed cycle MHD power generation with Fuji-1 blow-down facility at Tokyo Institute of Technology are presented. Recently, a new disk generator (Disk-F4) has been installed and a new seed injection system has been introduced from IVTAN (Institute of High Temperature in Russia). The design concept of the new generator channel is focused mainly on the reliability of high power generation. The Mach number at the generator inlet and the thermal input are increased up to {approximately}2.8 and {approximately}3.0 MW, respectively. In the new seeding system, a melted seed material is pushed by a piston dozator, instead of gas-pressure-driven in the previous system. The controllability of seed fraction is markedly improved, and the large fluctuation as has been observed previously is diminished. In the power generation experiments with the new components, the maximum power output of 502kW and the enthalpy extraction ratio of 16.7% have been obtained. These values at the present stage are lower than the maximum values previously achieved in the facility. However, the reliable high power generation can be expected with the new generator. The behavior of plasma and fluid under high MHD interaction taking place in the generator channel is also discussed.
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.
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.
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.
Three-Dimensional Numerical Modeling of Magnetohydrodynamic Augmented Propulsion Experiment
NASA Technical Reports Server (NTRS)
Turner, M. W.; Hawk, C. W.; Litchford, R. J.
2009-01-01
Over the past several years, NASA Marshall Space Flight Center has engaged in the design and development of an experimental research facility to investigate the use of diagonalized crossed-field magnetohydrodynamic (MHD) accelerators as a possible thrust augmentation device for thermal propulsion systems. In support of this effort, a three-dimensional numerical MHD model has been developed for the purpose of analyzing and optimizing accelerator performance and to aid in understanding critical underlying physical processes and nonideal effects. This Technical Memorandum fully summarizes model development efforts and presents the results of pretest performance optimization analyses. These results indicate that the MHD accelerator should utilize a 45deg diagonalization angle with the applied current evenly distributed over the first five inlet electrode pairs. When powered at 100 A, this configuration is expected to yield a 50% global efficiency with an 80% increase in axial velocity and a 50% increase in centerline total pressure.
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
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.
Study of seed reporcessing systems for open cycle coal fired MHD power plants
Not Available
1980-07-01
If open-cycle coal-fired MHD power generation is to be commercially competitive, a large fraction of the potassium seed must be recycled. Cost of processing the seed for recycle must not be excessive and must be less than the cost of make up seed. A preliminary evaluation of the following processes was performed: PERC; formate; aqueous carbonate; modified tampella; scrubber, with and without removal of ash from spent seed; Tomlinson - Tampella; and electrodialysis and electrodialysis - deionization. Criteria considered in the evaluation included cost, state of development, seed loss, power requirements, availability, durability, key component risk, environmental impact, safety, controllability, and impurities buildup. None of the processes is fully proven for this type recycle operation. All require some degree of development. Results are presented in detail, and recommendations are included. (WHK)
Diagnostic development and support of MHD test facilities
Not Available
1990-01-01
The Diagnostic Instrumentation and Analysis Laboratory (DIAL) at 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 Heat Recovery/Seed Recovery 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 DIAL's computers. Technical support for the diagnostic needs of the national MHD research effort is being provided. DIAL 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. 9 figs., 1 tab.
Preliminary results in the NASA Lewis H2-O2 combustion MHD experiment
NASA Technical Reports Server (NTRS)
Smith, J. M.
1979-01-01
MHD (magnetohydrodynamic) power generation experiments were carried out in the NASA Lewis Research Center cesium-seeded H2-O2 combustion facility. This facility uses a neon-cooled cryomagnet capable of producing magnetic fields in excess of 5 tesla. The effects of power takeoff location, generator loading, B-field strength, and electrode breakdown on generator performance are discussed. The experimental data is compared to a theory based on one-dimensional flow with heat transfer, friction, and voltage drops.
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'.
The MHD disk generator as a multimegawatt power supply operating with chemical and nuclear sources
NASA Astrophysics Data System (ADS)
Louis, J. F.
The characteristics, performance and status of the MHD disk generator are reviewed as a potential multimegawatt power supply working with both chemical and nuclear sources. The disk generator is found to be a compact high interaction power unit with simple construction simple power conditioning and using a circular superconducting coil. The radial flow of the disk assures zero thrust in open loop operation and its construction simplicity may provide significant reliability and weight advantages. The disk generator can be operated as a high voltage, low current power supply. Experiments have shown the disk generator as high power (900 kW), high power density (500 MW/cu cm), high enthalpy extraction (15%) device which has been operated with electrical fields up to 37 kV/m. The disk generator can be operated in an open loop with either chemical or nuclear heat sources. In a closed cycle system, the disk generator can be used in a Braylon cycle using He working fluid and in a Rankin cycle using either potassium or lithium vapors as working fluid. In both cases, the generator operates in the non-equilibrium mode.
Ideal MHD stability of a spherical tokamak power plant and a component test facility.
Hole, M. J.; Wilson, H. R.; Abeysuriya, R.; Larson, J. W.
2010-12-01
We have investigated ideal MHD stability of two advanced spherical tokamak confinement concepts: the spherical tokamak power plant (STPP), a 3 GW concept fusion power plasma producing 1 GW of electric power, and the component test facility (CTF), a concept designed for in situ materials testing for ITER and beyond. Detailed stability studies for toroidal mode number n = 1, 2, 3 displacements are presented as a function of conformal wall radius R{sub w} and on-axis safety factor q{sub 0}. For the STPP marginal stability scans held the current profile fixed, but varied the total plasma current. For the CTF we have extended and parallelized earlier marginal stability scans to scan over both the plasma beta and q{sub 0} by varying the current profile to preserve the total plasma current. These confirm that both concepts are stable provided that the wall is sufficiently close and q{sub 0} sufficiently large (q{sub 0} > 2.8 for the power plant and q{sub 0} > 2.1 for the CTF). Both power plant and CTF configurations are found to be ballooning stable.
Results of closed cycle MHD power generation test with a helium-cesium working fluid
NASA Technical Reports Server (NTRS)
Sovie, R. J.
1977-01-01
The cross sectional dimensions of the MHD channel in the NASA Lewis closed loop facility were reduced to 3.8 x 11.4 cm. Tests were run in this channel using a helium-cesium working fluid at stagnation pressures of 160,000 n/M2, stagnation temperatures of 2000-2060 K and an entrance Mach number of 0.36. In these tests Faraday open circuit voltages of 200 V were measured which correspond to a Faraday field of 1750 V/M. Power generation tests were run for different groups of electrode configurations and channel lengths. Hall fields up to 1450 V/M were generated. Power extraction per electrode of 183 W and power densities of 1.7 MW/M3 were obtained. A total power output of 2 kW was generated for tests with 14 electrodes. The power densities obtained in this channel represent a factor of 3 improvement over those previously reported for the M = 0.2 channel.
Results of closed cycle MHD power generation tests with a helium-cesium working fluid
NASA Technical Reports Server (NTRS)
Sovie, R. J.
1977-01-01
The cross-sectional dimensions of the MHD channel in the NASA Lewis closed loop facility have been reduced to 3.8 x 11.4 cm. Tests were run in this channel using a helium-cesium working fluid at stagnation pressures of 1.6 x 10 to the 5th N/sq m, stagnation temperatures of 2000-2060 K and an entrance Mach number of 0.36. In these tests Faraday open circuit voltages of 200 V were measured which correspond to a Faraday field of 1750 V/m. Power generation tests were run for different groups of electrode configurations and channel lengths. Hall fields up to 1450 V/m were generated. Power extraction per electrode of 183 W and power densities of 1.7 MW/cu m have been obtained. A total power output of 2 kW was generated for tests with 14 electrodes. The power densities obtained in this channel represent a factor of 3 improvement over those reported for the m = 0.2 channel at the last EAM Symposium.
NASA Technical Reports Server (NTRS)
Staiger, P. J.; Penko, P. F.
1982-01-01
The conceptual design study of a potential early commercial MHD power plant (CSPEC) is described and the results are summarized. Each of two contractors did a conceptual design of an approximtely 1000 MWe open-cycle MHD/steam plant with oxygen enriched combustion air preheated to an intermediate temperatue in a metallic heat exchanger. The contractors were close in their overall plant efficiency estimates but differed in their capital cost and cost of electricity estimates, primarily because of differences in balance-of-plant material, contingency, and operating and maintenance cost estimates. One contractor concluded that its MHD plant design compared favorably in cost of electricity with conventional coal-fired steam plants. The other contractor is making such a comparison as part of a follow-on study. Each contractor did a preliminary investigation of part-load performance and plant availability. The results of NASA studies investigating the effect of plant size and oxidizer preheat temperature on the performance of CSPEC-type MHD plants are also described. The efficiency of a 1000 MWe plant is about three points higher than of a 200 MWe plant. Preheating to 1600 F gives an efficiency about one and one-half points higher than preheating to 800 F for all plant sizes. For each plant size and preheat temperature there is an oxidizer enrichment level and MHD generator length that gives the highest plant efficiency.
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.
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
Chang, S.L.; Lottes, S.A.; Petrick, M.
1994-06-01
A three-dimensional, two-phase, turbulent flow computer code was used to predict flow characteristics of seed particles and coal gas in the deswirl section of the CDIF MHD power train system. Seed material which has a great effect on the overall performance of the MHD system is injected in the deswirl against the swirling coal gas flow coming from the first stage combustor. While testing the MHD system, excessive seed material (70% more than theoretical value) was required to achieve design operating conditions. Calculations show that the swirling coal gas flow turns a 90 degree angle to minimize the swirl motion before entering a second stage combustor and many seed particles are too slow to react to the flow turning and deposit on the walls of the deswirl section. Some seed material deposited on the walls is covered by slag layer and removed from the gas flow. The reduction of seed material in the gas flow decreases MHD power generation significantly. A computational experiment was conducted and its results show that seed injection on the wall can be minimized by simply changing the seed injection and an optimum location was identified. If seed is injected from the location of choice, the seed deposition is reduced by a factor of 10 compared to the original case.
Two-dimensional Magnetohydrodynamics and Interstellar Plasma Turbulence
NASA Astrophysics Data System (ADS)
Spangler, Steven R.
1999-09-01
This paper is concerned with a physical understanding of the main features of interstellar plasma turbulence. Our observational knowledge of this turbulence is provided by radio-wave propagation observations, generically referred to as interstellar scintillations. Distinctive features of the observations are the nearly omnipresent anisotropy of scattering, revealed by elliptical rather than circular scattering disks, drastic differences in the magnitude of scattering between closely spaced lines of sight through the interstellar medium, evidence from Faraday rotation observations that the interstellar vector magnetic field changes markedly on small spatial scales, and the existence of a power-law spectrum of density irregularities over a wide range of spatial scales. This power-law density spectrum strongly suggests the existence of similar spatial power spectra for the other magnetohydrodynamic (MHD) variables such as flow velocity and magnetic field. In this paper, it is pointed out that the aforementioned features arise or may naturally be explained by an approximate theory of magnetohydrodynamic turbulence, two-dimensional magnetohydrodynamics. In this theory, the plasma turbulence is described by two scalar functions (a velocity stream function and one component of the magnetic vector potential) that are coupled by nonlinear partial differential equations. These equations are physically transparent, possess some relevant analytic results, and are easily solved numerically. Arguments for the relevance of this reduced plasma description are presented. Although obviously an incomplete description of the interstellar plasma, these equations provide plausible explanations for the observational features described above. Anisotropy of scattering arises as an obvious consequence of the conditions for validity of the two-dimensional MHD description, i.e., that spatial gradients along a large-scale magnetic field are much smaller than those perpendicular to the field
Not Available
1981-11-01
Program accomplishments in a continuing effort to demonstrate the feasibility of direct coal-fired, closed-cycle MHD power generation are reported. This volume contains the following appendices: (A) user's manual for 2-dimensional MHD generator code (2DEM); (B) performance estimates for a nominal 30 MW argon segmented heater; (C) the feedwater cooled Brayton cycle; (D) application of CCMHD in an industrial cogeneration environment; (E) preliminary design for shell and tube primary heat exchanger; and (F) plant efficiency as a function of output power for open and closed cycle MHD power plants. (WHK)
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.
NASA Technical Reports Server (NTRS)
Hals, F. A.
1981-01-01
Plants with a nominal output of 200 and 500 MWe and conforming to the same design configuration as the Task II plant were investigated. This information is intended to permit an assessment of the competitiveness of first generation MHD/steam plants with conventional steam plants over the range of 200 to 1000 MWe. The results show that net plant efficiency of the MHD plant is significantly higher than a conventional steam plant of corresponding size. The cost of electricity is also less for the MHD plant over the entire plant size range. As expected, the cost differential is higher for the larger plant and decreases with plant size. Even at the 200 MWe capacity, however, the differential in COE between the MHD plant and the conventional plant is sufficient attractive to warrant serious consideration. Escalating fuel costs will enhance the competitive position of MHD plants because they can utilize the fuel more efficiently than conventional steam plants.
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.
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.
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.
SPECTRA OF STRONG MAGNETOHYDRODYNAMIC TURBULENCE FROM HIGH-RESOLUTION SIMULATIONS
Beresnyak, Andrey
2014-04-01
Magnetohydrodynamic (MHD) turbulence is present in a variety of solar and astrophysical environments. Solar wind fluctuations with frequencies lower than 0.1 Hz are believed to be mostly governed by Alfvénic turbulence with particle transport depending on the power spectrum and the anisotropy of such turbulence. Recently, conflicting spectral slopes for the inertial range of MHD turbulence have been reported by different groups. Spectral shapes from earlier simulations showed that MHD turbulence is less scale-local compared with hydrodynamic turbulence. This is why higher-resolution simulations, and careful and rigorous numerical analysis is especially needed for the MHD case. In this Letter, we present two groups of simulations with resolution up to 4096{sup 3}, which are numerically well-resolved and have been analyzed with an exact and well-tested method of scaling study. Our results from both simulation groups indicate that the asymptotic power spectral slope for all energy-related quantities, such as total energy and residual energy, is around –1.7, close to Kolmogorov's –5/3. This suggests that residual energy is a constant fraction of the total energy and that in the asymptotic regime of Alfvénic turbulence magnetic and kinetic spectra have the same scaling. The –1.5 slope for energy and the –2 slope for residual energy, which have been suggested earlier, are incompatible with our numerics.
Spectra of Strong Magnetohydrodynamic Turbulence from High-resolution Simulations
NASA Astrophysics Data System (ADS)
Beresnyak, Andrey
2014-04-01
Magnetohydrodynamic (MHD) turbulence is present in a variety of solar and astrophysical environments. Solar wind fluctuations with frequencies lower than 0.1 Hz are believed to be mostly governed by Alfvénic turbulence with particle transport depending on the power spectrum and the anisotropy of such turbulence. Recently, conflicting spectral slopes for the inertial range of MHD turbulence have been reported by different groups. Spectral shapes from earlier simulations showed that MHD turbulence is less scale-local compared with hydrodynamic turbulence. This is why higher-resolution simulations, and careful and rigorous numerical analysis is especially needed for the MHD case. In this Letter, we present two groups of simulations with resolution up to 40963, which are numerically well-resolved and have been analyzed with an exact and well-tested method of scaling study. Our results from both simulation groups indicate that the asymptotic power spectral slope for all energy-related quantities, such as total energy and residual energy, is around -1.7, close to Kolmogorov's -5/3. This suggests that residual energy is a constant fraction of the total energy and that in the asymptotic regime of Alfvénic turbulence magnetic and kinetic spectra have the same scaling. The -1.5 slope for energy and the -2 slope for residual energy, which have been suggested earlier, are incompatible with our numerics.
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.
NASA Astrophysics Data System (ADS)
Toth, G.; Jia, X.; Chen, Y.; Markidis, S.; Peng, B.; Daldorff, L. K. S.; Tenishev, V.; Borovikov, D.; Haiducek, J. D.; Gombosi, T. I.; Glocer, A.; Dorelli, J.; Lapenta, G.
2015-12-01
We have recently developed a new modeling capability to embed the implicit Particle-in-Cell (PIC) model iPIC3D into the BATS-R-US magnetohydrodynamic model. The PIC domain can cover the regions where kinetic effects are most important, such as reconnection sites. The BATS-R-US code, on the other hand, can efficiently handle the rest of the computational domain where the MHD or Hall MHD description is sufficient with its block-adaptive grid. The current implementation of the MHD-EPIC model allows two-way coupled simulations in two and three dimensions with multiple embedded PIC regions. The MHD and PIC grids can have different grid resolutions. The MHD variables and the moments of the PIC distribution functions are interpolated and message passed in an efficient manner through the Space Weather Modeling Framework (SWMF). Both BATS-R-US and iPIC3D are massively parallel codes fully integrated into, run by and coupled through the SWMF. We have successfully applied the MHD-EPIC code to model Ganymede's magnetosphere. Using four PIC regions we have in effect performed a fully kinetic simulation of the moon's mini-magnetosphere with a grid resolution that is about 5 times finer than the ion inertial length. The Hall MHD model provides proper boundary conditions for the four PIC regions and connects them with each other and with the inner and outer outer boundary conditions of the much larger MHD domain. We compare our results with Galileo magnetic observations and find good overall agreement with both Hall MHD and MHD-EPIC simulations. The power spectrum for the small scale fluctuations, however, agrees with the data much better for the MHD-EPIC simulation than for Hall MHD. In the MHD-EPIC simulation, unlike in the pure Hall MHD results, we also find signatures of flux transfer events (FTEs) that agree very well with the observed FTE signatures both in terms of shape and amplitudes. We will also highlight our ongoing efforts to model the magnetospheres of Mercury and
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.
Closed cycle MHD power generation experiments in the NASA Lewis facility
NASA Technical Reports Server (NTRS)
Sovie, R. J.; Nichols, L. D.
1974-01-01
Discussion of the performance improvements achieved through some modifications made in the closed cycle MHD facility. These modifications include a redesign of the MHD duct interior, addition of mixing bars, increased electrical isolation, and experimentation with various cesium seed vaporization and injection techniques. Uniform Faraday and Hall voltage profiles were obtained, and the Faraday open circuit voltage varied from 90 to 100% of the ideal uBh.
NASA Technical Reports Server (NTRS)
Hals, F.; Kessler, R.; Swallom, D.; Westra, L.; Zar, J.; Morgan, W.; Bozzuto, C.
1980-01-01
The study deals with different 'moderate technology' entry-level commercial MHD power plants. Two of the reference plants are based on combustion of coal with air preheated in a high-temperature regenerative air heater separately fired with a low-BTU gas produced in a gasifier integrated with the power plant. The third reference plant design is based on the use of oxygen enriched combustion air. Performance calculations show that an overall power plant efficiency of the order of 44% can be reached with the use of oxygen enrichment.
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.
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.
Survey of MHD plant applications
NASA Technical Reports Server (NTRS)
Lynch, J. J.; Seikel, G. R.; Cutting, J. C.
1979-01-01
Open-cycle MHD is one of the major R&D efforts in the Department of Energy's program to meet the national goal of reducing U.S. dependence on oil through increased utilization of coal. MHD offers an effective way to use coal to produce electric power at low cost in a highly efficient and environmentally acceptable manner. Open-cycle MHD plants are categorized by the MHD combustor oxidizer, its temperature and the method of preheat. The paper discusses MHD baseline plant design, open-cycle MHD plant in the Energy Conversion Alternatives Study (ECAS), early commercial MHD plants, conceptual studies of the engineering test facility, retrofit (addition of an MHD topping cycle to an existing steam plant), and other potential applications and concepts. Emphasis is placed on a survey of both completed and ongoing studies to define both commercial and pilot plant design, cost, and performance.
Single channel double-duct liquid metal electrical generator using a magnetohydrodynamic device
Haaland, Carsten M.; Deeds, W. Edward
1999-01-01
A single channel double-duct liquid metal electrical generator using a magnetohydrodynamic (MHD) device. The single channel device provides useful output AC electric energy. The generator includes a two-cylinder linear-piston engine which drives liquid metal in a single channel looped around one side of the MHD device to form a double-duct contra-flowing liquid metal MHD generator. A flow conduit network and drive mechanism are provided for moving liquid metal with an oscillating flow through a static magnetic field to produce useful AC electric energy at practical voltages and currents. Variable stroke is obtained by controlling the quantity of liquid metal in the channel. High efficiency is obtained over a wide range of frequency and power output.
Single channel double-duct liquid metal electrical generator using a magnetohydrodynamic device
Haaland, C.M.; Deeds, W.E.
1999-07-13
A single channel double-duct liquid metal electrical generator using a magnetohydrodynamic (MHD) device. The single channel device provides useful output AC electric energy. The generator includes a two-cylinder linear-piston engine which drives liquid metal in a single channel looped around one side of the MHD device to form a double-duct contra-flowing liquid metal MHD generator. A flow conduit network and drive mechanism are provided for moving liquid metal with an oscillating flow through a static magnetic field to produce useful AC electric energy at practical voltages and currents. Variable stroke is obtained by controlling the quantity of liquid metal in the channel. High efficiency is obtained over a wide range of frequency and power output. 5 figs.
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.
Approximate Riemann Solvers for the Cosmic Ray Magnetohydrodynamical Equations
NASA Astrophysics Data System (ADS)
Kudoh, Yuki; Hanawa, Tomoyuki
2016-08-01
We analyze the cosmic-ray magnetohydrodynamic (CR MHD) equations to improve the numerical simulations. We propose to solve them in the fully conservation form, which is equivalent to the conventional CR MHD equations. In the fully conservation form, the CR energy equation is replaced with the CR "number" conservation, where the CR number density is defined as the three fourths power of the CR energy density. The former contains an extra source term, while latter does not. An approximate Riemann solver is derived from the CR MHD equations in the fully conservation form. Based on the analysis, we propose a numerical scheme of which solutions satisfy the Rankine-Hugoniot relation at any shock. We demonstrate that it reproduces the Riemann solution derived by Pfrommer et al. (2006) for a 1D CR hydrodynamic shock tube problem. We compare the solution with those obtained by solving the CR energy equation. The latter solutions deviate from the Riemann solution seriously, when the CR pressure dominates over the gas pressure in the post-shocked gas. The former solutions converge to the Riemann solution and are of the second order accuracy in space and time. Our numerical examples include an expansion of high pressure sphere in an magnetized medium. Fast and slow shocks are sharply resolved in the example. We also discuss possible extension of the CR MHD equations to evaluate the average CR energy.
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.
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.
Direct current power generation in self-excited liquid metal magnetohydrodynamic generators
NASA Astrophysics Data System (ADS)
Marty, Ph.
1991-12-01
Results of an analytical and experimental study of a self-excitated liquid-metal magnetohydrodynamic dc generator are reported. Expressions are proposed for the critical velocity and electrical efficiency; the calculated values of these parameters are compared with experimental results obtained for a mercury loop. The transition to the self-excitation regime is investigated numerically, and time dependences of the velocity and generated current are determined. It is shown that the magnitude of the remanent field has a strong effect on the transient period.
Chandran
2000-11-27
Scattering rates for a Goldreich-Sridhar (GS) spectrum of anisotropic, incompressible, magnetohydrodynamic turbulence are calculated in the quasilinear approximation. Because the small-scale fluctuations are constrained to have wave vectors nearly perpendicular to the background magnetic field, scattering is too weak to provide either the mean-free paths commonly used in Galactic cosmic-ray propagation models or the mean-free paths required for acceleration of cosmic rays at quasiparallel shocks. Where strong pitch-angle scattering occurs, it is due to fluctuations not described by the GS spectrum, such as fluctuations generated by streaming cosmic rays. PMID:11082620
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 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 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.
Not Available
1994-07-01
The Diagnostic Instrumentation and Analysis Laboratory (DIAL) at Mississippi State University (MSU) is developing diagnostic instruments for magnetohydrodynamic (MHD) power train data acquisition and for support of MHD component development test facilities. Microprocessor-controlled optical instruments, initially developed for Heat Recovery/Seed Recovery (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 DIAL`s computers. Technical support for the diagnostic needs of the national MHD research effort is being provided. DIAL personnel 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.
Shepard, W.S.; Cook, R.L.
1991-12-31
The Diagnostic Instrumentation and Analysis Laboratory (DIAL) at Mississippi State University (MSU) is developing diagnostic instruments for magnetohydrodynamic (MHD) power train data acquisition and for support of MHD component development test facilities. Microprocessor-controlled optical instruments, initially developed for Heat Recovery/Seed Recovery (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 DIAL`S computers. Technical support for the diagnostic needs of the national MHD research effort is being provided. DIAL personnel 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.
Open-cycle magnetohydrodynamic power plant with CO.sub.2 recycling
Berry, Gregory F.
1991-01-01
A method of converting the chemical energy of fossil fuel to electrical and mechanical energy with a MHD generator. The fossil fuel is mixed with preheated oxygen and carbon dioxide and a conducting seed of potassium carbonate to form a combustive and electrically conductive mixture which is burned in a combustion chamber. The burned combustion mixture is passed through a MHD generator to generate electrical energy. The burned combustion mixture is passed through a diffuser to restore the mixture approximately to atmospheric pressure, leaving a spent combustion mixture which is used to heat oxygen from an air separation plant and recycled carbon dioxide for combustion in a high temperature oxygen preheater and for heating water/steam for producing superheated steam. Relatively pure carbon dioxide is separated from the spent combustion mixture for further purification or for exhaust, while the remainder of the carbon dioxide is recycled from the spent combustion mixture to a carbon dioxide purification plant for removal of water and any nitrous oxides present, leaving a greater than 98% pure carbon dioxide. A portion of the greater then 98% pure carbon dioxide stream is recovered and the remainder is recycled to combine with the oxygen for preheating and combination with the fossil fuel to form a combustion mixture.
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.
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)
[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.
Numerical Modeling on Plasma Gases in an Explosively-Driven Magnetohydrodynamic Generator
NASA Astrophysics Data System (ADS)
Kim, Deok-Kyu; Seo, Min Su; Kim, Inho
2002-11-01
A time-dependent one-dimensional simulation has been carried out on the argon and air plasmas in an explosively-driven magnetohydrodynamic (MHD) power generator. To compute the thermodynamic properties of the plasma gases during the shock compression and jet extraction, we utilize the equation-of-state data calculated from a detailed physical model. The plasma conductivities are given by the mixing rule that compromises the weakly-ionized and fully-ionized limits. The effects of initial gas pressure and applied magnetic field strength are investigated for optimal design of the MHD power generator. For the case of the initial channel pressure of 400 torr and the magnetic field 0.3 T, the maximum output power is estimated up to 0.1 GW with the pulse duration 20 ms, which shows a good agreement with the measured profile.
NASA Technical Reports Server (NTRS)
Staigner, P. J.; Abbott, J. M.
1980-01-01
Two parallel contracted studies were conducted. Each contractor investigated three base cases and parametric variations about these base cases. Each contractor concluded that two of the base cases (a plant using separate firing of an advanced high temperature regenerative air heater with fuel from an advanced coal gasifier and a plant using an intermediate temperature metallic recuperative heat exchanger to heat oxygen enriched combustion air) were comparable in both performance and cost of electricity. The contractors differed in the level of their cost estimates with the capital cost estimates for the MHD topping cycle and the magnet subsystem in particular accounting for a significant part of the difference. The impact of the study on the decision to pursue a course which leads to an oxygen enriched plant as the first commercial MHD plant is described.
Status of power generation experiments in the NASA Lewis closed cycle MHD facility
NASA Technical Reports Server (NTRS)
Sovie, R. J.; Nichols, L. D.
1971-01-01
The design and operation of the closed cycle MHD facility is discussed and results obtained in recent experiments are presented. The main components of the facility are a compressor, recuperative heat exchanger, heater, nozzle, MHD channel with 28 pairs of thoriated tungsten electrodes, cesium condenser, and an argon cooler. The facility has been operated at temperatures up to 2100 K with a cesium-seeded argon working fluid. At low magnetic field strengths, the open circuit voltage, Hall voltage and short circuit current obtained are 90, 69, and 47 percent of the theoretical equilibrium values, respectively. Comparison of this data with a wall and boundary layer leakage theory indicates that the generator has shorting paths in the Hall direction.
An innovative demonstration of high power density in a compact MHD generator
NASA Astrophysics Data System (ADS)
Lineberry, J. T.; Schmidt, H. J.; Chapman, J. N.
1988-05-01
This document is the first semi-annual report for this project. It has been prepared in accordance with contractual reporting obligations and contains a written summary of the research work which has been performed since the beginning of the project through March 31, 1988. During this period, research work has included a variety of studies on several aspects of the overall project as was needed to scope out the requirements for proceeding with a detailed design of experimental hardware. One of the major objectives of these efforts was to provide a definition of operating conditions that are required to allow this MHD system to meet the program objectives. These background studies encompassed detailed analyses of the combustion of the aluminum/carbon (Al:C) solid fuel and evaluations of the gas dynamic characteristics of the combustion plasma produced by combustion. Another major effort was that of analyses and predictions of the performance of conceptual designs for the MHD generator. Both of these tasks were directed at obtaining necessary information which would allow geometric scaling of the experimental MHD system. A summary of the design studies that were performed is given within the body of this report.
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.
Bloom, M. H.
1980-01-01
The aim of this program is to contribute to certain facets of the development of the MHD/coal power system, and particularly the CDIF of DOE with regard to its flow train. Consideration is given specifically to the electrical power take-off, the diagnostic and instrumentation systems, the combustor and MHD channel technology, and electrode alternatives. Within the constraints of the program, high priorities were assigned to the problems of power take-off and the related characteristics of the MHD channel, and to the establishment of a non-intrusive, laser-based diagnostic system. The next priority was given to the combustor modeling and to a significantly improved analysis of particle combustion. Separate abstracts were prepared for nine of the ten papers included. One paper was previously included in the data base. (WHK)
NONIDEAL MAGNETOHYDRODYNAMIC TURBULENT DECAY IN MOLECULAR CLOUDS
Downes, T. P.; O'Sullivan, S.
2009-08-20
It is well known that nonideal magnetohydrodynamic (MHD) effects are important in the dynamics of molecular clouds: both ambipolar diffusion and possibly the Hall effect have been identified as significant. We present the results of a suite of simulations with a resolution of 512{sup 3} of turbulent decay in molecular clouds, incorporating a simplified form of both ambipolar diffusion and the Hall effect simultaneously. The initial velocity field in the turbulence is varied from being super-Alfvenic and hypersonic, through to trans-Alfvenic but still supersonic. We find that ambipolar diffusion increases the rate of decay of the turbulence increasing the decay from t {sup -1.25} to t {sup -1.4}. The Hall effect has virtually no impact in this regard. The power spectra of density, velocity, and the magnetic field are all affected by the nonideal terms, being steepened significantly when compared with ideal MHD turbulence with exponents. The density power-spectra components change from {approx}1.4 to {approx}2.1 for the ideal and nonideal simulations respectively, and power spectra of the other variables all show similar modifications when nonideal effects are considered. Again, the dominant source of these changes is ambipolar diffusion rather than the Hall effect. There is also a decoupling between the velocity field and the magnetic field at short length scales. The Hall effect leads to enhanced magnetic reconnection, and hence less power, at short length scales. The dependence of the velocity dispersion on the characteristic length scale is studied and found not to be power law in nature.
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.
Bloom, M.H.; Lederman, S.; Sforza, P.; Matalon, M.
1980-01-01
This is Part II of the Technical Progress Report on Tasks II-IV of the subject contract. It deals sequentially with Diagnostics and Instrumentation, the MHD Channel and the Combustor. During this period, a significant effort has gone into establishing a schematic design of a laser diagnostic system which can be applied to the flow-train of the MHD system, and to acquiring, assembling and shaking down a laboratory set-up upon which a prototype can be based. With further reference to the MHD Channel, a model analysis has been initiated of the two-dimensional MHD boundary layer between two electrodes in the limit of small magnetic Reynolds numbers with negligible effect of the flow on the applied magnetic field. An objective of this model study is the assessment of variations in initial conditions on the boundary layer behavior. Finally, the problem of combustion modeling has been studied on an initial basis. The open reports on this subject depict a high degree of empiricism, centering attention on global behavior mainly. A quasi-one-dimensional model code has been set-up to check some of the existing estimates. Also a code for equilibrium combustion has been activated.
Magnetohydrodynamic and hybrid simulations of broadband fluctuations near interplanetary shocks
Agim, Y.Z.; Vinas, A.F.; Goldstein, M.L.
1995-09-01
We present results of a theoretical study of evolution of a spectrum of finite amplitude right-hand elliptically polarized magnetohydrodynamic (MHD) waves. The analysis includes use of one-and-a-half-dimensional solutions of the equations that describe compressible MHD together with one-and-a-half-dimensional hybrid simulation of the phenomenon. The motivation of the study is to understand the origin and properties of finite amplitude waves often observed in the vicinity of collisionless shocks in the heliosphere. The solutions of the MHD equations are compared with both the results of the hybrid simulations and observations previously reported by Vinas et al. in the vicinity of a quasi-parallel interplanetary shock. The initial conditions of the MHD solutions were constructed to model the observed spectrum of magnetic and velocity fluctuations; plasma parameters were also chosen to replicate the observed parameters. For the typical parameters of {beta} = 0.5, {sigma}B/B{sub 0} = 0.25 and a spectrum of parallel propagating, circularly polarized dispersive waves, initially the density and magnetic energy density correlations grow due to the (nonlinear) ponderomotive effect. The spectral features below the ion cyclotron frequency are established quickly on the Alfvenic timescale but then persist and match closely the observed fluctuations. The parametric decay instabilities that subsequently appear further enhance the density fluctuations and produce a high-frequency magnetic power spectrum consistent with the spacecraft observation. The MHD and hybrid simulations extend the previous picture of wave generation by a beam-driven ion cyclotron instability to the fully nonlinear stage. 64 refs., 24 figs.
Louis, J F
1980-03-01
Separate entries were made in the data base for the four tasks which include: (1) investigation of electrical behavior in the vicinity of electrode and insulating walls; (2) studies of critical performance issues in the development of combustion disk generators; (3) development and testing of electrode modules, including studies of insulator properties; and (4) determination of coal combustion kinetics and ash behavior relevant to two-stage MHD combustors, and investigation of the mixing and flow aerodynamics of a high swirl geometry second stage. (WHK)
Magneto-hydrodynamics simulation study of deflagration mode in co-axial plasma accelerators
Sitaraman, Hariswaran; Raja, Laxminarayan L.
2014-01-15
Experimental studies by Poehlmann et al. [Phys. Plasmas 17(12), 123508 (2010)] on a coaxial electrode magnetohydrodynamic (MHD) plasma accelerator have revealed two modes of operation. A deflagration or stationary mode is observed for lower power settings, while higher input power leads to a detonation or snowplow mode. A numerical modeling study of a coaxial plasma accelerator using the non-ideal MHD equations is presented. The effect of plasma conductivity on the axial distribution of radial current is studied and found to agree well with experiments. Lower conductivities lead to the formation of a high current density, stationary region close to the inlet/breech, which is a characteristic of the deflagration mode, while a propagating current sheet like feature is observed at higher conductivities, similar to the detonation mode. Results confirm that plasma resistivity, which determines magnetic field diffusion effects, is fundamentally responsible for the two modes.
Magneto-hydrodynamics simulation study of deflagration mode in co-axial plasma accelerators
NASA Astrophysics Data System (ADS)
Sitaraman, Hariswaran; Raja, Laxminarayan L.
2014-01-01
Experimental studies by Poehlmann et al. [Phys. Plasmas 17(12), 123508 (2010)] on a coaxial electrode magnetohydrodynamic (MHD) plasma accelerator have revealed two modes of operation. A deflagration or stationary mode is observed for lower power settings, while higher input power leads to a detonation or snowplow mode. A numerical modeling study of a coaxial plasma accelerator using the non-ideal MHD equations is presented. The effect of plasma conductivity on the axial distribution of radial current is studied and found to agree well with experiments. Lower conductivities lead to the formation of a high current density, stationary region close to the inlet/breech, which is a characteristic of the deflagration mode, while a propagating current sheet like feature is observed at higher conductivities, similar to the detonation mode. Results confirm that plasma resistivity, which determines magnetic field diffusion effects, is fundamentally responsible for the two modes.
NASA Technical Reports Server (NTRS)
Marston, C. H.; Alyea, F. N.; Bender, D. J.; Davis, L. K.; Dellinger, T. C.; Hnat, J. G.; Komito, E. H.; Peterson, C. A.; Rogers, D. A.; Roman, A. J.
1980-01-01
The performance and cost of moderate technology coal-fired open cycle MHD/steam power plant designs which can be expected to require a shorter development time and have a lower development cost than previously considered mature OCMHD/steam plants were determined. Three base cases were considered: an indirectly-fired high temperature air heater (HTAH) subsystem delivering air at 2700 F, fired by a state of the art atmospheric pressure gasifier, and the HTAH subsystem was deleted and oxygen enrichment was used to obtain requisite MHD combustion temperature. Coal pile to bus bar efficiencies in ease case 1 ranged from 41.4% to 42.9%, and cost of electricity (COE) was highest of the three base cases. For base case 2 the efficiency range was 42.0% to 45.6%, and COE was lowest. For base case 3 the efficiency range was 42.9% to 44.4%, and COE was intermediate. The best parametric cases in bases cases 2 and 3 are recommended for conceptual design. Eventual choice between these approaches is dependent on further evaluation of the tradeoffs among HTAH development risk, O2 plant integration, and further refinements of comparative costs.
Magnetohydrodynamic Augmented Propulsion Experiment
NASA Technical Reports Server (NTRS)
Litchford, Ron J.
2008-01-01
Over the past several years, efforts have been under way to design and develop an operationally flexible research facility for investigating the use of cross-field MHD accelerators as a potential thrust augmentation device for thermal propulsion systems. The baseline configuration for this high-power experimental facility utilizes a 1.5-MWe multi-gas arc-heater as a thermal driver for a 2-MWe MHD accelerator, which resides in a large-bore 2-tesla electromagnet. A preliminary design study using NaK seeded nitrogen as the working fluid led to an externally diagonalized segmented MHD channel configuration based on an expendable heat-sink design concept. The current status report includes a review of engineering/design work and performance optimization analyses and summarizes component hardware fabrication and development efforts, preliminary testing results, and recent progress toward full-up assembly and testing
Magnetohydrodynamic Augmented Propulsion Experiment: I. Performance Analysis and Design
NASA Technical Reports Server (NTRS)
Litchford, R. J.; Cole, J. W.; Lineberry, J. T.; Chapman, J. N.; Schmidt, H. J.; Lineberry, C. W.
2003-01-01
The performance of conventional thermal propulsion systems is fundamentally constrained by the specific energy limitations associated with chemical fuels and the thermal limits of available materials. Electromagnetic thrust augmentation represents one intriguing possibility for improving the fuel composition of thermal propulsion systems, thereby increasing overall specific energy characteristics; however, realization of such a system requires an extremely high-energy-density electrical power source as well as an efficient plasma acceleration device. This Technical Publication describes the development of an experimental research facility for investigating the use of cross-field magnetohydrodynamic (MHD) accelerators as a possible thrust augmentation device for thermal propulsion systems. In this experiment,a 1.5-MW(sub e) Aerotherm arc heater is used to drive a 2-MW(sub e) MHD accelerator. The heatsink MHD accelerator is configured as an externally diagonalized, segmented channel, which is inserted into a large-bore, 2-T electromagnet. The performance analysis and engineering design of the flow path are described as well as the parameter measurements and flow diagnostics planned for the initial series of test runs.
MHD performance demonstration experiment, October 1, 1080-September 30, 1981
Whitehead, G. L.; Christenson, L. S.; Felderman, E. J.; Lowry, R. L.; Bordenet, E. J.
1981-12-01
The Arnold Engineering Development Center (AEDC) has been under contract with the Department of Energy (DOE) since December 1973 to conduct a magnetohydrodynamic (MHD) High Performance Demonstration Experiment (HPDE). The objective of this experimental research is to demonstrate the attainment of MHD performance on a sufficiently large scale to verify that projected commercial MHD objectives are possible. This report describes the testing of the system under power-producing conditions during the period from October 1, 1980 to September 30, 1981. Experimental results have been obtained with the channel configured in the Faraday mode. Test conditions were selected to produce low supersonic velocity along the entire channel length. Tests have been conducted at magnetic fields up to 4.1 Tesla (T) (70% of design). Up to 30.5 MW of power has been produced to date (60% of design) for an enthalpy extraction of approximately 11%. The high Hall voltage transient, observed during the previous series of tests has been reduced. The reduction is mostly probably due to the fuel and seed being introduced simultaneously. The replacement of the ATJ graphite caps on the electrode walls with pyrolytic graphite caps has resulted in significantly higher surface temperature. As a result, the voltage drop is some 60% of the cold wall voltage drop during the previous series of tests. However, the absolute value of the present voltage drop is still greater than the original design predictions. Test results indicate, however, that the overall enthalpy extraction objective can be achieved.
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.
Specific Mass Estimates for A Vapor Core Reactor With MHD
Knight, Travis; Smith, Blair; Anghaie, Samim
2002-07-01
This study investigated the development of a system concept for space power generation and nuclear electric propulsion based on a vapor core reactor (VCR) with magnetohydrodynamic (MHD) power conversion system, coupled to a magnetoplasma-dynamic (MPD) thruster. The VCR is a liquid-vapor core reactor concept operating with metallic uranium or uranium tetrafluoride (UF{sub 4}) vapor as the fissioning fuel and alkali metals or their fluorides as working fluid in a closed Rankine cycle with MHD energy conversion. Gaseous and liquid-vapor core reactors can potentially provide the highest reactor and cycle temperature among all existing or proposed fission reactor designs. This unique feature makes this reactor concept a very natural and attractive candidate for very high power (10 to 1000 MWe) and low specific mass (0.4 to 5 kg/kWe) nuclear electric propulsion (NEP) applications since the MHD output could be coupled with minimal power conditioning to MPD thrusters or other types of thruster for producing thrust at very high specific impulse (I{sub sp} 1500 to 10,000 s). The exceptional specific mass performance of an optimized VCRMHD- NEP system could lead to a dramatic reduction in the cost and duration of manned or robotic interplanetary as well as interstellar missions. The VCR-MHD-NEP system could enable very efficient Mars cargo transfers or short (<8 month) Mars round trips with less initial mass in low Earth orbit (IMLEO). The system could also enable highly efficient lunar cargo transfer and rapid missions to other destinations throughout the solar system. (authors)
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.
NASA Technical Reports Server (NTRS)
Sovie, R. J.; Winter, J. M.; Juhasz, A. J.; Berg, R. D.
1982-01-01
A conceptual design study of the MHD/steam plant that incorporates the use of oxygen enriched air preheated in a metallic heat exchanger as the combustor oxidant showed that this plant is the most attractive for early commercial applications. The variation of performance and cost was investigated as a function of plant size. The contractors' results for the overall efficiencies are in reasonable agreement considering the slight differences in their plant designs. NASA LeRC is reviewing cost and performance results for consistency with those of previous studies, including studies of conventional steam plants. LeRC in house efforts show that there are still many tradeoffs to be considered for these oxygen enriched plants and considerable variations can be made in channel length and level of oxygen enrichment with little change in overall plant efficiency.
NASA Astrophysics Data System (ADS)
Sovie, R. J.; Winter, J. M.; Juhasz, A. J.; Berg, R. D.
A conceptual design study of the MHD/steam plant that incorporates the use of oxygen enriched air preheated in a metallic heat exchanger as the combustor oxidant showed that this plant is the most attractive for early commercial applications. The variation of performance and cost was investigated as a function of plant size. The contractors' results for the overall efficiencies are in reasonable agreement considering the slight differences in their plant designs. NASA LeRC is reviewing cost and performance results for consistency with those of previous studies, including studies of conventional steam plants. LeRC in house efforts show that there are still many tradeoffs to be considered for these oxygen enriched plants and considerable variations can be made in channel length and level of oxygen enrichment with little change in overall plant efficiency.
MHD and Kinetic Modeling of the Ionospheres of Venus and Mars
Shinagawa, H.; Terada, N.
2009-06-16
It is widely recognized that both Venus and Mars possess no significant global intrinsic magnetic fields, and that the solar wind interacts directly with the upper atmospheres and ionospheres of Venus and Mars. In addition, local crustal magnetic fields are also present in various regions at Mars, suggesting that some regions of the Martian ionosphere are influenced not only by the solar wind but also by the crustal magnetic field. Previous studies have suggested that the basic structures of the ionospheres of the planets can be described by fluid and MHD(magnetohydrodynamic) processes. Various models of the ionospheres of Venus and Mars based on the MHD formulation have been constructed during the last two decades. Although the MHD approach has been successful in reproducing the ionospheres of the planets, some studies have indicated that MHD modeling is not necessarily appropriate in the regions of the topside ionosphere, the ionopause, and the magnetosheath, where the ion kinetic processes are likely to play an important role. The kinetic processes in the topside ionosphere might have significant influences even in the lower ionosphere. Thanks to a great progress made for computer power as well as the efficiency of calculations of the hybrid model, high-resolution kinetic models of the solar wind interaction with Venus and Mars, which self-consistently include the ionosphere, have been developed. In this paper, status of MHD and kinetic modeling of the ionospheres of Venus and Mars is briefly reviewed.
A Leaky Waveguide Model for MHD Wave Driven Winds from Coronal Holes
NASA Technical Reports Server (NTRS)
Davila, J. M.
1985-01-01
Magnetohydrodynamic (MHD) waves, driven by the large scale convective motions of the photosphere are suggested as a possible source of additional acceleration for the stellar wind. Most of the turbulent power in a coronal hole is carried by MHD waves with periods of a few hundred seconds or longer. This is evident from direct observations of turbulence in the solar photosphere, as well as in situ observations of turbulence in the solar wind. But waves with periods this long have wavelengths which are typically as large as the transverse scale of the coronal hole flux tube itself. For these waves boundary effects are important and the coronal hole must be treated as a waveguide. The propagation of MHD waves using this waveguide approach is discussed. The simple model presented demonstrates that coronal holes can act as waveguides for MHD waves. For typical solar parameters the waves are compressible and can generate a wave tensile force which tends to cancel at least part of the wave pressure force. This effect tends to decrease the efficiency of MHD wave acceleration.
Scaling of (MHD) instabilities in imploding plasma liners
Hussey, T.W.; Roderick, N.F.; Kloc, D.A.
1980-03-01
The dynamics of imploding foil plasmas is considered using first-order theory to model the implosion and to investigate the effects of magnetohydrodynamic instabilities on the structure of the plasma sheath. The effects of the acceleration-produced magnetohydrodynamic (MHD) Rayleigh-Taylor instability and a wall-associated instability are studied for a variety of plasma implosion times for several pulsed power drivers. The basic physics of these instabilities is identified and models are developed to explain both linear and nonlinear behavior. These models are compared with the results of detailed two-dimensional magnetohydrodynamic simulations. Expressions for linear Rayleigh-Taylor growth are developed showing its dependence on driving current, plasma conductivity, and density gradient scale length. A nonlinear saturation model, based on magnetic field diffusion, is developed. The model for a wall instability involves the interaction of the plasma sheath with the electrode wall and the material ablated from the electrode. The growth of this instability is shown to be limited by field diffusion. Comparison with two-dimensional simulations has been excellent.
System study of an MHD/gas turbine combined-cycle baseload power plant. HTGL report No. 134
Annen, K.D.
1981-08-01
The MHD/gas turbine combined-cycle system has been designed specifically for applications where the availability of cooling water is very limited. The base case systems which were studied consisted of an MHD plant with a gas turbine bottoming plant, and required no cooling water. The gas turbine plant uses only air as its working fluid and receives its energy input from the MHD exhaust gases by means of metal tube heat exchangers. In addition to the base case systems, vapor cycle variation systems were considered which included the addition of a vapor cycle bottoming plant to improve the thermal efficiency. These systems required a small amount of cooling water. The MHD/gas turbine systems were modeled with sufficient detail, using realistic component specifications and costs, so that the thermal and economic performance of the system could be accurately determined. Three cases of MHD/gas turbine systems were studied, with Case I being similar to an MHD/steam system so that a direct comparison of the performances could be made, with Case II being representative of a second generation MHD system, and with Case III considering oxygen enrichment for early commercial applications. The systems are nominally 800 MW/sub e/ to 1000 MW/sub e/ in size. The results show that the MHD/gas turbine system has very good thermal and economic performances while requiring either little or no cooling water. Compared to the MHD/steam system which has a cooling tower heat load of 720 MW, the Base Case I MHD/gas turbine system has a heat rate which is 13% higher and a cost of electricity which is only 7% higher while requiring no cooling water. Case II results show that an improved performance can be expected from second generation MHD/gas turbine systems. Case III results show that an oxygen enriched MHD/gas turbine system may be attractive for early commercial applications in dry regions of the country.
NASA Technical Reports Server (NTRS)
Sovie, R. J.
1976-01-01
The MHD channel in the NASA Lewis Research Center was redesigned and used in closed cycle power generation experiments with a helium-cesium working fluid. The cross sectional dimensions of the channel were reduced to 5 by 16.5 cm to allow operation over a variety of conditions. Experiments have been run at temperatures of 1900-2100 K and Mach numbers from 0.3 to 0.55 in argon and 0.2 in helium. Improvements in Hall voltage isolation and seed vaporization techniques have resulted in significant improvements in performance. Typical values obtained with helium are Faraday open circuit voltage 141 V (92% of uBh) at a magnetic field strength of 1.7 T, power outputs of 2.2 kw for tests with 28 electrodes and 2.1 kw for tests with 17 electrodes. Power densities of 0.6 MW/cu m and Hall fields of about 1100 V/m were obtained in the tests with 17 electrodes, representing a factor of 18 improvement over previously reported results. The V-I curves and current distribution data indicate that while near ideal equilibrium performance is obtained under some conditions, no nonequilibrium power has been generated to date.
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.
Long-term evolution of decaying magnetohydrodynamic turbulence in the multiphase interstellar medium
Kim, Chang-Goo; Basu, Shantanu E-mail: basu@uwo.ca
2013-12-01
Supersonic turbulence in the interstellar medium (ISM) is believed to decay rapidly within a flow crossing time irrespective of the degree of magnetization. However, this general consensus of decaying magnetohydrodynamic (MHD) turbulence relies on local isothermal simulations, which are unable to take into account the roles of the global structures of magnetic fields and the ISM. Utilizing three-dimensional MHD simulations including interstellar cooling and heating, we investigate decaying MHD turbulence within cold neutral medium sheets embedded in a warm neutral medium. The early evolution of turbulent kinetic energy is consistent with previous results for decaying compressible MHD turbulence characterized by rapid energy decay with a power-law form of E∝t {sup –1} and by a short decay time compared with the flow crossing time. If initial magnetic fields are strong and perpendicular to the sheet, however, long-term evolution of the kinetic energy shows that a significant amount of turbulent energy (∼0.2E {sub 0}) still remains even after 10 flow crossing times for models with periodic boundary conditions. The decay rate is also greatly reduced as the field strength increases for such initial and boundary conditions, but not if the boundary conditions are those for a completely isolated sheet. We analyze velocity power spectra of the remaining turbulence to show that in-plane, incompressible motions parallel to the sheet dominate at later times.
Not Available
1992-11-01
Westinghouse Advanced Energy Systems (WAES), through Contract No. DE-AC22-87PC79668 funded by US DOE/PETC, is conducting a conceptual design study to evaluate a coal-fired magnetohydrodynamic (MHD) retrofit of a utility plant of sufficient size to demonstrate the technical and future economic viability of an MHD system operating within an electric utility environment. The objective of this topical report is to document continuing seed regeneration system application studies and the definition of will system integration requirements for the Scholz MHD retrofit plant design. MHD power plants require the addition of a seeding material in the form of potassium to enhance the ionization of the high temperature combustion gas in the MHD channel. This process has an added environmental advantage compared to other types of coal-fired power plants in that the potassium combines with the naturally occurring sulfur in the coal to form a potassium sulfate flyash (K{sub 2}SO{sub 4}) which can be removed from the process by appropriate particulate control equipment. Up to 100% of the Sulfur in the coal can be removed by this process thereby providing environmentally clean power plant operation that is better than required by present and anticipated future New Source Performance Standards (NSPS).
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.
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.
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.
Phase transition-like behavior of magnetospheric substorms: Global MHD simulation results
NASA Astrophysics Data System (ADS)
Shao, X.; Sitnov, M. I.; Sharma, S. A.; Papadopoulos, K.; Goodrich, C. C.; Guzdar, P. N.; Milikh, G. M.; Wiltberger, M. J.; Lyon, J. G.
2003-01-01
Using nonlinear dynamical techniques, we statistically investigate whether the simulated substorms from global magnetohydrodynamic (MHD) models have a combination of global and multiscale features, revealed in substorm dynamics by [2000] and featured the phase transition-like behavior. We simulate seven intervals of total duration of 280 hours from the data set used in the above works [, 1985]. We analyze the input-output (vBs-pseudo AL index) system obtained from the global MHD model and compare the results to those inferred from the original set (vBs-observed AL index). The analysis of the coupled vBs-pseudo AL index system shows the first-order phase transition map, which is consistent with the map obtained for the vBs-observed AL index system. Although the comparison between observations and global MHD simulations for individual events may vary, the overall global transition pattern during the substorm cycle revealed by singular spectrum analysis (SSA) is statistically consistent between simulations and observations. The coupled vBs-pseudo AL index system also shows multiscale behavior (scale-invariant power law dependence) in SSA power spectrum. Besides, we find the critical exponent of the nonequilibrium transitions in the magnetosphere, which reflects the multiscale aspect of the substorm activity, different from power law frequency of autonomous systems. The exponent relates input and output parameters of the magnetosphere. We also discuss the limitations of the global MHD model in reproducing the multiscale behavior when compared to the real system.
Multimegawatt nuclear electric propulsion with gaseous and vapor core reactors with MHD
NASA Astrophysics Data System (ADS)
Knight, Travis; Anghaie, Samim; Smith, Blair; Houts, Michael
2001-02-01
This study investigated the development of a system concept for space power generation and nuclear electric propulsion based on a fissioning plasma core reactor (FPCR) with magnetohydrodynamic (MHD) power conversion system, coupled to a magnetoplasmadynamic (MPD) thruster. The FPCR is a liquid-vapor core reactor concept operating with metallic uranium or uranium tetrafluoride (UF4) vapor as the fissioning fuel and alkali metals or their fluorides as working fluid in a closed Rankine cycle with MHD energy conversion. Candidate working fluids include K, Li, Na, KF, LiF, NaF, etc. The system features core outlet temperatures of 3000 to 4000 K at pressures of about 1 to 10 MPa, MHD temperatures of 2000 to 3000 K, and radiator temperatures of 1200 to 2000 K. This combination of parameters offers the potential for low total system specific mass in the range of 0.4 to 0.6 kg/kWe. The MHD output could be coupled with minimal power conditioning to the variable specific impulse magnetoplasma rocket (VASIMR), MPD thrusters or other types of thruster for producing thrust at very high specific impulse (Isp=1500 to 10,000 s). .
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.
Possible signatures of nonlinear MHD waves in the solar wind: UVCS observations and models
NASA Technical Reports Server (NTRS)
Ofman, L.; Romoli, M.; Davila, J. M.; Poletto, G.; Kohl, J.; Noci, G.
1997-01-01
Recent ultraviolet coronagraph spectrometer (UVCS) white light channel observations are discussed. These data indicated quasi-periodic variations in the polarized brightness in the polar coronal holes. The Fourier power spectrum analysis showed significant peaks at about six minutes and possible fluctuations on longer time scales. The observations are consistent with the predictions of the nonlinear solitary-like wave model. The purpose of a planned study on plume and inter-plume regions of coronal holes, motivated by the result of a 2.5 magnetohydrodynamic model (MHD), is explained.
BOOK REVIEW: Nonlinear Magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Shafranov, V.
1998-08-01
equations of a plasma in a magnetic field (which will be used further in models of dynamic processes), approaches to the description of three dimensional (3-D) equilibrium are briefly discussed, and the basis of the theory of linear instabilities and the basic types of MHD instabilities, with account taken of ideal resistive modes, are considered. The value of the material of these chapters is that here in a brief form the results of numerous researches in this area are presented, and frequently with a fresh point of view of old results. Chapters 5 to 10 are devoted to the subject of the book, non-linear magnetohydrodynamics. In the introduction to Chapter 5 the author pays attention to the fact that long standing doubts about the feasibility of magnetic thermonuclear reactors because of inevitable instabilities of non-uniform plasmas have been overcome in the last two decades: the plasma in tokamaks is rather well confined, despite the presence of some instabilities. The latter, as a rule, result only in the redistribution of current and plasma pressure profiles and some increase of transport, but can also lead to extremely undesirable effects. In this connection in Chapter 5 the attention of the reader is directed to the physics of the most important plasma instabilities in tokamaks. Models of the development of external and internal kink modes in tokamaks are considered, including the `vacuum bubble' model in shearless plasmas, the evolution of the resistive tearing mode together with saturation of the magnetic islands arising at a tearing instability. The rather long Chapter 6 is devoted to the fundamentals of the magnetic hydrodynamic dissipative process in the magnetic field line reconnection. This process of rapid dissipation of the energy of a magnetic field, having in the simplest case different directions in two adjacent volumes of plasma, underlies the theory of the phenomenon of powerful flares in the solar chromosphere, resulting in the well-known `magnetic
Not Available
1995-02-01
The Diagnostic Instrumentation and Analysis Laboratory (DIAL) at Mississippi State University (MSU), under U.S. Department of Energy (DOE) Contract No. DE-AC02-80ET-15601, Diagnostic Development and Support of MHD Test Facilities, developed diagnostic instruments for magnetohydrodynamic (MHD) power train data acquisition and for support of MHD component development test facilities. Microprocessor-controlled optical instruments, initially developed for Heat Recovery/Seed Recovery (HRSR) support, were refined, and new systems to measure temperatures and gas-seed-slag stream characteristics were developed. To further data acquisition and analysis capabilities, the diagnostic systems were interfaced with DIAL`s computers. Technical support was provided for the diagnostic needs of the national MHD research effort. DIAL personnel also cooperated with government agencies and private industries to improve the transformation of research and development results into processes, products and services applicable to their needs. The initial contract, Testing and Evaluation of Heat Recovery/Seed Recovery, established a data base on heat transfer, slagging effects on heat transfer surfaces, metal durability, secondary combustor performance, secondary combustor design requirements, and other information pertinent to the design of HR/SR components at the Coal-Fired Flow Facility (CFFF). To accomplish these objectives, a combustion test stand was constructed that simulated MHD environments, and mathematical models were developed and evaluated for the heat transfer in hot-wall test sections. Two transitions occurred during the span of this contract. In May 1983, the objectives and title of the contract changed from Testing and Evaluation of Heat Recovery/Seed Recovery to Diagnostic Development and Support of MHD Test Facilities. In July 1988, the research laboratory`s name changed from the MHD Energy Center to the Diagnostic Instrumentation and Analysis Laboratory.
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 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 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).
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.
Dana, R.A.
1988-01-01
This Topical Report presents the results of Task 1 of the Feasibility Assessment for Space Based Multimegawatt MHD Power Systems program. It consists of two volumes. Volume 1 contains the results of the work performed in Task 1 as presented and discussed in Sections 2 through 6. Section 2 is an executive summary of the work. Section 3 contains a complete description of the space based multimegawatt MHD power system conceptual design. System performance and operations characteristics are also identified. It has been assumed in Task 1 that the system provides power to a Neutral Particle Beam (NPB) Weapon, for which generic load requirements are presented. Integration of the power system and NPB with alternative space launch vehicles is also discussed in this section. Section 4 contains a discussion of key technical issues and questions requiring additional investigation. Section 5 presents the Research and Development plan which is proposed for Task 2. Conclusions and Recommendations are contained in Section 6. Volume 2 of the report contains the System Requirements, Design Guidelines and Assumptions for the space based multimegawatt MHD power system. This is an initial system specification document which will be refined during the course of Task 2.
Murphree, D.L.; Cook, R.L.; Bauman, L.E.
1981-01-01
Highly efficient and environmentally acceptable, the coal-fired MHD power plant is an attractive facility for producing electricity. The design of its downstream system, however, presents technological risks which must be corrected if such a plant is to be commercially viable before the end of the century. The heat recovery/seed recovery system (HRSR) at its present stage is vulnerable to corrosion on the gas side of the radiant furnace, the secondary superheater, and the intermediate temperature air heater. Slagging and fouling of the heat transfer surface have yet to be eliminated. Gas chemistry, radiant heat transfer, and particulate removal are other problematic areas which are being researched in a DOE development program whose test activities at three facilities are contributing to an MHD/HRSR data base. In addition, a 20 MWt system to study HRSR design, is being now assembled in Tennessee.
NASA Technical Reports Server (NTRS)
Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.
1975-01-01
Terminal voltage measurements with various cathodes and anodes in a high power, quasi-steady magnetoplasmadynamic (MPD) are discussed. The magnitude of the current at the onset of voltage fluctuations is shown to be an increasing function of cathode area and a weaker decreasing function of anode area. Tests with a fluted cathode indicated that the fluctuations originate in the plasma adjacent to the cathode rather than at the cathode surface. Measurements of radiative output from an optical cavity aligned to examine the current-carrying portion of a two-dimensional, 56 kA magnetoplasmadynamic discharge reveal no lasing in that region, consistent with calculations of electron excitation and resonance radiation trapping. A voltage-swept double probe technique allows single-shot determination of electron temperature and electron number density in the recombining MPD exhaust flow. Current distributions within the cavity of MPD hollow cathodes for various static prefills with no injected mass flow are examined.
NASA Technical Reports Server (NTRS)
Sovie, R. J.
1976-01-01
A MHD channel, which was previously operated for over 500 hours of thermal operation, ten thermal cycles, and 200 cesium injection tests, was removed from the facility and redesigned. The cross sectional dimensions of the channel were reduced to 5 by 16.5 cm to allow operation over a variety of conditions. The redesigned channel has been operated for well over 300 hours, 10 thermal cycles, and 150 cesium injection tests with no problems. Experiments have been run at temperatures of 1900-2100 K and Mach numbers from 0.3 to 0.55 in argon and 0.2 in helium. The best results to date have been obtained in the helium tests. Power outputs of 2.2 kw for tests with 28 electrodes and 2.1 kw for tests with 17 electrodes were realized. Power densities of 0.6 MW/cu m and Hall fields of about 1,100 V/m were obtained in the tests with 17 electrodes.
NASA Astrophysics Data System (ADS)
Murakami, Tomoyuki; Zhuang, Yunqin; Okuno, Yoshihiro
2013-02-01
We describe high-density magnetohydrodynamic (MHD) energy conversion in a high-temperature seed-free argon plasma, for which a compact linear-shaped Faraday-type MHD electrical power generator is used. Short-time-duration single-pulse shock-tunnel-based experiments demonstrate the MHD energy conversion with varying total inflow temperature up to 9000 K and applied magnetic-flux density up to 4.0 T. The high-temperature plasma is transformed from the thermal-equilibrium state at the entrance to the weak-nonequilibrium state in the supersonic MHD channel. The discharge structure is reasonably homogeneous without suffering from serious streamer development. The power generation performance is monotonically improved by increasing total inflow temperature and strength of magnetic field. The enthalpy extraction efficiency of 13.1% and overall power density of 0.16 GW/m3 are attained. The local power density at the middle of the channel reaches 0.24 GW/m3.
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
Solar Wind Turbulence from MHD to Sub-ion Scales: High-resolution Hybrid Simulations
NASA Astrophysics Data System (ADS)
Franci, Luca; Verdini, Andrea; Matteini, Lorenzo; Landi, Simone; Hellinger, Petr
2015-05-01
We present results from a high-resolution and large-scale hybrid (fluid electrons and particle-in-cell protons) two-dimensional numerical simulation of decaying turbulence. Two distinct spectral regions (separated by a smooth break at proton scales) develop with clear power-law scaling, each one occupying about a decade in wavenumbers. The simulation results simultaneously exhibit several properties of the observed solar wind fluctuations: spectral indices of the magnetic, kinetic, and residual energy spectra in the magnetohydrodynamic (MHD) inertial range along with a flattening of the electric field spectrum, an increase in magnetic compressibility, and a strong coupling of the cascade with the density and the parallel component of the magnetic fluctuations at sub-proton scales. Our findings support the interpretation that in the solar wind, large-scale MHD fluctuations naturally evolve beyond proton scales into a turbulent regime that is governed by the generalized Ohm’s law.
Gas Core Reactor Numerical Simulation Using a Coupled MHD-MCNP Model
NASA Technical Reports Server (NTRS)
Kazeminezhad, F.; Anghaie, S.
2008-01-01
Analysis is provided in this report of using two head-on magnetohydrodynamic (MHD) shocks to achieve supercritical nuclear fission in an axially elongated cylinder filled with UF4 gas as an energy source for deep space missions. The motivation for each aspect of the design is explained and supported by theory and numerical simulations. A subsequent report will provide detail on relevant experimental work to validate the concept. Here the focus is on the theory of and simulations for the proposed gas core reactor conceptual design from the onset of shock generations to the supercritical state achieved when the shocks collide. The MHD model is coupled to a standard nuclear code (MCNP) to observe the neutron flux and fission power attributed to the supercritical state brought about by the shock collisions. Throughout the modeling, realistic parameters are used for the initial ambient gaseous state and currents to ensure a resulting supercritical state upon shock collisions.
Converging cylindrical shocks in ideal magnetohydrodynamics
Pullin, D. I.; Mostert, W.; Wheatley, V.; Samtaney, R.
2014-09-15
We consider a cylindrically symmetrical shock converging onto an axis within the framework of ideal, compressible-gas non-dissipative magnetohydrodynamics (MHD). In cylindrical polar co-ordinates we restrict attention to either constant axial magnetic field or to the azimuthal but singular magnetic field produced by a line current on the axis. Under the constraint of zero normal magnetic field and zero tangential fluid speed at the shock, a set of restricted shock-jump conditions are obtained as functions of the shock Mach number, defined as the ratio of the local shock speed to the unique magnetohydrodynamic wave speed ahead of the shock, and also of a parameter measuring the local strength of the magnetic field. For the line current case, two approaches are explored and the results compared in detail. The first is geometrical shock-dynamics where the restricted shock-jump conditions are applied directly to the equation on the characteristic entering the shock from behind. This gives an ordinary-differential equation for the shock Mach number as a function of radius which is integrated numerically to provide profiles of the shock implosion. Also, analytic, asymptotic results are obtained for the shock trajectory at small radius. The second approach is direct numerical solution of the radially symmetric MHD equations using a shock-capturing method. For the axial magnetic field case the shock implosion is of the Guderley power-law type with exponent that is not affected by the presence of a finite magnetic field. For the axial current case, however, the presence of a tangential magnetic field ahead of the shock with strength inversely proportional to radius introduces a length scale R=√(μ{sub 0}/p{sub 0}) I/(2 π) where I is the current, μ{sub 0} is the permeability, and p{sub 0} is the pressure ahead of the shock. For shocks initiated at r ≫ R, shock convergence is first accompanied by shock strengthening as for the strictly gas-dynamic implosion. The
Converging cylindrical shocks in ideal magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Pullin, D. I.; Mostert, W.; Wheatley, V.; Samtaney, R.
2014-09-01
We consider a cylindrically symmetrical shock converging onto an axis within the framework of ideal, compressible-gas non-dissipative magnetohydrodynamics (MHD). In cylindrical polar co-ordinates we restrict attention to either constant axial magnetic field or to the azimuthal but singular magnetic field produced by a line current on the axis. Under the constraint of zero normal magnetic field and zero tangential fluid speed at the shock, a set of restricted shock-jump conditions are obtained as functions of the shock Mach number, defined as the ratio of the local shock speed to the unique magnetohydrodynamic wave speed ahead of the shock, and also of a parameter measuring the local strength of the magnetic field. For the line current case, two approaches are explored and the results compared in detail. The first is geometrical shock-dynamics where the restricted shock-jump conditions are applied directly to the equation on the characteristic entering the shock from behind. This gives an ordinary-differential equation for the shock Mach number as a function of radius which is integrated numerically to provide profiles of the shock implosion. Also, analytic, asymptotic results are obtained for the shock trajectory at small radius. The second approach is direct numerical solution of the radially symmetric MHD equations using a shock-capturing method. For the axial magnetic field case the shock implosion is of the Guderley power-law type with exponent that is not affected by the presence of a finite magnetic field. For the axial current case, however, the presence of a tangential magnetic field ahead of the shock with strength inversely proportional to radius introduces a length scale R=sqrt{μ _0/p_0} I/(2 π ) where I is the current, μ0 is the permeability, and p0 is the pressure ahead of the shock. For shocks initiated at r ≫ R, shock convergence is first accompanied by shock strengthening as for the strictly gas-dynamic implosion. The diverging magnetic field
NASA Technical Reports Server (NTRS)
Retallick, F. D.
1980-01-01
Directly-fired, separately-fired, and oxygen-augmented MHD power plants incorporating a disk geometry for the MHD generator were studied. The base parameters defined for four near-optimum-performance MHD steam power systems of various types are presented. The finally selected systems consisted of (1) two directly fired cases, one at 1920 K (2996F) preheat and the other at 1650 K (2500 F) preheat, (2) a separately-fired case where the air is preheated to the same level as the higher temperature directly-fired cases, and (3) an oxygen augmented case with the same generator inlet temperature of 2839 (4650F) as the high temperature directly-fired and separately-fired cases. Supersonic Mach numbers at the generator inlet, gas inlet swirl, and constant Hall field operation were specified based on disk generator optimization. System pressures were based on optimization of MHD net power. Supercritical reheat stream plants were used in all cases. Open and closed cycle component costs are summarized and compared.
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.
Steady-state axisymmetric nonlinear magnetohydrodynamic solutions with various boundary conditions
NASA Astrophysics Data System (ADS)
Wang, Lile; Lou, Yu-Qing
2014-04-01
Axisymmetric magnetohydrodynamics (MHD) can be invoked for describing astrophysical magnetized flows and formulated to model stellar magnetospheres including main-sequence stars (e.g. the Sun), compact stellar objects [e.g. magnetic white dwarfs (MWDs), radio pulsars, anomalous X-ray pulsars, magnetars, isolated neutron stars, etc.] and planets as a major step forward towards a full three-dimensional model construction. Using powerful and reliable numerical solvers based on two distinct finite-difference method and finite-element method schemes of algorithm, we examine axisymmetric steady-state or stationary MHD models in Throumoulopoulos & Tasso, finding that their separable semi-analytic non-linear solutions are actually not unique given their specific selection of several free functionals and chosen boundary conditions. Similar situations of multiple non-linear solutions with the same boundary conditions actually also happen to force-free magnetic field models of Low & Lou. The multiplicity of non-linear steady MHD solutions gives rise to differences in the total energies contained in the magnetic fields and flow velocity fields as well as in the asymptotic behaviours approaching infinity, which may in turn explain why numerical solvers tend to converge to a non-linear solution with a lower energy than the corresponding separable semi-analytic one. By properly adjusting model parameters, we invoke semi-analytic and numerical solutions to describe different kinds of scenarios, including nearly parallel case and the situation in which the misalignment between the plasma flow and magnetic field is considerable. We propose that these MHD models are capable of describing the magnetospheres of MWDs as examples of applications with moderate conditions (including magnetic field) where the typical values of several important parameters are consistent with observations. Physical parameters can also be estimated based on such MHD models directly. We discuss the challenges
Corrosion and arc erosion in MHD channels
Rosa, R.J. . Dept. of Mechanical Engineering); Pollina, R.J. . Dept. of Mechanical Engineering Avco-Everett Research Lab., Everett, MA )
1991-10-01
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.
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.
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.
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.
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.
Observations of the parametric decay instability of nonlinear magnetohydrodynamic waves
Spangler, S.R.; Leckband, J.A.; Cairns, I.H.
1997-03-01
One of the most important nonlinear processes for Alfven and fast magnetosonic waves is the decay instability, in which a forward propagating magnetohydrodynamic (MHD) wave is converted into a forward propagating ion acoustic wave and a backward propagating MHD wave. Despite an extensive theoretical literature and numerous computer simulations of the process, there is minimal experimental or observational evidence for its existence. In this paper we report an extensive search for evidence of the decay instability in the MHD wave field upstream of the Earth`s bow shock. Twenty intervals of spacecraft magnetometer and density data with durations between 21 and 168 min were examined. The observational signature of the decay instability sought was a quasi-monochromatic feature in the density power spectrum, attributable to the daughter ion acoustic wave, at a frequency higher than the main wave features in the magnetic power spectra. Such a feature was in fact observed for the interval in which the theoretically predicted instability growth rate was highest, as well as in a second interval for which the instability was permitted with a slower growth rate. However, the data set also contains three long intervals of data in which the {open_quotes}decay line{close_quotes} signature is not seen, although theoretically permitted. The decay line is also absent in four shorter intervals in which the plasma {beta} is less than unity, and the instability accordingly facilitated. Possible reasons for the absence of the instability in these intervals are discussed, such as a finite bandwidth for the parent wave field and plasma kinetic effects. {copyright} {ital 1997 American Institute of Physics.}
Observations of the parametric decay instability of nonlinear magnetohydrodynamic waves
NASA Astrophysics Data System (ADS)
Spangler, Steven R.; Leckband, James A.; Cairns, Iver H.
1997-03-01
One of the most important nonlinear processes for Alfvén and fast magnetosonic waves is the decay instability, in which a forward propagating magnetohydrodynamic (MHD) wave is converted into a forward propagating ion acoustic wave and a backward propagating MHD wave. Despite an extensive theoretical literature and numerous computer simulations of the process, there is minimal experimental or observational evidence for its existence. In this paper we report an extensive search for evidence of the decay instability in the MHD wave field upstream of the Earth's bow shock. Twenty intervals of spacecraft magnetometer and density data with durations between 21 and 168 min were examined. The observational signature of the decay instability sought was a quasi-monochromatic feature in the density power spectrum, attributable to the daughter ion acoustic wave, at a frequency higher than the main wave features in the magnetic power spectra. Such a feature was in fact observed for the interval in which the theoretically predicted instability growth rate was highest, as well as in a second interval for which the instability was permitted with a slower growth rate. However, the data set also contains three long intervals of data in which the "decay line'' signature is not seen, although theoretically permitted. The decay line is also absent in four shorter intervals in which the plasma β is less than unity, and the instability accordingly facilitated. Possible reasons for the absence of the instability in these intervals are discussed, such as a finite bandwidth for the parent wave field and plasma kinetic effects.
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.
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 SIGNATURE OF INITIAL CONDITIONS ON MAGNETOHYDRODYNAMIC TURBULENCE
Dallas, V.; Alexakis, A. E-mail: alexakis@lps.ens.fr
2014-06-20
We demonstrate that the initial correlation between velocity and current density fluctuations can lead to the formation of enormous current sheets in freely evolving magnetohydrodynamic (MHD) turbulence. These coherent structures are observed at the peak of the energy dissipation rate and are the carriers of long-range correlations despite all of the nonlinear interactions during the formation of turbulence. The size of these structures spans our computational domain, dominating the scaling of the energy spectrum, which follows a E∝k {sup –2} power law. As the Reynolds number increases, the curling of the current sheets due to Kelvin-Helmholtz-type instabilities and reconnection modifies the scaling of the energy spectrum from k {sup –2} toward k {sup –5/3}. This transition occurs due to the decorrelation of the velocity and the current density which is proportional to Re{sub λ}{sup −3/2}. Finite Reynolds number behavior is observed without reaching a finite asymptote for the energy dissipation rate even for a simulation of Re{sub λ} ≅ 440 with 2048{sup 3} grid points. This behavior demonstrates that even state-of-the-art numerical simulations of the highest Reynolds numbers can be influenced by the choice of initial conditions and consequently they are inadequate to deduce unequivocally the fate of universality in MHD turbulence. Implications for astrophysical observations are discussed.
Energy Dissipation in Magnetohydrodynamic Turbulence: Coherent Structures or Nanoflares?
NASA Astrophysics Data System (ADS)
Zhdankin, Vladimir; Boldyrev, Stanislav; Perez, Jean Carlos; Tobias, Steven
2014-10-01
Energy dissipation in magnetohydrodynamic (MHD) turbulence is known to be highly intermittent, occurring mainly in current sheets. However, the question remains whether the overall energy dissipation is dominated by small (dissipation-scale) structures or by large (inertial-range) structures. To systematically investigate this question, we develop and apply a procedure to identify and characterize dissipative structures in numerical simulations of reduced MHD. We find that the probability distribution of energy dissipation rates exhibits a power law tail with index very close to the critical value of -2.0, indicating that structures of all intensities contribute equally to the overall energy dissipation. We then measure the characteristic spatial scales of structures using two methods: one based on the linear scales across the structure and the other based on the Minkowski functionals, which rigorously characterize the morphology of any shape. We find that energy dissipation is dominated by coherent structures with lengths and widths uniformly distributed across the inertial range, while thicknesses lie deep within the dissipative regime. As the Reynolds number is increased, structures become thinner and more numerous, while the energy dissipation continues to occur mainly in large-scale coherent structures. The current sheets therefore exhibit features of both coherent structures and nanoflares.
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.
Petrick, Michael; Pierson, Edward S.; Schreiner, Felix
1980-01-01
According to the present invention, coal combustion gas is the primary working fluid and copper or a copper alloy is the electrodynamic fluid in the MHD generator, thereby eliminating the heat exchangers between the combustor and the liquid-metal MHD working fluids, allowing the use of a conventional coalfired steam bottoming plant, and making the plant simpler, more efficient and cheaper. In operation, the gas and liquid are combined in a mixer and the resulting two-phase mixture enters the MHD generator. The MHD generator acts as a turbine and electric generator in one unit wherein the gas expands, drives the liquid across the magnetic field and thus generates electrical power. The gas and liquid are separated, and the available energy in the gas is recovered before the gas is exhausted to the atmosphere. Where the combustion gas contains sulfur, oxygen is bubbled through a side loop to remove sulfur therefrom as a concentrated stream of sulfur dioxide. The combustor is operated substoichiometrically to control the oxide level in the copper.
Hypersonic MHD Propulsion System Integration for the Mercury Lightcraft
Myrabo, L.N.; Rosa, R.J.
2004-03-30
Introduced herein are the design, systems integration, and performance analysis of an exotic magnetohydrodynamic (MHD) slipstream accelerator engine for a single-occupant 'Mercury' lightcraft. This ultra-energetic, laser-boosted vehicle is designed to ride a 'tractor beam' into space, transmitted from a future orbital network of satellite solar power stations. The lightcraft's airbreathing combined-cycle engine employs a rotary pulsed detonation thruster mode for lift-off and landing, and an MHD slipstream accelerator mode at hypersonic speeds. The latter engine transforms the transatmospheric acceleration path into a virtual electromagnetic 'mass-driver' channel; the hypersonic momentum exchange process (with the atmosphere) enables engine specific impulses in the range of 6000 to 16,000 seconds, and propellant mass fractions as low as 10%. The single-stage-to-orbit, highly reusable lightcraft can accelerate at 3 Gs into low Earth orbit with its throttle just barely beyond 'idle' power, or virtually 'disappear' at 30 G's and beyond. The objective of this advanced lightcraft design is to lay the technological foundations for a safe, very low cost (e.g., 1000X below chemical rockets) air and space transportation for human life in the mid-21st Century - a system that will be completely 'green' and independent of Earth's limited fossil fuel reserves.
Hypersonic MHD Propulsion System Integration for the Mercury Lightcraft
NASA Astrophysics Data System (ADS)
Myrabo, L. N.; Rosa, R. J.
2004-03-01
Introduced herein are the design, systems integration, and performance analysis of an exotic magnetohydrodynamic (MHD) slipstream accelerator engine for a single-occupant ``Mercury'' lightcraft. This ultra-energetic, laser-boosted vehicle is designed to ride a `tractor beam' into space, transmitted from a future orbital network of satellite solar power stations. The lightcraft's airbreathing combined-cycle engine employs a rotary pulsed detonation thruster mode for lift-off & landing, and an MHD slipstream accelerator mode at hypersonic speeds. The latter engine transforms the transatmospheric acceleration path into a virtual electromagnetic `mass-driver' channel; the hypersonic momentum exchange process (with the atmosphere) enables engine specific impulses in the range of 6000 to 16,000 seconds, and propellant mass fractions as low as 10%. The single-stage-to-orbit, highly reusable lightcraft can accelerate at 3 Gs into low Earth orbit with its throttle just barely beyond `idle' power, or virtually `disappear' at 30 G's and beyond. The objective of this advanced lightcraft design is to lay the technological foundations for a safe, very low cost (e.g., 1000X below chemical rockets) air and space transportation for human life in the mid-21st Century - a system that will be completely `green' and independent of Earth's limited fossil fuel reserves.
Mathematical modelling in MHD technology
Scheindlin, A.E.; Medin, S.A. )
1990-01-01
The technological scheme and the general parameters of the commercial scale pilot MHD power plant are described. The characteristics of the flow train components and the electrical equipment are discussed. The basic ideas of the mathematical modelling of the processes and the devices operation in MHD systems are considered. The application of different description levels in computer simulation is analyzed and the examples of typical solutions are presented.
Advanced Coal-Based Power Generations
NASA Technical Reports Server (NTRS)
Robson, F. L.
1982-01-01
Advanced power-generation systems using coal-derived fuels are evaluated in two-volume report. Report considers fuel cells, combined gas- and steam-turbine cycles, and magnetohydrodynamic (MHD) energy conversion. Presents technological status of each type of system and analyzes performance of each operating on medium-Btu fuel gas, either delivered via pipeline to powerplant or generated by coal-gasification process at plantsite.
Samim Anghaie
2002-08-13
Any reactor that utilizes fuel consisting of a fissile material in a gaseous state may be referred to as a gaseous core reactor (GCR). Studies on GCRs have primarily been limited to the conceptual phase, mostly due to budget cuts and program cancellations in the early 1970's. A few scientific experiments have been conducted on candidate concepts, primarily of static pressure fissile gas filling a cylindrical or spherical cavity surrounded by a moderating shell, such as beryllium, heavy water, or graphite. The main interest in this area of nuclear power generation is for space applications. The interest in space applications has developed due to the promise of significant enhancement in fuel utilization, safety, plant efficiency, special high-performance features, load-following capabilities, power conversion optimization, and other key aspects of nuclear power generation. The design of a successful GCR adapted for use in space is complicated. The fissile material studied in the pa st has been in a fluorine compound, either a tetrafluoride or a hexafluoride. Both of these molecules have an impact on the structural material used in the making of a GCR. Uranium hexafluoride as a fuel allows for a lower operating temperature, but at temperatures greater than 900K becomes essentially impossible to contain. This difficulty with the use of UF6 has caused engineers and scientists to use uranium tetrafluoride, which is a more stable molecule but has the disadvantage of requiring significantly higher operating temperatures. Gas core reactors have traditionally been studied in a steady state configuration. In this manner a fissile gas and working fluid are introduced into the core, called a cavity, that is surrounded by a reflector constructed of materials such as Be or BeO. These reactors have often been described as cavity reactors because the density of the fissile gas is low and criticality is achieved only by means of the reflector to reduce neutron leakage from the core
Depletion of nonlinearity in magnetohydrodynamic turbulence: Insights from analysis and simulations.
Gibbon, J D; Gupta, A; Krstulovic, G; Pandit, R; Politano, H; Ponty, Y; Pouquet, A; Sahoo, G; Stawarz, J
2016-04-01
It is shown how suitably scaled, order-m moments, D_{m}^{±}, of the Elsässer vorticity fields in three-dimensional magnetohydrodynamics (MHD) can be used to identify three possible regimes for solutions of the MHD equations with magnetic Prandtl number P_{M}=1. These vorticity fields are defined by ω^{±}=curlz^{±}=ω±j, where z^{±} are Elsässer variables, and where ω and j are, respectively, the fluid vorticity and current density. This study follows recent developments in the study of three-dimensional Navier-Stokes fluid turbulence [Gibbon et al., Nonlinearity 27, 2605 (2014)NONLE50951-771510.1088/0951-7715/27/10/2605]. Our mathematical results are then compared with those from a variety of direct numerical simulations, which demonstrate that all solutions that have been investigated remain in only one of these regimes which has depleted nonlinearity. The exponents q^{±} that characterize the inertial range power-law dependencies of the z^{±} energy spectra, E^{±}(k), are then examined, and bounds are obtained. Comments are also made on (a) the generalization of our results to the case P_{M}≠1 and (b) the relation between D_{m}^{±} and the order-m moments of gradients of magnetohydrodynamic fields, which are used to characterize intermittency in turbulent flows. PMID:27176387
Depletion of nonlinearity in magnetohydrodynamic turbulence: Insights from analysis and simulations
NASA Astrophysics Data System (ADS)
Gibbon, J. D.; Gupta, A.; Krstulovic, G.; Pandit, R.; Politano, H.; Ponty, Y.; Pouquet, A.; Sahoo, G.; Stawarz, J.
2016-04-01
It is shown how suitably scaled, order-m moments, Dm±, of the Elsässer vorticity fields in three-dimensional magnetohydrodynamics (MHD) can be used to identify three possible regimes for solutions of the MHD equations with magnetic Prandtl number PM=1 . These vorticity fields are defined by ω±=curlz±=ω ±j , where z± are Elsässer variables, and where ω and j are, respectively, the fluid vorticity and current density. This study follows recent developments in the study of three-dimensional Navier-Stokes fluid turbulence [Gibbon et al., Nonlinearity 27, 2605 (2014), 10.1088/0951-7715/27/10/2605]. Our mathematical results are then compared with those from a variety of direct numerical simulations, which demonstrate that all solutions that have been investigated remain in only one of these regimes which has depleted nonlinearity. The exponents q± that characterize the inertial range power-law dependencies of the z± energy spectra, E±(k ) , are then examined, and bounds are obtained. Comments are also made on (a) the generalization of our results to the case PM≠1 and (b) the relation between Dm± and the order-m moments of gradients of magnetohydrodynamic fields, which are used to characterize intermittency in turbulent flows.
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 Technical Reports Server (NTRS)
Harris, L. P.
1977-01-01
A 2000 MWe MHD/steam plant for central station applications has been designed and costed as part of the Energy Conversion Alternatives Study (ECAS). This plant is fueled by Illinois No. 6 coal, rejects heat through mechanical draft wet cooling towers, and includes coal processing equipment, seed reprocessing, electrical inversion of the MHD generator output and emission controls to current EPA standards. It yields an estimated overall efficiency of 0.483 (7066 Btu/kWe-hr), a capital cost of $718 per kWe (1975 dollars), and a cost of electricity at 65% capacity factor of 32 mills per kWe-hr. If the assumed life and reliability could be achieved with these performance parameters, the MHD system should prove attractive.
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.
RESONANCE BROADENING AND HEATING OF CHARGED PARTICLES IN MAGNETOHYDRODYNAMIC TURBULENCE
Lynn, Jacob W.; Parrish, Ian J.; Quataert, Eliot; Chandran, Benjamin D. G.
2012-10-20
The heating, acceleration, and pitch-angle scattering of charged particles by magnetohydrodynamic (MHD) turbulence are important in a wide range of astrophysical environments, including the solar wind, accreting black holes, and galaxy clusters. We simulate the interaction of high-gyrofrequency test particles with fully dynamical simulations of subsonic MHD turbulence, focusing on the parameter regime with {beta} {approx} 1, where {beta} is the ratio of gas to magnetic pressure. We use the simulation results to calibrate analytical expressions for test particle velocity-space diffusion coefficients and provide simple fits that can be used in other work. The test particle velocity diffusion in our simulations is due to a combination of two processes: interactions between particles and magnetic compressions in the turbulence (as in linear transit-time damping; TTD) and what we refer to as Fermi Type-B (FTB) interactions, in which charged particles moving on field lines may be thought of as beads sliding along moving wires. We show that test particle heating rates are consistent with a TTD resonance that is broadened according to a decorrelation prescription that is Gaussian in time (but inconsistent with Lorentzian broadening due to an exponential decorrelation function, a prescription widely used in the literature). TTD dominates the heating for v{sub s} >> v{sub A} (e.g., electrons), where v{sub s} is the thermal speed of species s and v{sub A} is the Alfven speed, while FTB dominates for v{sub s} << v{sub A} (e.g., minor ions). Proton heating rates for {beta} {approx} 1 are comparable to the turbulent cascade rate. Finally, we show that velocity diffusion of collisionless, large gyrofrequency particles due to large-scale MHD turbulence does not produce a power-law distribution function.
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
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)
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.
Laser production and heating of plasma for MHD application
NASA Technical Reports Server (NTRS)
Jalufka, N. W.
1988-01-01
Experiments have been made on the production and heating of plasmas by the absorption of laser radiation. These experiments were performed to ascertain the feasibility of using laser-produced or laser-heated plasmas as the input for a magnetohydrodynamic (MHD) generator. Such a system would have a broad application as a laser-to-electricity energy converter for space power transmission. Experiments with a 100-J-pulsed CO2 laser were conducted to investigate the breakdown of argon gas by a high-intensity laser beam, the parameters (electron density and temperature) of the plasma produced, and the formation and propagation of laser-supported detonation (LSD) waves. Experiments were also carried out using a 1-J-pulsed CO2 laser to heat the plasma produced in a shock tube. The shock-tube hydrogen plasma reached electron densities of approximately 10 to the 17th/cu cm and electron temperatures of approximately 1 eV. Absorption of the CO2 laser beam by the plasma was measured, and up to approximately 100 percent absorption was observed. Measurements with a small MHD generator showed that the energy extraction efficiency could be very large with values up to 56 percent being measured.
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.
Makwana, K. D. Cattaneo, F.; Zhdankin, V.; Li, H.; Daughton, W.
2015-04-15
Simulations of decaying magnetohydrodynamic (MHD) turbulence are performed with a fluid and a kinetic code. The initial condition is an ensemble of long-wavelength, counter-propagating, shear-Alfvén waves, which interact and rapidly generate strong MHD turbulence. The total energy is conserved and the rate of turbulent energy decay is very similar in both codes, although the fluid code has numerical dissipation, whereas the kinetic code has kinetic dissipation. The inertial range power spectrum index is similar in both the codes. The fluid code shows a perpendicular wavenumber spectral slope of k{sub ⊥}{sup −1.3}. The kinetic code shows a spectral slope of k{sub ⊥}{sup −1.5} for smaller simulation domain, and k{sub ⊥}{sup −1.3} for larger domain. We estimate that collisionless damping mechanisms in the kinetic code can account for the dissipation of the observed nonlinear energy cascade. Current sheets are geometrically characterized. Their lengths and widths are in good agreement between the two codes. The length scales linearly with the driving scale of the turbulence. In the fluid code, their thickness is determined by the grid resolution as there is no explicit diffusivity. In the kinetic code, their thickness is very close to the skin-depth, irrespective of the grid resolution. This work shows that kinetic codes can reproduce the MHD inertial range dynamics at large scales, while at the same time capturing important kinetic physics at small scales.
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.
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
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.
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.
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.
Ramrus, A.
1986-02-01
Objective of the study was to create conceptual designs of high voltage pulsers capable of simulating two types of electromagnetic pulses (EMPs) caused by a high-altitude nuclear burst; the slow rise time magnetohydrodynamic (MHD-EMP) and the fast rise time high-altitude EMP (HEMP). The pulser design was directed towards facilities capable of performing EMP vulnerability testing of components used in the national electric power system.
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.
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.
Reass, W.A.; Wurden, G.A.
1997-10-06
The operational characteristics and performance of the two channel 10 Megawatt MHD feedback control system as installed by Los Alamos National Laboratory on the Columbia University HBT-EP tokamak are described. In the present configuration, driving independent 300 {micro}H saddle coil sets, each channel can deliver 1100 Amperes and 16 kV peak to peak. Full power bandwidth is about 12 kHz, with capabilities at reduced power to 30 kHz. The present system topology is designed to suppress magnetohydrodynamic activity with m=2, n=1 symmetry. Application of either static (single phase) or rotating (twin phased) magnetic perturbations shows the ability to spin up or slow down the plasma, and also prevent (or cause) so-called ''mode-locking''. Open loop and active feedback experiments using a digital signal processor (DSP) have been performed on the HBT-EP tokamak and initial results show the ability to manipulate the plasma MHD mode frequency.
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.
S.S. Medley; N.N. Gorelenkov; R. Andre; R.E. Bell; D.S. Darrow; E.D. Fredrickson; S.M. Kaye; B.P. LeBlanc; A.L. Roquemore; and the NSTX Team
2004-03-15
MHD-induced energetic ion loss in neutral-beam-heated H-mode [high-confinement mode] discharges in NSTX [National Spherical Torus Experiment] is discussed. A rich variety of energetic ion behavior resulting from magnetohydrodynamic (MHD) activity is observed in the NSTX using a horizontally scanning Neutral Particle Analyzer (NPA) whose sightline views across the three co-injected neutral beams. For example, onset of an n = 2 mode leads to relatively slow decay of the energetic ion population (E {approx} 10-100 keV) and consequently the neutron yield. The effect of reconnection events, sawteeth, and bounce fishbones differs from that observed for low-n, low-frequency, tearing-type MHD modes. In this case, prompt loss of the energetic ion population occurs on a time scale of less than or equal to 1 ms and a precipitous drop in the neutron yield occurs. This paper focuses on MHD-induced ion loss during H-mode operation in NSTX. After H-mode onset, the NPA charge-exchange spectrum usually exhibits a significant loss of energetic ions only for E > E(sub)b/2 where E(sub)b is the beam injection energy. The magnitude of the energetic ion loss was observed to decrease with increasing tangency radius, R(sub)tan, of the NPA sightline, increasing toroidal field, B(sub)T, and increasing neutral-beam injection energy, E(sub)b. TRANSP modeling suggests that MHD-induced ion loss is enhanced during H-mode operation due to an evolution of the q and beam deposition profiles that feeds both passing and trapped ions into the region of low-n MHD activity. ORBIT code analysis of particle interaction with a model magnetic perturbation supported the energy selectivity of the MHD-induced loss observed in the NPA measurements. Transport analysis with the TRANSP code using a fast-ion diffusion tool to emulate the observed MHD-induced energetic ion loss showed significant modifications of the neutral- beam heating as well as the power balance, thermal diffusivities, energy confinement times
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.
NASA Astrophysics Data System (ADS)
Picologlou, B. F.; Batenin, V. M.
1981-01-01
The MHD generator was operated at its design parameters. New plasma diagnostic devices are described and include: a traversing dual electrical probe for determining distribution of electron concentrations, a traversing probe that includes a pitot tube for measuring total and static pressure, and a light detector for measuring plasma luminescence. Data are presented on heat flux distribution along the channel, the forest data of this type obtained for an MHD facility of such size. Results are given of experimental studies of plasma characteristics, gasdynamic, thermal, and electrical MHD channel performance, and temporal and spatial nonuniformities.
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.
NASA Technical Reports Server (NTRS)
Smith, M.; Nichols, L. D.; Seikel, G. R.
1974-01-01
Performance and power costs of H2-O2 combustion powered steam-MHD central power systems are estimated. Hydrogen gas is assumed to be transmitted by pipe from a remote coal gasifier into the city and converted to electricity in a steam MHD plant having an integral gaseous oxygen plant. These steam MHD systems appear to offer an attractive alternative to both in-city clean fueled conventional steam power plants and to remote coal fired power plants with underground electric transmission into the city. Status and plans are outlined for an experimental evaluation of H2-O2 combustion-driven MHD power generators at NASA Lewis Research Center.
Temporal and spatial turbulent spectra of MHD plasma and an observation of variance anisotropy
Schaffner, D. A.; Brown, M. R.; Lukin, V. S.
2014-08-01
The nature of magnetohydrodynamic (MHD) turbulence is analyzed through both temporal and spatial magnetic fluctuation spectra. A magnetically turbulent plasma is produced in the MHD wind tunnel configuration of the Swarthmore Spheromak Experiment. The power of magnetic fluctuations is projected into directions perpendicular and parallel to a local mean field; the ratio of these quantities shows the presence of variance anisotropy which varies as a function of frequency. Comparisons among magnetic, velocity, and density spectra are also made, demonstrating that the energy of the turbulence observed is primarily seeded by magnetic fields created during plasma production. Direct spatial spectra are constructed using multi-channel diagnostics and are used to compare to frequency spectra converted to spatial scales using the Taylor hypothesis. Evidence for the observation of dissipation due to ion inertial length scale physics is also discussed, as well as the role laboratory experiments can play in understanding turbulence typically studied in space settings such as the solar wind. Finally, all turbulence results are shown to compare fairly well to a Hall-MHD simulation of the experiment.
Possible uses for Phillips Laboratory MHD generator. Final report, 1 October 1994-30 August 1995
Turchi, P.J.
1995-08-01
There is interest in electromagnetic energy sources for applications to directed energy weapons. Candidates include portable conventional rotating machinery electric generators, magnetic flux compression generators (aka explosive generators, magnetocumulative generators or MCGs) based on explosive action, and magnetohydrodynamic (MHD) generators using chemical energy of explosives or rocket propellants. For portable high energy MHD generators, US technology base appeared to need rescue. The US has received a MHD device in the PAMlR-3U, developed in the former Soviet Union. The present discussion considers uses of this generator for programs on high-power microwave systems and other directed energy concepts. Future applications will be limited by development and funding of specific technical needs. A useful next step would be detailed design of a system to charge high-voltage pulsers. This design should include comparison of single-pulse switching to achieve high-voltage from an inductive storage coil (energy storage option) vs repetitive switching at low voltage, followed by custom built transformers (direct drive option).
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.
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.
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.
MHD integrated topping cycle project
NASA Astrophysics Data System (ADS)
1992-01-01
The overall objective of the project is to design and construct prototypical hardware for an integrated MHD topping cycle, and conduct long duration proof-of-concept tests of integrated system at the US DOE Component Development and Integration Facility in Butte, Montana. The results of the long duration tests will augment the existing engineering design data base on MHD power train reliability, availability, maintainability, and performance, and will serve as a basis for scaling up the topping cycle design to the next level of development, an early commercial scale power plant retrofit. The components of the MHD power train to be designed, fabricated, and tested include: A slagging coal combustor with a rated capacity of 50 MW thermal input, capable of operation with an Eastern (Illinois no. 6) or Western (Montana Rosebud) coal, a segmented supersonic nozzle, a supersonic MHD channel capable of generating at least 1.5 MW of electrical power, a segmented supersonic diffuser section to interface the channel with existing facility quench and exhaust systems, a complete set of current control circuits for local diagonal current control along the channel, and a set of current consolidation circuits to interface the channel with the existing facility inverter.
MHD Integrated Topping Cycle Project
Not Available
1992-01-01
The overall objective of the project is to design and construct prototypical hardware for an integrated MHD topping cycle, and conduct long duration proof-of-concept tests of integrated system at the US DOE Component Development and Integration Facility in Butte, Montana. The results of the long duration tests will augment the existing engineering design data base on MHD power train reliability, availability, maintainability, and performance, and will serve as a basis for scaling up the topping cycle design to the next level of development, an early commercial scale power plant retrofit. The components of the MHD power train to be designed, fabricated, and tested include: A slagging coal combustor with a rated capacity of 50 MW thermal input, capable of operation with an Eastern (Illinois {number sign}6) or Western (Montana Rosebud) coal, a segmented supersonic nozzle, a supersonic MHD channel capable of generating at least 1.5 MW of electrical power, a segmented supersonic diffuser section to interface the channel with existing facility quench and exhaust systems, a complete set of current control circuits for local diagonal current control along the channel, and a set of current consolidation circuits to interface the channel with the existing facility inverter.
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.
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.
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.
2D radiation-magnetohydrodynamic simulations of SATURN imploding Z-pinches
Hammer, J.H.; Eddleman, J.L.; Springer, P.T.
1995-11-06
Z-pinch implosions driven by the SATURN device at Sandia National Laboratory are modeled with a 2D radiation magnetohydrodynamic (MHD) code, showing strong growth of magneto-Rayleigh Taylor (MRT) instability. Modeling of the linear and nonlinear development of MRT modes predicts growth of bubble-spike structures that increase the time span of stagnation and the resulting x-ray pulse width. Radiation is important in the pinch dynamics keeping the sheath relatively cool during the run-in and releasing most of the stagnation energy. The calculations give x-ray pulse widths and magnitudes in reasonable agreement with experiments, but predict a radiating region that is too dense and radially localized at stagnation. We also consider peaked initial density profiles with constant imploding sheath velocity that should reduce MRT instability and improve performance. 2D krypton simulations show an output x-ray power > 80 TW for the peaked profile.
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.
Prospects for Nuclear Electric Propulsion Using Closed-Cycle Magnetohydrodynamic Energy Conversion
NASA Technical Reports Server (NTRS)
Litchford, R. J.; Bitteker, L. J.; Jones, J. E.
2001-01-01
Nuclear electric propulsion (NEP) has long been recognized as a major enabling technology for scientific and human exploration of the solar system, and it may conceivably form the basis of a cost-effective space transportation system suitable for space commerce. The chief technical obstacles to realizing this vision are the development of efficient, high-power (megawatt-class) electric thrusters and the development of low specific mass (less than 1 kg/kWe) power plants. Furthermore, comprehensive system analyses of multimegawatt class NEP systems are needed in order to critically assess mission capability and cost attributes. This Technical Publication addresses some of these concerns through a systematic examination of multimegawatt space power installations in which a gas-cooled nuclear reactor is used to drive a magnetohydrodynamic (MHD) generator in a closed-loop Brayton cycle. The primary motivation for considering MHD energy conversion is the ability to transfer energy out of a gas that is simply too hot for contact with any solid material. This has several intrinsic advantages including the ability to achieve high thermal efficiency and power density and the ability to reject heat at elevated temperatures. These attributes lead to a reduction in system specific mass below that obtainable with turbine-based systems, which have definite solid temperature limits for reliable operation. Here, the results of a thermodynamic cycle analysis are placed in context with a preliminary system analysis in order to converge on a design space that optimizes performance while remaining clearly within established bounds of engineering feasibility. MHD technology issues are discussed including the conceptual design of a nonequilibrium disk generator and opportunities for exploiting neutron-induced ionization mechanisms as a means of increasing electrical conductivity and enhancing performance and reliability. The results are then used to make a cursory examination of piloted
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.
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
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.
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.
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.
Magnetohydrodynamic simulations of global accretion disks with vertical magnetic fields
Suzuki, Takeru K.; Inutsuka, Shu-ichiro
2014-04-01
We report results of three-dimensional magnetohydrodynamical (MHD) simulations of global accretion disks threaded with weak vertical magnetic fields. We perform the simulations in the spherical coordinates with different temperature profiles and accordingly different rotation profiles. In the cases with a spatially constant temperature, because the rotation frequency is vertically constant in the equilibrium condition, general properties of the turbulence excited by magnetorotational instability are quantitatively similar to those obtained in local shearing box simulations. On the other hand, in the cases with a radially variable temperature profile, the vertical differential rotation, which is inevitable in the equilibrium condition, winds up the magnetic field lines in addition to the usual radial differential rotation. As a result, the coherent wound magnetic fields contribute to the Maxwell stress in the surface regions. We obtain nondimensional density and velocity fluctuations ∼0.1-0.2 at the midplane. The azimuthal power spectra of the magnetic fields show shallower slopes, ∼m {sup 0} – m {sup –1}, than those of velocity and density. The Poynting flux associated with the MHD turbulence drives intermittent and structured disk winds as well as sound-like waves toward the midplane. The mass accretion mainly occurs near the surfaces, and the gas near the midplane slowly moves outward in the time domain of the present simulations. The vertical magnetic fields are also dragged inward in the surface regions, while they stochastically move outward and inward around the midplane. We also discuss an observational implication of induced spiral structure in the simulated turbulent disks.
NASA Astrophysics Data System (ADS)
Babu, D. Harish; Narayana, P. V. Satya
2016-08-01
An analysis has been carried out to study the Joule heating effect on MHD heat transfer of an incompressible Jeffrey fluid due to a stretching porous sheet with power law heat flux and heat source. A constant magnetic field is applied normal to the stretching surface. The basic governing equations are reduced into the coupled nonlinear ordinary differential equations by using similarity transformations. The resulting equations are then solved numerically by shooting method with fourth order Runge-Kutta scheme. The effects of various physical parameters entering into the problem on dimensionless velocity and temperature distribution are discussed through graphs and tables. The results reveal that the momentum and thermal boundary layer thickness are significantly influenced by Deborah number (β), ratio of relaxation and retardation times parameter (λ), heat generation parameter (β*), Eckert number (Ec) and magnetic field parameter (M). A comparison with the previously published works shows excellent agreement.
Attig, R.C.
1996-10-09
The development of coal-fired magnetohydrodynamic (MHD) power can be viewed as consisting of two parts; the topping cycle and the bottoming cycle. The topping cycle consists of the coal combustor, MHD generator and associated components. The bottoming cycle consists of the heat recovery, steam generation, seed recovery/regeneration, emissions control (gas and particulate), ash handling and deposition, and materials evaluation. The report concentrates on the bottoming cycle, for which much of the technology was developed at the University of Tennessee Space Institute (UTSI). Because of the complexity of the required technology, a number of issues required investigation. Of specific concern regarding the bottoming cycle, was the design of the steam cycle components and emissions control. First, the high combustion temperatures and the use of large quantities of potassium in the MHD combustor results in a difference in the composition of the gases entering the bottoming cycle compared to conventional systems. Secondly, a major goal of the UTSI effort was to use a variety of coals in the MHD system, especially the large reserves of high-sulfur coals available in the United States.
Solar-driven liquid metal magnetohydrodynamic generator
NASA Technical Reports Server (NTRS)
Lee, J. H.; Hohl, F.
1981-01-01
A solar oven heated by concentrated solar radiation as the heat source of a liquid metal magnetohydrodynamic (LMMHD) power generation system is proposed. The design allows the production of electric power in space, as well as on Earth, at high rates of efficiency. Two types of the solar oven suitable for the system are discussed.
Solar-driven liquid metal magnetohydrodynamic generator
NASA Astrophysics Data System (ADS)
Lee, J. H.; Hohl, F.
1981-05-01
A solar oven heated by concentrated solar radiation as the heat source of a liquid metal magnetohydrodynamic (LMMHD) power generation system is proposed. The design allows the production of electric power in space, as well as on Earth, at high rates of efficiency. Two types of the solar oven suitable for the system are discussed.
The superconducting MHD-propelled ship YAMATO-1
Sasakawa, Yohei; Takezawa, Setsuo; Sugawara, Yoshinori; Kyotani, Yoshihiro
1995-04-01
In 1985 the Ship & Ocean Foundation (SOF) created a committee under the chairmanship of Mr. Yohei Sasakawa, Former President of the Ship & Ocean Foundation, and began researches into superconducting magnetohydrodynamic (MHD) ship propulsion. In 1989 SOF set to construction of a experimental ship on the basis of theoretical and experimental researches pursued until then. The experimental ship named YAMATO-1 became the world`s first superconducting MHD-propelled ship on her trial runs in June 1992. This paper describes the outline of the YAMATO-1 and sea trial test results.
Numerical Analysis of MHD Accelerator with Non-Equilibrium Air Plasma
NASA Astrophysics Data System (ADS)
Anwari, M.; H. Qazi, H.; Sukarsan; Harada, N.
2012-12-01
Magnetohydrodynamic (MHD) accelerator is proposed as a next generation propulsion system. It can be used to increase the performance of a propulsion system. The objective of this study is to investigate the performance of MHD accelerator using non-equilibrium air plasma as working gas. In this study, the fundamental performance of MHD accelerator such as flow performance and electrical performance is evaluated at different levels of applied magnetic field using 1-D numerical simulation. The numerical simulation is developed based on a set of differential equations with MHD approximation. To solve this set of differential equations the MacCormack scheme is used. A specified channel designed and developed at NASA Marshall Space Flight Centre is used in the numerical simulation. The composition of the simulated air plasma consists of seven species, namely, N2, N, O2, O, NO, NO+, and e-. The performance of the non-equilibrium MHD accelerator is also compared with the equilibrium MHD accelerator.
Treatment of MHD turbulence with non-equipartition and anisotropy
NASA Astrophysics Data System (ADS)
Zhou, Ye; Matthaeus, W. H.
2005-11-01
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 we discuss a phenomenology for such ``non-equipartitioned'' MHD flow. We suggest two conditions for a MHD flow to transition to strong turbulent flow, 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, we point out that the dynamics and anisotropy of MHD fluctuations is 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 non-equipartition effects.
Sub-Alfvenic Non-Ideal MHD Turbulence Simulations with Ambipolar Diffusion: I. Turbulence Statistics
Klein, R I; Li, P S; McKee, C F; Fisher, R
2008-04-10
Most numerical investigations on the role of magnetic fields in turbulent molecular clouds (MCs) are based on ideal magneto-hydrodynamics (MHD). However, MCs are weakly ionized, so that the time scale required for the magnetic field to diffuse through the neutral component of the plasma by ambipolar diffusion (AD) can be comparable to the dynamical time scale. We have performed a series of 256{sup 3} and 512{sup 3} simulations on supersonic but sub-Alfvenic turbulent systems with AD using the Heavy-Ion Approximation developed in Li et al. (2006). Our calculations are based on the assumption that the number of ions is conserved, but we show that these results approximately apply to the case of time-dependent ionization in molecular clouds as well. Convergence studies allow us to determine the optimal value of the ionization mass fraction when using the heavy-ion approximation for low Mach number, sub-Alfvenic turbulent systems. We find that ambipolar diffusion steepens the velocity and magnetic power spectra compared to the ideal MHD case. Changes in the density PDF, total magnetic energy, and ionization fraction are determined as a function of the AD Reynolds number. The power spectra for the neutral gas properties of a strongly magnetized medium with a low AD Reynolds number are similar to those for a weakly magnetized medium; in particular, the power spectrum of the neutral velocity is close to that for Burgers turbulence.
The Generation and Damping of Propagating MHD Kink Waves in the Solar Atmosphere
NASA Astrophysics Data System (ADS)
Morton, R. J.; Verth, G.; Hillier, A.; Erdélyi, R.
2014-03-01
The source of the non-thermal energy required for the heating of the upper solar atmosphere to temperatures in excess of a million degrees and the acceleration of the solar wind to hundreds of kilometers per second is still unclear. One such mechanism for providing the required energy flux is incompressible torsional Alfvén and kink magnetohydrodynamic (MHD) waves, which are magnetically dominated waves supported by the Sun's pervasive and complex magnetic field. In particular, propagating MHD kink waves have recently been observed to be ubiquitous throughout the solar atmosphere, but, until now, critical details of the transport of the kink wave energy throughout the Sun's atmosphere were lacking. Here, the ubiquity of the waves is exploited for statistical studies in the highly dynamic solar chromosphere. This large-scale investigation allows for the determination of the chromospheric kink wave velocity power spectra, a missing link necessary for determining the energy transport between the photosphere and corona. Crucially, the power spectra contain evidence for horizontal photospheric motions being an important mechanism for kink wave generation in the quiescent Sun. In addition, a comparison with measured coronal power spectra is provided for the first time, revealing frequency-dependent transmission profiles, suggesting that there is enhanced damping of kink waves in the lower corona.
The generation and damping of propagating MHD kink waves in the solar atmosphere
Morton, R. J.; Verth, G.; Erdélyi, R.; Hillier, A. E-mail: g.verth@sheffield.ac.uk
2014-03-20
The source of the non-thermal energy required for the heating of the upper solar atmosphere to temperatures in excess of a million degrees and the acceleration of the solar wind to hundreds of kilometers per second is still unclear. One such mechanism for providing the required energy flux is incompressible torsional Alfvén and kink magnetohydrodynamic (MHD) waves, which are magnetically dominated waves supported by the Sun's pervasive and complex magnetic field. In particular, propagating MHD kink waves have recently been observed to be ubiquitous throughout the solar atmosphere, but, until now, critical details of the transport of the kink wave energy throughout the Sun's atmosphere were lacking. Here, the ubiquity of the waves is exploited for statistical studies in the highly dynamic solar chromosphere. This large-scale investigation allows for the determination of the chromospheric kink wave velocity power spectra, a missing link necessary for determining the energy transport between the photosphere and corona. Crucially, the power spectra contain evidence for horizontal photospheric motions being an important mechanism for kink wave generation in the quiescent Sun. In addition, a comparison with measured coronal power spectra is provided for the first time, revealing frequency-dependent transmission profiles, suggesting that there is enhanced damping of kink waves in the lower corona.
Globus, Noemie; Levinson, Amir
2014-11-20
We construct a semi-analytic model for magnetohydrodynamic (MHD) flows in Kerr geometry that incorporates energy loading via neutrino annihilation on magnetic field lines threading the horizon. We compute the structure of the double-flow established in the magnetisphere for a wide range of energy injection rates and identify the different operation regimes. At low injection rates, the outflow is powered by the spinning black hole via the Blandford-Znajek mechanism, whereas at high injection rates, it is driven by the pressure of the plasma deposited on magnetic field lines. In the intermediate regime, both processes contribute to the outflow formation. The parameter that quantifies the load is the ratio of the net power injected below the stagnation radius and the maximum power that can be extracted magnetically from the black hole.
Broken Ergodicity in Two-Dimensional Homogeneous Magnetohydrodynamic Turbulence
NASA Technical Reports Server (NTRS)
Shebalin, John V.
2010-01-01
Two-dimensional (2-D) homogeneous magnetohydrodynamic (MHD) turbulence has many of the same qualitative features as three-dimensional (3-D) homogeneous MHD turbulence.The se features include several ideal invariants, along with the phenomenon of broken ergodicity. Broken ergodicity appears when certain modes act like random variables with mean values that are large compared to their standard deviations, indicating a coherent structure or dynamo.Recently, the origin of broken ergodicity in 3-D MHD turbulence that is manifest in the lowest wavenumbers was explained. Here, a detailed description of the origins of broken ergodicity in 2-D MHD turbulence is presented. It will be seen that broken ergodicity in ideal 2-D MHD turbulence can be manifest in the lowest wavenumbers of a finite numerical model for certain initial conditions or in the highest wavenumbers for another set of initial conditions.T he origins of broken ergodicity in ideal 2-D homogeneous MHD turbulence are found through an eigen analysis of the covariance matrices of the modal probability density functions.It will also be shown that when the lowest wavenumber magnetic field becomes quasi-stationary, the higher wavenumber modes can propagate as Alfven waves on these almost static large-scale magnetic structures
Observation of MHD Instabilities Driven by Energetic Electrons in the Large Helical Device
NASA Astrophysics Data System (ADS)
Mitsutaka, Isobe; Kunihiro, Ogawa; Akihiro, Shimizu; Masaki, Osakabe; Shin, Kubo; Toi, K.; LHD Experiment Group
2015-04-01
Coherent magnetic fluctuations in an acoustic range of frequency have been regularly observed in low-density (ne < 0.2×1019 m-3) plasmas with strong second harmonic electron cyclotron resonance heating (ECRH) on the Large Helical Device. Hard X-ray measurements indicated that energetic electrons are generated in these ECRH discharges. The magnetic fluctuations are suppressed in higher density discharges where energetic electrons are not present. The ECRH power modulation experiment indicated that the observed magnetohydrodynamic (MHD) mode has an acoustic nature rather than an Alfvénic nature. supported by the Grant-in-Aid for Encouragement of Scientists from the Japan Society for the Promotion of Science (No. 20656150). This work was also partly supported by the JSPS-NRF-NSFC A3 Foresight Program in the field of Plasma Physics (NSFC: No. 11261140328 and NRF: No. 2012K2A2A6000443)
Ultra-High-Resolution Observations of MHD Waves in Photospheric Magnetic Structures
NASA Astrophysics Data System (ADS)
Jess, D. B.; Verth, G.
2016-02-01
This chapter reviews the recent observations of waves and oscillations manifesting in fine-scale magnetic structures in the solar photosphere, which are often interpreted as the "building blocks' of the magnetic Sun. The authors found, through phase relationships between the various waveforms, that small-scale magnetic bright points (MBPs) in the photosphere demonstrated signatures of specific magnetoacoustic waves, in particular the sausage and kink modes. Modern magnetohydrodynamic (MHD) simulations of the lower solar atmosphere clearly show how torsional motions can easily be induced in magnetic elements in the photosphere through the processes of vortical motions and/or buffeting by neighboring granules. The authors detected significant power associated with high-frequency horizontal motions, and suggested that these cases may be especially important in the creation of a turbulent environment that efficiently promotes Alfvén wave dissipation.
A note on convective heat transfer of an MHD Jeffrey fluid over a stretching sheet
Ahmed, Jawad; Shahzad, Azeem; Khan, Masood; Ali, Ramzan
2015-11-15
This article focuses on the exact solution regarding convective heat transfer of a magnetohydrodynamic (MHD) Jeffrey fluid over a stretching sheet. The effects of joule and viscous dissipation, internal heat source/sink and thermal radiation on the heat transfer characteristics are taken in account in the presence of a transverse magnetic field for two types of boundary heating process namely prescribed power law surface temperature (PST) and prescribed heat flux (PHF). Similarity transformations are used to reduce the governing non-linear momentum and thermal boundary layer equations into a set of ordinary differential equations. The exact solutions of the reduced ordinary differential equations are developed in the form of confluent hypergeometric function. The influence of the pertinent parameters on the temperature profile is examined. In addition the results for the wall temperature gradient are also discussed in detail.
A note on convective heat transfer of an MHD Jeffrey fluid over a stretching sheet
NASA Astrophysics Data System (ADS)
Ahmed, Jawad; Shahzad, Azeem; Khan, Masood; Ali, Ramzan
2015-11-01
This article focuses on the exact solution regarding convective heat transfer of a magnetohydrodynamic (MHD) Jeffrey fluid over a stretching sheet. The effects of joule and viscous dissipation, internal heat source/sink and thermal radiation on the heat transfer characteristics are taken in account in the presence of a transverse magnetic field for two types of boundary heating process namely prescribed power law surface temperature (PST) and prescribed heat flux (PHF). Similarity transformations are used to reduce the governing non-linear momentum and thermal boundary layer equations into a set of ordinary differential equations. The exact solutions of the reduced ordinary differential equations are developed in the form of confluent hypergeometric function. The influence of the pertinent parameters on the temperature profile is examined. In addition the results for the wall temperature gradient are also discussed in detail.
Finite dissipation and intermittency in magnetohydrodynamics.
Mininni, P D; Pouquet, A
2009-08-01
We present an analysis of data stemming from numerical simulations of decaying magnetohydrodynamic (MHD) turbulence up to grid resolution of 1536(3) points and up to Taylor Reynolds number of approximately 1200 . The initial conditions are such that the initial velocity and magnetic fields are helical and in equipartition, while their correlation is negligible. Analyzing the data at the peak of dissipation, we show that the dissipation in MHD seems to asymptote to a constant as the Reynolds number increases, thereby strengthening the possibility of fast reconnection events in the solar environment for very large Reynolds numbers. Furthermore, intermittency of MHD flows, as determined by the spectrum of anomalous exponents of structure functions of the velocity and the magnetic field, is stronger than that of fluids, confirming earlier results; however, we also find that there is a measurable difference between the exponents of the velocity and those of the magnetic field, reminiscent of recent solar wind observations. Finally, we discuss the spectral scaling laws that arise in this flow. PMID:19792189
Hall-magnetohydrodynamic small-scale dynamos.
Gómez, Daniel O; Mininni, Pablo D; Dmitruk, Pablo
2010-09-01
Magnetic field generation by dynamo action is often studied within the theoretical framework of magnetohydrodynamics (MHD). However, for sufficiently diffuse media, the Hall effect may become non-negligible. We present results from three-dimensional simulations of the Hall-MHD equations subjected to random nonhelical forcing. We study the role of the Hall effect in the dynamo efficiency for different values of the Hall parameter. For small values of the Hall parameter, the small-scale dynamo is more efficient, displaying faster growth and saturating at larger amplitudes of the magnetic field. For larger values of the Hall parameter, saturation of the magnetic field is reached at smaller amplitudes than in the MHD case. We also study energy transfer rates among spatial scales and show that the Hall effect produces a reduction of the direct energy cascade at scales larger than the Hall scale, therefore leading to smaller energy dissipation rates. Finally, we present results stemming from simulations at large magnetic Prandtl numbers, which is the relevant regime in the hot and diffuse interstellar medium. In the range of magnetic Prandtl numbers considered, the Hall effect moves the peak of the magnetic energy spectrum as well as other relevant magnetic length scales toward the Hall scale. PMID:21230195
Imbalanced relativistic force-free magnetohydrodynamic turbulence
Cho, Jungyeon; Lazarian, A.
2014-01-01
When magnetic energy density is much larger than that of matter, as in pulsar/black hole magnetospheres, the medium becomes force-free and we need relativity to describe it. As in non-relativistic magnetohydrodynamics (MHD), Alfvénic MHD turbulence in the relativistic limit can be described by interactions of counter-traveling wave packets. In this paper, we numerically study strong imbalanced MHD turbulence in such environments. Here, imbalanced turbulence means the waves traveling in one direction (dominant waves) have higher amplitudes than the opposite-traveling waves (sub-dominant waves). We find that (1) spectrum of the dominant waves is steeper than that of sub-dominant waves, (2) the anisotropy of the dominant waves is weaker than that of sub-dominant waves, and (3) the dependence of the ratio of magnetic energy densities of dominant and sub-dominant waves on the ratio of energy injection rates is steeper than quadratic (i.e., b{sub +}{sup 2}/b{sub −}{sup 2}∝(ϵ{sub +}/ϵ{sub −}){sup n} with n > 2). These results are consistent with those obtained for imbalanced non-relativistic Alfvénic turbulence. This corresponds well to the earlier reported similarity of the relativistic and non-relativistic balanced magnetic turbulence.
Lattice Boltzmann formulation for Braginskii magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Dellar, Paul
2012-03-01
We present a lattice Boltzmann formulation of the Braginskii magnetohydrodynamic equations that describe large-scale motions in strongly magnetised plasmas. Fluid quantities, density, velocity and stress, are represented by a finite set of distribution functions associated with particles moving on a square or cubic lattice. Equilibrium distributions are constructed from Hermite moment expansions, so slowly varying solutions of the discrete kinetic equation exactly satisfy the Navier--Stokes or MHD momentum equations. Electromagnetic quantities are represented by a second kinetic equation for a set of vector-valued distribution functions. Maxwell's equations and the resistive MHD induction equation may be recovered from slowly varying solutions using different scalings. The resulting algorithm, comprising only local operations at grid points and data copying between adjacent points, readily lends itself to large-scale parallel computations. We modify the collision operator to apply different relaxation times to components of the stress parallel and perpendicular to the local magnetic field, simulating a form of the Braginskii MHD equations encountered in astrophysics. Large shears develop in simulations where the fluid velocity perpendicular to the field lines reverses.
Concomitant Hamiltonian and topological structures of extended magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Lingam, Manasvi; Miloshevich, George; Morrison, Philip J.
2016-07-01
The paper describes the unique geometric properties of ideal magnetohydrodynamics (MHD), and demonstrates how such features are inherited by extended MHD, viz. models that incorporate two-fluid effects (the Hall term and electron inertia). The generalized helicities, and other geometric expressions for these models are presented in a topological context, emphasizing their universal facets. Some of the results presented include: the generalized Kelvin circulation theorems; the existence of two Lie-dragged 2-forms; and two concomitant helicities that can be studied via the Jones polynomial, which is widely utilized in Chern-Simons theory. The ensuing commonality is traced to the existence of an underlying Hamiltonian structure for all the extended MHD models, exemplified by the presence of a unique noncanonical Poisson bracket, and its associated energy.
FLASH magnetohydrodynamic simulations of shock-generated magnetic field experiments
NASA Astrophysics Data System (ADS)
Tzeferacos, P.; Fatenejad, M.; Flocke, N.; Gregori, G.; Lamb, D. Q.; Lee, D.; Meinecke, J.; Scopatz, A.; Weide, K.
2012-12-01
We report the results of benchmark FLASH magnetohydrodynamic (MHD) simulations of experiments conducted by the University of Oxford High Energy Density Laboratory Astrophysics group and its collaborators at the Laboratoire pour l'Utilisation des Lasers Intenses (LULI). In these experiments, a long-pulse laser illuminates a target in a chamber filled with Argon gas, producing shock waves that generate magnetic fields via the Biermann battery mechanism. We first outline the implementation of 2D cylindrical geometry in the unsplit MHD solver in FLASH and present results of verification tests. We then describe the results of benchmark 2D cylindrical MHD simulations of the LULI experiments using FLASH that explore the impact of external fields along with the possibility of magnetic field amplification by turbulence that is associated with the shock waves and that is induced by a grid placed in the gas-filled chamber.
D.S. Darrow; S.S. Medley; A.L. Roquemore; W.W. Heidbrink; A. Alekseyev; F.E. Cecil; J. Egedal; V.Ya. Goloborod'ko; N.N. Gorelenkov; M. Isobe; S. Kaye; M. Miah; F. Paoletti; M.H. Redi; S.N. Reznik; A. Rosenberg; R. White; D. Wyatt; V.A. Yavorskij
2002-10-15
A range of effects may make fast ion confinement in spherical tokamaks worse than in conventional aspect ratio tokamaks. Data from neutron detectors, a neutral particle analyzer, and a fast ion loss diagnostic on the National Spherical Torus Experiment (NSTX) indicate that neutral beam ion confinement is consistent with classical expectations in quiescent plasmas, within the {approx}25% errors of measurement. However, fast ion confinement in NSTX is frequently affected by magnetohydrodynamic (MHD) activity, and the effect of MHD can be quite strong.
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)
Toward 3D MHD modeling of neoclassical tearing mode suppression by ECCD
NASA Astrophysics Data System (ADS)
Pratt, J.; Westerhof, E.
2012-09-01
We propose a framework to extend the magnetohydrodynamic (MHD) equations to include electron cyclotron current drive (ECCD) and discuss previous models proposed by Giruzzi et al. [2] and by Hegna and Callen [3]. To model neoclassical tearing mode (NTM) instabilities and study the growth of magnetic islands as NTMs evolve, we employ the nonlinear reduced-MHD simulation JOREK. We present tearing-mode growth-rate calculations from JOREK simulations.
NASA Technical Reports Server (NTRS)
Barth, Timothy
2005-01-01
The role of involutions in energy stability of the discontinuous Galerkin (DG) discretization of Maxwell and magnetohydrodynamic (MHD) systems is examined. Important differences are identified in the symmetrization of the Maxwell and MHD systems that impact the construction of energy stable discretizations using the DG method. Specifically, general sufficient conditions to be imposed on the DG numerical flux and approximation space are given so that energy stability is retained These sufficient conditions reveal the favorable energy consequence of imposing continuity in the normal component of the magnetic induction field at interelement boundaries for MHD discretizations. Counterintuitively, this condition is not required for stability of Maxwell discretizations using the discontinuous Galerkin method.
Koga, D; Chian, A C-L; Hada, T; Rempel, E L
2008-02-13
Magnetohydrodynamic (MHD) turbulence is commonly observed in the solar wind. Nonlinear interactions among MHD waves are likely to produce finite correlation of the wave phases. For discussions of various transport processes of energetic particles, it is fundamentally important to determine whether the wave phases are randomly distributed (as assumed in the quasi-linear theory) or have a finite coherence. Using a method based on the surrogate data technique, we analysed the GEOTAIL magnetic field data to evaluate the phase coherence in MHD turbulence in the Earth's foreshock region. The results demonstrate the existence of finite phase correlation, indicating that nonlinear wave-wave interactions are in progress. PMID:17681910
NASA Technical Reports Server (NTRS)
Curtis, Steven
1999-01-01
Global MHD (magnetohydrodynamic) simulations have shown a remarkable ability to describe the global dynamics of geospace. The limitations of the physical approximations underlying MHD would seem to limit the effectiveness of these codes, since kinetic and hybrid effects should manifest themselves by cross-scale coupling from microscales to mesoscales to global scales. However three effects appear to allow the codes to operate much more successfully than one would at first believe. They are:(l) the globally self-consistent nature of the codes with very well defined exterior boundary conditions (the solar wind) which allows the proper intercommunication between magnetospheric regions on MHD scales, (2) the control by global dynamics of the boundary layer locations where micro and meso scale processes operate, and (3) the critical role of numerical diffusion and with a sufficiently high resolution grid, the use of an empirical resistivity term, which if set at a level where the major magnetosphere boundaries properly calibrate against their observed locations, appear to well represent the effects of kinetic and hybrid processes on the global dynamics. The effectiveness of the global MHD codes, which have been developed under the ISTP mission, in describing Wind, Polar and Geotail observations, as well as ground-based observations are described. Particular emphasis is placed upon the Polar imaging data which when combined with ground-based data and global MHD-based synthetic aurora and convection patterns provide a powerful tool in understanding the final link in the solar-terrestrial chain: coupling into the atmosphere and ionosphere.
Energy dissipation in magnetohydrodynamic turbulence: coherent structures or 'nanoflares'?
Zhdankin, Vladimir; Boldyrev, Stanislav; Perez, Jean Carlos; Tobias, Steven M.
2014-11-10
We investigate the intermittency of energy dissipation in magnetohydrodynamic (MHD) turbulence by identifying dissipative structures and measuring their characteristic scales. We find that the probability distribution of energy dissipation rates exhibits a power-law tail with an index very close to the critical value of –2.0, which indicates that structures of all intensities contribute equally to energy dissipation. We find that energy dissipation is uniformly spread among coherent structures with lengths and widths in the inertial range. At the same time, these structures have thicknesses deep within the dissipative regime. As the Reynolds number is increased, structures become thinner and more numerous, while the energy dissipation continues to occur mainly in large-scale coherent structures. This implies that in the limit of high Reynolds number, energy dissipation occurs in thin, tightly packed current sheets which nevertheless span a continuum of scales up to the system size, exhibiting features of both coherent structures and nanoflares previously conjectured as a coronal heating mechanism.
Energy Dissipation in Magnetohydrodynamic Turbulence: Coherent Structures or "Nanoflares"?
NASA Astrophysics Data System (ADS)
Zhdankin, Vladimir; Boldyrev, Stanislav; Perez, Jean Carlos; Tobias, Steven M.
2014-11-01
We investigate the intermittency of energy dissipation in magnetohydrodynamic (MHD) turbulence by identifying dissipative structures and measuring their characteristic scales. We find that the probability distribution of energy dissipation rates exhibits a power-law tail with an index very close to the critical value of -2.0, which indicates that structures of all intensities contribute equally to energy dissipation. We find that energy dissipation is uniformly spread among coherent structures with lengths and widths in the inertial range. At the same time, these structures have thicknesses deep within the dissipative regime. As the Reynolds number is increased, structures become thinner and more numerous, while the energy dissipation continues to occur mainly in large-scale coherent structures. This implies that in the limit of high Reynolds number, energy dissipation occurs in thin, tightly packed current sheets which nevertheless span a continuum of scales up to the system size, exhibiting features of both coherent structures and nanoflares previously conjectured as a coronal heating mechanism.
MHD considerations for a self-cooled liquid lithium blanket
NASA Astrophysics Data System (ADS)
Sze, D. K.; Mattas, R. F.; Hull, A. B.; Picologlou, B. F.; Smith, D. L.
1992-03-01
The magnetohydrodynamic (MHD) effects can present a feasibility issue for a self-cooled liquid metal blanket of magnetically confined fusion reactors, especially the inboard regime of a tokamak. This pressure drop can be significantly reduced by using an insulated wall structure. A self-healing insulating coating has been identified, which will reduce the pressure drop by more than a factor of 10. The future research direction to further quantify the performance of this coating is also outlined.
Gas-Kinetic Theory Based Flux Splitting Method for Ideal Magnetohydrodynamics
NASA Technical Reports Server (NTRS)
Xu, Kun
1998-01-01
A gas-kinetic solver is developed for the ideal magnetohydrodynamics (MHD) equations. The new scheme is based on the direct splitting of the flux function of the MHD equations with the inclusion of "particle" collisions in the transport process. Consequently, the artificial dissipation in the new scheme is much reduced in comparison with the MHD Flux Vector Splitting Scheme. At the same time, the new scheme is compared with the well-developed Roe-type MHD solver. It is concluded that the kinetic MHD scheme is more robust and efficient than the Roe- type method, and the accuracy is competitive. In this paper the general principle of splitting the macroscopic flux function based on the gas-kinetic theory is presented. The flux construction strategy may shed some light on the possible modification of AUSM- and CUSP-type schemes for the compressible Euler equations, as well as to the development of new schemes for a non-strictly hyperbolic system.
Analysis and design of an ultrahigh temperature hydrogen-fueled MHD generator
NASA Technical Reports Server (NTRS)
Moder, Jeffrey P.; Myrabo, Leik N.; Kaminski, Deborah A.
1993-01-01
A coupled gas dynamics/radiative heat transfer analysis of partially ionized hydrogen, in local thermodynamic equilibrium, flowing through an ultrahigh temperature (10,000-20,000 K) magnetohydrodynamic (MHD) generator is performed. Gas dynamics are modeled by a set of quasi-one-dimensional, nonlinear differential equations which account for friction, convective and radiative heat transfer, and the interaction between the ionized gas and applied magnetic field. Radiative heat transfer is modeled using nongray, absorbing-emitting 2D and 3D P-1 approximations which permit an arbitrary variation of the spectral absorption coefficient with frequency. Gas dynamics and radiative heat transfer are coupled through the energy equation and through the temperature- and density-dependent absorption coefficient. The resulting nonlinear elliptic problem is solved by iterative methods. Design of such MHD generators as onboard, open-cycle, electric power supplies for a particular advanced airbreathing propulsion concept produced an efficient and compact 128-MWe generator characterized by an extraction ratio of 35.5 percent, a power density of 10,500 MWe/cu m, and a specific (extracted) energy of 324 MJe/kg of hydrogen. The maximum wall heat flux and total wall heat load were 453 MW/sq m and 62 MW, respectively.
MHD Contractors' Review Meeting: Abstracts
NASA Astrophysics Data System (ADS)
The objectives of the Integrated Topping Cycle project are to design, construct, and deliver all prototypical hardware necessary to conduct long duration integrated MHD topping cycle proof-of-concept tests at the Component Development and Integration Facility (CDIF) in Butte, Montana. The results of the long duration tests will augment the existing engineering data base on MHD power train reliability, maintainability, durability, and performance, and will serve as a basis for scaling up to the early commercial scale power plant retrofit. The components of the MHD power train to be designed, fabricated, and tested include the following three systems: (1) a slagging coal combustion subsystem with a rated capacity of 50 MW thermal input, capable of operation with eastern (Illinois) or western (Montana Rosebud) coal; (2) a channel subsystem consisting of a segmented supersonic nozzle, channel (with current controls), and diffuser, capable of power output of 1.5 MW(sub e); and (3) a current consolidation subsystem to interface the channel with the existing facility inverter.
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.
NASA Astrophysics Data System (ADS)
Tomida, Kengo; Okuzumi, Satoshi; Machida, Masahiro N.
2015-03-01
The transport of angular momentum by magnetic fields is a crucial physical process in the formation and evolution of stars and disks. Because the ionization degree in star-forming clouds is extremely low, nonideal magnetohydrodynamic (MHD) effects such as ambipolar diffusion and ohmic dissipation work strongly during protostellar collapse. These effects have significant impacts in the early phase of star formation as they redistribute magnetic flux and suppress angular momentum transport by magnetic fields. We perform three-dimensional nested-grid radiation magnetohydrodynamic simulations including ohmic dissipation and ambipolar diffusion. Without these effects, magnetic fields transport angular momentum so efficiently that no rotationally supported disk is formed even after the second collapse. Ohmic dissipation works only in a relatively high density region within the first core and suppresses angular momentum transport, enabling formation of a very small rotationally supported disk after the second collapse. With both ohmic dissipation and ambipolar diffusion, these effects work effectively in almost the entire region within the first core and significant magnetic flux loss occurs. As a result, a rotationally supported disk is formed even before a protostellar core forms. The size of the disk is still small, about 5 AU at the end of the first core phase, but this disk will grow later as gas accretion continues. Thus, the nonideal MHD effects can resolve the so-called magnetic braking catastrophe while keeping the disk size small in the early phase, which is implied from recent interferometric observations.
Contributions from space technology to central power generation
NASA Technical Reports Server (NTRS)
Dicks, J. B., Jr.
1972-01-01
The central power crisis, and the present and relatively near-time contributions that aerospace technology is making to help solve this crisis are discussed. The principal emphasis is placed on the prospects of aerospace derived magnetohydrodynamic (MHD) large scale power generation. The strides that the Soviet Union is making in this field with the startup of the new U-25 plant near Moscow, having a total power capability of 75 MW, are reviewed. A much smaller program in the U.S. is outlined, and prospects of future benefits are discussed.
New Exact Relations for Helicities in Hall Magnetohydrodynamic Turbulence
NASA Astrophysics Data System (ADS)
Banerjee, Supratik; Galtier, Sebastien
2016-04-01
Hall magnetohydrodynamics is a mono-fluid plasma model appropriate for probing Final{some of the} physical processes (other than pure kinetic effects) at length scales smaller than the scales of standard MHD. In sub-ionic space plasma turbulence (e.g. the solar wind) this fluid model has been proved to be useful. Three-dimensional incompressible Hall magnetohydrodynamics (MHD) possesses three inviscid invariants which are the total energy, the magnetic helicity and the generalized helicity. In this presentation, we would like to discuss new exact relations for helicities (magnetic helicities and generalized helicities) which are derived for homogeneous stationary (not necessarily isotropic) Hall MHD turbulence (and also for its inertialess electron MHD limit) in the asymptotic limit of large Reynolds numbers. The universal laws are written only in terms of mixed second-order structure functions, i.e. the scalar product of two different increments and are written simply as ηM = di < δ ( {b} × {j}) \\cdot δ {b} >, with ηM the average magnetic helicity flux rate, {b} the magnetic field, {j} the current and ± ηG = < δ ( {v} × {Ω} ) \\cdot δ {Ω} > , with ηM the average generalized helicity flux rate, {v} the fluid velocity and {Ω} = {b} + dI {ω} being the generalized helicity where ω is simply the fluid vorticity ( = nabla × {v}). It provides, therefore, a direct measurement of the dissipation rates for the corresponding helicities even in case of an anisotropic plasma turbulence. This study shows that the generalized helicity cascade is strongly linked to the left polarized fluctuations while the magnetic helicity cascade is linked to the right polarized fluctuations. The newly derived relations also show that like energy, a non-zero helicity flux can only be associated to a departure of Beltrami flow state. {Reference} S. Banerjee & S. Galtier, {Chiral Exact Relations for Helicities in Hall Magnetohydrodynamic Turbulence} (submitted).
NASA Astrophysics Data System (ADS)
Burke, B. J.; Kruger, S. E.; Hegna, C. C.; Zhu, P.; Snyder, P. B.; Sovinec, C. R.; Howell, E. C.
2010-03-01
A linear benchmark between the linear ideal MHD stability codes ELITE [H. R. Wilson et al., Phys. Plasmas 9, 1277 (2002)], GATO [L. Bernard et al., Comput. Phys. Commun. 24, 377 (1981)], and the extended nonlinear magnetohydrodynamic (MHD) code, NIMROD [C. R. Sovinec et al.., J. Comput. Phys. 195, 355 (2004)] is undertaken for edge-localized (MHD) instabilities. Two ballooning-unstable, shifted-circle tokamak equilibria are compared where the stability characteristics are varied by changing the equilibrium plasma profiles. The equilibria model an H-mode plasma with a pedestal pressure profile and parallel edge currents. For both equilibria, NIMROD accurately reproduces the transition to instability (the marginally unstable mode), as well as the ideal growth spectrum for a large range of toroidal modes (n =1-20). The results use the compressible MHD model and depend on a precise representation of "ideal-like" and "vacuumlike" or "halo" regions within the code. The halo region is modeled by the introduction of a Lundquist-value profile that transitions from a large to a small value at a flux surface location outside of the pedestal region. To model an ideal-like MHD response in the core and a vacuumlike response outside the transition, separate criteria on the plasma and halo Lundquist values are required. For the benchmarked equilibria the critical Lundquist values are 108 and 103 for the ideal-like and halo regions, respectively. Notably, this gives a ratio on the order of 105, which is much larger than experimentally measured values using Te values associated with the top of the pedestal and separatrix. Excellent agreement with ELITE and GATO calculations are made when sharp boundary transitions in the resistivity are used and a small amount of physical dissipation is added for conditions very near and below marginal ideal stability.
Picologlou, B F; Batenin, V M
1981-01-01
A description of the main results obtained during Tests No. 6 and 7 at the U-25B Facility using the new channel No. 2 is presented. The purpose of these tests was to operate the MHD generator at its design parameters. Described here are new plasma diagnostic devices: a traversing dual electrical probe for determining distribution of electron concentrations, and a traversing probe that includes a pitot tube for measuring total and static pressure, and a light detector for measuring plasma luminescence. Data are presented on heat flux distribution along the channel, the first data of this type obtained for an MHD facility of such size. Results are given of experimental studies of plasma characteristics, gasdynamic, thermal, and electrical MHD channel performance, and temporal and spatial nonuniformities. Typical modes of operation are analyzed by means of local electrical analyses. Computer models are used to obtain predictions for both localized and overall generator characteristics. These theoretical predictions agree closely with the results of the local analyses, as well as with measurements of the overall gasdynamic and electrical characteristics of the generator.
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
Broken Ergodicity in MHD Turbulence in a Spherical Domain
NASA Technical Reports Server (NTRS)
Shebalin, John V.; wang, Yifan
2011-01-01
Broken ergodicity (BE) occurs in Fourier method numerical simulations of ideal, homogeneous, incompressible magnetohydrodynamic (MHD) turbulence. Although naive statistical theory predicts that Fourier coefficients of fluid velocity and magnetic field are zero-mean random variables, numerical simulations clearly show that low-wave-number coefficients have non-zero mean values that can be very large compared to the associated standard deviation. In other words, large-scale coherent structure (i.e., broken ergodicity) in homogeneous MHD turbulence can spontaneously grow out of random initial conditions. Eigenanalysis of the modal covariance matrices in the probability density functions of ideal statistical theory leads to a theoretical explanation of observed BE in homogeneous MHD turbulence. Since dissipation is minimal at the largest scales, BE is also relevant for resistive magnetofluids, as evidenced in numerical simulations. Here, we move beyond model magnetofluids confined by periodic boxes to examine BE in rotating magnetofluids in spherical domains using spherical harmonic expansions along with suitable boundary conditions. We present theoretical results for 3-D and 2-D spherical models and also present computational results from dynamical simulations of 2-D MHD turbulence on a rotating spherical surface. MHD turbulence on a 2-D sphere is affected by Coriolus forces, while MHD turbulence on a 2-D plane is not, so that 2-D spherical models are a useful (and simpler) intermediate stage on the path to understanding the much more complex 3-D spherical case.
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
A theory of MHD instability of an inhomogeneous plasma jet
NASA Astrophysics Data System (ADS)
Leonovich, Anatoly S.
2011-06-01
A problem of the stability of an inhomogeneous axisymmetric plasma jet in a parallel magnetic field is solved. The jet boundary becomes, under certain conditions, unstable relative to magnetosonic oscillations (Kelvin-Helmholtz instability) in the presence of a shear flow at the jet boundary. Because of its internal inhomogeneity the plasma jet has resonance surfaces, where conversion takes place between various modes of plasma magnetohydrodynamic (MHD) oscillations. Propagating in inhomogeneous plasma, fast magnetosonic waves drive the Alfven and slow magnetosonic (SMS) oscillations, tightly localized across the magnetic shells, on the resonance surfaces. MHD oscillation energy is absorbed in the neighbourhood of these resonance surfaces. The resonance surfaces disappear for the eigenmodes of SMS waves propagating in the jet waveguide. The stability of the plasma MHD flow is determined by competition between the mechanisms of shear flow instability on the boundary and wave energy dissipation because of resonant MHD-mode coupling. The problem is solved analytically, in the Wentzel, Kramers, Brillouin (WKB) approximation, for the plasma jet with a boundary in the form of a tangential discontinuity over the radial coordinate. The Kelvin-Helmholtz instability develops if plasma flow velocity in the jet exceeds the maximum Alfven speed at the boundary. The stability of the plasma jet with a smooth boundary layer is investigated numerically for the basic modes of MHD oscillations, to which the WKB approximation is inapplicable. A new 'unstable mode of MHD oscillations has been discovered which, unlike the Kelvin-Helmholtz instability, exists for any, however weak, plasma flow velocities.
Evaluation of materials for the MHD steam bottoming plant
Natesan, K.; Swift, W.M.
1989-05-01
Test data have been obtained on the corrosion of several commercial ASME-coded alloys and their weldments by exposing internally cooled ring specimens to simulated magnetohydrodynamics (MHD) environments. The specimens, coated with a K/sub 2/SO/sub 4/-rich deposit, were exposed for times up to 2000 h at metal temperatures of 762, 593, and 567/degree/C to simulated MHD conditions for the intermediate-temperature air heater (ITAH), ITAH transition region (transition from a low- to medium-chromium alloy to a high-chromium steel), and secondary superheater (SSH), respectively. This paper discusses, in detail, the observed corrosion scale morphologies of various exposed specimens. Data on scale thickness, depth of intergranular penetration, and metal recession are presented, and the results are used to assess the corrosion behavior of various materials for application in the MHD steam bottoming plant. 6 refs., 7 figs., 3 tabs.
Outline of fast analyzer for MHD equilibrium FAME
NASA Astrophysics Data System (ADS)
Sakata, Shinya; Haginoya, Hirofumi; Tsuruoka, Takuya; Aoyagi, Tetsuo; Saito, Naoyuki; Harada, Hiroo; Tani, Keiji; Watanabe, Hideto
1994-02-01
The FAME (Fast Analyzer for Magnetohydrodynamic (MHD) Equilibrium) system has been developed in order to provide more than 100 MHD equilibria in time series which are enough for the non-stationary analysis of the experimental data of JT-60 within about 20 minutes shot interval. The FAME is an MIMD type small scale parallel computer with 20 microprocessors which are connected by a multi-stage switching system. The maximum theoretical speed is 250 MFLOPS. For the software system of FAME, MHD equilibrium analysis code SELENE and its input data production code FBI are tuned up taking the parallel processing into consideration. Consequently, the computational performance of the FAME system becomes more than 7 times faster than the existing general purpose computer FACOM M780-10s. This report summarizes the outline of the FAME system including hardware, soft-ware and peripheral equipments.
MHD Simulations of Thermal Plasma Jets in Coaxial Plasma Accelerators
NASA Astrophysics Data System (ADS)
Subramaniam, Vivek; Raja, Laxminarayan
2015-09-01
The development of a magneto-hydrodynamics (MHD) numerical tool to study high energy density thermal plasma in coaxial plasma accelerators is presented. The coaxial plasma accelerator is a device used simulate the conditions created at the confining wall of a thermonuclear fusion reactor during an edge localized mode (ELM) disruption event. This is achieved by creating magnetized thermal plasma in a coaxial volume which is then accelerated by the Lorentz force to form a high velocity plasma jet. The simulation tool developed solves the resistive MHD equation using a finite volume method (FVM) framework. The acceleration and subsequent demagnetization of the plasma as it travels down the length of the accelerator is simulated and shows good agreement with experiments. Additionally, a model to study the thermalization of the plasma at the inlet is being developed in order to give self-consistent initial conditions to the MHD solver.
High Resolution Simulations of Relativistic Hydrodynamic and MHD Turbulence
NASA Astrophysics Data System (ADS)
Zrake, Jonathan; MacFadyen, A.
2013-01-01
We present a program of simulations designed to investigate the basic properties of relativistic hydrodynamic and magnetohydrodynamic (MHD) turbulence. We employ a well-tested 5th-order accurate numerical scheme at resolutions of up to 2048^3 zones for hydrodynamic turbulence, and a minimally diffusive 2nd-order scheme at resolutions of up to 1024^3 in the case of relativistic MHD. For the hydrodynamic case, we simulate a relativistically hot gas in a cubic periodic domain continuously driven at large scales with Lorentz factor of about 3. We find that relativistic turbulent velocity fluctuations with Γ β > 1 persist from the driving scale down to scales an order of magnitude smaller, demonstrating the existence of a sustained relativistic turbulent cascade. The power spectrum of the fluid 4-velocity is broadly Kolmogorov-like, roughly obeying a power law with 5/3 index between scales 1/10 and 1/100 of the domain. Departures from 5/3 scaling are larger for the power spectrum of 3-velocity. We find that throughout the inertial interval, 25% of power is in dilatational modes, which obey strict power law scaling between 1/2 and 1/100 of the domain with an index of 1.88. Our program also explores turbulent amplification of magnetic fields in the conditions of merging neutron stars, using a realistic equation of state for dense nuclear matter (ρ ˜ 10^13 g/cm^3). We find that very robustly, seed fields are amplified to magnetar strength (≥ 4 * 10^16 Gauss) within ˜1 micro-second for fluid volumes near the size of the NS crust thickness <10 meters. We present power spectra of the kinetic and magnetic energy taken long into the fully stationary evolution of the highest resolution models, finding the magnetic energy to be in super-equipartition (4 times larger) with the kinetic energy through the inertial range. We believe that current global simulations of merging NS binaries are insufficiently resolved for studying field amplification via turbulent processes
Large amplitude MHD waves upstream of the Jovian bow shock
NASA Technical Reports Server (NTRS)
Goldstein, M. L.; Smith, C. W.; Matthaeus, W. H.
1983-01-01
Observations of large amplitude magnetohydrodynamics (MHD) waves upstream of Jupiter's bow shock are analyzed. The waves are found to be right circularly polarized in the solar wind frame which suggests that they are propagating in the fast magnetosonic mode. A complete spectral and minimum variance eigenvalue analysis of the data was performed. The power spectrum of the magnetic fluctuations contains several peaks. The fluctuations at 2.3 mHz have a direction of minimum variance along the direction of the average magnetic field. The direction of minimum variance of these fluctuations lies at approximately 40 deg. to the magnetic field and is parallel to the radial direction. We argue that these fluctuations are waves excited by protons reflected off the Jovian bow shock. The inferred speed of the reflected protons is about two times the solar wind speed in the plasma rest frame. A linear instability analysis is presented which suggests an explanation for many of the observed features of the observations.
Magnetic fields in Planetary Nebulae: paradigms and related MHD frontiers
NASA Astrophysics Data System (ADS)
Blackman, Eric G.
2009-04-01
Many, if not all, post AGB stellar systems swiftly transition from a spherical to a powerful aspherical pre-planetary nebula (pPNE) outflow phase before waning into a PNe. The pPNe outflows require engine rotational energy and a mechanism to extract this energy into collimated outflows. Just radiation and rotation are insufficient but a symbiosis between rotation, differential rotation and large scale magnetic fields remains promising. Present observational evidence for magnetic fields in evolved stars is suggestive of dynamically important magnetic fields, but both theory and observation are rife with research opportunity. I discuss how magnetohydrodynamic outflows might arise in pPNe and PNe and distinguish different between approaches that address shaping vs. those that address both launch and shaping. Scenarios involving dynamos in single stars, binary driven dynamos, or accretion engines cannot be ruled out. One appealing paradigm involves accretion onto the primary post-AGB white dwarf core from a low mass companion whose decaying accretion supply rate owers first the pPNe and then the lower luminosity PNe. Determining observational signatures of different MHD engines is a work in progress. Accretion disk theory and large scale dynamos pose many of their own fundamental challenges, some of which I discuss in a broader context.
In Situ Magnetohydrodynamic Energy Generation for Planetary Entry Vehicles
NASA Astrophysics Data System (ADS)
Ali, H. K.; Braun, R. D.
2014-06-01
This work aims to study the suitability of multi-pass entry trajectories for harnessing of vehicle kinetic energy through magnetohydrodynamic power generation from the high temperature entry plasma. Potential mission configurations are analyzed.
SCALING PROPERTIES OF SMALL-SCALE FLUCTUATIONS IN MAGNETOHYDRODYNAMIC TURBULENCE
Perez, Jean Carlos; Mason, Joanne; Boldyrev, Stanislav; Cattaneo, Fausto E-mail: j.mason@exeter.ac.uk E-mail: cattaneo@flash.uchicago.edu
2014-09-20
Magnetohydrodynamic (MHD) turbulence in the majority of natural systems, including the interstellar medium, the solar corona, and the solar wind, has Reynolds numbers far exceeding the Reynolds numbers achievable in numerical experiments. Much attention is therefore drawn to the universal scaling properties of small-scale fluctuations, which can be reliably measured in the simulations and then extrapolated to astrophysical scales. However, in contrast with hydrodynamic turbulence, where the universal structure of the inertial and dissipation intervals is described by the Kolmogorov self-similarity, the scaling for MHD turbulence cannot be established based solely on dimensional arguments due to the presence of an intrinsic velocity scale—the Alfvén velocity. In this Letter, we demonstrate that the Kolmogorov first self-similarity hypothesis cannot be formulated for MHD turbulence in the same way it is formulated for the hydrodynamic case. Besides profound consequences for the analytical consideration, this also imposes stringent conditions on numerical studies of MHD turbulence. In contrast with the hydrodynamic case, the discretization scale in numerical simulations of MHD turbulence should decrease faster than the dissipation scale, in order for the simulations to remain resolved as the Reynolds number increases.
General polytropic magnetohydrodynamic cylinder under self-gravity
NASA Astrophysics Data System (ADS)
Lou, Yu-Qing; Xing, Heng-Rui
2016-02-01
Based on general polytropic (GP) magnetohydrodynamics (MHD), we offer a self-similar dynamic formalism for a magnetized, infinitely long, axially uniform cylinder of axisymmetry under self-gravity with radial and axial flows and with helical magnetic field. We identify two major classes of solution domains and obtain a few valuable MHD integrals in general. We focus on one class that has the freedom of prescribing a GP dynamic equation of state including the isothermal limit and derive analytic asymptotic solutions for illustration. In particular, we re-visit the isothermal MHD problem of Tilley & Pudritz (TP) and find that TP's main conclusion regarding the MHD solution behaviour for a strong ring magnetic field of constant toroidal flux-to-mass ratio Γϕ to be incorrect. As this is important for conceptual scenarios, MHD cylinder models, testing numerical codes and potential observational diagnostics of magnetized filaments in various astrophysical contexts, we show comprehensive theoretical analysis and reasons as well as extensive numerical results to clarify pertinent points in this Letter. In short, for any given Γϕ value be it small or large, the asymptotic radial scaling of the reduced mass density α(x) at sufficiently large x should always be ˜x-4 instead of ˜x-2 contrary to the major claim of TP.
Statistics of passive tracers in three-dimensional magnetohydrodynamic turbulence
Busse, Angela; Mueller, Wolf-Christian; Homann, Holger; Grauer, Rainer
2007-12-15
Magnetohydrodynamic (MHD) turbulence is studied from the Lagrangian viewpoint by following fluid particle tracers in high resolution direct numerical simulations. Results regarding turbulent diffusion and dispersion as well as Lagrangian structure functions are presented. Whereas turbulent single-particle diffusion exhibits essentially the same behavior in Navier-Stokes and MHD turbulence, two-particle relative dispersion in the MHD case differs significantly from the Navier-Stokes behavior. This observation is linked to the local anisotropy of MHD turbulence which is clearly reflected by quantities measured in a Lagrangian frame of reference. In the MHD case the Lagrangian structure functions display a lower level of intermittency as compared to the Navier-Stokes case contrasting Eulerian results. This is not only true for short time increments [H. Homann, R. Grauer, A. Busse, and W.-C. Mueller, J. Plasma Phys. 73, 821 (2007)] but also holds for increments up to the order of the integral time scale. The apparent discrepancy can be explained by the difference in the characteristic shapes of fluid particle trajectories in the vicinity of most singular dissipative structures.
Makwana, K. D.; Zhdankin, V.; Li, H.; Daughton, W.; Cattaneo, F.
2015-04-10
We performed simulations of decaying magnetohydrodynamic (MHD) turbulence with a fluid and a kinetic code. The initial condition is an ensemble of long-wavelength, counter-propagating, shear-Alfvén waves, which interact and rapidly generate strong MHD turbulence. The total energy is conserved and the rate of turbulent energy decay is very similar in both codes, although the fluid code has numerical dissipation, whereas the kinetic code has kinetic dissipation. The inertial range power spectrum index is similar in both the codes. The fluid code shows a perpendicular wavenumber spectral slope of k-1.3⊥k⊥-1.3. The kinetic code shows a spectral slope of k-1.5⊥k⊥-1.5 for smallermore » simulation domain, and k-1.3⊥k⊥-1.3 for larger domain. We then estimate that collisionless damping mechanisms in the kinetic code can account for the dissipation of the observed nonlinear energy cascade. Current sheets are geometrically characterized. Their lengths and widths are in good agreement between the two codes. The length scales linearly with the driving scale of the turbulence. In the fluid code, their thickness is determined by the grid resolution as there is no explicit diffusivity. In the kinetic code, their thickness is very close to the skin-depth, irrespective of the grid resolution. Finally, this work shows that kinetic codes can reproduce the MHD inertial range dynamics at large scales, while at the same time capturing important kinetic physics at small scales.« less
Makwana, K. D.; Zhdankin, V.; Li, H.; Daughton, W.; Cattaneo, F.
2015-04-10
We performed simulations of decaying magnetohydrodynamic (MHD) turbulence with a fluid and a kinetic code. The initial condition is an ensemble of long-wavelength, counter-propagating, shear-Alfvén waves, which interact and rapidly generate strong MHD turbulence. The total energy is conserved and the rate of turbulent energy decay is very similar in both codes, although the fluid code has numerical dissipation, whereas the kinetic code has kinetic dissipation. The inertial range power spectrum index is similar in both the codes. The fluid code shows a perpendicular wavenumber spectral slope of k-1.3⊥k⊥-1.3. The kinetic code shows a spectral slope of k-1.5⊥k⊥-1.5 for smaller simulation domain, and k-1.3⊥k⊥-1.3 for larger domain. We then estimate that collisionless damping mechanisms in the kinetic code can account for the dissipation of the observed nonlinear energy cascade. Current sheets are geometrically characterized. Their lengths and widths are in good agreement between the two codes. The length scales linearly with the driving scale of the turbulence. In the fluid code, their thickness is determined by the grid resolution as there is no explicit diffusivity. In the kinetic code, their thickness is very close to the skin-depth, irrespective of the grid resolution. Finally, this work shows that kinetic codes can reproduce the MHD inertial range dynamics at large scales, while at the same time capturing important kinetic physics at small scales.
Optimum performance of MHD-augumented chemical rocket thrusters for space propulsion applications
Schulz, R.J.; Chapman, J.N.
1995-12-31
The use of magnetohydrodynamic (MHD) acceleration of a chemical rocket exhaust stream, to augment the thrust of small, space-propulsion type chemical thrusters was examined, with the purpose of identifying {open_quotes}optimum{close_quotes} performance. Optimum performance is defined herein as the highest spacecraft acceleration levels with concurrent highest specific impulse, that the hybrid propulsion system can generate, given a fixed mass flow of propellant and fixed chamber pressure (150 psia). The exhaust nozzle-MHD channel selected was of the simplest kind, a three-segmented Faraday generator, for simplicity in design, manufacture, and power control circuit assembly. The channel expanded in only one plane or direction, the plane intersecting the electrodes. The distance between the side walls was fixed. Three different fuel oxidizer combinations were investigated: H{sub 2} - O{sub 2}, fuel oil - O{sub 2}, and hydrazine - nitrogen tetroxide. These represent the spectrum of typical liquid rocket propellants. The fraction of the propellant flow representing potassium, as K{sub 2}CO{sub 3}, was kept constant at 1/2 percent of the total propellant flow. The results of the study verify that the MHD-augmented chemical thruster will be an important propulsion system option for space missions requiring accelerations of the order of milli-gravities with specific impulses of the order of 4,000 seconds. The system study showed that a 3-segmented, diverging Faraday channel with about a 2{degrees} divergence angle, enclosed by a 4 Tesla magnet, was capable of providing exhaust gas exit velocities of the order of 40000 m/s for all three propellant combinations. Hence, a hybrid propulsion system of the type identified here is capable of providing thrusts of the order of 400 Newtons, spacecraft accelerations of the order 2 milli-gravities, with electric power requirements of about 2.4 megawatts, based on propellant total mass flow rates of about 10 grams per second.
Robust preconditioners for incompressible MHD models
NASA Astrophysics Data System (ADS)
Ma, Yicong; Hu, Kaibo; Hu, Xiaozhe; Xu, Jinchao
2016-07-01
In this paper, we develop two classes of robust preconditioners for the structure-preserving discretization of the incompressible magnetohydrodynamics (MHD) system. By studying the well-posedness of the discrete system, we design block preconditioners for them and carry out rigorous analysis on their performance. We prove that such preconditioners are robust with respect to most physical and discretization parameters. In our proof, we improve the existing estimates of the block triangular preconditioners for saddle point problems by removing the scaling parameters, which are usually difficult to choose in practice. This new technique is applicable not only to the MHD system, but also to other problems. Moreover, we prove that Krylov iterative methods with our preconditioners preserve the divergence-free condition exactly, which complements the structure-preserving discretization. Another feature is that we can directly generalize this technique to other discretizations of the MHD system. We also present preliminary numerical results to support the theoretical results and demonstrate the robustness of the proposed preconditioners.
NASA Astrophysics Data System (ADS)
Mansour, M. A.; El-Hakiem, M. A.; El Kabeir, S. M.
2000-10-01
Steady laminar boundary layer analysis of heat and mass transfer characteristics in magnetohydrodynamic (MHD) flow of a micropolar fluid on a circular cylinder maintained at uniform heat and mass flux has been conducted. The solution of the energy equation inside the boundary layer is obtained as a power series of the distance measured along the surface from the front stagnation point of the cylinder. The results of dimensionless temperature, Nusselt number, wall shear stress, wall couple stress and Sherwood number have been presented graphically for various values of the material parameters. The results indicate that the micropolar fluids display a reduction in drag as well as heat transfer rate when compared with Newtonian fluids.
Magnetohydrodynamic stability of a compound liquid jet
NASA Astrophysics Data System (ADS)
Radwan, Ahmed E.
1989-10-01
The magnetohydrodynamics (MHD) stability of a compound nonmiscible fluid jet is discussed. A general eigenvalue relation, for that model which involves the fluid inertia, capillarity and electromagnetic forces, is derived. The model is capillary unstable only for small axisymmetric disturbances and stable for the rest. The magnetic fields interior and exterior to the gas-mantle jet have always a stabilizing influence. The radii ratio of the concentric jets plays an important role in the (instability) stability states and are (decreasing) increasing with increasing magnetic field intensity as the exterior radius is much larger than the interior radius; under some restrictions of the radii ratio and above a certain value of the magnetic field the capillary instability is omitted and completely suppressed and then stability sets in. The latter result is verified analytically and confirmed numerically in the case in which the cylindrical surface of the outer jet is sited at infinity.
General Relativistic Magnetohydrodynamic Simulations of Collapsars
NASA Technical Reports Server (NTRS)
Mizuno, Yosuke; Yamada, S.; Koider, S.; Shipata, K.
2005-01-01
We have performed 2.5-dimensional general relativistic magnetohydrodynamic (MHD) simulations of collapsars including a rotating black hole. Initially, we assume that the core collapse has failed in this star. A rotating black hole of a few solar masses is inserted by hand into the calculation. The simulation results show the formation of a disklike structure and the generation of a jetlike outflow near the central black hole. The jetlike outflow propagates and accelerated mainly by the magnetic field. The total jet velocity is approximately 0.3c. When the rotation of the black hole is faster, the magnetic field is twisted strongly owing to the frame-dragging effect. The magnetic energy stored by the twisting magnetic field is directly converted to kinetic energy of the jet rather than propagating as an Alfven wave. Thus, as the rotation of the black hole becomes faster, the poloidal velocity of the jet becomes faster.
NASA Astrophysics Data System (ADS)
Nazirov, R. R.; Rabinovich, B. I.; Mytarev, A. I.
2008-06-01
This paper is a continuation of [1 3] and a generalization of the results for a rotating spacecraft with cavities partially filled with liquid and equipped with an operational magnetohydrodynamic (MHD) element in the loop of its attitude control. This element makes possible the creation of hingeless systems of stabilization and orientation that do not require rocket propellant consumption. The application of an MHD element is considered for stabilization in the mode of spin-up of a spacecraft not having gyroscopic stability.
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.
Numerical Simulation of Turbulent MHD Flows Using an Iterative PNS Algorithm
NASA Technical Reports Server (NTRS)
Kato, Hiromasa; Tannehill, John C.; Mehta, Unmeel B.
2003-01-01
A new parabolized Navier-Stokes (PNS) algorithm has been developed to efficiently compute magnetohydrodynamic (MHD) flows in the low magnetic Reynolds number regime. In this regime, the electrical conductivity is low and the induced magnetic field is negligible compared to the applied magnetic field. The MHD effects are modeled by introducing source terms into the PNS equation which can then be solved in a very efficient manner. To account for upstream (elliptic) effects, the flowfields are computed using multiple streamwise sweeps with an iterated PNS algorithm. Turbulence has been included by modifying the Baldwin-Lomax turbulence model to account for MHD effects. The new algorithm has been used to compute both laminar and turbulent, supersonic, MHD flows over flat plates and supersonic viscous flows in a rectangular MHD accelerator. The present results are in excellent agreement with previous complete Navier-Stokes calculations.
A Meshless Method for Magnetohydrodynamics and Applications to Protoplanetary Disks
NASA Astrophysics Data System (ADS)
McNally, Colin P.
2012-08-01
This thesis presents an algorithm for simulating the equations of ideal magnetohydrodynamics and other systems of differential equations on an unstructured set of points represented by sample particles. Local, third-order, least-squares, polynomial interpolations (Moving Least Squares interpolations) are calculated from the field values of neighboring particles to obtain field values and spatial derivatives at the particle position. Field values and particle positions are advanced in time with a second order predictor-corrector scheme. The particles move with the fluid, so the time step is not limited by the Eulerian Courant-Friedrichs-Lewy condition. Full spatial adaptivity is implemented to ensure the particles fill the computational volume, which gives the algorithm substantial flexibility and power. A target resolution is specified for each point in space, with particles being added and deleted as needed to meet this target. Particle addition and deletion is based on a local void and clump detection algorithm. Dynamic artificial viscosity fields provide stability to the integration. The resulting algorithm provides a robust solution for modeling flows that require Lagrangian or adaptive discretizations to resolve. The code has been parallelized by adapting the framework provided by Gadget-2. A set of standard test problems, including one part in a million amplitude linear MHD waves, magnetized shock tubes, and Kelvin-Helmholtz instabilities are presented. Finally we demonstrate good agreement with analytic predictions of linear growth rates for magnetorotational instability in a cylindrical geometry. We provide a rigorous methodology for verifying a numerical method on two dimensional Kelvin-Helmholtz instability. The test problem was run in the Pencil Code, Athena, Enzo, NDSPHMHD, and Phurbas. A strict comparison, judgment, or ranking, between codes is beyond the scope of this work, although this work provides the mathematical framewor! k needed for such a
NASA Astrophysics Data System (ADS)
Stone, James M.; Norman, Michael L.
1992-06-01
In this, the second of a series of three papers, we continue a detailed description of ZEUS-2D, a numerical code for the simulation of fluid dynamical flows in astrophysics including a self-consistent treatment of the effects of magnetic fields and radiation transfer. In this paper, we give a detailed description of the magnetohydrodynamical (MHD) algorithms in ZEUS-2D. The recently developed constrained transport (CT) algorithm is implemented for the numerical evolution of the components of the magnetic field for MHD simulations. This formalism guarantees the numerically evolved field components will satisfy the divergence-free constraint at all times. We find, however, that the method used to compute the electromotive forces must be chosen carefully to propagate accurately all modes of MHD wave families (in particular shear Alfvén waves). A new method of computing the electromotive force is developed using the method of characteristics (MOC). It is demonstrated through the results of an extensive series of MHD test problems that the resulting hybrid MOC-CT method provides for the accurate evolution of all modes of MHD wave families.
Theoretical study of anisotropic MHD turbulence with low magnetic Reynolds number
NASA Astrophysics Data System (ADS)
Sukoriansky, Semion; Zemach, Efi
2016-03-01
Flows of electrically conducting fluids under the action of external magnetic field present an example of strongly anisotropic turbulence. Such flows are not only important for different engineering applications, but also provide an interesting framework for studies of quasi-two-dimensional turbulence with strongly modified transport properties in easily controllable laboratory experiments. We present theoretical results that advance our understanding of magnetohydrodynamic (MHD) flows with low magnetic Reynolds number by treating this phenomenon within the quasi-normal scale elimination (QNSE) theory. Previous applications of the theory to turbulent flows with stable stratification and solid body rotation have demonstrated that QNSE is a powerful tool for studies of anisotropic turbulent flows. We derive expressions for scale-dependent eddy viscosities and eddy diffusivities in the directions parallel and normal to the external magnetic field and investigate progressive anisotropization of turbulent transport of momentum and passive scalar. The theory yields analytical expressions for anisotropic one-dimensional spectra of MHD turbulence. In particular, the theory sheds light upon the modification of the Kolmogorov k-5/3 spectrum by anisotropic Ohmic (Joule) dissipation.
MHD Coal-Fired Flow Facility. Quarterly/annual technical progress report, October-December 1979
Dicks, J. B.; Chapman, J. N.; Crawford, L. W.
1980-02-01
In this Fourth Quarterly/Annual Report submitted under DOE contracts EX-76-C-01-1760 and DE-AC02-79ET10815, the University of Tennessee Space Institute (UTSI) reports on significant activity, task status, planned research, testing, and development, and conclusions for the Magnetohydrodynamics (MHD) Coal-Fired Flow Facility (CFFF) and the Research and Development Laboratory. Work on the CFFF progressed with only minor problems. Total construction activity for all site work presently awarded is nearly 98% complete. Water analysis shows that Woods Reservoir baseline conditions are within EPA or Tennessee drinking water standards. For the primary combustor, the vitiation heater and primary combustor fabrication drawings were completed and the nozzle design was completed. The drum module for the radiant slagging furnace was awarded. On the MHD Power Generator, development continued in several areas of advanced analysis including development of time-dependent models for use with the one-dimensional code. For seed regeneration, the tentative determination is that the Tomlinson Tampella is the most economically viable method. With regard to capped electrode erosion, investigations have shown that the major degradation of the cladding still present is at the leading edge of the capped anode. To alleviate this, plans are to hot work the noble metal in the bending operation. In resolving another problem, a system employing the modified line-reversal method has been assembled and successfully tested to measure absolute plasma temperatures.
Nonlinear magnetohydrodynamic stability
NASA Technical Reports Server (NTRS)
Bauer, F.; Betancourt, O.; Garabedian, P.
1981-01-01
The computer code developed by Bauer et al. (1978) for the study of the magnetohydrodynamic equilibrium and stability of a plasma in toroidal geometry is extended so that the growth rates of instabilities may be estimated more accurately. The original code, which is based on the variational principle of ideal magnetohydrodynamics, is upgraded by the introduction of a nonlinear formula for the growth rate of an unstable mode which acts as a quantitative measure of instability that is important in estimating numerical errors. The revised code has been applied to the determination of the nonlinear saturation, ballooning modes and beta limits for tokamaks, stellarators and torsatrons.
Gao, Feng; Kreidermacher, Adam; Fritsch, Ingrid; Heyes, Colin D
2013-05-01
Redox magnetohydrodynamics (MHD) is a promising technique for developing new electrochemical-based microfluidic flow devices with unique capabilities, such as easily switching flow direction and adjusting flow speeds and flow patterns as well as avoiding bubble formation. However, a detailed description of all the forces involved and predicting flow patterns in confined geometries is lacking. In addition to redox-MHD, density gradients caused by the redox reactions also play important roles. Flow in these devices with small fluid volumes has mainly been characterized by following microbead motion by optical microscopy either by particle tracking velocimetry (PTV) or by processing the microbead images by particle image velocimetry (PIV) software. This approach has limitations in spatial resolution and dimensionality. Here we use fluorescence correlation spectroscopy (FCS) to quantitatively and accurately measure flow speeds and patterns in the ~5-50 μm/s range in redox-MHD-based microfluidic devices, from which 3D flow maps are obtained with a spatial resolution down to 2 μm. The 2 μm spatial resolution flow speeds map revealed detailed flow profiles during redox-MHD in which the velocity increases linearly from above the electrode and reaches a plateau across the center of the cell. By combining FCS and video-microscopy (with PTV and PIV processing approaches), we are able to quantify a vertical flow of ~10 μm/s above the electrodes as a result of density gradients caused by the redox reactions and follow convection flow patterns. Overall, combining FCS, PIV, and PTV analysis of redox-MHD is a powerful combination to more thoroughly characterize the underlying forces in these promising microfluidic devices. PMID:23537496
Gao, Feng; Kreidermacher, Adam; Fritsch, Ingrid; Heyes, Colin D.
2013-01-01
Redox magnetohydrodynamics (MHD) is a promising technique for developing new electrochemical-based microfluidic flow devices with unique capabilities, such as easily switching flow direction, adjusting flow speeds and flow patterns as well as avoiding bubble formation. However, a detailed description of all the forces involved and predicting flow patterns in confined geometries is lacking. In addition to redox-MHD, density gradients caused by the redox reactions also play important roles. Flow in these devices with small fluid volumes has mainly been characterized by following microbead motion by optical microscopy either by particle tracking velocimetry (PTV) or by processing the microbead images by particle image velocimetry (PIV) software. This approach has limitations in spatial resolution and dimensionality. Here we use fluorescence correlation spectroscopy (FCS) to quantitatively and accurately measure flow speeds and patterns in the ~5-50 μm/s range in redox-MHD-based microfluidic devices, from which 3D flow maps are obtained with a spatial resolution down to 2 μm. The 2 μm spatial resolution flow speeds map revealed detailed flow profiles during redox-MHD in which the velocity increases linearly from above the electrode, and reaches a plateau across the center of the channel. By combining FCS and video-microscopy (with PTV and PIV processing approaches), we are able to quantify a vertical flow of ~10 μm/s above the electrodes as a result of density gradients caused by the redox reactions and follow convection flow patterns. Overall, combining FCS, PIV and PTV analysis of redox-MHD is a powerful combination to more thoroughly characterize the underlying forces in these promising microfluidic devices. PMID:23537496
Dissipation of Molecular Cloud Turbulence by Magnetohydrodynamic Shockwaves
NASA Astrophysics Data System (ADS)
Lehmann, Andrew; Wardle, Mark
2015-08-01
The character of star formation is intimately related to the supersonic magnetohydrodynamic (MHD) turbulent dynamics of the giant molecular clouds in which stars form. A significant amount of the turbulent energy dissipates in low velocity shock waves. These shocks cause molecular line cooling of the compressed and heated gas, and so their radiative signatures probe the nature of the turbulence. In MHD fluids the three distinct families of shocks—fast, intermediate and slow—differ in how they compress and heat the molecular gas, and so observational differences between them may also distinguish driving modes of turbulent regions.Here we use a two-fluid model to compare the characteristics of one-dimensional fast and slow MHD shocks. Fast MHD shocks are magnetically driven, forcing ion species to stream through the neutral gas ahead of the shock front. This magnetic precursor heats the gas sufficiently to create a large, warm transition zone where all the fluid variables only weakly change in the shock front. In contrast, slow MHD shocks are driven by gas pressure where neutral species collide with ion species in a thin hot slab that closely resembles an ordinary gas dynamic shock.We computed observational diagnostics for fast and slow shocks at velocities vs = 2-4 km/s and preshock Hydrogen nuclei densities n(H) = 102-4 cm-3. We followed the abundances of molecules relevant for a simple oxygen chemistry and include cooling by CO, H2 and H2O. Estimates of intensities of CO rotational lines show that high-J lines, above J = 6→5, are more strongly excited in slow MHD shocks. We discuss how these shocks could help interpret recently observed anomalously strong mid- and high-J CO lines emitted by warm gas in the Milky Way and external galaxies, and implications for simulations of MHD turbulence.
NASA Astrophysics Data System (ADS)
Branover, Herman; Mond, Michael; Unger, Yeshajahu
The present collection of papers on MHD-related uses of liquid metal flows and their applications discusses topics in laminar MHD flows, MHD power generation, metallurgical MHD applications, and two-phase MHD flows. Attention is given to MHD flows with closed streamlines, nonlinear waves in liquid metals under a transverse magnetic field, liquid-metal MHD conversion of nuclear energy to electricity, the testing of optimized MHD conversion ('OMACON') systems, and aspects of a liquid-metal induction generator. Also discussed are MHD effects in liquid-metal breeder reactors, a plasma-driven MHD powerplant, modeling the recirculating flows in channel-induction surfaces, the hydrodynamics of aluminum reduction cells, free-surface determination in a levitation-melting process, the parametric interactions of waves in bubbly liquid metals, and the occurrence of cavitation in water jets.
Electron magnetohydrodynamics: dynamics and turbulence.
Lyutikov, Maxim
2013-11-01
We consider dynamics and turbulent interaction of whistler modes within the framework of inertialess electron magnetohydrodynamics (EMHD). We argue that there is no energy principle in EMHD: any stationary closed configuration is neutrally stable. On the other hand, the relaxation principle, the long term evolution of a weakly dissipative system towards Taylor-Beltrami state, remains valid in EMHD. We consider the turbulent cascade of whistler modes. We show that (i) harmonic whistlers are exact nonlinear solutions; (ii) collinear whistlers do not interact (including counterpropagating); (iii) waves with the same value of the wave vector k(1)=k(2) do not interact; (iv) whistler modes have a dispersion that allows a three-wave decay, including into a zero frequency mode; (v) the three-wave interaction effectively couples modes with highly different wave numbers and propagation angles. In addition, linear interaction of a whistler with a single zero mode can lead to spatially divergent structures via parametric instability. All these properties are drastically different from MHD, so that the qualitative properties of the Alfvén turbulence can not be transferred to the EMHD turbulence. We derive the Hamiltonian formulation of EMHD, and using Bogoliubov transformation reduce it to the canonical form; we calculate the matrix elements for the three-wave interaction of whistlers. We solve numerically the kinetic equation and show that, generally, the EMHD cascade develops within a broad range of angles, while transiently it may show anisotropic, nearly two-dimensional structures. Development of a cascade depends on the forcing (nonuniversal) and often fails to reach a steady state. Analytical estimates predict the spectrum of magnetic fluctuations for the quasi-isotropic cascade [proportionality]k(-2). The cascade remains weak (not critically balanced). The cascade is UV local, while the infrared locality is weakly (logarithmically) violated. PMID:24329368
Electron magnetohydrodynamics: Dynamics and turbulence
NASA Astrophysics Data System (ADS)
Lyutikov, Maxim
2013-11-01
We consider dynamics and turbulent interaction of whistler modes within the framework of inertialess electron magnetohydrodynamics (EMHD). We argue that there is no energy principle in EMHD: any stationary closed configuration is neutrally stable. On the other hand, the relaxation principle, the long term evolution of a weakly dissipative system towards Taylor-Beltrami state, remains valid in EMHD. We consider the turbulent cascade of whistler modes. We show that (i) harmonic whistlers are exact nonlinear solutions; (ii) collinear whistlers do not interact (including counterpropagating); (iii) waves with the same value of the wave vector k1=k2 do not interact; (iv) whistler modes have a dispersion that allows a three-wave decay, including into a zero frequency mode; (v) the three-wave interaction effectively couples modes with highly different wave numbers and propagation angles. In addition, linear interaction of a whistler with a single zero mode can lead to spatially divergent structures via parametric instability. All these properties are drastically different from MHD, so that the qualitative properties of the Alfvén turbulence can not be transferred to the EMHD turbulence. We derive the Hamiltonian formulation of EMHD, and using Bogoliubov transformation reduce it to the canonical form; we calculate the matrix elements for the three-wave interaction of whistlers. We solve numerically the kinetic equation and show that, generally, the EMHD cascade develops within a broad range of angles, while transiently it may show anisotropic, nearly two-dimensional structures. Development of a cascade depends on the forcing (nonuniversal) and often fails to reach a steady state. Analytical estimates predict the spectrum of magnetic fluctuations for the quasi-isotropic cascade ∝k-2. The cascade remains weak (not critically balanced). The cascade is UV local, while the infrared locality is weakly (logarithmically) violated.
A pressure-based high resolution numerical method for resistive MHD
NASA Astrophysics Data System (ADS)
Xisto, Carlos M.; Páscoa, José C.; Oliveira, Paulo J.
2014-10-01
In the paper we describe in detail a numerical method for the resistive magnetohydrodynamic (MHD) equations involving viscous flow and report the results of application to a number of typical MHD test cases. The method is of the finite volume type but mixes aspects of pressure-correction and density based solvers; the algorithm arrangement is patterned on the well-known PISO algorithm, which is a pressure method, while the flux computation makes use of the AUSM-MHD scheme, which originates from density based methods. Five groups of test cases are addressed to verify and validate the method. We start with two resistive MHD cases, namely the Shercliff and Hunt flow problems, which are intended to validate the method for low-speed resistive MHD flows. The remaining three test cases, namely the cloud-shock interaction, the MHD rotor and the MHD blast wave, are standard 2D ideal MHD problems that serve to validate the method under high-speed flow and complex interaction of MHD shocks. Finally, we demonstrate the method with a more complex application problem, and discuss results of simulation for a quasi-bi-dimensional self-field magnetoplasmadynamic (MPD) thruster, for which we study the effect of cathode length upon the electromagnetic nozzle performance.
Martin, L. N.; Dmitruk, P.; Gomez, D. O.
2010-11-15
In this work we numerically test a model of Hall magnetohydrodynamics in the presence of a strong mean magnetic field: the reduced Hall magnetohydrodynamic model (RHMHD) derived by [Gomez et al., Phys. Plasmas 15, 102303 (2008)] with the addition of weak compressible effects. The main advantage of this model lies in the reduction of computational cost. Nevertheless, up until now the degree of agreement with the original Hall MHD system and the range of validity in a regime of turbulence were not established. In this work direct numerical simulations of three-dimensional Hall MHD turbulence in the presence of a strong mean magnetic field are compared with simulations of the weak compressible RHMHD model. The results show that the degree of agreement is very high (when the different assumptions of RHMHD, such as spectral anisotropy, are satisfied). Nevertheless, when the initial conditions are isotropic but the mean magnetic field is maintained strong, the results differ at the beginning but asymptotically reach a good agreement at relatively short times. We also found evidence that the compressibility still plays a role in the dynamics of these systems, and the weak compressible RHMHD model is able to capture these effects. In conclusion the weak compressible RHMHD model is a valid approximation of the Hall MHD turbulence in the relevant physical context.
Anisotropic scaling of magnetohydrodynamic turbulence.
Horbury, Timothy S; Forman, Miriam; Oughton, Sean
2008-10-24
We present a quantitative estimate of the anisotropic power and scaling of magnetic field fluctuations in inertial range magnetohydrodynamic turbulence, using a novel wavelet technique applied to spacecraft measurements in the solar wind. We show for the first time that, when the local magnetic field direction is parallel to the flow, the spacecraft-frame spectrum has a spectral index near 2. This can be interpreted as the signature of a population of fluctuations in field-parallel wave numbers with a k(-2)_(||) spectrum but is also consistent with the presence of a "critical balance" style turbulent cascade. We also find, in common with previous studies, that most of the power is contained in wave vectors at large angles to the local magnetic field and that this component of the turbulence has a spectral index of 5/3. PMID:18999759
Nonlinear entropy production operators for magnetohydrodynamic plasmas
Siregar, E.; Ghosh, S.; Goldstein, M.L.
1995-05-01
A method for constructing closure relations based on the invariants of the tensors representing nonequilibrium thermodynamic forcing within the plasma is presented. This approach leads to closure relations that describe all higher-order forcing effects contained within the continuum description. Nonlinear convective-momentum transport and nonlinear momentum-exchange operators are constructed as applications of the method. Closure is achieved by relating the pressure tensor to invariants of the rate of strain tensor, and the momentum-exchange operator to invariants of the gradient of magnetic field tensor. These operators lead to positive definite viscous and Joule entropy production and enhance high wave number dissipative couplings over all other dissipative couplings. The nonlinear dissipative action is localized in physical space, where velocity and magnetic gradients are large, while allowing nearly ideal behavior elsewhere. The operators are computationally tested against the standard magnetohydrodynamic (MHD) operators using three-dimensional configurations that lead to vortex street formation and magnetic reconnection. The nonlinear operators allow greater spatial structure and have flatter modal energy spectra than the standard MHD dissipation operators. Closures that describe the plasma response to nonequilibrium thermodynamic forcing of all orders can be constructed using this approach. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
Magneto-hydrodynamically stable axisymmetric mirrorsa)
NASA Astrophysics Data System (ADS)
Ryutov, D. D.; Berk, H. L.; Cohen, B. I.; Molvik, A. W.; Simonen, T. C.
2011-09-01
Making axisymmetric mirrors magnetohydrodynamically (MHD) stable opens up exciting opportunities for using mirror devices as neutron sources, fusion-fission hybrids, and pure-fusion reactors. This is also of interest from a general physics standpoint (as it seemingly contradicts well-established criteria of curvature-driven instabilities). The axial symmetry allows for much simpler and more reliable designs of mirror-based fusion facilities than the well-known quadrupole mirror configurations. In this tutorial, after a summary of classical results, several techniques for achieving MHD stabilization of the axisymmetric mirrors are considered, in particular: (1) employing the favorable field-line curvature in the end tanks; (2) using the line-tying effect; (3) controlling the radial potential distribution; (4) imposing a divertor configuration on the solenoidal magnetic field; and (5) affecting the plasma dynamics by the ponderomotive force. Some illuminative theoretical approaches for understanding axisymmetric mirror stability are described. The applicability of the various stabilization techniques to axisymmetric mirrors as neutron sources, hybrids, and pure-fusion reactors are discussed; and the constraints on the plasma parameters are formulated.
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.
Realistic magnetohydrodynamical simulation of solar local supergranulation
NASA Astrophysics Data System (ADS)
Ustyugov, Sergey D.
2010-12-01
Three-dimensional numerical simulations of solar surface magnetoconvection using realistic model physics are conducted. The thermal structure of convective motions into the upper radiative layers of the photosphere, the main scales of convective cells and the penetration depths of convection are investigated. We take part of the solar photosphere with a size of 60×60 Mm2 in the horizontal direction and of depth 20 Mm from the level of the visible solar surface. We use a realistic initial model of the sun and apply the equation of state and opacities of stellar matter. The equations of fully compressible radiation magnetohydrodynamics (MHD) with dynamical viscosity and gravity are solved. We apply (i) the conservative total variation diminishing (TVD) difference scheme for MHD, (ii) the diffusion approximation for radiative transfer and (iii) dynamical viscosity from subgrid-scale modeling. In simulation, we take a uniform two-dimensional grid in the horizontal plane and a nonuniform grid in the vertical direction with the number of cells being 600×600×204. We use 512 processors with distributed memory multiprocessors on the supercomputer MVS-100k at the Joint Computational Centre of the Russian Academy of Sciences.
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.
Large-scale quasi-geostrophic magnetohydrodynamics
Balk, Alexander M.
2014-12-01
We consider the ideal magnetohydrodynamics (MHD) of a shallow fluid layer on a rapidly rotating planet or star. The presence of a background toroidal magnetic field is assumed, and the 'shallow water' beta-plane approximation is used. We derive a single equation for the slow large length scale dynamics. The range of validity of this equation fits the MHD of the lighter fluid at the top of Earth's outer core. The form of this equation is similar to the quasi-geostrophic (Q-G) equation (for usual ocean or atmosphere), but the parameters are essentially different. Our equation also implies the inverse cascade; but contrary to the usual Q-G situation, the energy cascades to smaller length scales, while the enstrophy cascades to the larger scales. We find the Kolmogorov-type spectrum for the inverse cascade. The spectrum indicates the energy accumulation in larger scales. In addition to the energy and enstrophy, the obtained equation possesses an extra (adiabatic-type) invariant. Its presence implies energy accumulation in the 30° sector around zonal direction. With some special energy input, the extra invariant can lead to the accumulation of energy in zonal magnetic field; this happens if the input of the extra invariant is small, while the energy input is considerable.
Magnetohydrodynamic waves in fusion and astrophysical plasmas.
NASA Astrophysics Data System (ADS)
Goedbloed, J. P.
Macroscopic plasma dynamics in both controlled thermonuclear confinement machines and in the atmospheres of X-ray emitting stars is described by the equations of magnetohydrodynamics. This provides a vast area of overlapping research activities which is presently actively pursued. In this lecture the author concentrates on some important differences in the dynamics of the two confined plasma systems related to the very different geometries that are encountered and, thus, the role of the different boundary conditions that have to be posed. As a result, the basic MHD waves in a tokamak are quite different from those found in a solar magnetic flux tube. The result is that, whereas the three well-known MHD waves can be traced stepwise in the curved geometry of a tokamak, their separate existence is eliminated right from the start in a line-tied coronal loop because line-tying in general conflicts with the phase relationships between the vector components of the three velocity fields. The consequences are far-reaching, viz. completely different resonant frequencies and continuous spectra, absence of rational magnetic surfaces, and irrelevance of local marginal stability theory for coronal magnetic loops.
Status of Magnetohydrodynamic Augmented Propulsion Experiment
NASA Technical Reports Server (NTRS)
Litchford, Ron J.; Lineberry, John T.
2007-01-01
Over the past several years, efforts have been under way to design and develop an operationally flexible research facility for investigating the use of cross-field MHD accelerators as a potential thrust augmentation device for thermal propulsion systems, The baseline configuration for this high-power experimental facility utilizes a 1,5-MW, multi-gas arc-heater as a thermal driver for a 2-MW, MHD accelerator, which resides in a large-bore 2-tesla electromagnet. A preliminary design study using NaK seeded nitrogen as the working fluid led to an externally diagonalized segmented MHD channel configuration based on an expendable beat-sink design concept. The current status report includes a review of engineering/design work and performance optimization analyses and summarizes component hardware fabrication and development efforts, preliminary testing results, and recent progress toward full-up assembly and testing
Statistical Theory of the Ideal MHD Geodynamo
NASA Technical Reports Server (NTRS)
Shebalin, J. V.
2012-01-01
A statistical theory of geodynamo action is developed, using a mathematical model of the geodynamo as a rotating outer core containing an ideal (i.e., no dissipation), incompressible, turbulent, convecting magnetofluid. On the concentric inner and outer spherical bounding surfaces the normal components of the velocity, magnetic field, vorticity and electric current are zero, as is the temperature fluctuation. This allows the use of a set of Galerkin expansion functions that are common to both velocity and magnetic field, as well as vorticity, current and the temperature fluctuation. The resulting dynamical system, based on the Boussinesq form of the magnetohydrodynamic (MHD) equations, represents MHD turbulence in a spherical domain. These basic equations (minus the temperature equation) and boundary conditions have been used previously in numerical simulations of forced, decaying MHD turbulence inside a sphere [1,2]. Here, the ideal case is studied through statistical analysis and leads to a prediction that an ideal coherent structure will be found in the form of a large-scale quasistationary magnetic field that results from broken ergodicity, an effect that has been previously studied both analytically and numerically for homogeneous MHD turbulence [3,4]. The axial dipole component becomes prominent when there is a relatively large magnetic helicity (proportional to the global correlation of magnetic vector potential and magnetic field) and a stationary, nonzero cross helicity (proportional to the global correlation of velocity and magnetic field). The expected angle of the dipole moment vector with respect to the rotation axis is found to decrease to a minimum as the average cross helicity increases for a fixed value of magnetic helicity and then to increase again when average cross helicity approaches its maximum possible value. Only a relatively small value of cross helicity is needed to produce a dipole moment vector that is aligned at approx.10deg with the
Forest, C. B.
2002-11-15
The project is designed to understand current and magnetic field generation in plasmas and other magnetohydrodynamic systems. The experiments will investigate the generation of a dynamo using liquid Na.
NASA Technical Reports Server (NTRS)
Musielak, Z. E.; Rosner, R.
1988-01-01
Magnetohydrodynamic (MHD) wave energy fluxes for late-type stars are calculated, using previously obtained formulae for the source functions for the generation of MHD waves in a stratified, but otherwise uniform, turbulent atmosphere; the magnetic fields in the wave generation region are assumed to be homogeneous. In contradiction to previous results, it is shown that in this uniform magnetic field case there is no significant increase in the efficiency of MHD wave generation, at least within the theory's limits of applicability. The major results are that the MHD energy fluxes calculated for late-type stars are less than those obtained for compressible modes in the magnetic field-free case, and that these MHD energy fluxes do not vary enough for a given spectral type to explain the observed range of UV and X-ray fluxes from such stars. It is therefore concluded that MHD waves in stellar atmospheres with homogeneous magnetic fields in the wave generation region cannot explain the observed stellar coronal emissions; if such MHD waves are responsible for a significant component of stellar coronal heating, then nonuniform fields within the generation region must be appealed to.
Validation of Magnetospheric Magnetohydrodynamic Models
NASA Astrophysics Data System (ADS)
Curtis, Brian
Magnetospheric magnetohydrodynamic (MHD) models are commonly used for both prediction and modeling of Earth's magnetosphere. To date, very little validation has been performed to determine their limits, uncertainties, and differences. In this work, we performed a comprehensive analysis using several commonly used validation techniques in the atmospheric sciences to MHD-based models of Earth's magnetosphere for the first time. The validation techniques of parameter variability/sensitivity analysis and comparison to other models were used on the OpenGGCM, BATS-R-US, and SWMF magnetospheric MHD models to answer several questions about how these models compare. The questions include: (1) the difference between the model's predictions prior to and following to a reversal of Bz in the upstream interplanetary field (IMF) from positive to negative, (2) the influence of the preconditioning duration, and (3) the differences between models under extreme solar wind conditions. A differencing visualization tool was developed and used to address these three questions. We find: (1) For a reversal in IMF Bz from positive to negative, the OpenGGCM magnetopause is closest to Earth as it has the weakest magnetic pressure near-Earth. The differences in magnetopause positions between BATS-R-US and SWMF are explained by the influence of the ring current, which is included in SWMF. Densities are highest for SWMF and lowest for OpenGGCM. The OpenGGCM tail currents differ significantly from BATS-R-US and SWMF; (2) A longer preconditioning time allowed the magnetosphere to relax more, giving different positions for the magnetopause with all three models before the IMF Bz reversal. There were differences greater than 100% for all three models before the IMF Bz reversal. The differences in the current sheet region for the OpenGGCM were small after the IMF Bz reversal. The BATS-R-US and SWMF differences decreased after the IMF Bz reversal to near zero; (3) For extreme conditions in the solar
MHD Instabilities Occurring Near/AT the Transport Barrier, Including Loss of Confinement in H-Modes
L. L. Lao
1999-09-01
In configurations with transport barriers the improved edge and core confinement leads to large pressure gradient and large edge bootstrap current density which often drive magnetohydrodynamic (MHD) instabilities terminating the discharge or reducing the discharge performance. The edge and the core transport barriers deteriorate or are completely lost. In this presentation, recent experimental and theoretical developments concerning MHD instabilities occurring near/at the edge and the core transport barriers are summarized emphasizing the dominant instabilities and the comparison with theory.
On the theory of MHD waves in a shear flow of a magnetized turbulent plasma
NASA Astrophysics Data System (ADS)
Mishonov, Todor M.; Maneva, Yana G.; Dimitrov, Zlatan D.; Hristov, Tihomir S.
The set of equations for magnetohydrodynamic (MHD) waves in a shear flow is consecutively derived. This investigation is devoted on the wave heating of space plasmas. The proposed scenario involves the presence of a self-sustained turbulence and magnetic field. In the framework of Langevin--Burgers approach the influence of the turbulence is described by an additional external random force in the MHD system. Kinetic equation for the spectral density of the slow magnetosonic (Alfvénic) mode is derived in the short wavelength (WKB) approximation. The results show a pressing need for conduction of numerical Monte Carlo (MC) simulations with a random driver to take into account the influence of the long wavelength modes and to give a more precise analytical assessment of the short ones. Realistic MC calculations for the heating rate and shear stress tensor should give an answer to the perplexing problem for the missing viscosity in accretion disks and reveal why the quasars are the most powerful sources of light in the universe. It is supposed that the heating mechanism by alfvén waves absorption is common for many kinds of space plasmas from solar corona to active galactic nuclei and the solution of these longstanding puzzles deserves active interdisciplinary research. The work is illustrated by typical solutions of MHD equations and their spectral densities obtained by numerical calculations or by analytical solutions with the help of Heun functions. The amplification coefficient of slow magnetosonic wave in shear flow is analytically calculated. Pictorially speaking, if in WKB approximation we treat Alfvén waves as particles -- this amplification is effect of ``lasing of alfvons.''
Global and Kinetic MHD Simulation by the Gpic-MHD Code
NASA Astrophysics Data System (ADS)
Hiroshi, Naitou; Yusuke, Yamada; Kenji, Kajiwara; Wei-li, Lee; Shinji, Tokuda; Masatoshi, Yagi
2011-10-01
In order to implement large-scale and high-beta tokamak simulation, a new algorithm of the electromagnetic gyrokinetic PIC (particle-in-cell) code was proposed and installed on the Gpic-MHD code [Gyrokinetic PIC code for magnetohydrodynamic (MHD) simulation]. In the new algorithm, the vorticity equation and the generalized Ohm's law along the magnetic field are derived from the basic equations of the gyrokinetic Vlasov, Poisson, and Ampere system and are used to describe the spatio-temporal evolution of the field quantities of the electrostatic potential varphi and the longitudinal component of the vector potential Az. The basic algorithm is equivalent to solving the reduced-MHD-type equations with kinetic corrections, in which MHD physics related to Alfven modes are well described. The estimation of perturbed electron pressure from particle dynamics is dominant, while the effects of other moments are negligible. Another advantage of the algorithm is that the longitudinal induced electric field, ETz = -∂Az/∂t, is explicitly estimated by the generalized Ohm's law and used in the equations of motion. Furthermore, the particle velocities along the magnetic field are used (vz-formulation) instead of generalized momentums (pz-formulation), hence there is no problem of ‘cancellation', which would otherwise appear when Az is estimated from the Ampere's law in the pz-formulation. The successful simulation of the collisionless internal kink mode by the new Gpic-MHD with realistic values of the large-scale and high-beta tokamaks revealed the usefulness of the new algorithm.
Magneto-hydrodynamically stable axisymmetric mirrors
NASA Astrophysics Data System (ADS)
Ryutov, Dmitri
2010-11-01
The achievement of high beta (60%) plasma with near classical confinement in a linear axisymmetric magnetic configuration has sparked interest in the Gas Dynamic Trap concept. The significance of these results is that they can be projected directly to a neutron source for materials testing. The possibility of axisymmetric mirrors (AM) being magneto-hydrodynamically (MHD) stable is also of interest from a general physics standpoint (as it seemingly contradicts to well-established criteria of curvature-driven instabilities). The axial symmetry allows for much simpler and more reliable designs of mirror-based fusion facilities than the well-known quadrupole mirror configurations. In this tutorial, after a brief summary of classical results (in particular of the Rosenbluth-Longmire theory and of the energy principle as applied to AM) several approaches towards achieving MHD stabilization of the AM will be considered: 1) Employing the favorable field-line curvature in the end tanks; 2) Using the line-tying effect; 3) Setting the plasma in a slow or fast differential rotation; 4) Imposing a divertor configuration on the solenoidal magnetic field; 5) Controlling the plasma dynamics by the ponderomotive force; 6) Other techniques. Several of these approaches go beyond pure MHD and require accounting for finite Larmor radius effects and trapped particle modes. Some illuminative theoretical approaches for understanding axisymmetric mirror stability will be described. Wherever possible comparison of theoretical and experimental results on AM will be provided. The applicability of the various stabilization techniques to axisymmetric mirrors as neutron sources, hybrids, and pure-fusion reactors will be discussed and the constraints on the plasma parameters will be formulated. Prepared by LLNL under Contract DE-AC52-07NA27344.
MHD mixed convection flow of power law non-Newtonian fluids over an isothermal vertical wavy plate
NASA Astrophysics Data System (ADS)
Mirzaei Nejad, Mehrzad; Javaherdeh, K.; Moslemi, M.
2015-09-01
Mixed convection flow of electrically conducting power law fluids along a vertical wavy surface in the presence of a transverse magnetic field is studied numerically. Prandtl coordinate transformation together with the spline alternating direction implicit method is employed to solve the boundary layer equations. The influences of both flow structure and dominant convection mode on the overall parameters of flow and heat transfer are well discussed. Also, the role of magnetic field in controlling the boundary layers is investigated. The variation of Nusselt number and skin friction coefficient are studied as functions of wavy geometry, magnetic field, buoyancy force and material parameters. Results reveal the interrelation of the contributing factors.
A Global Magnetohydrodynamic Model of Jovian Magnetosphere
NASA Technical Reports Server (NTRS)
Walker, Raymond J.; Sharber, James (Technical Monitor)
2001-01-01
The goal of this project was to develop a new global magnetohydrodynamic model of the interaction of the Jovian magnetosphere with the solar wind. Observations from 28 orbits of Jupiter by Galileo along with those from previous spacecraft at Jupiter, Pioneer 10 and 11, Voyager I and 2 and Ulysses, have revealed that the Jovian magnetosphere is a vast, complicated system. The Jovian aurora also has been monitored for several years. Like auroral observations at Earth, these measurements provide us with a global picture of magnetospheric dynamics. Despite this wide range of observations, we have limited quantitative understanding of the Jovian magnetosphere and how it interacts with the solar wind. For the past several years we have been working toward a quantitative understanding of the Jovian magnetosphere and its interaction with the solar wind by employing global magnetohydrodynamic simulations to model the magnetosphere. Our model has been an explicit MHD code (previously used to model the Earth's magnetosphere) to study Jupiter's magnetosphere. We continue to obtain important insights with this code, but it suffers from some severe limitations. In particular with this code we are limited to considering the region outside of 15RJ, with cell sizes of about 1.5R(sub J). The problem arises because of the presence of widely separated time scales throughout the magnetosphere. The numerical stability criterion for explicit MHD codes is the CFL limit and is given by C(sub max)(Delta)t/(Delta)x less than 1 where C(sub max) is the maximum group velocity in a given cell, (Delta)x is the grid spacing and (Delta)t is the time step. If the maximum wave velocity is C(sub w) and the flow speed is C(sub f), C(sub max) = C(sub w) + C(sub f). Near Jupiter the Alfven wave speed becomes very large (it approaches the speed of light at one Jovian radius). Operating with this time step makes the calculation essentially intractable. Therefore under this funding we have been designing a
A Global Magnetohydrodynamic Model of Jovian Magnetosphere
NASA Astrophysics Data System (ADS)
Walker, Raymond J.
2001-01-01
The goal of this project was to develop a new global magnetohydrodynamic model of the interaction of the Jovian magnetosphere with the solar wind. Observations from 28 orbits of Jupiter by Galileo along with those from previous spacecraft at Jupiter, Pioneer 10 and 11, Voyager I and 2 and Ulysses, have revealed that the Jovian magnetosphere is a vast, complicated system. The Jovian aurora also has been monitored for several years. Like auroral observations at Earth, these measurements provide us with a global picture of magnetospheric dynamics. Despite this wide range of observations, we have limited quantitative understanding of the Jovian magnetosphere and how it interacts with the solar wind. For the past several years we have been working toward a quantitative understanding of the Jovian magnetosphere and its interaction with the solar wind by employing global magnetohydrodynamic simulations to model the magnetosphere. Our model has been an explicit MHD code (previously used to model the Earth's magnetosphere) to study Jupiter's magnetosphere. We continue to obtain important insights with this code, but it suffers from some severe limitations. In particular with this code we are limited to considering the region outside of 15RJ, with cell sizes of about 1.5RJ. The problem arises because of the presence of widely separated time scales throughout the magnetosphere. The numerical stability criterion for explicit MHD codes is the CFL limit and is given by Cmax)(Delta)t/(Deltax less than 1 where Cmax is the maximum group velocity in a given cell, (Delta)x is the grid spacing and (Delta)t is the time step. If the maximum wave velocity is Cw and the flow speed is Cf, Cmax = Cw + Cf. Near Jupiter the Alfven wave speed becomes very large (it approaches the speed of light at one Jovian radius). Operating with this time step makes the calculation essentially intractable. Therefore under this funding we have been designing a new MHD model that will be able to compute
MHD aspects of fire-hose type instabilities
NASA Astrophysics Data System (ADS)
Wang, B.; Hau, L.
2003-12-01
In a homogeneous anisotropic plasma the magnetohydrodynamic (MHD) Alfvén wave may become unstable for p∥ > pperpendicular to + B2/μ 0. Recently a new type of fire-hose instability is found by Hellinger and Matsumoto [2000] that has maximum growth rate occurring for oblique propagation and may grow faster than the Alfvén mode. This new mode is compressional and may be more efficient at destroying pressure anisotropy than the standard fire hose. In this study we examines the fire-hose type (p∥ > pperpendicular to ) instabilities based on the linear and nonlinear double-polytropic MHD theory. It is shown that there exist two types of MHD fire-hose instabilities associated with the intermediate and slow modes, respectively, and with suitable choice of polytropic exponents the linear instability criteria become the same as those based on the Vlasov theory in the hydromagnetic limit. Moreover, the properties of the nonlinear MHD fire-hose instabilities are found to have great similarities with those obtained from the kinetic theory and hybrid simulation. In particular, the classical fire-hose instability evolves toward the linear fire-hose stability threshold while the nonlinear marginal stability associated with the new fire hose is well below the condition of β ∥ - β perpendicular to = 2 but complies with less stringent linear stability threshold for MHD slow-mode wave.
Dynamo action in dissipative, forced, rotating MHD turbulence
NASA Astrophysics Data System (ADS)
Shebalin, John V.
2016-06-01
Magnetohydrodynamic (MHD) turbulence is an inherent feature of large-scale, energetic astrophysical and geophysical magnetofluids. In general, these are rotating and are energized through buoyancy and shear, while viscosity and resistivity provide a means of dissipation of kinetic and magnetic energy. Studies of unforced, rotating, ideal (i.e., non-dissipative) MHD turbulence have produced interesting results, but it is important to determine how these results are affected by dissipation and forcing. Here, we extend our previous work and examine dissipative, forced, and rotating MHD turbulence. Incompressibility is assumed, and finite Fourier series represent turbulent velocity and magnetic field on a 643 grid. Forcing occurs at an intermediate wave number by a method that keeps total energy relatively constant and allows for injection of kinetic and magnetic helicity. We find that 3-D energy spectra are asymmetric when forcing is present. We also find that dynamo action occurs when forcing has either kinetic or magnetic helicity, with magnetic helicity injection being more important. In forced, dissipative MHD turbulence, the dynamo manifests itself as a large-scale coherent structure that is similar to that seen in the ideal case. These results imply that MHD turbulence, per se, may play a fundamental role in the creation and maintenance of large-scale (i.e., dipolar) stellar and planetary magnetic fields.
An approximate Riemann solver for magnetohydrodynamics (that works in more than one dimension)
NASA Technical Reports Server (NTRS)
Powell, Kenneth G.
1994-01-01
An approximate Riemann solver is developed for the governing equations of ideal magnetohydrodynamics (MHD). The Riemann solver has an eight-wave structure, where seven of the waves are those used in previous work on upwind schemes for MHD, and the eighth wave is related to the divergence of the magnetic field. The structure of the eighth wave is not immediately obvious from the governing equations as they are usually written, but arises from a modification of the equations that is presented in this paper. The addition of the eighth wave allows multidimensional MHD problems to be solved without the use of staggered grids or a projection scheme, one or the other of which was necessary in previous work on upwind schemes for MHD. A test problem made up of a shock tube with rotated initial conditions is solved to show that the two-dimensional code yields answers consistent with the one-dimensional methods developed previously.
A blowup criterion for viscous, compressible, and heat-conductive magnetohydrodynamic flows
NASA Astrophysics Data System (ADS)
Du, Lili; Wang, Yongfu
2015-09-01
In this paper, we proved a blowup criterion for the two-dimensional (2D) viscous, compressible, and heat-conducting magnetohydrodynamic (MHD) flows for Cauchy problem, which depends only on the divergence of the velocity vector field, as well as for the case of bounded domain with Dirichlet boundary conditions. This result indicates that the nature of the blowup for compressible models of viscous media in 2D space is similar to the barotropic compressible Navier-Stokes equations and does not depend on further sophistication of the MHD model. More precisely, taking into account the magnetic effects and heat conductivity does not introduce any new features in the blowup mechanism of full MHD flows, especially, which is independent of the temperature and the magnetic field. The results also imply the global regularity of the strong solution to compressible MHD flows, provided that velocity divergence remains bounded.
Statistical Analysis of Current Sheets in Three-dimensional Magnetohydrodynamic Turbulence
NASA Astrophysics Data System (ADS)
Zhdankin, Vladimir; Uzdensky, Dmitri A.; Perez, Jean C.; Boldyrev, Stanislav
2013-07-01
We develop a framework for studying the statistical properties of current sheets in numerical simulations of magnetohydrodynamic (MHD) turbulence with a strong guide field, as modeled by reduced MHD. We describe an algorithm that identifies current sheets in a simulation snapshot and then determines their geometrical properties (including length, width, and thickness) and intensities (peak current density and total energy dissipation rate). We then apply this procedure to simulations of reduced MHD and perform a statistical analysis on the obtained population of current sheets. We evaluate the role of reconnection by separately studying the populations of current sheets which contain magnetic X-points and those which do not. We find that the statistical properties of the two populations are different in general. We compare the scaling of these properties to phenomenological predictions obtained for the inertial range of MHD turbulence. Finally, we test whether the reconnecting current sheets are consistent with the Sweet-Parker model.
The role of magnetohydrodynamics in heliospheric space plasma physics research
NASA Technical Reports Server (NTRS)
Dryer, Murray; Smith, Zdenka Kopal; Wu, Shi Tsan
1988-01-01
Magnetohydrodynamics (MHD) is a fairly recent extension of the field of fluid mechanics. While much remains to be done, it has successfully been applied to the contemporary field of heliospheric space plasma research to evaluate the 'macroscopic picture' of some vital topics via the use of conducting fluid equations and numerical modeling and simulations. Some representative examples from solar and interplanetary physics are described to demonstrate that the continuum approach to global problems (while keeping in mind the assumptions and limitations therein) can be very successful in providing insight and large scale interpretations of otherwise intractable problems in space physics.
Magnetic reversals in a simple model of magnetohydrodynamics.
Benzi, Roberto; Pinton, Jean-François
2010-07-01
We study a simple magnetohydrodynamical approach in which hydrodynamics and MHD turbulence are coupled in a shell model, with given dynamo constraints in the large scales. We consider the case of a low Prandtl number fluid for which the inertial range of the velocity field is much wider than that of the magnetic field. Random reversals of the magnetic field are observed and it shown that the magnetic field has a nontrivial evolution--linked to the nature of the hydrodynamics turbulence. PMID:20867710
Ring current instabilities in the magnetohydrodynamic frequency range
NASA Technical Reports Server (NTRS)
Hasegawa, A.; Chen, L.
1992-01-01
This report summarizes recent theoretical developments in ring current plasma instabilities in the magnetohydrodynamic (MHD) frequency range but with the effect of finite Larmor radius, and discusses its relevance to satellite-based observations. Possible instabilities are the bounce resonant instabilities caused by a humped energy distribution, the drift mirror instability caused by an anisotropic pressure and the drift wave type instability caused by a combination of drift-bounce resonance and reduced Alfven frequency due to a high beta loading of the flux tube. Here, beta is proportional to plasma/magnetic pressures. Mechanisms leading to turbulence are also discussed.
MAGNETOHYDRODYNAMIC SIMULATION OF A SIGMOID ERUPTION OF ACTIVE REGION 11283
Jiang Chaowei; Feng Xueshang; Wu, S. T.; Hu Qiang E-mail: fengx@spaceweather.ac.cn E-mail: qh0001@uah.edu
2013-07-10
Current magnetohydrodynamic (MHD) simulations of the initiation of solar eruptions are still commonly carried out with idealized magnetic field models, whereas the realistic coronal field prior to eruptions can possibly be reconstructed from the observable photospheric field. Using a nonlinear force-free field extrapolation prior to a sigmoid eruption in AR 11283 as the initial condition in an MHD model, we successfully simulate the realistic initiation process of the eruption event, as is confirmed by a remarkable resemblance to the SDO/AIA observations. Analysis of the pre-eruption field reveals that the envelope flux of the sigmoidal core contains a coronal null and furthermore the flux rope is prone to a torus instability. Observations suggest that reconnection at the null cuts overlying tethers and likely triggers the torus instability of the flux rope, which results in the eruption. This kind of simulation demonstrates the capability of modeling the realistic solar eruptions to provide the initiation process.
Hamiltonian magnetohydrodynamics: Lagrangian, Eulerian, and dynamically accessible stability—Theory
Andreussi, T.; Morrison, P. J.; Pegoraro, F.
2013-09-15
Stability conditions of magnetized plasma flows are obtained by exploiting the Hamiltonian structure of the magnetohydrodynamics (MHD) equations and, in particular, by using three kinds of energy principles. First, the Lagrangian variable energy principle is described and sufficient stability conditions are presented. Next, plasma flows are described in terms of Eulerian variables and the noncanonical Hamiltonian formulation of MHD is exploited. For symmetric equilibria, the energy-Casimir principle is expanded to second order and sufficient conditions for stability to symmetric perturbation are obtained. Then, dynamically accessible variations, i.e., variations that explicitly preserve invariants of the system, are introduced and the respective energy principle is considered. General criteria for stability are obtained, along with comparisons between the three different approaches.