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1

Magnetohydrodynamic power generation

NASA Technical Reports Server (NTRS)

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.

Smith, J. L.

1984-01-01

2

NASA Technical Reports Server (NTRS)

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

1981-01-01

3

This paper summarizes a method to evaluate the possible effects of magnetohydrodynamic-electromagnetic pulse (MHD-EMP) on power systems. This method is based on the approach adapted to study the impact of geomagnetic storms on power systems. The paper highlights the similarities and differences between the two phenomena. Also presented are areas of concern which are anticipated from MHD-EMP on the overall system operation. 12 refs., 1 fig.

Legro, J.R.; Abi-Samra, N.C.; Crouse, J.C.; Tesche, F.M.

1985-01-01

4

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.

Barnes, P.R. (Oak Ridge National Lab., TN (United States)); Tesche, F.M. (Tesche (F.M.), Dallas, TX (United States)); Vance, E.F. (Vance (E.F.), Fort Worth, TX (United States))

1992-03-01

5

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.

Barnes, P.R. [Oak Ridge National Lab., TN (United States); Tesche, F.M. [Tesche (F.M.), Dallas, TX (United States); Vance, E.F. [Vance (E.F.), Fort Worth, TX (United States)

1992-03-01

6

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. [Tesche (F.M.), Dallas, TX (United States); Barnes, P.R. [Oak Ridge National Lab., TN (United States); Meliopoulos, A.P.S. [Georgia Inst. of Tech., Atlanta, GA (United States). Dept. of Electrical Engineering

1992-02-01

7

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. (Tesche (F.M.), Dallas, TX (United States)) [Tesche (F.M.), Dallas, TX (United States); Barnes, P.R. (Oak Ridge National Lab., TN (United States)) [Oak Ridge National Lab., TN (United States); Meliopoulos, A.P.S. (Georgia Inst. of Tech., Atlanta, GA (United States). Dept. of Electrical Engineering) [Georgia Inst. of Tech., Atlanta, GA (United States). Dept. of Electrical Engineering

1992-02-01

8

ERIC Educational Resources Information Center

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)

Kantrowitz, Arthur; Rosa, Richard J.

1975-01-01

9

NASA Technical Reports Server (NTRS)

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.

Rigo, H. S.; Bercaw, R. W.; Burkhart, J. A.; Mroz, T. S.; Bents, D. J.; Hatch, A. M.

1981-01-01

10

NASA Technical Reports Server (NTRS)

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.

1981-01-01

11

ELECTROOSMOSIS AND THERMAL EFFECTS IN MAGNETOHYDRODYNAMIC (MHD) MICROPUMPS USING 3D MHD

ELECTROOSMOSIS AND THERMAL EFFECTS IN MAGNETOHYDRODYNAMIC (MHD) MICROPUMPS USING 3D MHD EQUATIONS of Vaibhav D. Patel: Electroosmosis and Thermal Effects in Magnetohydrodynamic (MHD) Micropumps Using 3D MHD in Magnetohydrodynamic (MHD) Micropumps Using 3D MHD Equations by Vaibhav D. Patel Masters of Science in Mechanical

Kassegne, Samuel Kinde

12

NASA Technical Reports Server (NTRS)

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.

1981-01-01

13

An innovative demonstration of high power density in a compact MHD (magnetohydrodynamic) generator

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.

Schmidt, H.J.; Lineberry, J.T.; Chapman, J.N.

1990-06-01

14

DESIGN & EXPERIMENTATION OF HIGH CURRENT DENSITY DC MAGNETOHYDRODYNAMIC (MHD) MICROPUMP

DESIGN & EXPERIMENTATION OF HIGH CURRENT DENSITY DC MAGNETOHYDRODYNAMIC (MHD) MICROPUMP Nguyen: Design, Fabrication, & Experimentation of DC MHD Micropump OF THE THESIS Design, Fabrication, & Experimentation of DC MHD Micropump by Bao Thanh Nguyen Master of Science

Kassegne, Samuel Kinde

15

Hypervelocity plasmas with strong MHD (magnetohydrodynamic) interactions

NASA Astrophysics Data System (ADS)

Use of body forces to inject energy into a plasma offers certain advantages over simple energy addition by Ohmic heating. To achieve ever-increasing levels of energy per unit mass by this strategy requires detailed and thorough understanding of high-interaction magnetohydrodynamics (HIMHD) through realistic computer simulation. Such simulation is possible by the existing, HIMHD codes provided they undergo further validation in the high-interaction regime through systematic experiments. The present work has carried out a critical assessment of several methods for achieving high-interaction, high-magnetic Reynolds number MHD flows. It indicates that continuous flow (as contrasted to pulsed flow) plasmajet-drive MHD devices offer the greatest advantages and potential for validating the STD/MHD codes at high MHD interaction over a wide range of parameters with the greatest confidence. It has led to the definition of specific plasmajet-driven experiments, utilizing existing equipment, as the most effective way to carry out this task.

Demetriades, S. T.; Maxwell, C. D.

1984-12-01

16

Magnetohydrodynamic (MHD) channel corner seal

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.

Spurrier, Francis R. (Pittsburgh, PA)

1980-01-01

17

Theoretical and experimental study of MHD (magnetohydrodynamic) micropump

This paper presents a novel micropump of which pumping mechanism is based upon magnetohydrodynamic (MHD) principles. MHD is the study of flow of electrically conducting liquids in electric and magnetic fields. Lorentz force is the pumping source of conductive, aqueous solutions in the MHD micropump. Conducting fluid in the microchannel of the MHD micropump is driven by Lorentz force in

Jaesung Jang; Seung S. Lee

2000-01-01

18

NASA Technical Reports Server (NTRS)

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.

1981-01-01

19

Mesofluidic magnetohydrodynamic power generation

Much of the previous research into magnetohydrodynamics has involved large-scale systems. This thesis explores the miniaturization and use of devices to convert the power dissipated within an expanding gas flow into ...

Fucetola, Jay J

2012-01-01

20

Explosively-driven magnetohydrodynamic (MHD) generator studies

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.

Agee, F.J.; Lehr, F.M. [Phillips Lab., Kirtland AFB, NM (United States); Vigil, M.; Kaye, R. [Sandia National Labs., Albuquerque, NM (United States); Gaudet, J.; Shiffler, D. [New Mexico Univ., Albuquerque, NM (United States)

1995-08-01

21

Hypervelocity plasmas with strong MHD (magnetohydrodynamic) interactions

Use of body forces to inject energy into a plasma offers certain advantages over simple energy addition by Ohmic heating. To achieve ever-increasing levels of energy per unit mass by this strategy requires detailed and thorough understanding of high-interaction magnetohydrodynamics (HIMHD) through realistic computer simulation. Such simulation is possible by the existing, HIMHD codes provided they undergo further validation in

S. T. Demetriades; C. D. Maxwell

1984-01-01

22

NASA Technical Reports Server (NTRS)

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.

1981-01-01

23

NASA Technical Reports Server (NTRS)

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.

Tsu, T. C.

1976-01-01

24

NASA Technical Reports Server (NTRS)

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.

Hoover, D. Q.

1976-01-01

25

Eigenvalues, Eigenvectors and Symmetrization of the Magneto-Hydrodynamic (MHD) Equations

Eigenvalues, Eigenvectors and Symmetrization of the Magneto-Hydrodynamic (MHD) Equations Antony, the eight wave MHD equations proposed by Powell [1] and also studied by Roe [2,3] can be written as t + xj of the conservative variables w, the MHD equations can be written as w t + xi Fi(w) + S(w) = 0 where w

Stanford University

26

Pulse Detonation Rocket Magnetohydrodynamic Power Experiment

NASA Technical Reports Server (NTRS)

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.

Litchford, R. J.; Jones, J. E.; Dobson, C. C.; Cole, J. W.; Thompson, B. R.; Plemmons, D. H.; Turner, M. W.

2003-01-01

27

Magnetohydrodynamics is a branch of the physical sciences dealing with the electromagnetic fields and electrically conduction gases and liquids. Examples of MHD are everywhere, from stars and nuclear fusion to applications like MHD electrical power generation, i.e. when electrical conductors cut magnetic field lines, an electromotive force (EMF) is induced. If electrodes and external circuits are connected, current will flow.

K. D. Parks; A. C. Sheth

1988-01-01

28

Open-cycle MHD power conditioning and control requirements definition

NASA Astrophysics Data System (ADS)

A generic inverter configuration is defined, and the relevant characteristics of line and forced commutated inverters are compared and evaluated for their suitability for magnetohydrodynamic (MHD) power application. The interface requirements of an MHD channel inverter utility interactive system are defined, and a forced commutated inverter meeting these requirements is described. The results of a set of tests using this inverter are described along with recommendations for future work in this field.

Petty, S.; Williams, K.

1980-03-01

29

Integrated Pulse Detonation Propulsion and Magnetohydrodynamic Power

NASA Technical Reports Server (NTRS)

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 negligible influence on system thrust and that the measured I(sub sp) of the system (200 sec) exceeded that computed for an equivalent nozzleless rocket (120 sec).

Litchford, R. J.; Lyles, Garry M. (Technical Monitor)

2001-01-01

30

Magnetohydrodynamic Power Generation in the Laboratory Simulated Martian Entry Plasma

NASA Technical Reports Server (NTRS)

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.

Vuskovic, L.; Popovic, S.; Drake, J.; Moses, R. W.

2005-01-01

31

Momentum Transport in DIII-D Discharges with and Without Magnetohydrodynamics (MHD) Activity

Two phases of a DIII-D discharge with and without magnetohydrodynamics (MHD) activity are analysed using ONETWO code. The toroidal momentum flux is extracted from experimental data and compared with the predictions by neoclassical theory, Gyro-Landau fluid transport model (GLF23) and Multi-Mode model (MMM95). It is found that without MHD activities GLF23 and MMM95 provide a reasonable description while with MHD activity no model alone can fully describe the experimental momentum flux. For the phase with MHD activity a simple model of resonant magnetic drag is tested and it cannot fully explain the plasma slowing down observed in experiment.

Park, Jin Myung [ORNL

2009-02-01

32

Laser-powered MHD generators for space application

NASA Technical Reports Server (NTRS)

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.

Jalufka, N. W.

1986-01-01

33

Performance of rf-assisted magnetohydrodynamics power generator

The present paper describes the performance of a radio-frequency (rf) electromagnetic-field-assisted magnetohydrodynamics (MHD) electrical power generator and compares it to a multiple-load MHD generator. rf heating which is superimposed on self-excited Joule heating preionizes cesium-seeded helium gas independent of the in situ loading conditions, whereby Hall potential profile is improved and electron temperature is increased. Furthermore, the dynamic stabilization effect cancels ionization instability and homogenizes plasma structure, which is the most important superiority of the rf-power assistance over a conventional plasma actuation by loading-rate control. The power-generating performance is significantly improved with the aid of the rf power under wide seeding and loading conditions, where the electrical load-matching characteristic is slightly changed.

Murakami, Tomoyuki; Okuno, Yoshihiro; Yamasaki, Hiroyuki [Department of Energy Sciences, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan)

2005-11-15

34

Integrated Pulse Detonation Propulsion and Magnetohydrodynamic Power

NASA Technical Reports Server (NTRS)

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 exerted a negligible influence on system thrust and that the measured I(sub sp) of the system (200 see) exceeded that computed for an equivalent nozzleless rocket (120 see).

Litchford, Ron J.

2001-01-01

35

Investigations for biogas operated MHD power generators

Biogas is produced from the anaerobic fermentation of the organic matter containing cellulose, such as agricultural wastes, human wastes, animal wastes, etc. It contains methane (50-70%), carbon dioxide (30-50%), and very small amounts of hydrogen and hydrogen sulphide. Adequate quantities of raw material to generate biogas are normally available in rural areas, and therefore, there is a possibility that almost all the energy requirements of the rural sector may be fulfilled by biogas. Presently in the rural sector, biogas is used mainly to provide thermal energy (for cooking, etc.), and up to a limited extent, to meet the electrical energy requirements by running electrical generators with engines powered by a mixture of oil and biogas. In this paper, the authors propose a scheme in which biogas can be used to generate electricity more efficiently by using magnetohydrodynamic (MHD) power generators. Investigations have been carried out to make feasibility studies for biogas-operated open cycle MHD power generators. Composition, temperature and electrical conductivity of the seeded (with potassium) combustion products of biogas-air/oxygen systems have been analytically investigated for different percentages of CO/sub 2/ in biogas and at various combustor pressures for a seeding ratio of 1 percent by weight. The effect of preheating and enrichment of air on temperature and electrical conductivity of the seeded combustion plasmas has also been studied.

Dahiya, R.P.; Chand, A.; Sharma, S.C.

1983-12-01

36

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.

Not Available

1987-06-01

37

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

G. F. Berry; V. Minkov; M. Petrick

1981-01-01

38

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

Gregory F. Berry; Vladimir Minkov; Michael Petrick

1988-01-01

39

NASA Technical Reports Server (NTRS)

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.

Holman, R. R.; Lippert, T. E.

1976-01-01

40

MHD power conversion system for NERVA reactor

NASA Astrophysics Data System (ADS)

Optimized linear magnetohydrodynamic (MHD) systems to produce 200 MWe for 1000 seconds are defined. For the specific mission envisioned, a mass flow of 45.36 Kg/sec (100 lbs/sec) of hydrogen is available to the system. Westinghouse NERVA reactor technology can heat this mass flow of hydrogen to 2550 K at a pressure of 12 atm. This hydrogen flow is assumed to be seeded with cesium to obtain the required MHD generator conductivity. For each MHD system concept considered, the MHD generator design was optimized in terms of operating Mach number, load parameter, and cesium seed fraction. The simplest concept, an open-cycle MHD system, is optimized by minimizing the total magnet plus cesium seed mass. The resulting magnet and magnet plus seed mass are 44092 and 54143 Kg respectively. The second concept considered was an open-cycle MHD system with seed recovery and reuse. It is optimized by minimizing the magnet mass. The resulting magnet mass is 40110 Kg. A third concept, a closed-cycle MHD system, was also considered. If only equilibrium conductivity is considered, cesium seeded hydrogen is shown to be the more attractive than cesium seeded helium, and the optimum generator would be identical to that for the open-cycle MHD system with seed recovery.

Seikel, G. R.; Condit, W. C.

1985-01-01

41

Overview of nuclear MHD power conversion for multi-megawatt electric propulsion

NASA Astrophysics Data System (ADS)

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. .

Smith, Blair M.; Knight, Travis W.; Anghaie, Samim

2001-02-01

42

NASA Technical Reports Server (NTRS)

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.

Benyo, Theresa L.

2010-01-01

43

WhiskyMHD: Numerical Code for General Relativistic Magnetohydrodynamics

NASA Astrophysics Data System (ADS)

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.

Baiotti, Luca; Giacomazzo, Bruno; Hawke, Ian; et al.

2010-10-01

44

Pulse Detonation Rocket MHD Power Experiment

NASA Technical Reports Server (NTRS)

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 magnet assembly were then installed on Marshall Space Flight Center's (MSFC's) rectangular channel pulse detonation research engine. Magnetohydrodynamic (MHD) electrical power extraction experiments were carried out for a range of load impedances in which cesium hydroxide seed (dissolved in methanol) was sprayed into the gaseous oxygen/hydrogen propellants. Positive power extraction was obtained, but preliminary analysis of the data indicated that the plasma electrical conductivity is lower than anticipated and the near-electrode voltage drop is not negligible. It is believed that the electrical conductivity is reduced due to a large population of negative OH ions. This occurs because OH has a strong affinity for capturing free electrons. The effect of near-electrode voltage drop is associated with the high surface-to-volume ratio of the channel (1-inch by 1-inch cross-section) where surface effects play a dominant role. As usual for MHD devices, higher performance will require larger scale devices. Overall, the gathered data is extremely valuable from the standpoint of understanding plasma behavior and for developing empirical scaling laws.

Litchford, Ron J.; Cook, Stephen (Technical Monitor)

2002-01-01

45

Coal-gasification/MHD/steam-turbine combined-cycle (GMS) power generation

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.

Lytle, J.M.; Marchant, D.D.

1980-11-01

46

Rapporteur report: MHD electric power plants

NASA Technical Reports Server (NTRS)

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.

Seikel, G. R.

1980-01-01

47

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

Tomoyuki Murakami; Yoshihiro Okuno

2008-01-01

48

Simulation of high-frequency solar wind power spectra using Hall magnetohydrodynamics

Solar wind frequency spectra show a distinct steepening of the f-5\\/3 power law inertial range spectrum at frequencies above the Doppler-shifted ion cyclotron frequency. This is commonly attributed to dissipation due to wave-particle interactions. We consider the extent to which this steepening can be described, using a magnetohydrodynamic formulation that includes the Hall term. An important characteristic of Hall MHD

S. Ghosh; E. Siregar; D. A. Roberts; M. L. Goldstein

1996-01-01

49

MHD power plant instrumentation and control

The Electric Power Research Institute (EPRI) has awarded a contract to the MHD Development Corporation (MDC) to develop instrumentation and control requirements and strategies for commercial MHD power plants. MDC subcontracted MSE to do the technical development required. MSE is being assisted by Montana State University (MSU) for the topping cycle development. A computer model of a stand-alone MHD/steam plant is being constructed. The plant is based on the plant design set forth in the MDC proposal to the Federal Clean Coal Technology 5 solicitation. It consists of an MHD topping plant, a Heat Recovery Seed Recovery (HRSR) plant, and a steam turbo-generator. The model is based on the computer code used for a study of the Corette plant retrofitted with an MHD plant. Additional control strategies, based on MHD testing results and current steam bottoming plant control data, will be incorporated. A model will be devised and implemented for automatic control of the plant. Requirements regarding instrumentation and actuators will be documented. Instrumentation and actuators that are not commercially available will be identified. The role and desired characteristics of an expert system in the automated control scheme is being investigated. Start-up and shutdown procedures will be studied and load change dynamic performance will be evaluated. System response to abnormal topping cycle and off-design system operation will be investigated. This includes use of MHD topping cycle models which couple gasdynamic and electrical behavior for the study of controlling of the MHD topping cycle. A curvefitter, which uses cubic Hermitian spline interpolation functions in as many as five dimensions, allows much more accurate reproduction of nonlinear, multidimensional functions. This project will be the first to investigate plant dynamics and control using as many as seven independent variables or control inputs to the MHD topping cycle.

Lofftus, D.; Rudberg, D. [MSE Inc., Butte, MT (United States); Johnson, R.; Hammerstrom, D. [Montana State Univ., Bozeman, MT (United States)

1993-12-31

50

NASA Astrophysics Data System (ADS)

This dissertation describes the details of the development of a general, stable and efficient computer code for simulating transient, three-dimensional fluid flows with properly chosen computational boundaries as well as physical boundaries. The topics in the description include: (1) the numerical techniques used in the computer code, which includes a refined version of an existing algorithm for solving the Navier-Stokes and the magnetohydrodynamic (MHD) equations, (2) extensive usage of a fast solver for linear systems of equations, (3) application of the method of characteristics to solving multi-dimensional MHD time -dependent boundary conditions, and (4) a series of numerical experiments to validate the numerical techniques and the computer coding. And finally, a simulation case is done on a shear motion induced phenomena in the solar corona that serves as an example application to demonstrate the usefulness of the computer code. The algorithm developed in this study for solving the difference equations of the Navier-Stokes and MHD equations is called the Nimble Implicit Continuous-fluid Eulerian (NICE), algorithm which is a refined version of the FICE algorithm (Hu and Wu, Journal of Computational Physics 55 (1984), 33). The NICE algorithm is a pressure-based algorithm that solves the equations through a single-loop iteration in which the velocity field is solved within a predictor step and corrected by the corrector that results from a Poisson-type pressure correction equation which simultaneously satisfies the continuity equation, the momentum equation, and the equation of state. All of the formulated difference equations are expressed in linear systems of equations and solved by the solver that incorporates an incomplete pre-condition technique called the Dupont-Kendall -Rachford (DKR) partial factorization and the ORTHOMIN accelerator procedure in an iterative manner. The time-dependent boundary conditions are formulated in such a way that through boundary treatments the characteristic method can apply to any kind of time-dependent boundary conditions for multi-dimensional MHD problems. Among them are the non-reflecting and coupled boundary conditions which are developed and applied in this study. The numerical experiments to verify this code include a time-dependent compressible flow, a steady incompressible Hartmann flow, and a time-dependent plasma critical shear flow. In the numerical experiment for plasma critical shear flow, the results suggest a mechanism which could be used to explain the observed non-thermal line broadening in solar active regions during quiescent periods by a transition to MHD 'non-equilibrium' with the generation of MHD waves from the lower solar atmosphere.

Sun, Ming-Tsung

51

Use of body forces to inject energy into a plasma offers certain advantages over simple energy addition by Ohmic heating. To achieve ever-increasing levels of energy per unit mass by this strategy requires detailed and thorough understanding of high-interaction magnetohydrodynamics (HIMHD) through realistic computer simulation. Such simulation is possible by the existing, HIMHD codes provided they undergo further validation in the high-interaction regime through systematic experiments. The present work has carried out a critical assessment of several methods for achieving high-interaction, high-magnetic Reynolds number MHD flows. It indicates that continuous flow (as contrasted to pulsed flow) plasmajet-drive MHD devices offer the greatest advantages and potential for validating the STD/MHD codes at high MHD interaction over a wide range of parameters with the greatest confidence. It has led to the definition of specific plasmajet-driven experiments, utilizing existing equipment, as the most effective way to carry out this task.

Demetriades, S.T.; Maxwell, C.D.

1984-12-01

52

A technical and economic analysis of H2-O2Cs MHD peak power production of electricity

In magnetohydrodynamic power generation, a high velocity, electrically conducting fluid is magnetically decelerated to produce electricity directly without need of turbine or generator. The most convenient working fluids are high temperature combustion products. High thermal efficiencies can be expected from a hydrogen-oxygen combustion MHD unit in which the exhaust is condensed in a closed system, creating a low pressure at

P. C. Stangeby

1974-01-01

53

In addition to the initial transients designated as fast transient high-altitude EMP (HEMP) and intermediate time EMP, electromagnetic signals are also perceived at times from seconds to hundreds of seconds after a high-altitude nuclear burst. This signal has been defined by the term magnetohydrodynamic-electromagnetic pulse (MHD-EMP). The MHD-EMP phenomena has been both detected in actual weapon tests and predicted from theoretical models. This volume documents a preliminary research effort to investigate the nature and coupling of the MHD-EMP environments to electric power systems, define the construction of approximate system response network models, and document the development of a unified methodology to assess equipment and systematic vulnerability. The MHD-EMP environment is compared to a qualitatively similar natural event, the electromagnetic environment produced by geomagnetic storms.

Legro, J.R.; Abi-Samra, N.C.; Tesche, F.M.

1985-05-01

54

Micro optical fiber display switch based on the magnetohydrodynamic (MHD) principle

NASA Astrophysics Data System (ADS)

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.

Lian, Kun; Heng, Khee-Hang

2001-09-01

55

A version of extended magnetohydrodynamics (MHD) that incorporates electron inertia is obtained by constructing an action principle. Unlike MHD which freezes in magnetic flux, the present theory freezes in an alternative flux related to the electron canonical momentum. The associated Hamiltonian formulation is derived and reduced models that have previously been used to describe collisionless reconnection are obtained.

Lingam, M; Tassi, E

2014-01-01

56

Magnetohydrodynamic (MHD) interactions present a tantalizing opportunity to control hypersonic flows without the need for strong shock waves, high entropy gain, and movable control surfaces. An MHD interaction, however, requires a conductive flowfield. At Mach numbers too low for thermal ionization, flow energies may still be sufficient to justify the cost of an efficient external ionization scheme. In this work,

Robert C. Murray

2006-01-01

57

NASA Technical Reports Server (NTRS)

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.

Wu, S. T.

1987-01-01

58

NASA Astrophysics Data System (ADS)

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.

Winkler, J.; Dahotre, N. B.; Boss, W.

59

Experiments in Magnetohydrodynamics

ERIC Educational Resources Information Center

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)

Rayner, J. P.

1970-01-01

60

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. (Naperville, IL); Minkov, Vladimir (Skokie, IL); Petrick, Michael (Joliet, IL)

1988-01-01

61

Gigawatt, Closed Cycle, Vapor Core-Mhd Space Power System Conceptual Design Study

NASA Astrophysics Data System (ADS)

A conceptual design study for a closed cycle gigawatt electric space power system has been conducted. The closed cycle static operation reduces power system interaction effects upon the space craft. This system utilizes a very high temperature (5500 K) plasma core reactor and a magnetohydrodynamic (MHD) power conversion subsystem to provide a power density of about 8 kWe/kg (0.13 kg/kWe) for several kilo-seconds. Uranium vapor is the fuel. Candidate working fluids are metal vapors such as lithium or calcium. The system is based on a Rankine cycle to minimize the electromagnetic pumping power requirement. The fission fragment induced nonequilibrium ionization in the plasma in the MHD power duct provides the plasma electric conductivity for gigawatt power generation. Waste heat is rejected utilizing lithium heat pipes at temperatures just below 2000 K, thus minimizing the radiator area requirement. Key technology issues are identified, including the containment of the 5500 K 'sun-liken plasma at 4 to 0 MPa In a reflector moderated, gas/vapor filled cavity core reactor. A promising scheme to protect the refractory metal reactor inner wall is presented, together with a heating load analysis in the wall. This scheme utilizes an ablating film of liquid lithium/calcium that evaporates into the cavity core to become the working fluid of the cycle.

Wetch, Joseph R.; Rhee, Hyop S.; Koester, J. Kent; Goodman, Julius; Maya, Issac

1988-04-01

62

Evaluation of the ECAS open cycle MHD power plant design

NASA Technical Reports Server (NTRS)

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.

Seikel, G. R.; Staiger, P. J.; Pian, C. C. P.

1978-01-01

63

NASA Astrophysics Data System (ADS)

Very low specific-mass power generation in space is possible using Vapor Core Reactors with Magnetohydrodynamic (VCR/MHD) generator. These advanced reactors at the conceptual design level have potential for the generation of tens to hundreds of megawatts of power in space with specific mass of about 1 kg/kWe. Power for nuclear electric propulsion (NEP) is possible with almost direct power conditioning and coupling of the VCR/MHD power output to the VASIMR engine, MPD, and a whole host of electric thrusters. The VCR/MHD based NEP system is designed to power space transportation systems that dramatically reduce the mission time for human exploration of the entire solar system or for aggressive long-term robotic missions. There are more than 40 years of experience in the evaluation of the scientific and technical feasibility of gas and vapor core reactor concepts. The proposed VCR is based on the concept of a cavity reactor made critical through the use of a reflector such as beryllium or beryllium oxide. Vapor fueled cavity reactors that are considered for NEP applications operate at maximum core center and wall temperatures of 4000 K and 1500K, respectively. A recent investigation has resulted in the conceptual design of a uranium tetrafluoride fueled vapor core reactor coupled to a MHD generator. Detailed neutronic design and cycle analyses have been performed to establish the operating design parameters for 10 to 200 MWe NEP systems. An integral system engineering-simulation code is developed to perform parametric analysis and design optimization studies for the VCR/MHD power system. Total system weight and size calculated based on existing technology has proven the feasibility of achieving exceptionally low specific mass (? ~1 kg/kWe) with a VCR/MHD powered system.

Knight, Travis; Anghaie, Samim

2004-02-01

64

A nonvariational code for calculating three-dimensional MHD (magnetohydrodynamic) equilibria

Details are presented of the PIES code, which uses a nonvariational algorithm for calculating fully three-dimensional MHD equilibria. The MHD equilibrium equations are directly iterated in special coordinates to find self-consistent currents and magnetic fields for given pressure and current profiles and for a given outermost magnetic surface. Three important advantages of this approach over previous methods are the ease with which net current profiles can be imposed, the explicit treatment of resonances, and the ability to handle magnetic islands and stochastic field lines. The convergence properties of the code are studied for several axisymmetric and nonaxisymmetric finite-..beta.. equilibria that have magnetic surfaces. 36 refs., 14 figs., 3 tabs.

Greenside, H.S.; Reiman, A.H.; Salas, A.

1987-09-01

65

Design study of superconducting magnets for a combustion magnetohydrodynamic (MHD) generator

NASA Technical Reports Server (NTRS)

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.

Thome, R. J.; Ayers, J. W.

1977-01-01

66

MHD conversion of solar energy. [space electric power system

NASA Technical Reports Server (NTRS)

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.

Lau, C. V.; Decher, R.

1978-01-01

67

Experimental determination of the MHD-EMP effects on power distribution transformers

It is a well-established fact that geomagnetic storms influence electrical power transmission and distribution systems. Previous cases of such storms in the northern latitudes have resulted in occasional power disruptions, and in some cases, damage to transformers. These effects are caused by a time variation of the earth's magnetic field creating an induced electric field along the surface of the earth. This E-field acts as a voltage source along long power transmission or distribution lines, and if the line is connected to the earth at both ends, a quasi-dc current can flow. This current can cause unwanted saturation in the magnetic cores of transformers in the power system, and this, in turn produces harmonic distortion and transformer heating. This can lead to system upset (shutdown) and possibly transformer burn-out. The detonation of a high altitude nuclear explosion is also known to affect the magnetosphere, producing late-time variations of the earth's magnetic field for several hundreds of seconds. Known as the magnetohydrodynamic electromagnetic pulse (MHD-EMP), or E{sub 3}, this environment is of particular concern to electrical power systems in the event of a nuclear attack. Although the MHD-EMP induced currents can be significantly larger in magnitude, they last for a shorter period of time than do those from a geomagnetic storm. The effect of this environment compounds the adverse effects of the early-time high altitude EMP (HEMP) environment, posing a potentially serious threat to the electrical system. The present paper documents an experimental program designed to better understand the behavior of distribution-class transformers subjected to quasi-dc current excitation. Given the knowledge of the MHD-EMP-induced current flowing in a long power line, and the transformer response characteristics obtained in this program, it will be possible to make more accurate assessments of the behavior of the overall power system to EMP. 7 refs., 5 figs.

McConnell, B.W.; Barnes, P.R. (Oak Ridge National Lab., TN (United States)); Tesche, F.M. (Tesche (F.M.), Dallas, TX (United States))

1991-01-01

68

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.

Zhu, X. S.; Wang, H. N.; Du, Z. L.; Fan, Y. L., E-mail: xszhu@bao.ac.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2013-05-10

69

Magnetohydrodynamic flows of liquid metals in rectangular ducts with thin conducting walls 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. A significant fraction of the fluid flow is concentrated in the boundary layers adjacent to the side walls which are parallel to the magnetic field. This paper describes the analysis and numerical methods for obtaining 3-D solutions for flow parameters outside these layers, without solving explicitly for the layers themselves. Numerical solutions are presented for cases which are relevant to the flows of liquid metals in fusion reactor blankets. Experimental results obtained from the ALEX experiments at Argonne National Laboratory are used to validate the numerical code. In general, the agreement is excellent. 5 refs., 14 figs.

Hua, T.Q.; Walker, J.S.; Picologlou, B.F.; Reed, C.B.

1988-07-01

70

MAGNETOHYDRODYNAMIC WAVES AND CORONAL HEATING: UNIFYING EMPIRICAL AND MHD TURBULENCE MODELS

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.

Sokolov, Igor V.; Van der Holst, Bart; Oran, Rona; Jin, Meng; Manchester, Ward B. IV; Gombosi, Tamas I. [Department of AOSS, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 (United States)] [Department of AOSS, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 (United States); Downs, Cooper [Predictive Science Inc., 9990 Mesa Rim Road, Suite 170, San Diego, CA 92121 (United States)] [Predictive Science Inc., 9990 Mesa Rim Road, Suite 170, San Diego, CA 92121 (United States); Roussev, Ilia I. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)] [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Evans, Rebekah M., E-mail: igorsok@umich.edu [NASA Goddard Space Flight Center, Space Weather Lab, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States)

2013-02-10

71

NASA Technical Reports Server (NTRS)

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.

Wang, A. H.; Wu, S. T.; Liu, Yang; Hathaway, D.

2008-01-01

72

NASA Astrophysics Data System (ADS)

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.

Aini Mat, Nor Azian; Arifin, Norihan Md.; Nazar, Roslinda; Ismail, Fudziah; Bachok, Norfifah

2013-09-01

73

Fusion Power Plants Using Minimum Activity Blankets and MHD Conversion.

National Technical Information Service (NTIS)

The paper describes a concept for fusion power plants which uses a minimum activity blanket, and MHD for the conversion, to electricity, of the heat deposited in the blanket by neutrons and gamma rays. Two types of blanket design are considered. In the fi...

R. J. Rosa, J. R. Powell

1975-01-01

74

Design study of superconducting magnets for a combustion magnetohydrodynamic /MHD/ generator

NASA Technical Reports Server (NTRS)

Results are presented for a trade-off and preliminary design study on concepts of a superconducting magnet system for a combustion MHD generator test facility. The main objective is to gain insight into the magnitude of the project in terms of physical characteristics and cost. The net result of a first-phase evaluation of attractive design alternatives is to concentrate subsequent efforts on (1) a racetrack coil geometry with an operating temperature of 4.2 K, (2) a racetrack coil geometry with an operating temperature of 2.0 K, and (3) a rectangular saddle coil geometry with an operating temperature of 4.2 K. All three systems are to produce 8 T, and use NbTi superconductor and iron for field enhancement. Design characteristics of the three systems are described. It is shown that the racetrack and rectangular saddle coil geometries seem most suitable for this application, the former because of its simplicity and the latter because of its efficient use of material. Advantages of the rectangular saddle over the two other systems are stressed.

Thome, R. J.; Ayers, J. W.; Hrycaj, T. M.; Burkhart, J. A.

1978-01-01

75

Impinging jet separators for liquid metal magnetohydrodynamic power cycles

NASA Technical Reports Server (NTRS)

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).

Bogdanoff, D. W.

1973-01-01

76

Performance calculations for 1000 MWe MHD/steam power plants

NASA Technical Reports Server (NTRS)

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.

Pian, C. C. P.

1981-01-01

77

Energy analysis of MHD-steam and MHD-gas-steam power plants integrated with coal gasification

The paper presents energy analysis of combined two media (MHD-steam) and three media (MHD-gas-steam) power plants of high efficiency of conversion of chemical energy of fuel into electric energy integrated with coal gasification. The goal of this paper is to show the possibility of obtaining the high efficiency (about 60%) of the conversion of chemical energy of coal into electric energy in combined power plants with the open cycle MHD generators. The base of performed energy analysis are the elaborated mathematical models: of gas generator, of combustion chamber of MHD generator, of MHD channel, of high-temperature heater of oxygen, nitrogen and air, of steam generator and the cycle of steam turbine and of the cycle of gas turbine, and also the computer programmes, elaborated on the base of these models for numerical simulation of the processes of energy conversion in these elements. The elaborated mathematical model of the process of coal gasification for MHD-steam power plants allows to calculate: composition, physical properties and energy parameters of gas produced in the process of coal gasification, the consumption and temperature of gasifying medium and both the chemical and energy efficiency of coal gasification. Gas produced in the process of coal gasification is directed to combustion chamber of MHD generator after desulphurization. The mathematical model of physical, chemical and energy processes in combustion chamber of MHD generator allows to determine the temperature of oxidizer and its enrichment in oxygen necessary to obtain the plasma parameters desired for optimum process of energy conversion in MHD channel. The mathematical model of energy conversion in open cycle MHD channel was presented in paper. This model allows to perform numerical simulation of energy conversion process and to determine optimum parameters of plasma at the inlet to the channel necessary to obtain maximum efficiency of energy conversion.

Zaporowski, B.; Roszkiewicz, J.; Sroka, K. [Poznan Univ. of Technology (Poland)

1995-12-31

78

Plasma plume MHD power generator and method

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.

Hammer, J.H.

1993-08-10

79

Multifluid Magnetohydrodynamic Turbulent Decay

NASA Astrophysics Data System (ADS)

It is generally believed that turbulence has a significant impact on the dynamics and evolution of molecular clouds and the star formation that occurs within them. Non-ideal magnetohydrodynamic (MHD) effects are known to influence the nature of this turbulence. We present the results of a suite of 5123 resolution simulations of the decay of initially super-Alfvénic and supersonic fully multifluid MHD turbulence. We find that ambipolar diffusion increases the rate of decay of the turbulence while the Hall effect has virtually no impact. The decay of the kinetic energy can be fitted as a power law in time and the exponent is found to be -1.34 for fully multifluid MHD turbulence. The power spectra of density, velocity, and magnetic field are all steepened significantly by the inclusion of non-ideal terms. The dominant reason for this steepening is ambipolar diffusion with the Hall effect again playing a minimal role except at short length scales where it creates extra structure in the magnetic field. Interestingly we find that, at least at these resolutions, the majority of the physics of multifluid turbulence can be captured by simply introducing fixed (in time and space) resistive terms into the induction equation without the need for a full multifluid MHD treatment. The velocity dispersion is also examined and, in common with previously published results, it is found not to be power law in nature.

Downes, T. P.; O'Sullivan, S.

2011-03-01

80

Experiments on H2-O2MHD power generation

NASA Technical Reports Server (NTRS)

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.

Smith, J. M.

1980-01-01

81

Gyroscopic analog for magnetohydrodynamics

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.

Holm, D.D.

1982-07-20

82

Gyroscopic analog for magnetohydrodynamics

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.

Holm, D.D.

1981-01-01

83

Government research and development summaries: Magnetohydrodynamic project briefs. Irregular

Magnetohydrodynamic Project Briefs describe the status of all R and D programs submitted to the Power Information Center by the government sponsors in energy conversion involving the magnetohydrodynamic (MHD) interaction between electromagnetic fields and electrically conducting fields, including fuels, materials, plasma dynamics, and combustion. The document is not to be reproduced, in whole or in part, for dissemination outside your own organization nor may it be reproduced for advertising or sales promotion purposes.

Not Available

1993-01-01

84

Government research and development summaries: Magnetohydrodynamic project briefs. Irregular

Magnetohydrodynamic Project Briefs describe the status of all R and D programs submitted to the Power Information Center by the government sponsors in energy conversion involving the magnetohydrodynamic (MHD) interaction between electromagnetic fields and electrically conducting fields, including fuels, materials, plasma dynamics, and combustion. The document is not to be reproduced, in whole or in part, for dissemination outside your own organization nor may it be reproduced for advertising or sales promotion purposes.

NONE

1995-03-01

85

Government research and development summaries: Magnetohydrodynamic project briefs. Irregular

Magnetohydrodynamic Project Briefs describe the status of all R and D programs submitted to the Power Information Center by the government sponsors in energy conversion involving the magnetohydrodynamic (MHD) interaction between electromagnetic fields and electrically conducting fields, including fuels, materials, plasma dynamics, and combustion. The document is not to be reproduced, in whole or in part, for dissemination outside your own organization nor may it be reproduced for advertising or sales promotion purposes.

Not Available

1994-01-01

86

Magnetohydrodynamic generator electrode

An improved electrode for use as a current collector in the channel of a magnetohydrodynamic (MHD) generator utilizes an elongated monolithic cap of dense refractory material compliantly mounted to the MHD channel frame for collecting the current. The cap has a central longitudinal channel which contains a first layer of porous refractory ceramic as a high-temperature current leadout from the

D. D. Marchant; D. H. Killpatrick; H. Herman; K. D. Kuczen

1977-01-01

87

Use of body forces to inject energy into a plasma offers certain advantages over simple energy addition by Ohmic heating. To achieve ever-increasing levels of energy per unit mass by this strategy requires detailed and thorough understanding of high-interaction magnetohydrodynamics (HIMHD) through realistic computer simulation. Such simulation is possible by the existing, HIMHD codes provided they undergo further validation in

S. T. Demetriades; C. D. Maxwell

1984-01-01

88

Three-Dimensional Flow Analysis in a Faraday-Type MHD Generator

This paper studies the development and analysis of the 3D flow fields in a Faraday-type magnetohydrodynamic (MHD) generator. A large-scale pulsed MHD generator with a Faraday channel of 4.5 m has demonstrated the maximum electric power output of 510 MW. The results of the present development and simulation are compared with the experimental results of the pulsed ldquoSakhalinrdquo MHD generator

Triwahju Hardianto; Nobuomi Sakamoto; Nobuhiro Harada

2008-01-01

89

Preliminary design procedure for high power density MHD generators

NASA Astrophysics Data System (ADS)

The steps to be taken in the preliminary design of a high power density, segmented Faraday or diagonal, open-cycle MHD generator are formalized. The recommended design procedure starts with the optimum choice of the combustion chamber pressure. The optimization is based on a semi-empirical expression of the effective power density, developed by Smith and Nichols. As a result of this optimization, a rough estimate of the realizable power density is made, which yields the order of magnitude of the transverse dimension keeping the length-to-diameter ratio around 10 for the desired power output. It is then recommended that the area variation and length be calculated on the basis of an isothermal core flow. This preliminary shape of the duct will serve as the base on which alterations can be made by a computer to accommodate wall effects in detailed design stage that will follow the preliminary consideration. An alternate route for the preliminary design is provided by using scaling laws. Starting with a well-designed generator which is demonstrably high in power density, dynamically similar units can be produced using these laws. The laws are developed following the modern procedure of ordering. Numerical examples are provided to illustrate the procedure.

Lu, P. C.

1980-12-01

90

Numerical simulations of strong incompressible magnetohydrodynamic turbulence

Magnetised plasma turbulence pervades the universe and is likely to play an important role in a variety of astrophysical settings. Magnetohydrodynamics (MHD) provides the simplest theoretical framework in which phenomenological models for the turbulent dynamics can be built. Numerical simulations of MHD turbulence are widely used to guide and test the theoretical predictions; however, simulating MHD turbulence and accurately measuring its scaling properties is far from straightforward. Computational power limits the calculations to moderate Reynolds numbers and often simplifying assumptions are made in order that a wider range of scales can be accessed. After describing the theoretical predictions and the numerical approaches that are often employed in studying strong incompressible MHD turbulence, we present the findings of a series of high-resolution direct numerical simulations. We discuss the effects that insufficiencies in the computational approach can have on the solution and its physical interpretation.

Mason, J.; Cattaneo, F. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637 (United States); Perez, J. C. [Space Science Center and Department of Physics, University of New Hampshire, Durham, New Hampshire 03824 (United States); Boldyrev, S. [Department of Physics, University of Wisconsin at Madison, 1150 University Ave, Madison, Wisconsin 53706 (United States)

2012-05-15

91

MHD POWER EXTRACTION FROM COLD HYPERSONIC AIR FLOWS WITH EXTERNAL IONIZERS

are shown to allow control and stable operation of MHD channels in cold high-speed flows. To avoid excessive) technology to hypersonics have been proposed. One new concept, called AJAX, was suggested in Russia about 20 years ago.1, 2 A key element of AJAX is a MHD power generator at the inlet of the airbreathing

Miles, Richard

92

Downstream component corrosion in coal-fired MHD power plants

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.

White, M. K.

1980-06-01

93

Parametric study of potential early commercial MHD power plants

NASA Technical Reports Server (NTRS)

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.

Hals, F. A.

1979-01-01

94

System studies of coal fired-closed cycle MHD for central station power plants

NASA Technical Reports Server (NTRS)

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.

Zauderer, B.

1976-01-01

95

NASA Technical Reports Server (NTRS)

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.

Dellinger, T. C.; Hnat, J. G.; Marston, C. H.

1979-01-01

96

Parametric study of potential early commercial power plants Task 3-A MHD cost analysis

NASA Technical Reports Server (NTRS)

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.

1983-01-01

97

Magnetohydrodynamic Turbulence

NASA Astrophysics Data System (ADS)

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.

Montgomery, David C.

2004-01-01

98

NASA Technical Reports Server (NTRS)

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.

Wu, S. T.; Guo, W. P.

1997-01-01

99

Local anisotropy and power spectra in magnetohydrodynamic turbulence

NASA Astrophysics Data System (ADS)

Correlation and spectral anisotropy play important roles in solar wind and astrophysical plasmas, having significant impact on descriptions of the turbulence cascade, particle scattering, the nature of kinetic dissipation, and the transport of turbulence. Anisotropy emerges dynamically in MHD, producing stronger gradients across the large-scale mean magnetic field than along it, and occurring both globally and locally. Recently, properties of correlation anisotropy have been investigated through numerical simulations, showing the effect is intensified for more localized estimates of the mean magnetic field. The mathematical formulation of this property shows that local anisotropy mixes second-order with higher order correlations [1]. Sensitivity of local statistical estimates to higher order correlations can be understood in connection with the stochastic coordinate system inherent in such formulations. We demonstrate this in specific cases, and illustrate the connection to higher order statistics by showing the sensitivity of local anisotropy to phase randomization, after which the global measure of anisotropy is recovered at all scales of averaging. This study establishes that anisotropy of the local structure function is not a measure of anisotropy of the energy spectrum, but is rather related to higher order statistics. [1] Matthaeus et al, Astrophys. J., 750, 103 (2012)

Matthaeus, W. H.; Servidio, S.; Dmitruk, P.; Carbone, V.; Oughton, S.; Wan, M.; Osman, K. T.

2012-12-01

100

A summary of the ECAS MHD power plant results

NASA Technical Reports Server (NTRS)

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.

Seikel, G. R.; Harris, L. P.

1976-01-01

101

Electromagnetic Pulse and the Electric Power Network.

National Technical Information Service (NTIS)

This paper defines the nuclear electromagnetic pulse (EMP) - electric power system interaction problem. A description of high altitude EMP (HEMP) characteristics, source region EMP (SREMP) characteristics, and magnetohydrodynamics EMP (MHD-EMP) characteri...

K. W. Klein, P. R. Barnes, H. W. Zaininger

1984-01-01

102

Formation Interuniversitaire de Physique Magnetohydrodynamics

Equations . . . . . . . . . . . . . . . . 9 1.6 The Conservation of Vorticity . . . . . . . . . . . . . . . . . . 11 2 Magnetohydrodynamics (MHD) 14 2.1 Magnetic Forces . . . . . . . . . . . . . . . . . . . . . . . . . . 54 3 #12;1 Fundamentals 1.1 Opening Comment The behavior of a gas subject to large

Balbus, Steven

103

MGMHD. Multigrid 3-D Magnetohydrodynamics

MGMHD is a three-dimensional code for the analysis of magnetohydrodynamic (MHD) channels (generators, diffusers, and thrusters) for compressible and incompressible, laminar and turbulent, iso- and noniso-thermal fluids.

Bouillard, J.X.; Berry, G.F.; Krazinski, J.L. [Argonne National Laboratory, IL (United States); Vanka, S.P. [University of Illinois, Urbana, IL (United States)

1992-02-19

104

Series solution for MHD channel flow of a Jeffery fluid

This paper is concerned with the magnetohydrodynamic (MHD) flow of a Jeffery fluid in a porous channel. Series solution to the nonlinear problem is constructed by a powerful analytic approach namely the homotopy analysis method (HAM). Convergence of the series solution is established. The obtained solutions are analyzed by plotting graphs.

T. Hayat; R. Sajjad; S. Asghar

2010-01-01

105

Series solution for MHD channel flow of a Jeffery fluid

NASA Astrophysics Data System (ADS)

This paper is concerned with the magnetohydrodynamic (MHD) flow of a Jeffery fluid in a porous channel. Series solution to the nonlinear problem is constructed by a powerful analytic approach namely the homotopy analysis method (HAM). Convergence of the series solution is established. The obtained solutions are analyzed by plotting graphs.

Hayat, T.; Sajjad, R.; Asghar, S.

2010-09-01

106

Power conditioning and control requirements of coal fired MHD generators

NASA Astrophysics Data System (ADS)

The operational characteristics of coal fired open-cycle linear MHD generators are presented. The salient features of loading and control requirements of Faraday and diagonal generators are analyzed and circuits that meet these requirements are presented. Consolidation and current control circuits are discussed elaborating on the design considerations for operating them with MHD generators. Such circuits are shown to have relatively low losses reflecting in higher than 98-99% efficiencies.

Demirjian, A. M.; Quijano, I. M.

1981-01-01

107

AC magnetohydrodynamic microfluidic switch

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.

Lemoff, A V; Lee, A P

2000-03-02

108

Ultrahigh temperature vapor core reactor-MHD system for space nuclear electric power

NASA Technical Reports Server (NTRS)

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.

Maya, Isaac; Anghaie, Samim; Diaz, Nils J.; Dugan, Edward T.

1991-01-01

109

NASA Astrophysics Data System (ADS)

The current magnetohydrodynamic MHD program being implemented is a result of a consensus established in public meetings held by the Department of Energy in 1984. The public meetings were followed by the formulation of a June 1984 Coal-Fired MHD Preliminary Transition and Program Plan. This plan focused on demonstrating the proof-of-concept (POC) of coal-fired MHD electric power plants by the early 1990s. MHD test data indicate that while there are no fundamental technical barriers impeding the development of MHD power plants, technical risk remains. To reduce the technical risk three key subsystems (topping cycle, bottoming cycle, and seed regeneration) are being assembled and tested separately. The program does not require fabrication of a complete superconducting magnet, but rather the development and testing of superconductor cables. The topping cycle system test objectives can be achieved using a conventional iron core magnet system already in place at a DOE facility. Systems engineering-derived requirements and analytical modeling to support scale-up and component design guide the program. In response to environmental, economic, engineering, and utility acceptance requirements, design choices and operating modes are tested and refined to provide technical specifications for meeting commercial criteria. These engineering activities are supported by comprehensive and continuing systems analyses to establish realistic technical requirements and cost data. Essential elements of the current program are to: develop technical and environmental data for the integrated MHD topping cycle and bottoming cycle systems through POC testing (1000 and 4000 hours, respectively); design, construct, and operate a POC seed regeneration system capable of processing spent seed materials from the MHD bottoming cycle; prepare conceptual designs for a site specific MHD retrofit plant; and continue supporting research necessary for system testing.

1990-10-01

110

ECONOMIC COMPARISON OF MHD EQUILIBRIUM OPTIONS FOR ADVANCED STEADY STATE TOKAMAK POWER PLANTS

ECONOMIC COMPARISON OF MHD EQUILIBRIUM OPTIONS FOR ADVANCED STEADY STATE TOKAMAK POWER PLANTS D for commercial tokamak power plants. The economic prospects of future designs are compared for several tokamak for future power plants. 1. INTRODUCTION The development path to economical and environ- mentally attractive

Najmabadi, Farrokh

111

Efficient magnetohydrodynamic simulations on graphics processing units with CUDA

NASA Astrophysics Data System (ADS)

Magnetohydrodynamic (MHD) simulations based on the ideal MHD equations have become a powerful tool for modeling phenomena in a wide range of applications including laboratory, astrophysical, and space plasmas. In general, high-resolution methods for solving the ideal MHD equations are computationally expensive and Beowulf clusters or even supercomputers are often used to run the codes that implemented these methods. With the advent of the Compute Unified Device Architecture (CUDA), modern graphics processing units (GPUs) provide an alternative approach to parallel computing for scientific simulations. In this paper we present, to the best of the author's knowledge, the first implementation of MHD simulations entirely on GPUs with CUDA, named GPU-MHD, to accelerate the simulation process. GPU-MHD supports both single and double precision computations. A series of numerical tests have been performed to validate the correctness of our code. Accuracy evaluation by comparing single and double precision computation results is also given. Performance measurements of both single and double precision are conducted on both the NVIDIA GeForce GTX 295 (GT200 architecture) and GTX 480 (Fermi architecture) graphics cards. These measurements show that our GPU-based implementation achieves between one and two orders of magnitude of improvement depending on the graphics card used, the problem size, and the precision when comparing to the original serial CPU MHD implementation. In addition, we extend GPU-MHD to support the visualization of the simulation results and thus the whole MHD simulation and visualization process can be performed entirely on GPUs.

Wong, Hon-Cheng; Wong, Un-Hong; Feng, Xueshang; Tang, Zesheng

2011-10-01

112

Magnetohydrodynamic Augmented Propulsion Experiment

NASA Technical Reports Server (NTRS)

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 that an MHD accelerator can be an effective augmentation system for increasing engine exhaust velocity. More specifically, the experiment is intended to show that electromagnetic effects are effective at producing flow acceleration whereas electrothermal effects do not cause unacceptable heating of the working fluid. The MHD accelerator was designed as an externally diagonalized segmented Faraday channel, which will be inserted into an existing 2-tesla electromagnet. This allows the external power to be connected through two terminals thereby minimizing the complexity and cost associated with powering each segment independently. The design of the accelerator and other components in the flow path has been completed and fabrication activities are underway. This paper provides a full description of MAPX including performance analysis, design, and test plans, and current status.

Litchford, Ron J.; Cole, John; Lineberry, John; Chapman, Jim; Schmidt, Harold; Cook, Stephen (Technical Monitor)

2002-01-01

113

Study of System Stabilization of Disk Type MHD Power Generation by Damping Resistor

NASA Astrophysics Data System (ADS)

Effects of installed SDR (System Dumping Resistors) on the stability of open-cycle disk MHD generator and synchronous generator system connected in parallel to power transmission lines are numerically studied. Usually the SDR is used to absorb the output energy of synchronous generator and to get stability of the power transmission system when faults occur in the A.C. power transmission lines. In this paper, we propose to apply the SDR in the D.C. lines between the MHD generator and the primary side of connected line-commutated inverters. We show that the SDR is effective for the system stability by a time dependent numerical analysis.

Hayanose, Nobuhiko; Inui, Yoshitaka; Ishikawa, Motoo

114

Multimegawatt NEP with vapor core reactor MHD

NASA Astrophysics Data System (ADS)

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. .

Smith, Blair; Knight, Travis; Anghaie, Samim

2002-01-01

115

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.

Seyler, C. E. [School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853 (United States); Martin, M. R. [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States)

2011-01-15

116

Exploratory study of several advanced nuclear-MHD power plant systems.

NASA Technical Reports Server (NTRS)

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.

Williams, J. R.; Clement, J. D.; Rosa, R. J.; Yang, Y. Y.

1973-01-01

117

Arc mode molten seed electrodes for MHD power generation

NASA Astrophysics Data System (ADS)

Experiments have been conducted in an electric furnace at atmospheric pressure with the object of investigating the seed arcing characteristics and electrical conductivities of seed materials, and ceramic consumption rates by seed arcing. Many important facts have been clarified from these experiments, namely that the arcing behaviors of molten seeds resemble closely those of mercury in a mercury rectifier, the cathode voltage drop of K2CO3 seed is close to that obtained for the copper electrode in an MHD channel, the molten seed has an electrical conductivity comparable to those of advanced ceramic electrodes, and so on. These results show that so-called 'arc mode molten seed electrodes' are highly promising for practical application. The arc mode molten seed cathodes for commercial MHD generating channels are discussed.

Korenaga, S.; Imai, H.; Masuda, T.

1982-04-01

118

Magnetohydrodynamic lattice Boltzmann simulations of turbulence and rectangular jet flow

Magnetohydrodynamic (MHD) investigations of decaying isotropic turbulence and rectangular jets (RJ) are carried out. A novel MHD lattice Boltzmann scheme that combines multiple relaxation time (MRT) parameters for the velocity field with a single...

Riley, Benjamin Matthew

2009-05-15

119

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)

Not Available

1981-11-01

120

The five most promising systems of introduction and recovery of seed were selected for comparison for an open-cycle MHD power station. These systems are: (1) dry introduction and removal with bag filters, (2) dry introduction and removal by combined electrostatic precipitators, (3) wet introduction and removal by a high pressure turbulent washer with prehumidifying in a foam apparatus, (4) wet

I. L. Montinskii; A. R. Monastyrskaia; L. K. Khokhlov

1976-01-01

121

Radiative heat exchange in the combustion chamber of an MHD electric power plant using methane gas

A method is proposed for calculating radiative thermal fluxes on the wall of the combustion chamber of an MHD electric power plant operating with methane gas. The calculations are performed on the basis of spectral characteristics of the molecular components of the combustion products and ionizing potassium impurity, with allowance for multiple reflection of radiation from the wall of the

L. M. Biberman; M. B. Zhelezniak; A. Kh. Mnatsakanian; A. G. Rotinov; S. A. Tager

1980-01-01

122

NASA Astrophysics Data System (ADS)

If power is required in space for more than a large fraction of a day, steady state power sources (such as solar and nuclear) will have the lightest system weight. If megawatts of power are needed, closed cycle MHD systems (if successfully developed) have the potential of being very light and highly efficient. Such MHD generators are uniquely capable of fully exploiting advances in high-temperature reactor technology which could make up to 2500 K long-life, iner-gas-cooled reactors feasible. A particularly attractive MHD system is a turbo-MHD cycle which has a turbine driven compressor. It potentially have very low specific mass, high efficiency, and relatively low MHD generator enthalpy extraction.

Seikel, G. R.; Zauderer, B.

123

MHD Boundary Layer Flow of Dilatant Fluid in a Divergent Channel with Suction or Blowing

An analysis is carried out to study a steady magnetohydrodynamic (MHD) boundary layer flow of an electrically conducting incompressible power-law non-Newtonian fluid through a divergent channel. The channel walls are porous and subjected to either suction or blowing of equal magnitude of the same kind of fluid on both walls. The fluid is permeated by a magnetic field produced by

Bhattacharyya Krishnendu; G. C. Layek

2011-01-01

124

Results from study of potential early commercial MHD power plants and from recent ETF design work

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

F. Hals; R. Kessler; D. Swallom; L. Westra; J. Zar; W. Morgan; C. Bozzuto

1980-01-01

125

NUMERICAL ANALYSIS OF TWO PARTITIONED METHODS FOR UNCOUPLING EVOLUTIONARY MHD FLOWS

NUMERICAL ANALYSIS OF TWO PARTITIONED METHODS FOR UNCOUPLING EVOLUTIONARY MHD FLOWS W. LAYTON, H. TRANAND C. TRENCHEA Abstract. Magnetohydrodynamics (MHD) studies the dynamics of electrically conducting terrestrial applications, MHD flows occur at low magnetic Reynold numbers. We introduce two partitioned

Trenchea, Catalin

126

Thermodynamic Cycle Analysis of Magnetohydrodynamic-Bypass Hypersonic Airbreathing Engines

NASA Technical Reports Server (NTRS)

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.

Litchford, R. J.; Cole, J. W.; Bityurin, V. A.; Lineberry, J. T.

2000-01-01

127

Global Magnetohydrodynamic Modeling of the Solar Corona.

National Technical Information Service (NTIS)

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 ...

J. A. Linker

1997-01-01

128

Global Magnetohydrodynamic Modeling of the Solar Corona.

National Technical Information Service (NTIS)

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 investig...

J. A. Linker

2001-01-01

129

Optimization of fuel composition in open-cycle magnetohydrodynamic power generation

NASA Astrophysics Data System (ADS)

To design an MHD generator in such a way as to reduce its size and weight, the fuel composition corresponding to the maximum power density must be determined. A technique making this determination possible is described. It involves a calculation of the power density resulting from the combustion of a given inlet fuel composition as a function of temperature and pressure for several electrode configurations at a magnetic field strength of 2-6 T. The chemical composition of the combustion products at the specified temperature and pressure are calculated with a computer program. These composition data are then used in calculating the electrical conductivity and Hall parameter at the specified conditions. Gas velocities are calculated at the entrance to the electrode channel employing the energy conservation equation for compressible flow, assuming no friction or heat losses.

Harris, C. F.; Myerson, A. S.

1982-04-01

130

Multi-Symplectic Magnetohydrodynamics

A multi-symplectic formulation of ideal magnetohydrodynamics (MHD) is developed based on a 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 $\\tilde{\\bf A}$ where $\\alpha=\\tilde{\\bf A}{\\bf\\cdot}d{\\bf x}$ is Lie dragged with the flow, where ${\\bf B}=\

G. M. Webb; J. F. McKenzie; G. P. Zank

2013-12-17

131

Scale-locality of magnetohydrodynamic turbulence

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.

Aluie, Hussein [Los Alamos National Laboratory; Eyink, Gregory L [JOHNS HOPKINS UNIV.

2009-01-01

132

The infinite interface limit of multiple-region relaxed magnetohydrodynamics

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.

Dennis, G. R.; Dewar, R. L.; Hole, M. J. [Research School of Physics and Engineering, Australian National University, ACT 0200 (Australia); Hudson, S. R. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States)

2013-03-15

133

MHD performance demonstration experiment, FY 1974 to FY 1984

NASA Astrophysics Data System (ADS)

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.

Whitehead, G. L.; Christensen, L. S.; Felderman, R. J.

1984-06-01

134

Segmented electrode increases operating pressure of MHD accelerator

NASA Technical Reports Server (NTRS)

Circumferentially segmented-ring electrode replaces the solid-ring electrode in a basic magnetohydrodynamic /MHD/ accelerator. This produces diffuse discharges at pressures as high as 100 atmospheres.

1965-01-01

135

Performance calculations for 200-1000 MWe MHD/steam power plants

NASA Technical Reports Server (NTRS)

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.

Staiger, P. J.

1981-01-01

136

Optimization of the oxidant supply system for combined cycle MHD power plants

NASA Technical Reports Server (NTRS)

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.

Juhasz, A. J.

1982-01-01

137

Results from conceptual design study of potential early commercial MHD/steam power plants

NASA Technical Reports Server (NTRS)

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.

Hals, F.; Kessler, R.; Swallom, D.; Westra, L.; Zar, J.; Morgan, W.; Bozzuto, C.

1981-01-01

138

Methods of reducing energy consumption of the oxidant supply system for MHD/steam power plants

NASA Technical Reports Server (NTRS)

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.

Juhasz, A. J.

1983-01-01

139

Methods of reducing energy consumption of the oxidant supply system for MHD/steam power plants

NASA Technical Reports Server (NTRS)

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.

Juhasz, A. J.

1983-01-01

140

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.

R. L. Dewar; R. Mills; M. J. Hole

2008-10-14

141

Parabolized Navier-Stokes Code for Computing Magneto-Hydrodynamic Flowfields

NASA Technical Reports Server (NTRS)

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'.

Mehta, Unmeel B. (Technical Monitor); Tannehill, J. C.

2003-01-01

142

Kinetics of the desulfurization of an exhausted ionizing additive in a MHD electric power plant

NASA Astrophysics Data System (ADS)

The removal of sulfur oxides from exhaust gases is an acute problem in the operation of open-cycle MHD power plants. This paper proposes a method for calculating the rate of reaction between potassium sulfate and hydrogen at temperatures of 1033-1073 K. The method is based on the assumption that the process occurs in two stages: activated adsorption and a reaction in the adsorbed phase. An experimental desulfurization unit operating on these principles is described, and results of calculations are compared with experimental data.

Vizel, Ia. M.; Ibragimov, R. A.; Mostinskii, I. L.

1980-07-01

143

Kinetics of the desulfurization of an exhausted ionizing additive in a MHD electric power plant

NASA Astrophysics Data System (ADS)

The removal of sulfur oxides from exhaust gases is an acute problem in the operation of open-cycle MHD power plants. This paper proposes a method for calculating the rate of reaction between potassium sulfate and hydrogen at temperatures of 1033-1073 K. The method is based on the assumption that the process occurs in two stages: activated adsorption and a reaction in the adsorbed phase. An experimental desulfurization unit operating on these principles is described, and results of calculations are compared with experimental data.

Vizel, Ia. M.; Ibragimov, R. A.; Mostinskii, I. L.

1981-01-01

144

MHD Analysis of Dual Coolant Pb-17Li Blanket for ARIES-CS C. Mistrangelo1

MHD Analysis of Dual Coolant Pb-17Li Blanket for ARIES-CS C. Mistrangelo1 , A. R. Raffray2 of magnetohydrodynamic (MHD) flows in the poloidal channels that distribute the liquid metal in the breeder units has into account a number of feasibility issues related to magnetohydrodynamics (MHD). If the breeding liquid metal

Raffray, A. RenÃ©

145

Reduced resistive MHD with general density I: Model and stability results

Reduced resistive MHD with general density I: Model and stability results B. DesprÂ´es and R. Sart]. Reduced resistive magnetohydrodynamic (MHD) models have been proposed [5] to investigate a special type. In this work we focus on mathematical aspects of reduced resistive magnetohydrodynamic (MHD) models

146

Magnetohydrodynamic viscous flow over a nonlinearly moving surface: Closed-form solutions

NASA Astrophysics Data System (ADS)

In this paper, the magnetohydrodynamic (MHD) flow over a nonlinearly (power-law velocity) moving surface is investigated analytically and solutions are presented for a few special conditions. The solutions are obtained in closed forms with hyperbolic functions. The effects of the magnetic, the wall moving, and the mass transpiration parameters are discussed. These solutions are important to show the flow physics as well as to be used as bench mark problems for numerical validation and development of new solution schemes.

Fang, Tiegang

2014-05-01

147

Prospects for energy recovery from plastic waste gasifiers by means of MHD topping cycle

In this paper the authors present a feasibility study of a combined MagnetoHydroDynamic (MHD) and steam turbine plant in which the working gas is made of burnt plastic waste. The possibility of MHD retrofit of existing plant, especially fed by fossil fuel, is well known, and has been studied both for its economical and environmental benefits. The environmental impact and the elimination of pollution agents has become a prime necessity in waste digestion. Furthermore, plants in which the production of electrical power by means of burnt gases produced in the digestion process have been designed and built. In this field an MHD integration plant could be very attractive. This feasibility study has been developed by simulating an ideal plant with a plastic incinerator, an MHD device and conventional steam turbines. As a result, the simulations have indicated economic and environmental advantages with notable efficiency improvements in the generation of electrical power.

Geri, A.; Verdone, N.; Salvini, A.

1999-12-01

148

The Effect of Hall and FLR terms on the Development of MHD Turbulence Spectra

Solar wind magnetic spectra often show a steepening of the k-5\\/3-power law inertial range cascade at scales shorter than the ion gyro radius. Density spectra often show flattening at adjacent scales. We include the Hall term and a Finite Larmor Radius (FLR) term in a two-and-one-half-dimensional compressible magnetohydrodynamic (MHD) system of equations to model high frequency solar wind power spectra

D. C. Smith; S. Ghosh; D. A. Roberts; M. L. Goldstein

2002-01-01

149

Preliminary results in the NASA Lewis H2-O2 combustion MHD experiment

NASA Technical Reports Server (NTRS)

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.

Smith, J. M.

1979-01-01

150

Multi-region relaxed magnetohydrodynamics with anisotropy and flow

NASA Astrophysics Data System (ADS)

We present an extension of the multi-region relaxed magnetohydrodynamics (MRxMHD) equilibrium model that includes pressure anisotropy and general plasma flows. This anisotropic extension to our previous isotropic model is motivated by Sun and Finn's model of relaxed anisotropic magnetohydrodynamic equilibria. We prove that as the number of plasma regions becomes infinite, our anisotropic extension of MRxMHD reduces to anisotropic ideal MHD with flow. The continuously nested flux surface limit of our MRxMHD model is the first variational principle for anisotropic plasma equilibria with general flow fields.

Dennis, G. R.; Hudson, S. R.; Dewar, R. L.; Hole, M. J.

2014-07-01

151

Plasma relaxation and topological aspects in Hall magnetohydrodynamics

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.

Shivamoggi, B. K. [University of Central Florida, Orlando, Florida 32816-1364 (United States)

2012-07-15

152

Hyperbolic Divergence Cleaning for the MHD Equations

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

A. Dedner; F. Kemm; D. Kroner; C.-D. Munz; T. Schnitzer; M. Wesenberg

2002-01-01

153

Gravitational Radiation from Primordial Helical MHD Turbulence

We consider gravitational waves (GWs) generated by primordial inverse-cascade helical magneto-hydrodynamical (MHD) turbulence produced by bubble collisions at the electroweak phase transitions (EWPT). Compared to the unmagnetized EWPT case, the spectrum of MHD-turbulence-generated GWs peaks at lower frequency with larger amplitude and can be detected by the proposed Laser Interferometer Space Antenna (LISA).

Tina Kahniashvili; Grigol Gogoberidze; Bharat Ratra

2008-02-25

154

Helically forced MHD flows in confined cylindrical geometries

Helically forced MHD flows in confined cylindrical geometries Malcolm Roberts1 , Matthieu Leroy1 the resistive magnetohydrodynamic (MHD) equations. A helical magnetic field is imposed via boundary conditions be used in complex geometries is also proposed. Keywords: MHD, self-organization, confined geometry

Boyer, Edmond

155

Dust Transport in MRI Turbulent Disks: Ideal and Non-ideal MHD with Ambipolar Diffusion

We study dust transport in turbulent protoplanetary disks using three-dimensional global unstratified magnetohydrodynamic (MHD) simulations including Lagrangian dust particles. The turbulence is driven by the magnetorotational instability (MRI) with either ideal or non-ideal MHD that includes ambipolar diffusion (AD). In ideal MHD simulations, the surface density evolution (except for dust that drifts fastest), turbulent diffusion, and vertical scale height of dust can all be reproduced by simple one-dimensoinal and/or analytical models. However, in AD dominated simulations which simulate protoplanetary disks beyond 10s of AU, the vertical scale height of dust is larger than previously predicted. To understand this anomaly in more detail, we carry out both unstratified and stratified local shearing box simulations with Lagrangian particles, and find that turbulence in AD dominated disks has very different properties (e.g., temporal autocorrelation functions and power spectra) than turbulence in ideal MHD disk...

Zhu, Zhaohuan; Bai, Xue-Ning

2014-01-01

156

Ideal MHD stability of a spherical tokamak power plant and a component test facility.

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.

Hole, M. J.; Wilson, H. R.; Abeysuriya, R.; Larson, J. W. (CLS-CI); ( MCS); (Australian National Univ.); (Univ. of York); (Univ. of Sydney)

2010-12-01

157

Ideal MHD stability of a spherical tokamak power plant and a component test facility

NASA Astrophysics Data System (ADS)

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 Rw and on-axis safety factor q0. 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 q0 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 q0 sufficiently large (q0 > 2.8 for the power plant and q0 > 2.1 for the CTF). Both power plant and CTF configurations are found to be ballooning stable.

Hole, M. J.; Wilson, H. R.; Abeysuriya, R.; Larson, J. W.

2010-12-01

158

Results of closed cycle MHD power generation test with a helium-cesium working fluid

NASA Technical Reports Server (NTRS)

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.

Sovie, R. J.

1977-01-01

159

This is the first in a series of papers that introduces a new paradigm for understanding the jet in M87: a collimated relativistic flow in which strong magnetic fields play a dominant dynamical role. Here, we focus on the flow downstream of HST-1-an essentially stationary flaring feature that ejects trails of superluminal components. We propose that these components are quad relativistic magnetohydrodynamic shock fronts (forward/reverse fast and slow modes) in a narrow jet with a helically twisted magnetic structure. And we demonstrate the properties of such shocks with simple one-dimensional numerical simulations. Quasi-periodic ejections of similar component trails may be responsible for the M87 jet substructures observed further downstream on 10{sup 2}-10{sup 3} pc scales. This new paradigm requires the assimilation of some new concepts into the astrophysical jet community, particularly the behavior of slow/fast-mode waves/shocks and of current-driven helical kink instabilities. However, the prospects of these ideas applying to a large number of other jet systems may make this worth the effort.

Nakamura, Masanori [Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218 (United States); Garofalo, David; Meier, David L., E-mail: nakamura@stsci.ed, E-mail: david.a.garofalo@jpl.nasa.go, E-mail: david.l.meier@jpl.nasa.go [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

2010-10-01

160

NASA Technical Reports Server (NTRS)

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.

Staiger, P. J.; Penko, P. F.

1982-01-01

161

Numerical measurements of the spectrum in magnetohydrodynamic turbulence.

We report the results of an extensive set of direct numerical simulations of forced, incompressible, magnetohydrodynamic (MHD) turbulence with a strong guide field. The aim is to resolve the controversy regarding the power-law exponent (alpha, say) of the field-perpendicular energy spectrum E(k) proportional variant k(alpha). The two main theoretical predictions alpha=-3/2 and alpha=-5/3 have both received some support from differently designed numerical simulations. Our calculations have a resolution of 512(3) mesh points, a strong guide field, and an anisotropic simulation domain and implement a broad range of large-scale forcing routines, including those previously reported in the literature. Our findings indicate that the spectrum of well-developed, strong incompressible MHD turbulence with a strong guide field is E(k) proportional variant k(-3/2). PMID:18517529

Mason, Joanne; Cattaneo, Fausto; Boldyrev, Stanislav

2008-03-01

162

Use of MHD systems in hypersonic aircraft

The possibilities of using magnetohydrodynamic (MHD) systems on hypersonic aircraft are discussed. The distinctive features\\u000a of using MHD systems in the flow path of ramjet engines are examined. A quasi-one-dimensional mathematical model for the engine\\u000a is presented which includes the MHD interaction with the flow. It is shown that the specific impulse of an engine system can\\u000a be raised by

V. L. Fraishtadt; A. L. Kuranov; E. G. Sheikin

1998-01-01

163

Radiative heat exchange in the combustion chamber of an MHD electric power plant using methane gas

NASA Astrophysics Data System (ADS)

A method is proposed for calculating radiative thermal fluxes on the wall of the combustion chamber of an MHD electric power plant operating with methane gas. The calculations are performed on the basis of spectral characteristics of the molecular components of the combustion products and ionizing potassium impurity, with allowance for multiple reflection of radiation from the wall of the chamber. It is shown that the effect of particles of vaporizing impurity on the optical properties of the working medium is insignificant. It follows from the calculations that emission from the potassium impurity atoms amounts to about one half the radiative thermal flux density received on the wall, the magnitude of which reaches 2-3 MW/sq m.

Biberman, L. M.; Zhelezniak, M. B.; Mnatsakanian, A. Kh.; Rotinov, A. G.; Tager, S. A.

1980-09-01

164

Study of seed-reprocessing systems for open-cycle coal-fired MHD power plants.

NASA Astrophysics Data System (ADS)

Of the several processes that are capable of separating sulfur from potassium sulfate, the process developed by Pittsburgh Energy Research Center (PERC), and the Formate process were selected for the detailed mass and energy balance calculations. As a basis for the calculations, an MHD power plant of 450 Mwt size and burning Illinois no. 6 coal was selected. In the mass balance calculations, the role played by various trace impurities was included to the extent of current knowledge about such impurities and their impacts on process chemistry. The results given should be considered as preliminary values because various simplifying assumptions were made and factors such as heat losses and component efficiencies were excluded. On the basis of net energy requirements, the Formate process showed a slight advantage; however, it produced a potentially unacceptable sludge as the sulfur containing waste.

Sheth, A.

1980-07-01

165

GPSAP/V2 with applications to open-cycle MHD systems

NASA Astrophysics Data System (ADS)

A systems analysis technique for analyzing lumped component systems is presented. The computer coding is generated by employing simple preprocessor statements to establish system configurations, constraints, and objective functions. A hybrid equation solver and a sequential programming method for solving constrained optimization problems are described. Recursive calling capabilities are used in both equation solver and optimizer. The build up Jacobians and Hessians of the constraints and objective functions are retained, reducing computing time during parameter studies. A collection of simple first order models for analysis of open cycle magnetohydrodynamics (MHD) power plant applications is presented. Simple MHD system configurations are presented and analyzed.

Geyer, H. K.

1981-01-01

166

NASA Astrophysics Data System (ADS)

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.

Dewar, R. L.; Mills, R.; Hole, M. J.

2009-05-01

167

THE 2D MHD EQUATIONS WITH HORIZONTAL DISSIPATION AND HORIZONTAL MAGNETIC DIFFUSION

THE 2D MHD EQUATIONS WITH HORIZONTAL DISSIPATION AND HORIZONTAL MAGNETIC DIFFUSION CHONGSHENG CAO1 to the 2D incompressible magnetohydrodynamic (MHD) equations with horizontal dissipation and horizontal of the aforementioned MHD equations. 1. Introduction The MHD equations govern the dynamics of the velocity

Wu, Jiahong

168

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 quasi-parallel 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.

Benjamin D. G. Chandran

2000-08-30

169

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

Chandran

2000-11-27

170

Reduced Models of MHD Turbulence: Implications for Density Fluct... http Models of MHD Turbulence: Implications for Density Fluctuations and Anisotropic Spectra A. Bhattacharjee in the derivation of reduced models for weakly compressible magnetohydrodynamic (MHD) turbulence are discussed

Ng, Chung-Sang

171

Elements of magnetohydrodynamics with the Hall current. I - Nonlinear phenomena

A general theory of ideal magnetohydrodynamics (MHD) in the presence of a Hall current is developed. The basic equations describing a Hall-current fluid consist of the quasi-linear partial differential equations of ideal MHD with Ohm's law written in a form that includes the Hall effect. General properties of the nonlinear equations are discussed, and the characteristics of these equations are

P. Rosenau; J. A. Tataronis; G. Conn

1979-01-01

172

NASA Technical Reports Server (NTRS)

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.

Hals, F. A.

1981-01-01

173

Ideal Magnetohydrodynamic Stability of the NCSX

The ideal magnetohydrodynamic (MHD) stability of the National Compact Stellarator Experiment (NCSX) is extensively analyzed using the most advanced three-dimensional MHD codes. It is shown that the NCSX is stable to finite-n MHD modes, including the vertical mode, external kink modes and ballooning modes. However, high-n external kink modes that peak near the plasma edge are found to be weakly unstable. A global calculation shows that finite-n ballooning modes are significantly more stable than the local infinite-n modes.

Fu, GuoYong [Princeton Plasma Physics Laboratory (PPPL); Isaev, Maxim Yu [Kurchatov Institute, Moscow, Russia; Ku, Long-Poe [Princeton Plasma Physics Laboratory (PPPL); Mikhailov, M [Kurchatov Institute, Moscow, Russia; Redi, M H [Princeton Plasma Physics Laboratory (PPPL); Sanchez, Raul [ORNL; Subbotin, A [Kurchatov Institute, Moscow, Russia; Hirshman, Steven Paul [ORNL; Cooper, W Anthony [CRPP/EPFL, Association Euratom-Suisse, Lausanne, Switzerland; Monticello, D. [Princeton Plasma Physics Laboratory (PPPL); Reiman, A H [Princeton Plasma Physics Laboratory (PPPL); Zarnstorff, M. C. [Princeton Plasma Physics Laboratory (PPPL)

2007-01-01

174

An unsplit staggered mesh scheme for multidimensional magnetohydrodynamics

We introduce an unsplit staggered mesh scheme (USM) for multidimensional magnetohydrodynamics (MHD) that uses a constrained transport (CT) method with high-order Godunov fluxes and incorporates a new data reconstruction–evolution algorithm for second-order MHD interface states. In this new algorithm, the USM scheme includes so-called “multidimensional MHD terms”, proportional to ?·B, in a dimensionally-unsplit way in a single update. This data

Dongwook Lee; Anil E. Deane

2009-01-01

175

A simulation of the IPS variations from a magnetohydrodynamical simulation

NASA Technical Reports Server (NTRS)

Calculations of the variations of interplanetary scintillation (IPS) from a disturbance simulated by a 3-D magnetohydrodynamical (MHD) model of the solar wind are presented. The simulated maps are compared with observations and it is found that the MHD model reproduces the qualitative features of observed disturbances. The disturbance produced by the MHD simulation is found to correspond in strength with the weakest disturbance which can be reliably detected by existing single station IPS observations.

Tappin, S. J.; Dryer, M.; Han, S. M.; Wu, S. T.

1987-01-01

176

Analysis of Magnetohydrodynamic Flow in Microfluidics

Over the last three decades, numerical and experimental fluid dynamic studies have been well documented for optimization of device performance in general fluid dynamics, prediction and analysis of physiological flows, fluid-structure interactions in biological systems, and effectiveness of drug delivery systems in lab on chip devices. Magnetohydrodynamics (MHD) is a proven and a routinely used technology not only in various

Yogendra Panta; Wei Lin

2009-01-01

177

Global Magnetohydrodynamic Modeling of the Solar Corona

NASA Technical Reports Server (NTRS)

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.

Linker, Jon A.

2001-01-01

178

NASA Technical Reports Server (NTRS)

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.

Hals, F.; Kessler, R.; Swallom, D.; Westra, L.; Zar, J.; Morgan, W.; Bozzuto, C.

1980-01-01

179

Magnetohydrodynamic stability comparison theorems revisited

Magnetohydrodynamic (MHD) stability comparison theorems are presented for several different plasma models, each one corresponding to a different level of collisionality: a collisional fluid model (ideal MHD), a collisionless kinetic model (kinetic MHD), and two intermediate collisionality hybrid models (Vlasov-fluid and kinetic MHD-fluid). Of particular interest is the re-examination of the often quoted statement that ideal MHD makes the most conservative predictions with respect to stability boundaries for ideal modes. Some of the models have already been investigated in the literature and we clarify and generalize these results. Other models are essentially new and for them we derive new comparison theorems. Three main conclusions can be drawn: (1) it is crucial to distinguish between ergodic and closed field line systems; (2) in the case of ergodic systems, ideal MHD does indeed make conservative predictions compared to the other models; (3) in closed line systems undergoing perturbations that maintain the closed line symmetry this is no longer true. Specifically, when the ions are collisionless and their gyroradius is finite, as in the Vlasov-fluid model, there is no compressibility stabilization. The Vlasov-fluid model is more unstable than ideal MHD. The reason for this is related to the wave-particle resonance associated with the perpendicular precession drift motion of the particles (i.e., the ExB drift and magnetic drifts), combined with the absence of any truly toroidally trapped particles. The overall conclusion is that to determine macroscopic stability boundaries for ideal modes for any magnetic geometry using a simple conservative approach, one should analyze the ideal MHD energy principle for incompressible displacements.

Cerfon, Antoine J.; Freidberg, Jeffrey P. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, 167 Albany Street, Cambridge, Massachusetts 02139 (United States)

2011-01-15

180

Open-cycle MHD systems analysis

NASA Astrophysics Data System (ADS)

Five variant configurations of a coal burning open cycle magnetohydrodynamic electric power generating facility were studied for evaluation as candidate first generation power plants. A material and energy balance and cycle analysis was performed for each case to provide information for the conceptual designs and costing of all major MHD related components and subsystems as well as specification of other state of the art components. A economic comparison was made of each design by developing the cost of electricity based on component costs, estimates of operation and maintenance requirements, and the performance of each plant from the system analyses. An overall description of each plant is provided along with discussions of critical component and process development. An oxygen enriched OCMHD plant design was identified as an attractive candidate for first generation utility service. This plant design appears to offer competitive costs of electricity and minimizes development risk.

Lippert, T. E.; Weeks, K. D.

1980-02-01

181

Collisionless magnetohydrodynamic turbulence in two dimensions

In this paper we give a formulation of two-dimensional (2D) collisionless magnetohydrodynamic (MHD) turbulence that includes the effects of both electron inertia and electron pressure (or parallel electron compressibility) and is applicable to strongly magnetized collisionless plasmas. We place particular emphasis on the departures from the 2D classical MHD turbulence results produced by the collisionless MHD effects. We investigate the fractal/multi-fractal aspects of spatial intermittency. The fractal model for intermittent collisionless MHD turbulence appears to be able to describe the observed k{sup -1} spectrum in the solar wind. Multi-fractal scaling behaviors in the inertial range are first deduced, and are then extrapolated down to the dissipative microscales. We then consider a parabolic-profile model for the singularity spectrum f ({alpha}), as an explicit example of a multi-fractal scenario. These considerations provide considerable insights into the basic mechanisms underlying spatial intermittency in 2D fully developed collisionless MHD turbulence.

Shivamoggi, Bhimsen K. [University of Central Florida, Orlando, FL 32816-1364 (United States)]. E-mail: bhimsens@pegasus.cc.ucf.edu

2005-05-01

182

NASA Astrophysics Data System (ADS)

The Magnetohydrodynamics package in the ALE radiation-hydrodynamics ICF design code Hydra is based upon a three-dimensional vector finite element method. This defines a set of spaces and differential operators that maintain the zero divergence of the magnetic field exactly. It is fully implicit in time and second order accurate in space. We discuss several improvements to the MHD package. The first addition is an anisotropic tensor based heat conduction method. The second improvement is a method for solving the magnetic diffusion equation for all of the element types resulting from point and line singularities including tetrahedral and pyramid elements. Finally a new magnetic flux advection method was implemented based on the method by A.C Robinson, et al.ootnotetextA.C. Robinson, J. H. J. Niederhaus, V. G. Weirs, E. Love, Int. J. Numer. Meth. Fluids, 65, 1438 (2011)

Koning, J. M.; Kerbel, G. D.; Marinak, M. M.

2011-11-01

183

This paper investigates the effects of thermal radiation on the magnetohydrodynamic (MHD) flow and heat transfer over a nonlinear\\u000a shrinking porous sheet. The surface velocity of the shrinking sheet and the transverse magnetic field are assumed to vary\\u000a as a power function of the distance from the origin. The temperature dependent viscosity and the thermal conductivity are\\u000a also assumed to

G. C. Shit; R. Haldar

2011-01-01

184

NONIDEAL MAGNETOHYDRODYNAMIC TURBULENT DECAY IN MOLECULAR CLOUDS

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.

Downes, T. P. [School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland); O'Sullivan, S. [National Centre for Plasma Science and Technology, Dublin City University, Glasnevin, Dublin 9 (Ireland)], E-mail: turlough.downes@dcu.ie

2009-08-20

185

Survey of MHD plant applications

NASA Technical Reports Server (NTRS)

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.

Lynch, J. J.; Seikel, G. R.; Cutting, J. C.

1979-01-01

186

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.

Not Available

1994-07-01

187

Magnetohydrodynamic Augmented Propulsion Experiment

NASA Technical Reports Server (NTRS)

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

Litchford, Ron J.

2008-01-01

188

MHD simple waves and the divergence wave

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.

Webb, G. M. [Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Pogorelov, N. V.; Zank, G. P. [Department of Physics, The University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, Huntsville, AL 35805 (United States)

2010-03-25

189

We present a model for nonlinear decay of the weak wave in three-dimensional incompressible magnetohydrodynamic (MHD) turbulence. We show that the decay rate is different for parallel and perpendicular waves. We provide a general formula for arbitrarily directed waves and discuss particular limiting cases known in the literature. We test our predictions with direct numerical simulations of wave decay in three-dimensional MHD turbulence, and discuss the influence of turbulent damping on the development of linear instabilities in the interstellar medium and on other important astrophysical processes.

Andrey Beresnyak; Alex Lazarian

2008-05-06

190

Free boundary skin current MHD (magnetohydrodynamic) equilibria

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.

Reusch, M.F.

1988-02-01

191

On the MHD Acceleration of Astrophysical Jets

We present a 2.5D magnetohydrodynamic (MHD) simulation of the acceleration of a collimated jet from a magnetized accretion\\u000a disk. We employ a MHD Adaptive Mesh Refinement (AMR) code (FLASH—University of Chicago). Thanks to this tool we can follow\\u000a the evolution of the system for many dynamical timescales with a high-spatial resolution. Assuming an initial condition in\\u000a which a Keplerian disk,

Claudio Zanni; Attilio Ferrari; Silvano Massaglia; Gianluigi Bodo; Paola Rossi

2004-01-01

192

Micromachined magnetohydrodynamic actuators and sensors

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.

Lee, Abraham P. (Walnut Creek, CA); Lemoff, Asuncion V. (Union City, CA)

2000-01-01

193

On One-Fluid MHD Models with Electron Inertia Keiji Kimura

On One-Fluid MHD Models with Electron Inertia Keiji Kimura Supervised by P. J. Morrison August 21, 2012 Abstract We investigate the limitations of various MHD models that include electron inertia density. 1 Introduction The usual ideal magnetohydrodynamic (MHD) model is often used in various fields

Lebovitz, Norman

194

Study of Magnetic Relaxation in Plasmas Using a Parallel Implicit MHD Solver

Study of Magnetic Relaxation in Plasmas Using a Parallel Implicit MHD Solver by Ogden S. Jones Using a Parallel Implicit MHD Solver by Ogden S. Jones Chairperson of Supervisory Committee: Prof. D the time-dependent, non- ideal magnetohydrodynamic (MHD) equations. The algorithm is a finite-volume scheme

Shumlak, Uri

195

A statistical study of magnetosphereionosphere coupling in the LyonFedderMobarry global MHD model

A statistical study of magnetosphereÂionosphere coupling in the LyonÂFedderÂMobarry global MHD, the use of global magnetohydrodynamic (MHD) models is probably the most challenging to implement, but it also holds the greatest promise for accurate specification. One key feature of most global MHD models

196

Arbitrary order exactly divergence-free central discontinuous Galerkin methods for ideal MHD

Arbitrary order exactly divergence-free central discontinuous Galerkin methods for ideal MHD, NY 12180-3590, United States Abstract Ideal magnetohydrodynamic (MHD) equations consist of a set proposed for ideal MHD equations. In this paper, we further develop such methods with higher order accuracy

Li, Fengyan

197

NON-UNIFORM DECAY OF MHD EQUATIONS WITH AND WITHOUT MAGNETIC DIFFUSION

NON-UNIFORM DECAY OF MHD EQUATIONS WITH AND WITHOUT MAGNETIC DIFFUSION RUBÃ?N AGAPITO AND MARIA decay is optimal. 1. INTRODUCTION We consider the Magnetohydrodynamics equations (MHD) in two and three dimensions. We deal with questions regarding long time behavior of solutions to the MHD with and without

Schonbek, Maria

198

Semi-implicit Treatment of the Hall Term in Finite Volume, MHD Computations

Semi-implicit Treatment of the Hall Term in Finite Volume, MHD Computations by Julian Tercero in Finite Volume, MHD Computations by Julian Tercero Becerra Sagredo Chairperson of Supervisory Committee Ph term into the time- dependent, non-ideal magnetohydrodynamic (MHD) equations. A semi-implicit method

Shumlak, Uri

199

On the possibility of using an electromagnetic ionosphere in global MHD simulations

On the possibility of using an electromagnetic ionosphere in global MHD simulations P. Janhunen magnetohydrodynamic (MHD) simu- lations of the Earth's magnetosphere must be coupled with a dynamical ionospheric) from the magnetospheric MHD variables at the ionospheric boundary. The ionospheric potential is solved

Paris-Sud XI, UniversitÃ© de

200

MESSENGER Observations of Magnetohydrodynamic Waves in the Solar Corona from Faraday Rotation

NASA Astrophysics Data System (ADS)

During the declining phase of the longest solar minimum in a century, the arrival of the MESSENGER spacecraft at superior conjunction allowed the measurement of magnetohydrodynamic (MHD) waves in the solar corona with its 8 GHz radio frequency signal. MHD waves crossing the line of sight were measured via Faraday rotation fluctuations (FRFs) in the plane of polarization (PP) of MESSENGER's signal. FRFs in previous observations of the solar corona (at greater offset distances) consisted of a turbulent spectrum that decreased in power with increasing frequency and distance from the Sun. Occasionally a spectral line, a distinct peak in the power spectral density spectrum around 4 to 8 mHz, was also observed in these early data sets at offset distances of about 5 to 10 solar radii. The MESSENGER FRF data set shows a spectral line at an offset distance between 1.55 to 1.85 solar radii with a frequency of 0.6±0.2 mHz. Other possible spectral lines may be at 1.2, 1.7, and 4.5 mHz; MHD waves with these same frequencies have been observed in X-ray data traveling along closed coronal loops at lower offset distances. An initial analysis of the MESSENGER spectral line(s) shows behavior similar to turbulent spectra: decreasing power with increasing frequency and distance from the Sun. Here we detail the steps taken to process the MESSENGER change in PP data set for the MHD wave investigation.

Jensen, E. A.; Nolan, M.; Bisi, M. M.; Chashei, I.; Vilas, F.

2013-07-01

201

We present new 3D magnetohydrodynamic (MHD) simulations of a supernova-driven, stratified interstellar medium. These simulations were run using the Waagan (2009) positivity preserving scheme for ideal MHD implemented in the Flash code. The scheme is stable even for the Mach numbers approaching 100 found in this problem. We have previously shown that the density distribution arising from hydrodynamical versions of

Mordecai-Mark Mac Low; Alex S. Hill; M. Ryan Joung; Knut Waagan; Christian Klingenberg; Kenneth Wood; Robert A. Benjamin; Christoph Federrath; L. Matthew Haffner

2011-01-01

202

Electromagnetic pulse and the electric power network

This paper defines the nuclear electromagnetic pulse (EMP) - electric power system interaction problem. A description of high altitude EMP (HEMP) characteristics, source region EMP (SREMP) characteristics, and magnetohydrodynamics EMP (MHD-EMP) characteristics are presented. The results of initial calculations of EMP induced surges on electric power transmission and distribution lines are presented and compared with lightning induced surges. Potential EMP impacts on electric power systems are discussed, and an overview of the Department of Energy (DOE) EMP research program is presented.

Klein, K.W.; Barnes, P.R.; Zaininger, H.W.

1984-01-01

203

Operational analysis of open-cycle MHD

NASA Astrophysics Data System (ADS)

Open cycle magnetohydrodynamic (OCMHD) conceptual power plant designs are studied in the context of a utility system to form a better basis for understanding their design, design requirements, and market possibilities. Based on assumed or projected plant costs and performance characteristics, assumed economics and escalation factors, and one coal supply and delivery scenario, overall and regional OCMHD utility market possibilities are reviewed. Additionally, for one hypothetical utility system a generation expansion plan is developed that includes OCMHD as a baseload power generating station. The impact on generation system economics and operation of alternating selected MHD plant cost and performance characteristics is reviewed. Baseload plant availability is shown as an important plant design consideration, and a general methodology and data base is developed to assess the impact on design and cost of various reliability decisions. An overall plant availability goal is set and the required availabilities of various MHD high technology components are derived to meet the plant goal. The approach is then extended to projecting channel life goals for various plant design configurations and assumptions.

Lippert, T. E.; McCutchan, D. A.

1980-07-01

204

Nonlinear subcritical magnetohydrodynamic beta limit

NASA Astrophysics Data System (ADS)

Published gyrokinetic simulations have had difficulty operating beyond about half the ideal magnetohydrodynamic (MHD) critical beta limit with stationary and low transport levels in some well-established reference cases. Here it is demonstrated that this limitation is unlikely due to numerical instability, but rather appears to be a nonlinear subcritical MHD beta limit [R. E. Waltz, Phys. Rev. Lett. 55, 1098 (1985)] induced by the locally enhanced pressure gradients from the diamagnetic component of the nonlinearly driven (zero frequency) zonal flows. Strong evidence that the zonal flow corrugated pressure gradient profiles can act as a MHD-like beta limit unstable secondary equilibrium is provided. It is shown that the addition of sufficient E ×B shear or operation closer to drift wave instability threshold, thereby reducing the high-n drift wave turbulence nonlinear pumping of the zonal flows, can allow the normal high-n ideal MHD beta limit to be reached with low transport levels. Example gyrokinetic simulations of experimental discharges are provided: one near the high-n beta limit reasonably matches the low transport levels needed when the high experimental level of E ×B shear is applied; a second experimental example at moderately high beta appears to be limited by the subcritical beta.

Waltz, R. E.

2010-07-01

205

Nonlinear subcritical magnetohydrodynamic beta limit

Published gyrokinetic simulations have had difficulty operating beyond about half the ideal magnetohydrodynamic (MHD) critical beta limit with stationary and low transport levels in some well-established reference cases. Here it is demonstrated that this limitation is unlikely due to numerical instability, but rather appears to be a nonlinear subcritical MHD beta limit[R. E. Waltz, Phys. Rev. Lett. 55, 1098 (1985)] induced by the locally enhanced pressure gradients from the diamagnetic component of the nonlinearly driven (zero frequency) zonal flows. Strong evidence that the zonal flow corrugated pressure gradient profiles can act as a MHD-like beta limit unstable secondary equilibrium is provided. It is shown that the addition of sufficient ExB shear or operation closer to drift wave instability threshold, thereby reducing the high-n drift wave turbulence nonlinear pumping of the zonal flows, can allow the normal high-n ideal MHD beta limit to be reached with low transport levels. Example gyrokinetic simulations of experimental discharges are provided: one near the high-n beta limit reasonably matches the low transport levels needed when the high experimental level of ExB shear is applied; a second experimental example at moderately high beta appears to be limited by the subcritical beta.

Waltz, R. E. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)

2010-07-15

206

Multiscaling in Hall-Magnetohydrodynamic Turbulence: Insights from a Shell Model

NASA Astrophysics Data System (ADS)

We show that a shell-model version of the three-dimensional Hall-magnetohydrodynamic (3D Hall-MHD) equations provides a natural theoretical model for investigating the multiscaling behaviors of velocity and magnetic structure functions. We carry out extensive numerical studies of this shell model, obtain the scaling exponents for its structure functions, in both the low-k and high-k power-law ranges of three-dimensional Hall-magnetohydrodynamic, and find that the extended-self-similarity procedure is helpful in extracting the multiscaling nature of structure functions in the high-k regime, which otherwise appears to display simple scaling. Our results shed light on intriguing solar-wind measurements.

Banerjee, Debarghya; Ray, Samriddhi Sankar; Sahoo, Ganapati; Pandit, Rahul

2013-10-01

207

The effects of nonresonating hot ions on the spectrum of magnetohydrodynamic (MHD) waves and instabilities in tokamaks are studied in the limit when the width of the hot ion drift orbits is much larger than the radial scale length of the MHD perturbations. Due to the large magnetic drift velocities the hot ions cannot contribute to the MHD perturbations directly,

S. E. Sharapov; A. B. Mikhailovskii; G. T. A. Huysmans

2004-01-01

208

The effects of nonresonating hot ions on the spectrum of magnetohydrodynamic (MHD) waves and instabilities in tokamaks are studied in the limit when the width of the hot ion drift orbits is much larger than the radial scale length of the MHD perturbations. Due to the large magnetic drift velocities the hot ions cannot contribute to the MHD perturbations directly,

S. E. Sharapov; A. B. Mikhailovskii; G. T. A. Huysmans

2004-01-01

209

The Exact Solution of the Riemann Problem in Relativistic MHD

We discuss the procedure for the exact solution of the Riemann problem in special relativistic magnetohydrodynamics (MHD). We consider both initial states leading to a set of only three waves analogous to the ones in relativistic hydrodynamics, as well as generic initial states leading to the full set of seven MHD waves. Because of its generality, the solution presented here could serve as an important test for those numerical codes solving the MHD equations in relativistic regimes.

B. Giacomazzo; L. Rezzolla

2005-07-25

210

NASA Astrophysics Data System (ADS)

Time dependent r-z two-dimensional numerical simulations with LES technique have been carried out in order to clarify the plasma fluid behavior and power generation characteristics of the disk MHD generator under the rated operation conditions demonstrated in the closed loop experimental facility at Tokyo Tech. The generator currently installed could suffer from the non-uniform and low electrical conductivity, and the boundary layer separation even under the rated operation conditions. The large amount of generated electric power is consumed in the boundary layer separation region, which reduces a net output power. Reducing the back pressure and improving the inlet plasma conditions surely provide the higher generator performance. The influence of 90 degree bend downstream duct on the generator performance is found to be not marked.

Ohno, Jun; Liberati, Alessandro; Murakami, Tomoyuki; Okuno, Yoshihiro

211

used, including fluctuations with wave vectors k parallel to the ambient large-scale magnetic field B0 field B0. The magnetic fluctuations on scales ,l0 , denoted B1, are small compared to B0 and are treated-Sridhar Power Spectrum Benjamin D. G. Chandran* Department of Physics & Astronomy, University of Iowa, Iowa City

Chandran, Ben

212

NASA Technical Reports Server (NTRS)

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.

Staigner, P. J.; Abbott, J. M.

1980-01-01

213

MHD simulations with the FLASH code

The FLASH code developed at the University of Chicago Flash Center is a modular, general-purpose, adaptive, parallel simulation code capable of handling compressible flow problems in various physical, in particular astrophysical, environments. Starting with version release 2.0, the FLASH code supports the equations of magnetohydrodynamics (MHD). In this paper, we will describe the present state of the code and the

Timur Linde

2002-01-01

214

Statistical Properties of Dissipative MHD Accelerators

We use exact orbit integration to investigate particle acceleration in a Gauss field proxy of magnetohydrodynamic (MHD) turbulence. Regions where the electric current exceeds a critical threshold are declared to be `dissipative' and endowed with super-Dreicer electric field ${\\\\bf E}_\\\\Omega = \\\\eta {\\\\bf j}$. In this environment, test particles (electrons) are traced and their acceleration to relativistic energies is studied.

Kaspar Arzner; Loukas Vlahos; Bernard Knaepen; Nicolas Denewet

2005-01-01

215

MHD Shocks in Coronal Mass Ejections.

National Technical Information Service (NTIS)

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 nonline...

R. S. Steinolfson

1991-01-01

216

Energy Dissipation in Magnetohydrodynamic Turbulence: Coherent Structures or "Nanoflares"?

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 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 co...

Zhdankin, Vladimir; Perez, Jean Carlos; Tobias, Steven M

2014-01-01

217

NASA Technical Reports Server (NTRS)

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.

Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

1975-01-01

218

Embedding a Hall MHD plasma sheet simulation inside the Lyon-Fedder-Mobarry global MHD model

We have developed a 3D Hall magnetohydrodynamic (MHD) model with the goal of embedding this high-resolution module into the plasma sheet region of the Lyon-Fedder-Mobarry global MHD model. We intend to investigate the effect of the Hall term on the size and structure of fast flow channels observed in the plasma sheet. Owing to insufficient spatial spacecraft coverage of plasma

T. Guild; H. Spence; J. Lyon; C. Goodrich; V. Merkin; L. Kepko

2005-01-01

219

MHD performance demonstration experiment, October 1, 1080-September 30, 1981

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.

Whitehead, G. L.; Christenson, L. S.; Felderman, E. J.; Lowry, R. L.; Bordenet, E. J.

1981-12-01

220

NASA Astrophysics Data System (ADS)

The effects of nonresonating hot ions on the spectrum of magnetohydrodynamic (MHD) waves and instabilities in tokamaks are studied in the limit when the width of the hot ion drift orbits is much larger than the radial scale length of the MHD perturbations. Due to the large magnetic drift velocities the hot ions cannot contribute to the MHD perturbations directly, but two main effects of the hot ions, the hot-ion density-dependent effect and the hot-ion pressure-dependent effect, influence the MHD perturbations indirectly. The physics of both effects is elucidated and it is shown that both these effects can be described in MHD approach. A new code, MISHKA-H (MISHKA including the hot-ion indirect effects), is developed as an extension of the ideal MHD code MISHKA-D [Huysmans et al., Phys. Plasmas 8, 4292 (2002)]. Analytical benchmarks for this code are given. Results of the MISHKA-H code on Alfvén spectrum in a shear-reversed discharges with ion-cyclotron resonance frequency (ICRF) heating are presented. Modeling of Alfvén cascades and their transition into toroidal Alfvén eigenmodes in shear-reversed tokamak equilibrium is considered. The hot-ion effect on the unstable branch of the MHD spectrum is studied for the test case of an n=1 ideal MHD internal kink mode, which is relevant to short-period sawteeth in low-density plasmas observed in Joint European Torus (JET) [Rebut et al., Proceedings of the 10th International Conference, Plasma Physics and Controlled Nuclear Fusion, London (International Atomic Energy Agency, Vienna, 1985), Vol. I, p. 11] experiments with high-power ICRF heating.

Sharapov, S. E.; Mikhailovskii, A. B.; Huysmans, G. T. A.

2004-05-01

221

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)

Louis, J F

1980-03-01

222

Feasibility of the inflow disk generator for open-cycle MHD power generation

NASA Astrophysics Data System (ADS)

A feasibility study of the inflow disk MHD generator for baseload applications was performed. Each design element, i.e., the combustor, the inlet flow path, the generator channel, the diffuser and the magnet, was studied in detail in order to provide a comprehensive assessment of the inflow disk generator. Based on these results, the performance of the inflow disk generator was calculated for two different thermal inputs: 1250 MW(th) and 2500 MW(th). It was shown that the performance of the inflow disk generator is similar to that of the diagonal generator within the uncertainty of the analysis.

Nakamura, T.; Lear, W. E.; Eustis, R. H.

1981-01-01

223

Converging cylindrical shocks in ideal magnetohydrodynamics

NASA Astrophysics Data System (ADS)

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{? _0/p_0} I/(2 ? ) where I is the current, ?0 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 then slows the shock Mach number growth producing a maximum followed by monotonic reduction towards magnetosonic conditions, even as the shock accelerates toward the axis. A parameter space of initial shock Mach number at a given radius is explored and the implications of the present results for inertial confinement fusion are discussed.

Pullin, D. I.; Mostert, W.; Wheatley, V.; Samtaney, R.

2014-09-01

224

NASA Astrophysics Data System (ADS)

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.

Murphree, D. L.; Cook, R. L.; Bauman, L. E.; Benton, R. D.; Probert, P. B.; Selby, R. C.

1981-01-01

225

Search for Stable Magnetohydrodynamic Equilibria in Barotropic Stars.

NASA Astrophysics Data System (ADS)

It is now believed that magnetohydrodynamic equilibria can exist in stably stratified stars due to the seminal works of Braithwaite & Spruit (2004) and Braithwaite & Nordlund (2006). What is still not known is whether magnetohydrodynamic equilibria can exist in a barotropic star, in which stable stratification is not present. It has been conjectured by Reisenegger (2009) that there will likely not exist any magnetohydrodynamical equilibria in barotropic stars. We aim to test this claim by presenting preliminary MHD simulations of barotropic stars using the three dimensional stagger code of Nordlund & Galsgaard (1995).

Mitchell, J. P.; Braithwaite, J.; Langer, N.; Reisenegger, A.; Spruit, H.

2014-08-01

226

Five model flows of increasing complexity belonging to the class of stationary two-dimensional planar field-aligned magnetohydrodynamic (MHD) flows are presented which are well suited to the quantitative evaluation of MHD codes. The physical properties of these five flows are investigated using characteristic theory. Grid convergence criteria for flows belonging to this class are derived from characteristic theory, and grid convergence

H. De Sterck; A. Cs??k; D. Vanden Abeele; S. Poedts; H. Deconinck

2001-01-01

227

Drift-magnetohydrodynamical model of error-field penetration in tokamak plasmas

A previously published magnetohydrodynamical (MHD) model of error-field penetration in tokamak plasmas is extended to take drift-MHD physics into account. In particular, diamagnetic and semicollisional effects are both fully incorporated into the analysis. The new model is used to examine the scaling of the penetration threshold in ohmic tokamak plasmas.

Cole, A.; Fitzpatrick, R. [Institute for Fusion Studies, Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)

2006-03-15

228

Tokamak Magnetohydrodynamic Equilibrium States with Axisymmetric Boundary and a 3D Helical Core

Magnetohydrodynamic (MHD) equilibrium states with imposed axisymmetric boundary are computed in which a spontaneous bifurcation develops to produce an internal three-dimensional (3D) configuration with a helical structure in addition to the standard axisymmetric system. Equilibrium states with similar MHD energy levels are shown to develop very different geometric structures. The helical equilibrium states resemble saturated internal kink mode structures.

Cooper, W. A.; Graves, J. P.; Pochelon, A.; Sauter, O.; Villard, L. [Ecole Polytechnique Federale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, CH-1015 Lausanne (Switzerland)

2010-07-16

229

Global magnetohydrodynamic simulations on multiple GPUs

NASA Astrophysics Data System (ADS)

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.

Wong, Un-Hong; Wong, Hon-Cheng; Ma, Yonghui

2014-01-01

230

Multimegawatt nuclear electric propulsion with gaseous and vapor core reactors with MHD

NASA Astrophysics Data System (ADS)

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). .

Knight, Travis; Anghaie, Samim; Smith, Blair; Houts, Michael

2001-02-01

231

State Estimation for Linearized MHD Flow J. Chandrasekar, O. Barrero, A. Ridley, D. S. Bernstein, and B. De Moor Abstract-- A state estimation problem for linearized magnetohydrodynamic(MHD) flow is considered. The ideal MHD equations governing the flow of plasma in a three- dimensional channel

232

State Estimation for Linearized MHD Flow J. Chandrasekar, O. Barrero, A. Ridley, D. S. Bernstein, and B. De Moor Abstract--- A state estimation problem for linearized magnetohydrodynamic(MHD) flow is considered. The ideal MHD equations governing the flow of plasma in a threeÂ dimensional channel

233

Phys. Plasmas April 2007 Eigenvalue problems for Beltrami fields arising in a 3-D toroidal MHD, 2007) A generalized energy principle for finite-pressure, toroidal magnetohydrodynamic (MHD) equilib- ria in general three-dimensional configurations is proposed. The full set of ideal-MHD constraints

Dewar, Robert L.

234

Action principles for extended magnetohydrodynamic models

NASA Astrophysics Data System (ADS)

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.

Keramidas Charidakos, I.; Lingam, M.; Morrison, P. J.; White, R. L.; Wurm, A.

2014-09-01

235

Possible signatures of nonlinear MHD waves in the solar wind: UVCS observations and models

NASA Technical Reports Server (NTRS)

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.

Ofman, L.; Romoli, M.; Davila, J. M.; Poletto, G.; Kohl, J.; Noci, G.

1997-01-01

236

Reflection Properties of Gravito-MHD Waves in an Inhomogeneous Horizontal Magnetic Field

NASA Astrophysics Data System (ADS)

We derive the dispersion equation for gravito-magnetohydrodynamical (MHD) waves in an isothermal, gravitationally stratified plasma with a horizontal inhomogeneous magnetic field. Sound and Alfvén speeds are constant. Under these conditions, it is possible to derive analytically the equations for gravito-MHD waves. The high values of the viscous and magnetic Reynolds numbers in the solar atmosphere imply that the dissipative terms in the MHD equations are negligible, except in layers around the positions where the frequency of the MHD wave equals the local Alfvén or slow wave frequency. Outside these layers the MHD waves are accurately described by the equations of ideal MHD.

Jovanovi?, G.

2014-11-01

237

NASA Technical Reports Server (NTRS)

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.

Sovie, R. J.; Winter, J. M.; Juhasz, A. J.; Berg, R. D.

1982-01-01

238

Gravitational Radiation from Primordial Helical Inverse Cascade MHD Turbulence

We consider the generation of gravitational waves by primordial helical inverse cascade magnetohydrodynamic (MHD) turbulence produced by bubble collisions at the electroweak phase transition. We extend the previous study \\cite{kgr08} by considering both currently discussed models of MHD turbulence. For popular electroweak phase transition parameter values, the generated gravitational wave spectrum is only weakly dependent on the MHD turbulence model. Compared to the unmagnetized electroweak phase transition case, the spectrum of MHD-turbulence-generated gravitational waves peaks at lower frequency with larger amplitude and can be detected by the proposed Laser Interferometer Space Antenna

Tina Kahniashvili; Leonardo Campanelli; Grigol Gogoberidze; Yurii Maravin; Bharat Ratra

2008-09-11

239

Computation of multi-region relaxed magnetohydrodynamic equilibria

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.

Hudson, S. R.; Lazerson, S. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States); Dewar, R. L.; Dennis, G.; Hole, M. J.; McGann, M.; Nessi, G. von [Plasma Research Laboratory, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2012-11-15

240

Computation of Multi-region Relaxed Magnetohydrodynamic Equilibria

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.

S.R. Hudson, R.L. Dewar, G. Dennis, M.J. Hole, M. McGann, G. von Nessi and S. Lazerson

2013-03-29

241

A new code, MISHKA-D (Drift MHD), has been developed as an extension of the ideal magnetohydrodynamics (MHD) code MISHKA-1 in order to investigate the finite gyroradius stabilizing effect of ion diamagnetic drift frequency, omega*i, on linear ideal MHD eigenmodes in tokamaks in general toroidal geometry. The MISHKA-D code gives a self-consistent computation of both stable and unstable eigenmodes with eigenvalues

G. T. A. Huysmans; S. E. Sharapov; A. B. Mikhailovskii; W. Kerner

2001-01-01

242

A new code, MISHKA-D (Drift MHD), has been developed as an extension of the ideal magnetohydrodynamics (MHD) code MISHKA-1 in order to investigate the finite gyroradius stabilizing effect of ion diamagnetic drift frequency, ?*i, on linear ideal MHD eigenmodes in tokamaks in general toroidal geometry. The MISHKA-D code gives a self-consistent computation of both stable and unstable eigenmodes with eigenvalues

G. T. A. Huysmans; S. E. Sharapov; A. B. Mikhailovskii; W. Kerner

2001-01-01

243

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.

Not Available

1995-02-01

244

Study of Magnetohydrodynamic Surface Waves on Liquid Gallium

Magnetohydrodynamic (MHD) surface waves on liquid gallium are studied theoretically and experimentally in the small magnetic Reynolds number limit. A linear dispersion relation is derived when a horizontal magnetic field and a horizontal electric current is imposed. No wave damping is found in the shallow liquid limit while waves always damp in the deep liquid limit with a magnetic field

Hantao Ji; William Fox; David Pace; H. L. Rappaport

2004-01-01

245

Role of the Hall Current in Magnetohydrodynamic Dynamos

A theoretical mean field closure for Hall magnetohydrodynamics (Hall-MHD) is developed to investigate magnetic field generation through dynamo processes in low electron density astrophysical systems. We show that by modifying the dynamics of microscopic flows, the Hall currents could have a profound impact on the generation of macroscopic magnetic fields. As an illustrative example, we show how dynamo waves are

Pablo D. Mininni; Daniel O. Gomez; Swadesh M. Mahajan

2003-01-01

246

Resistive MHD Simulations of Laminar Round Jets with Application to Magnetic Nozzle Flows

This thesis investigates fundamental flows of resistive magnetohydrodynamics (MHD) by a new numerical tool based on the gas-kinetic method. The motivation for this work stems from the need to analyze the mechanisms of plasma detachment...

Araya, Daniel

2012-02-14

247

The rocket technology dates back as far as medieval China. Used initially for entertainment and religious practices over time rockets evolved into weapons and finally into means of transportation. Today, we are nearing the top of the rockets' capabilities. Although, for now they are the only way for us to send anything into space we are becoming more and more aware of the limitations of this technology. It is essential that we invent other means of propelling probes and other interplanetary vehicles through space. The authors had performed a series of magnetohydrodynamic simulations using the University of Chicago's Flash package to find out whether the interactions between the Solar Wind and the conducting ring with the electric current would occur. The MHD simulations gave the results similar to the monte-carlo calculations performed by dr Charles Danforth [1] from the University of Colorado. It is the authors' conclusion that the promising results should encourage further study of the phenomenon and the po...

Kisiel, T

2007-01-01

248

Supersonic regime of the Hall-magnetohydrodynamics resistive tearing instability

An earlier analysis of the Hall-magnetohydrodynamics (MHD) tearing instability [E. Ahedo and J. J. Ramos, Plasma Phys. Controlled Fusion 51, 055018 (2009)] is extended to cover the regime where the growth rate becomes comparable or exceeds the sound frequency. Like in the previous subsonic work, a resistive, two-fluid Hall-MHD model with massless electrons and zero-Larmor-radius ions is adopted and a linear stability analysis about a force-free equilibrium in slab geometry is carried out. A salient feature of this supersonic regime is that the mode eigenfunctions become intrinsically complex, but the growth rate remains purely real. Even more interestingly, the dispersion relation remains of the same form as in the subsonic regime for any value of the instability Mach number, provided only that the ion skin depth is sufficiently small for the mode ion inertial layer width to be smaller than the macroscopic lengths, a generous bound that scales like a positive power of the Lundquist number.

Ahedo, Eduardo [Universidad Politecnica de Madrid, 28040 Madrid (Spain); Ramos, Jesus J. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2012-07-15

249

Magnetohydrodynamic normal mode analysis of plasma with equilibrium pressure anisotropy

In this work, we generalise linear magnetohydrodynamic (MHD) stability theory to include equilibrium pressure anisotropy in the fluid part of the analysis. A novel 'single-adiabatic' (SA) fluid closure is presented which is complementary to the usual 'double-adiabatic' (CGL) model and has the advantage of naturally reproducing exactly the MHD spectrum in the isotropic limit. As with MHD and CGL, the SA model neglects the anisotropic perturbed pressure and thus loses non-local fast-particle stabilisation present in the kinetic approach. Another interesting aspect of this new approach is that the stabilising terms appear naturally as separate viscous corrections leaving the isotropic SA closure unchanged. After verifying the self-consistency of the SA model, we re-derive the projected linear MHD set of equations required for stability analysis of tokamaks in the MISHKA code. The cylindrical wave equation is derived analytically as done previously in the spectral theory of MHD and clear predictions are made for ...

Fitzgerald, M; Qu, Z S

2014-01-01

250

MHD simulations with the FLASH code

NASA Astrophysics Data System (ADS)

The FLASH code developed at the University of Chicago Flash Center is a modular, general-purpose, adaptive, parallel simulation code capable of handling compressible flow problems in various physical, in particular astrophysical, environments. Starting with version release 2.0, the FLASH code supports the equations of magnetohydrodynamics (MHD). In this paper, we will describe the present state of the code and the integration of the MHD module into the code framework. We will further describe specific implementation details of the FLASH MHD module. Finally, we will provide examples of simulations of ideal and resistive MHD fluids and of self-gravitating magnetized plasmas. The FLASH code is available for public distribution. Both information regarding code licensing and code distribution can be found at the Flash Center web site: http://flash.uchicago.edu.

Linde, Timur

2002-03-01

251

Numerical simulations for MHD coronal seismology

NASA Astrophysics Data System (ADS)

Magnetohydrodynamic (MHD) processes are important for the transfer of energy over large scales in plasmas and so are essential to understanding most forms of dynamical activity in the solar atmosphere. The introduction of transverse structuring into models for the corona modifies the behavior of MHD waves through processes such as dispersion and mode coupling. Exploiting our understanding of MHD waves with the diagnostic tool of coronal seismology relies upon the development of sufficiently detailed models to account for all the features in observations. The development of realistic models appropriate for highly structured and dynamical plasmas is often beyond the domain of simple mathematical analysis and so numerical methods are employed. This paper reviews recent numerical results for seismology of the solar corona using MHD.

Pascoe, David James

2014-07-01

252

The MHD equations are considered along with the Rayleigh-Taylor instability, linearized equations and the energy principle, toroidal instabilities, high beta tokamaks, nonlinear instability theory, resistive instabilities, and a comparison between theory and experiment. The characteristics of the MHD equilibrium are examined, taking into account force balance equations, surface quantities, the q-value, the Grad-Shafranov equation, an example of bifurcation related to

G. Bateman

1978-01-01

253

Magnetohydrodynamics Accelerator Research into Advanced Hypersonics (MARIAH). Part 2

NASA Technical Reports Server (NTRS)

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.

Baughman, Jack A.; Micheletti, David A.; Nelson, Gordon L.; Simmons, Gloyd A.

1997-01-01

254

Magnetohydrodynamics Accelerator Research Into Advanced Hypersonics (MARIAH). Part 1

NASA Technical Reports Server (NTRS)

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.

Micheletti, David A.; Baughman, Jack A.; Nelson, Gordon L.; Simmons, Gloyd A.

1997-01-01

255

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 quasi-parallel 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.

Chandran, B D G

2000-01-01

256

Method for manufacturing magnetohydrodynamic electrodes

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.

Killpatrick, Don H. (Orland Park, IL); Thresh, Henry R. (Palos Heights, IL)

1982-01-01

257

Advanced Coal-Based Power Generations

NASA Technical Reports Server (NTRS)

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.

Robson, F. L.

1982-01-01

258

Perfect magnetohydrodynamics as a field theory

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.

Bekenstein, Jacob D.; Betschart, Gerold [Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904 (Israel)

2006-10-15

259

DIFFUSIVE ACCELERATION OF PARTICLES AT OBLIQUE, RELATIVISTIC, MAGNETOHYDRODYNAMIC SHOCKS

Diffusive shock acceleration (DSA) at relativistic shocks is expected to be an important acceleration mechanism in a variety of astrophysical objects including extragalactic jets in active galactic nuclei and gamma-ray bursts. These sources remain good candidate sites for the generation of ultrahigh energy cosmic rays. In this paper, key predictions of DSA at relativistic shocks that are germane to the production of relativistic electrons and ions are outlined. The technique employed to identify these characteristics is a Monte Carlo simulation of such diffusive acceleration in test-particle, relativistic, oblique, magnetohydrodynamic (MHD) shocks. Using a compact prescription for diffusion of charges in MHD turbulence, this approach generates particle angular and momentum distributions at any position upstream or downstream of the shock. Simulation output is presented for both small angle and large angle scattering scenarios, and a variety of shock obliquities including superluminal regimes when the de Hoffmann-Teller frame does not exist. The distribution function power-law indices compare favorably with results from other techniques. They are found to depend sensitively on the mean magnetic field orientation in the shock, and the nature of MHD turbulence that propagates along fields in shock environs. An interesting regime of flat-spectrum generation is addressed; we provide evidence for it being due to shock drift acceleration, a phenomenon well known in heliospheric shock studies. The impact of these theoretical results on blazar science is outlined. Specifically, Fermi Large Area Telescope gamma-ray observations of these relativistic jet sources are providing significant constraints on important environmental quantities for relativistic shocks, namely, the field obliquity, the frequency of scattering, and the level of field turbulence.

Summerlin, Errol J. [Heliospheric Physics Laboratory, Code 672, NASA's Goddard Space Flight Center, Greenbelt, MD 20770 (United States); Baring, Matthew G., E-mail: errol.summerlin@nasa.gov, E-mail: baring@rice.edu [Department of Physics and Astronomy, MS 108, Rice University, Houston, TX 77251 (United States)

2012-01-20

260

RESONANCE BROADENING AND HEATING OF CHARGED PARTICLES IN MAGNETOHYDRODYNAMIC TURBULENCE

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.

Lynn, Jacob W. [Physics Department, University of California, Berkeley, CA 94720 (United States); Parrish, Ian J.; Quataert, Eliot [Astronomy Department and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720 (United States); Chandran, Benjamin D. G., E-mail: jacob.lynn@berkeley.edu [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States)

2012-10-20

261

Broken Ergodicity in MHD Turbulence

NASA Technical Reports Server (NTRS)

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.

Shebalin, John V.

2010-01-01

262

Suppression MHD instabilities by IBW heating in HT-7 Tokamak

In HT-7 tokamak, the m= 2/1 tearing mode can be effectively suppressed by the ion bernstein wave (IBW) when the location of power deposition is near the q=2 rational surface. Off-axis electron heating and greatly increase of electron density was observed, in the meantime, the particle confinement appears to be improved with the increased of the central line averaged electron density and the drop of Da emission. Induced large ne gradients and pressures were spatially correlated with the IBW deposition profile by theoretical calculation >. It is suggested that off-axis IBW heating modifies the electron pressure profile, and so the current density profile could be redistributed resulting in the suppression of the magnetohydrodynamics (MHD) instability. It provides an integrated way for making combined effects on both the stabilization of tearing modes and controlling of pressure profile.

C. M. Qin; Y. P. Zhao; X. J. Zhang; P. Xu; Y. Yang; the HT-7 team

2010-01-20

263

NASA Technical Reports Server (NTRS)

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.

Retallick, F. D.

1980-01-01

264

Magnetohydrodynamic Propulsion for the Classroom

NASA Astrophysics Data System (ADS)

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.

Font, Gabriel I.; Dudley, Scott C.

2004-10-01

265

MHD Modeling of the Interaction Between the Solar Wind and Solar System Objects

Magnetohydrodynamic (MHD) models of plasma can be used to model many phenomena in the solar system. In this work we investigate the use of a general MHD solver - the Flash code - for the simulation of the interac- tion between the solar wind and solar system objects. As a test case we simulate the three-dimensional solar wind interaction with

Andreas Ekenbäck; Mats Holmström

2004-01-01

266

Note: Tangential x-ray diagnosis for investigating fast MHD events in EAST tokamak

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.

Li Erzhong; Hu Liqun; Chen Kaiyun; Zhang Jizong; Chen Yiebin; Zhou Ruijie; Gan Kaifu; Liu Yong [Institute of Plasma Physics, Chinese Academy of Science, Hefei 230031 (China)

2010-10-15

267

Coherent Eigenmodes in Homogeneous MHD Turbulence

NASA Technical Reports Server (NTRS)

The statistical mechanics of Fourier models of ideal, homogeneous, incompressible magnetohydrodynamic (MHD) turbulence is discussed, along with their relevance for dissipative magnetofluids. Although statistical theory predicts that Fourier coefficients of fluid velocity and magnetic field are zero-mean random variables, numerical simulations clearly show that certain coefficients have a non-zero mean value that can be very large compared to the associated standard deviation, i.e., we have coherent structure. We use eigenanalysis of the modal covariance matrices in the probability density function to explain this phenomena in terms of `broken ergodicity', which is defined to occur when dynamical behavior does not match ensemble predictions on very long time-scales. We provide examples from 2-D and 3-D magnetohydrodynamic simulations of homogeneous turbulence, and show new results from long-time simulations of MHD turbulence with and without a mean magnetic field

Shebalin, John V.

2010-01-01

268

MHD processes in the outer heliosphere

NASA Technical Reports Server (NTRS)

The magnetic field measurements from Voyager and the magnetohydrodynamic (MHD) processes in the outer heliosphere are reviewed. A bibliography of the experimental and theoretical work concerning magnetic fields and plasmas observed in the outer heliosphere is given. Emphasis in this review is on basic concepts and dynamical processes involving the magnetic field. The theory that serves to explain and unify the interplanetary magnetic field and plasma observations is magnetohydrodynamics. Basic physical processes and observations that relate directly to solutions of the MHD equations are emphasized, but obtaining solutions of this complex system of equations involves various assumptions and approximations. The spatial and temporal complexity of the outer heliosphere and some approaches for dealing with this complexity are discussed.

Burlaga, L. F.

1984-01-01

269

A high altitude nuclear burst, detonated at a height of 50 km or more, causes two types of electromagnetic pulses (EMP) - high altitude EMP (HEMP) and magnetohydrodynamic EMP (MHD-EMP). This high altitude EMP scenario is of principal concern when assessing the effects of EMP on electric power systems, because the total United States can be simultaneously illuminated by HEMP and MHD-EMP can cover a large area of up to several hundred kilometers in diameter. The purpose of this project was first to define typical electrical power system characteristics for EMP analysis, and second, to determine reasonable worst case EMP induced surges on overhead electric power system transmission and distribution lines for reasonable assumptions, using unclassified HEMP and MHD-EMP electric field waveforms.

Zaininger, H.W.

1984-08-01

270

Hypersonic MHD Propulsion System Integration for the Mercury Lightcraft

NASA Astrophysics Data System (ADS)

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.

Myrabo, L. N.; Rosa, R. J.

2004-03-01

271

Statistical Properties of Dissipative MHD Accelerators

We use exact orbit integration to investigate particle acceleration in a\\u000aGauss field proxy of magnetohydrodynamic (MHD) turbulence. Regions where the\\u000aelectric current exceeds a critical threshold are declared to be `dissipative'\\u000aand endowed with super-Dreicer electric field ${\\\\bf E}_\\\\Omega = \\\\eta {\\\\bf j}$.\\u000aIn this environment, test particles (electrons) are traced and their\\u000aacceleration to relativistic energies is studied.

Kaspar Arzner; Loukas Vlahos; Bernard Knaepen; Nicolas Denewet

2004-01-01

272

Low-frequency pressure and magnetic oscillations observed by Cluster in the plasma sheet are investigated with the aim of determining if they are magnetohydrodynamic (MHD) eigenmodes. We analyze the plasma sheet crossing occurring on 22 August 2001, as the magnetosphere was first quiet and then active, and compare the observations with theoretical results concerning the MHD propagation in a Harris sheet.

P. Louarn; G. Fruit; E. Budnik; J. A. Sauvaud; C. Jacquey; D. Le Quéau; H. Rème; E. Lucek; A. Balogh

2004-01-01

273

ANALYTIC APPROXIMATE SEISMOLOGY OF PROPAGATING MAGNETOHYDRODYNAMIC WAVES IN THE SOLAR CORONA

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.

Goossens, M.; Soler, R. [Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, B-3001 Leuven (Belgium); Arregui, I. [Instituto de Astrofisica de Canarias, Via Lactea s/n, E-38205 La Laguna, Tenerife (Spain); Terradas, J., E-mail: marcel.goossens@wis.kuleuven.be [Solar Physics Group, Departament de Fisica, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

2012-12-01

274

Variational approach to nonlinear gravity-driven instabilities in a MHD setting

We establish a variational framework for nonlinear instabilities in a setting of the ideal magnetohydrodynamic (MHD) equations. We apply a variational method to various kind of smooth steady states which are shown to be nonlinearly unstable for both incompressible and compressible ideal MHD equations. Destabilizing effect of compressibility is justified as well as stabilizing effect of magnetic field lines arising in MHD dynamics, which distinguishes from the Rayleigh-Taylor instability in the absence of magnetic field lines.

Hyung Ju Hwang

2005-09-15

275

Advected Invariants in Magnetohydrodynamics and Gas Dynamics

NASA Astrophysics Data System (ADS)

In this paper we discuss conservation laws in ideal magnetohydrodynamics (MHD) and gas dynamics associated with advected invariants. The invariants in some cases, can be related to fluid relabelling symmetries associated with the Lagrangian map. There are different classes of invariants that are advected or Lie dragged with the flow. Simple examples are the advection of the entropy S (a 0-form), and the conservation of magnetic flux (an invariant 2-form advected with the flow). The magnetic flux conservation law is equivalent to Faraday's equation. We discuss the gauge condition required for the magnetic helicity to be advected with the flow. The conditions for the cross helicity to be an invariant are discussed. We discuss the different variants of helicity in fluid dynamics and in MHD, including: fluid kinetic helicity, cross helicity, magnetic helicity, Ertel's theorem and potential vorticity, the Hollman invariant, and the Godbillon Vey invariant for special flows for which the magnetic helicity is zero.

Webb, G. M.; Hu, Q.; McKenzie, J. F.; Dasgupta, B.; Zank, G. P.

2014-05-01

276

Numerical Methods for Radiation Magnetohydrodynamics in Astrophysics

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.

Klein, R I; Stone, J M

2007-11-20

277

Compression of magnetohydrodynamic simulation data using singular value decomposition

NASA Astrophysics Data System (ADS)

Numerical calculations of magnetic and flow fields in magnetohydrodynamic (MHD) simulations can result in extensive data sets. Particle-based calculations in these MHD fields, needed to provide closure relations for the MHD equations, will require communication of this data to multiple processors and rapid interpolation at numerous particle orbit positions. To facilitate this analysis it is advantageous to compress the data using singular value decomposition (SVD, or principal orthogonal decomposition, POD) methods. As an example of the compression technique, SVD is applied to magnetic field data arising from a dynamic nonlinear MHD code. The performance of the SVD compression algorithm is analyzed by calculating Poincaré plots for electron orbits in a three-dimensional magnetic field and comparing the results with uncompressed data.

del-Castillo-Negrete, D.; Hirshman, S. P.; Spong, D. A.; D'Azevedo, E. F.

2007-03-01

278

Compression of Magnetohydrodynamic Simulation Data Using Singular Value Decomposition

NASA Astrophysics Data System (ADS)

Numerical calculations of magnetic and flow fields in magnetohydrodynamic (MHD) simulations can result in extensive data sets. Particle-based calculations in these MHD fields, needed to provide closure relations for the MHD equations, will require communication of this data to multiple processors and rapid interpolation at numerous particle orbit positions. To facilitate this analysis it is advantageous to compress the data using Singular Value Decomposition (SVD, or Principal Orthogonal Decomposition, POD) methods. As an example of the compression technique, SVD is applied to magnetic field data arising from a dynamic nonlinear MHD code. The performance of the SVD compression algorithm is analyzed by calculating Poincaré plots for electron orbits in a three-dimensional magnetic field and comparing the results with uncompressed data.

Hirshman, S. P.; Del-Castillo-Negrete, D.; Spong, D. A.; D'Azevedo, E. F.

2006-10-01

279

The complete set of Casimirs in Hall-magnetohydrodynamics

A procedure for determining all the Casimir constants of motion in magnetohydrodynamics (MHD) [E. Hameiri, Phys. Plasmas 11, 3423 (2004)] is extended to Hall-MHD. We obtain and solve differential equations for the variational derivatives of all the Casimirs, which must be satisfied for any dynamically accessible motion in Hall-MHD. In an extension of the more commonly considered Hall-MHD model, we also include the electron fluid entropy. The most interesting case for plasma confinement, which is usually true for axisymmetric configurations but desirable in general, is when both the magnetic field and the ion velocity field form the two separate families of nested toroidal surfaces. The Casimirs are then three functionals for each surface, involving the fluxes of certain vector fields and the number of particles contained in each. We also determine a family of independent Casimirs in a general configuration.

Kawazura, Yohei [Graduate School of Frontier Sciences, University of Tokyo Kashiwa, Chiba 277-8561 (Japan); Hameiri, Eliezer [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States)

2012-08-15

280

On the question of hysteresis in Hall magnetohydrodynamic reconnection

Controversy has been raised regarding the cause of hysteresis, or bistability, of solutions to the equations that govern the geometry of the reconnection region in Hall magnetohydrodynamic (MHD) systems. This brief communication presents a comparison of the frameworks within which this controversy has arisen and illustrates that the Hall MHD hysteresis originally discovered numerically by Cassak et al. [Phys. Rev. Lett. 95, 235002 (2005)] is a different phenomenon from that recently reported by Zocco et al. [Phys. Plasmas 16, 110703 (2009)] on the basis of analysis and simulations in electron MHD with finite electron inertia. We demonstrate that the analytic prediction of hysteresis in EMHD does not describe or explain the hysteresis originally reported in Hall MHD, which is shown to persist even in the absence of electron inertia.

Sullivan, Brian P.; Bhattacharjee, A.; Huang Yimin [Center for Integrated Computation and Analysis of Reconnection and Turbulence, University of New Hampshire, Space Science Center, Durham, New Hampshire 03824 (United States)

2010-11-15

281

Broken Symmetry and Coherent Structure in MHD Turbulence

NASA Technical Reports Server (NTRS)

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.

Shebalin, John V.

2007-01-01

282

Linear wave propagation in relativistic magnetohydrodynamics

The properties of linear Alfven, slow, and fast magnetoacoustic waves for uniform plasmas in relativistic magnetohydrodynamics (MHD) are discussed, augmenting the well-known expressions for their phase speeds with knowledge on the group speed. A 3+1 formalism is purposely adopted to make direct comparison with the Newtonian MHD limits easier and to stress the graphical representation of their anisotropic linear wave properties using the phase and group speed diagrams. By drawing these for both the fluid rest frame and for a laboratory Lorentzian frame which sees the plasma move with a three-velocity having an arbitrary orientation with respect to the magnetic field, a graphical view of the relativistic aberration effects is obtained for all three MHD wave families. Moreover, it is confirmed that the classical Huygens construction relates the phase and group speed diagram in the usual way, even for the lab frame viewpoint. Since the group speed diagrams correspond to exact solutions for initial conditions corresponding to a localized point perturbation, their formulae and geometrical construction can serve to benchmark current high-resolution algorithms for numerical relativistic MHD.

Keppens, R. [Centre for Plasma-Astrophysics, K.U. Leuven, Celestijnenlaan 200B, 3001 Heverlee (Belgium); Leuven Mathematical Modeling and Computational Science Centre, K.U. Leuven (Belgium); FOM-Institute for Plasma Physics, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands) and Astronomical Institute, Utrecht University (Netherlands); Meliani, Z. [Centre for Plasma-Astrophysics, K.U. Leuven, Celestijnenlaan 200B, 3001 Heverlee (Belgium)

2008-10-15

283

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.

Petrick, Michael (Joliet, IL); Pierson, Edward S. (Chicago, IL); Schreiner, Felix (Mokena, IL)

1980-01-01

284

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.

Ramrus, A.

1986-02-01

285

MHD modeling of magnetized target fusion experiments.

Magnetized Target Fusion (MTF) is an alternate approach to controlled fusion in which a dense (0(1017-'8 cm-')), preheated (O(200 ev)), and magnetized (0( 100 kG)) target plasma is hydrodynamically compressed by an imploding liner. If electron thermal conduction losses are magnetically suppressed, relatively slow O(1 cm/microsecond) 'liner-on-plasma' compressions may be practical, using liners driven by inexpensive electrical pulsed power. Target plasmas need to remain relatively free of potentially cooling contaminants during formation and compression. Magnetohydrodynamic (MHD) calculations including detailed effects of radiation, heat conduction, and resistive field diffusion have been used to model separate target plasma (Russian MAGO, Field Reversed Configuration at Los Alamos National Laboratory) and liner implosion experiments (without plasma fill), such as recently performed at the Air Force Research Laboratory (Albuquerque). Using several different codes, proposed experiments in which such liners are used to compress such target plasmas are now being modeled in one and two dimensions. In this way, it is possible to begin to investigate important issues for the design of such proposed liner-on-plasma fusion experiments. The competing processes of implosion, heating, mixing, and cooling will determine the potential for such MTF experiments to achieve fusion conditions.

Sheehey, P. T. (Peter T.); Faehl, Rickey J.; Kirkpatrick, R. C. (Ronald C.); Lindemuth, I. R. (Irvin R.)

2001-01-01

286

MHD--Developing New Technology to Meet the Energy Crisis

ERIC Educational Resources Information Center

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)

Fitch, Sandra S.

1978-01-01

287

NASA Technical Reports Server (NTRS)

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.

Harris, L. P.

1977-01-01

288

The distribution of flares, statistics of magnetohydrodynamic turbulence and coronal heating

NASA Astrophysics Data System (ADS)

In this paper theoretical evidence in favor of the hypothesis that coronal dissipation occurs in bursts at very small spatial scales is presented. Each individual burst, though unobservable and energetically insignificant, is thought to represent the building block of coronal activity. In this framework, a large number of coherently triggered bursts is what appears as one of the many observed solar atmospheric events (i.e., blinkers, heating events, explosive events, flashes, microflares, flares,...). Histograms of such events, when computed, in terms of total energy, duration and peak luminosity appear to display power-law behavior. Simulations of the energy dissipation in the simplest possible forced magnetohydrodynamic (MHD) system, admitting reconnection events, indeed displays such kind of behavior: dissipative events of varying intensity, size and duration may be defined, whose distributions follow power laws. The meaning of cellular automaton models, introduced to describe the power-law statistics of observed energetic events on the Sun, i.e., solar flares, is then discussed. Finally, a minimal set of constraints necessary to render such automaton models more relevant for the description of dynamic phenomena described by magnetohydrodynamic equations is introduced.

Einaudi, G.; Velli, M.

1999-11-01

289

A nuclear detonation at altitudes several hundred kilometers above the earth will severely distort the earth's magnetic field and result in a strong magnetohyrodynamic electromagnetic pulse (MHD-EMP). The geomagnetic disturbance interacts with the soil to induce current and horizontal electric gradients. The geomagnetic disturbance interacts with the soil to induced current and horizontal electric gradients in the earth. MHD-EMP, also called E3 since it is the third component of the high-altitude EMP (HEMP), lasts over 100 s after the exoatmospheric burst. MHD-EMP is similar to solar geomagnetic storms in it's global and low frequency (less than 1 Hz) nature except that E3 can be much more intense with a far shorter duration. When the MHD-EMP gradients are integrated over great distances by power lines, communication cables, or other long conductors, the induced voltages are significant. (The horizontal gradients in the soil are too small to induce major responses by local interactions with facilities.) The long pulse waveform for MHD-EMP-induced currents on long lines has a peak current of 200 A and a time-to-half-peak of 100 s. If this current flows through transformer windings, it can saturate the magnetic circuit and cause 60 Hz harmonic production. To mitigate the effects of MHD-EMP on a facility, long conductors must be isolated from the building and the commercial power harmonics and voltage swings must be addressed. The transfer switch would be expected to respond to the voltage fluctuations as long as the harmonics have not interfered with the switch control circuitry. The major sources of MHD-EMP induced currents are the commercial power lines and neutral; neutral current indirect coupling to the facility power or ground system via the metal fence, powered gate, parking lights, etc; metal water pipes; phone lines; and other long conductors that enter or come near the facility. The major source of harmonics is the commercial power system.

Barnes, P.R.; Vance, E.F.

1992-01-01

290

Laser production and heating of plasma for MHD application

NASA Technical Reports Server (NTRS)

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.

Jalufka, N. W.

1988-01-01

291

Dynamic Alignment and Exact Scaling Laws in MHD Turbulence

Magnetohydrodynamic (MHD) turbulence is pervasive in astrophysical systems. Recent high-resolution numerical simulations suggest that the energy spectrum of strong incompressible MHD turbulence is $E(k_{\\perp})\\propto k_{\\perp}^{-3/2}$. So far, there has been no phenomenological theory that simultaneously explains this spectrum and satisfies the exact analytic relations for MHD turbulence due to Politano & Pouquet. Indeed, the Politano-Pouquet relations are often invoked to suggest that the spectrum of MHD turbulence instead has the Kolmogorov scaling -5/3. Using geometrical arguments and numerical tests, here we analyze this seeming contradiction and demonstrate that the -3/2 scaling and the Politano-Pouquet relations are reconciled by the phenomenon of scale-dependent dynamic alignment that was recently discovered in MHD turbulence.

Stanislav Boldyrev; Joanne Mason; Fausto Cattaneo

2006-05-09

292

The nonlinear dynamics of outflows driven by magnetic explosion on the surface of a compact star is investigated through special relativistic magnetohydrodynamic simulations. We adopt, as the initial equilibrium state, a spherical stellar object embedded in hydrostatic plasma which has a density {rho}(r) {proportional_to} r{sup -}{alpha} and is threaded by a dipole magnetic field. The injection of magnetic energy at the surface of a compact star breaks the equilibrium and triggers a two-component outflow. At the early evolutionary stage, the magnetic pressure increases rapidly around the stellar surface, initiating a magnetically driven outflow. A strong forward shock driven outflow is then excited. The expansion velocity of the magnetically driven outflow is characterized by the Alfven velocity on the stellar surface and follows a simple scaling relation v{sub mag} {proportional_to} v{sub A}{sup 1/2}. When the initial density profile declines steeply with radius, the strong shock is accelerated self-similarly to relativistic velocity ahead of the magnetically driven component. We find that it evolves according to a self-similar relation {Gamma}{sub sh} {proportional_to} r{sub sh}, where {Gamma}{sub sh} is the Lorentz factor of the plasma measured at the shock surface r{sub sh}. A purely hydrodynamic process would be responsible for the acceleration mechanism of the shock driven outflow. Our two-component outflow model, which is the natural outcome of the magnetic explosion, can provide a better understanding of the magnetic active phenomena on various magnetized compact stars.

Matsumoto, Jin; Asano, Eiji; Shibata, Kazunari [Kwasan and Hida Observatories, Kyoto University, Kyoto (Japan); Masada, Youhei, E-mail: jin@kusastro.kyoto-u.ac.jp [Graduate School of System Informatics, Department of Computational Science, Kobe University, Kobe (Japan)

2011-05-20

293

2D radiation-magnetohydrodynamic simulations of SATURN imploding Z-pinches

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.

Hammer, J.H.; Eddleman, J.L.; Springer, P.T. [and others

1995-11-06

294

Solar-driven liquid metal magnetohydrodynamic generator

NASA Technical Reports Server (NTRS)

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.

Lee, J. H.; Hohl, F.

1981-01-01

295

Prospects for Nuclear Electric Propulsion Using Closed-Cycle Magnetohydrodynamic Energy Conversion

NASA Technical Reports Server (NTRS)

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 Mars missions during the 2018 opportunity.

Litchford, R. J.; Bitteker, L. J.; Jones, J. E.

2001-01-01

296

Hydrodynamic and magnetohydrodynamic computations inside a rotating sphere

Numerical solutions of the incompressible magnetohydrodynamic (MHD) equations are reported for the interior of a rotating, perfectly-conducting, rigid spherical shell that is insulator-coated on the inside. A previously-reported spectral method is used which relies on a Galerkin expansion in Chandrasekhar Kendall vector eigenfunctions of the curl. The new ingredient in this set of computations is the rigid rotation of the

P. D. Mininni; D. C. Montgomery; L. Turner

2007-01-01

297

The rocket technology dates back as far as medieval China. Used initially for entertainment and religious practices over time rockets evolved into weapons and finally into means of transportation. Today, we are nearing the top of the rockets' capabilities. Although, for now they are the only way for us to send anything into space we are becoming more and more aware of the limitations of this technology. It is essential that we invent other means of propelling probes and other interplanetary vehicles through space. The authors had performed a series of magnetohydrodynamic simulations using the University of Chicago's Flash package to find out whether the interactions between the Solar Wind and the conducting ring with the electric current would occur. The MHD simulations gave the results similar to the monte-carlo calculations performed by dr Charles Danforth [1] from the University of Colorado. It is the authors' conclusion that the promising results should encourage further study of the phenomenon and the possibility of using it in practice.

T. Kisiel; M. Soida

2007-12-10

298

We were funded via the Common HPC Software Support Initiative (CHSSI) from 2000-2002 to develop a fully 3D arbitrary-coordinate parallel time-domain magnetohydrodynamic (MHD) simulation code - the CEA-10 project. CEA-10 built upon the single-fluid MHD, arbitrary Lagrangian-Eulerian multiblock, multitemperature, simulation environment called MACH3 (Multibloch Arbitrary Coordinate Hydromagnetics in 3D). The CEA-10 software underwent successful beta testing and review in December

Jeff MacGillivray; David A. Burke; M. H. Frese; S. Frese; Jess Neri; J. W. Schumer

2003-01-01

299

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, and toroidal beta. A proper accounting of energetic ion loss is therefore important for accurate analysis of power balance and transport in plasmas exhibiting MHD-induced energetic ion loss.

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

300

the adaptive mesh refinement grid code FLASH with the new MHD solver de- veloped by Waagan et al. IntroductionMHD Simulations of a Supernova-driven ISM Alex S Hill1, MR Joung2,5, RA Benjamin3, LM Haffner1, C present new 3D magnetohydrodynamic (MHD) simula- tions of a supernova-driven, stratified ISM. We have

Wisconsin at Madison, University of

301

Numerical flow simulation in the slagging stage of an MHD coal combustor

NASA Astrophysics Data System (ADS)

MHD is a process for efficiently converting the energy in coal into electricity. The MHD process imposes some unique conditions on the coal combustor. First, the MHD process requires an electrically conductive gas stream. This is accomplished by burning the coal at a very high temperature, approaching 3000 K, by means of oxygen enrichment, and by seeding the combustion products with an easily ionized compound such as potassium carbonate. Second, it is desirable to prevent most of the coal slag from reaching the MHD channel. This is done by separating most of the slag from the gas stream in the combustor. A design criterion for MHD coal combustors in 90 percent slag rejection. The design of magnetohydrodynamics (MHD) combustors can be greatly enhanced by examining the flow patterns in existing MHD combustors. This article presents the present results of an effort to examine these flow patterns using numerical techniques.

Norton, O. P.; Skaggs, A.; Bouchillon, C. W.

302

Magnetohydrodynamic generator electrode

An improved electrode for use as a current collector in the channel of a magnetohydrodynamid (MHD) generator utilizes an elongated monolithic cap of dense refractory material compliantly mounted to the MHD channel frame for collecting the current. The cap has a central longitudinal channel which contains a first layer of porous refractory ceramic as a high-temperature current leadout from the

David D. Marchant; Don H. Killpatrick; Harold Herman; Kenneth D. Kuczen

1979-01-01

303

Magnetohydrodynamic generator electrode

An improved electrode for use as a current collector in the channel of a magetohydrodynamid (MHD) generator utilizes an elongated monolithic cap of dense refractory material compliantly mounted to the MHD channel frame for collecting the current. The cap has a central longitudinal channel which contains a first layer of porous refractory ceramic as a high-temperature current leadout from the

D. D. Marchant; D. H. Killpatrick; H. Herman; K. D. Kuczen

1979-01-01

304

Dipole Alignment in Rotating MHD Turbulence

NASA Technical Reports Server (NTRS)

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.

Shebalin, John V.; Fu, Terry; Morin, Lee

2012-01-01

305

Incorporating Radiative Transfer Into The Athena MHD Code

Incorporating Radiative Transfer Into The Athena MHD Code Kareem Sorathia Advisor: Dr. Chris significant advances: Â· The discovery that the principal method of angular momentum transport is driven by MHD turbulence Â· Increases in computing power have made MHD simulations of accreting plasma possible RHMD

Yorke, James

306

Magnetohydrodynamic cellular automata

NASA Technical Reports Server (NTRS)

A generalization of the hexagonal lattice gas model of Frisch, Hasslacher and Pomeau is shown to lead to two-dimensional magnetohydrodynamics. The method relies on the ideal point-wise conservation law for vector potential.

Montgomery, David; Doolen, Gary D.

1987-01-01

307

Magnetic levitation and MHD propulsion

NASA Astrophysics Data System (ADS)

Magnetic levitation and MHD propulsion are now attracting attention in several countries. Different superconducting MagLev and MHD systems will be described concentrating on, above all, the electromagnetic aspect. Some programmes occurring throughout the world will be described. Magnetic levitated trains could be the new high speed transportation system for the 21st century. Intensive studies involving MagLev trains using superconductivity have been carried out in Japan since 1970. The construction of a 43 km long track is to be the next step. In 1991 a six year programme was launched in the United States to evaluate the performances of MagLev systems for transportation. The MHD (MagnetoHydroDynamic) offers some interesting advantages (efficiency, stealth characteristics, ...) for naval propulsion and increasing attention is being paid towards it nowadays. Japan is also up at the top with the tests of Yamato I, a 260 ton MHD propulsed ship. Depuis quelques années nous assistons à un redémarrage de programmes concernant la lévitation et la propulsion supraconductrices. Différents systèmes supraconducteurs de lévitation et de propulsion seront décrits en examinant plus particulièrement l'aspect électromagnétique. Quelques programmes à travers le monde seront abordés. Les trains à sustentation magnétique pourraient constituer un nouveau mode de transport terrestre à vitesse élevée (500 km/h) pour le 21^e siècle. Les japonais n'ont cessé de s'intéresser à ce système avec bobine supraconductrice. Ils envisagent un stade préindustriel avec la construction d'une ligne de 43 km. En 1991 un programme américain pour une durée de six ans a été lancé pour évaluer les performances des systèmes à lévitation pour le transport aux Etats Unis. La MHD (Magnéto- Hydro-Dynamique) présente des avantages intéressants pour la propulsion navale et un regain d'intérêt apparaît à l'heure actuelle. Le japon se situe là encore à la pointe des développements actuels avec en particulier les premiers essais en rade de Kobe de Yamato I, navire de 260 tonnes, entraîné par MHD.

Tixador, P.

1994-04-01

308

NASA Technical Reports Server (NTRS)

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.

Smith, M.; Nichols, L. D.; Seikel, G. R.

1974-01-01

309

Embedding a Hall MHD plasma sheet simulation inside the Lyon-Fedder-Mobarry global MHD model

NASA Astrophysics Data System (ADS)

We have developed a 3D Hall magnetohydrodynamic (MHD) model with the goal of embedding this high-resolution module into the plasma sheet region of the Lyon-Fedder-Mobarry global MHD model. We intend to investigate the effect of the Hall term on the size and structure of fast flow channels observed in the plasma sheet. Owing to insufficient spatial spacecraft coverage of plasma sheet flow bursts, we appeal to global simulations possessing similar tail flow channels to assess the relative importance of the Hall term in plasma sheet transport. Current global ideal MHD models, however, contain features that are highly resolution dependent. The Hall term imposes a physical size scale on the equations in the plasma sheet, and we plan to quantify the effect of that term on the characteristics of fast flow channels.

Guild, T.; Spence, H.; Lyon, J.; Goodrich, C.; Merkin, V.; Kepko, L.

2005-12-01

310

Magnetohydrodynamics and its hazard assessment

NASA Astrophysics Data System (ADS)

Potential occupational and environmental hazards of a typical combined open-cycle MHD/steam cycle power plant are critically assessed on the basis of direct/indirect research information. Among the potential occupational hazards, explosion at the coal feed system or at the superconducting magnet; combustor rupture in a confined pit; high intensity dc magnetic field exposure at the channel; and combustion products leakage from the pressurized systems are of primary concern. While environmental emissions of SO(x), NO(x) and fine particulates are considered under control in experimental scale, control effectiveness at high capacity operation remains uncertain. Gaseous emission of some highly toxic trace elements including radioactive species may be of concern without gas cleaning device in the MHD design.

Chan, W.-T.

1981-11-01

311

Global invariants in ideal magnetohydrodynamic turbulence

Magnetohydrodynamic (MHD) turbulence is an important though incompletely understood factor affecting the dynamics of many astrophysical, geophysical, and technological plasmas. As an approximation, viscosity and resistivity may be ignored, and ideal MHD turbulence may be investigated by statistical methods. Incompressibility is also assumed and finite Fourier series are used to represent the turbulent velocity and magnetic field. The resulting model dynamical system consists of a set of independent Fourier coefficients that form a canonical ensemble described by a Gaussian probability density function (PDF). This PDF is similar in form to that of Boltzmann, except that its argument may contain not just the energy multiplied by an inverse temperature, but also two other invariant integrals, the cross helicity and magnetic helicity, each multiplied by its own inverse temperature. However, the cross and magnetic helicities, as usually defined, are not invariant in the presence of overall rotation or a mean magnetic field, respectively. Although the generalized form of the magnetic helicity is known, a generalized cross helicity may also be found, by adding terms that are linear in the mean magnetic field and angular rotation vectors, respectively. These general forms are invariant even in the presence of overall rotation and a mean magnetic field. We derive these general forms, explore their properties, examine how they extend the statistical theory of ideal MHD turbulence, and discuss how our results may be affected by dissipation and forcing.

Shebalin, John V. [Astromaterials Research Office, NASA Johnson Space Center, Houston, Texas 77058-3696 (United States)] [Astromaterials Research Office, NASA Johnson Space Center, Houston, Texas 77058-3696 (United States)

2013-10-15

312

Quantifying energetics and dissipation in magnetohydrodynamic turbulence

NASA Astrophysics Data System (ADS)

We perform a suite of two- and three-dimensional magnetohydrodynamic (MHD) simulations with the ATHENA code of the non-driven Kelvin-Helmholtz instability in the subsonic, weak magnetic field limit. Focusing the analysis on the non-linear turbulent regime, we quantify energy transfer on a scale-by-scale basis and identify the physical mechanisms responsible for energy exchange by developing the diagnostic known as spectral energy transfer function analysis. At late times when the fluid is in a state of MHD turbulence, magnetic tension mediates the dominant mode of energy injection into the magnetic reservoir, whereby turbulent fluid motions twist and stretch the magnetic field lines. This generated magnetic energy turbulently cascades to smaller scales, while being exchanged backwards and forwards with the kinetic energy reservoir, until finally being dissipated. Incorporating explicit dissipation pushes the dissipation scale to larger scales than if the dissipation were entirely numerical. For scales larger than the dissipation scale, we show that the physics of energy transfer in decaying MHD turbulence is robust to numerical effects.

Salvesen, Greg; Beckwith, Kris; Simon, Jacob B.; O'Neill, Sean M.; Begelman, Mitchell C.

2014-02-01

313

Energy Dissipation in Magnetohydrodynamic Turbulence: Coherent Structures or "Nanoflares"?

NASA Astrophysics Data System (ADS)

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.

Zhdankin, Vladimir; Boldyrev, Stanislav; Perez, Jean Carlos; Tobias, Steven M.

2014-11-01

314

Broken ergodicity in two-dimensional homogeneous magnetohydrodynamic turbulence

Two-dimensional (2D) homogeneous magnetohydrodynamic (MHD) turbulence has many of the same qualitative features as three-dimensional (3D) homogeneous MHD turbulence. These features include several ideal (i.e., nondissipative) invariants along with the phenomenon of broken ergodicity (defined as nonergodic behavior over a very long time). 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 3D MHD turbulence that is manifest in the lowest wavenumbers was found. Here, we study the origin of broken ergodicity in 2D MHD turbulence. It will be seen that broken ergodicity in ideal 2D 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. The origins of broken ergodicity in an ideal 2D homogeneous MHD turbulence are found through an eigenanalysis of the covariance matrices of the probability density function and by an examination of the associated entropy functional. When the values of ideal invariants are kept fixed and grid size increases, it will be shown that the energy in a few large modes remains constant, while the energy in any other mode is inversely proportional to grid size. Also, as grid size increases, we find that broken ergodicity becomes manifest at more and more wavenumbers.

Shebalin, John V. [Astromaterials Research and Exploration Science Office, NASA Johnson Space Center, Houston, Texas 77058-3696 (United States)

2010-09-15

315

Broken Ergodicity in Two-Dimensional Homogeneous Magnetohydrodynamic Turbulence

NASA Technical Reports Server (NTRS)

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

Shebalin, John V.

2010-01-01

316

NASA Astrophysics Data System (ADS)

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.

Picologlou, B. F.; Batenin, V. M.

1981-01-01

317

Fully developed, viscous liquid-metal flows and power losses in a rectangular channel in a uniform, external magnetic field were studied for moderate Hartmann numbers and different channel-aspect ratios. The channel was assumed to have insulating side walls parallel to the field, a perfectly conducting moving top wall, and a stationary bottom wall perpendicular to the field. Exact series solutions and numerical calculations are presented for velocity profiles, induced magnetic field distributions, current densities, voltage profiles, and viscous and joulean power losses. The joulean and viscous dissipation are computed from squared quantities involving infinite series with double summations for infinite M. The diverging series derived for the viscous power losses is made convergent by slightly modifying the velocity profile of the conducting fluid at the moving interface. The effect of the applied field is to produce an eddy current that accelerates the bulk fluid to velocities greater than those without the field, but because of the presence of the side walls, the velocities are less than in one-dimensional Couette flow. Except at small aspect ratios and Hartmann number, almost the entire power loss resulted from the component of the induced current parallel to the applied field.

Brown, S.H.; Reilly, P.J.; Sondergaard, N.A.

1987-07-15

318

High-Order Central ENO Finite-Volume Scheme for Ideal MHD A. Susantoa, L. Ivana,, H. De Stercka, C: Magnetohydrodynamics, CENO, ENO, High-Order Schemes, Adaptive Mesh Refinement, GLM 1. Introduction This paper proposes

De Sterck, Hans

319

FLASH magnetohydrodynamic simulations of shock-generated magnetic field experiments

NASA Astrophysics Data System (ADS)

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.

Tzeferacos, P.; Fatenejad, M.; Flocke, N.; Gregori, G.; Lamb, D. Q.; Lee, D.; Meinecke, J.; Scopatz, A.; Weide, K.

2012-12-01

320

Scaling properties of small-scale fluctuations in magnetohydrodynamic turbulence

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 Alfven 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...

Perez, J C; Boldyrev, S; Cattaneo, F

2014-01-01

321

Three Dimensional Simulations of Compressible Hall MHD Plasmas

NASA Astrophysics Data System (ADS)

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.

Shaikh, Dastgeer; Shukla, P. K.

2008-10-01

322

Three Dimensional Simulations of Compressible Hall MHD Plasmas

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.

Shaikh, Dastgeer; Shukla, P. K. [Center for Space Plasma and Aeronomy Research, University of Alabama in Huntsville, Huntsville, AL-35899 (United States) and Institut fuer Theoretische Physik IV and Centre for Plasma Science and Astrophysics, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2008-10-15

323

MHD Turbulence and Magnetic Dynamos

NASA Technical Reports Server (NTRS)

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 investigation, by greatly extending the statistical theory of ideal MHD turbulence. The mathematical details of broken ergodicity, in fact, give a quantitative explanation of how coherent structure, dynamic alignment and force-free states appear in turbulent magnetofluids. The relevance of these ideal results to real MHD turbulence occurs because broken ergodicity is most manifest in the ideal case at the largest length scales and it is in these largest scales that a real magnetofluid has the least dissipation, i.e., most closely approaches the behavior of an ideal magnetofluid. Furthermore, the effects grow stronger when cross and magnetic helicities grow large with respect to energy, and this is exactly what occurs with time in a real magnetofluid, where it is called selective decay. The relevance of these results found in ideal MHD turbulence theory to the real world is that they provide at least a qualitative explanation of why confined turbulent magnetofluids, such as the liquid iron that fills the Earth's outer core, produce stationary, large-scale magnetic fields, i.e., the geomagnetic field. These results should also apply to other planets as well as to plasma confinement devices on Earth and in space, and the effects should be manifest if Reynolds numbers are high enough and there is enough time for stationarity to occur, at least approximately. In the presentation, details will be given for both theoretical and numerical results, and references will be provided.

Shebalin, John V

2014-01-01

324

An Upwind Slope Limiter for PPM that Preserves Monotonicity in Magnetohydrodynamics

We introduce a hybridized slope limiter for PPM that combines a new upwind biased slope limiter with a conventional TVD slope limiter. We demonstrate that this hybrid upwind limiter reduces spurious numerical oscillations near discontinuities, and therefore can compute sharp, monotonized profiles in compressible flows when using PPM, especially in Magnetohydrodynamics (MHD) slowly moving shock regions. Our proposed approach first

D. Lee

2011-01-01

325

Study of small-amplitude magnetohydrodynamic surface waves on liquid metal

Magnetohydrodynamic (MHD) surface waves on liquid metal are studied theoretically and experimentally in the small magnetic Reynolds number limit. A linear dispersion relation is derived when a horizontal magnetic field and a horizontal electric current is imposed. Waves always damp in the deep liquid limit with a magnetic field parallel to the propagation direction. When the magnetic field is weak,

Hantao Ji; William Fox; David Pace; H. L. Rappaport

2005-01-01

326

Study of small-amplitude magnetohydrodynamic surface waves on liquid Hantao Ji,a)

Study of small-amplitude magnetohydrodynamic surface waves on liquid metal Hantao Ji,a) William Fox. In a table-top experiment, planar MHD surface waves on liquid gallium are studied in detail in the regime of weak magnetic field and deep liquid. A noninvasive diagnostic accurately measures surface waves

Ji, Hantao

327

MAGNETOHYDRODYNAMICS Vol. 46 (2010), No. 1, pp. 99111 NUMERICAL AND EXPERIMENTAL STUDIES

are ana- lyzed. The experiments are performed with In-Ga-Sn as a work fluid flowing in an outer FLOW IN A RECTANGULAR DUCT WITH A NON-CONDUCTING FLOW INSERT S. Smolentsev1 , Z. Xu2 , Ch. Pan2 , M consider magnetohydrodynamic (MHD) flows in a conducting rectangular duct with a non-conducting flow

Abdou, Mohamed

328

that these methods, applied to the simulation of a tokamak fusion reactor instability, yield approximations, algebraic multigrid, nested iteration 1 Introduction Magnetohydrodynamics (MHD) is a model of plasma physics that treats the plasma as a charged fluid. As a result, the set of partial differential equations

McCormick, Steve

329

In this work a systematic evaluation of ground and geostationary magnetic field predictions generated by a set of global magnetohydrodynamic (MHD) models is carried out. The evaluation uses four geospace storm events and ground magnetometer station and geostationary GOES data for comparisons between model output and observations. It is shown that metrics analysis of two different geospace parameters, i.e., geostationary

A. Pulkkinen; L. Rastätter; M. Kuznetsova; M. Hesse; A. Ridley; J. Raeder; H. J. Singer; A. Chulaki

2010-01-01

330

Magnetohydrodynamic effects on the flow of blood through a porous channel

Magnetohydrodynamic (MHD) principles used in the treatment of cardiovascular disorders are significant. To provide a generalized treatment for the flow of the blood through a porous channel under the influence of transverse magnetic field and different pressure gradients, a non-Newtonian fluid based on Eyring-Powell model is chosen for the analysis. An implicit finite difference method is adopted for the unsteady

B. Shanker; OSMA NIA

1995-01-01

331

The combined effects of Hall current and mass transfer on the unsteady magnetohydrodynamic (MHD) flow of a viscous fluid passing through a porous channel have been investigated. The flow in the fluid has been induced due to external pressure gradient. The closed form analytical solutions have been obtained for the velocity, temperature and concentration fields. The analytical expressions for non-dimensional

Ilyas Khan; Farhad Ali; Sharidan Shafie; Norzieha Mustapha

2011-01-01

332

Numerical solution of non-steady magnetohydrodynamic flow of blood through a porous channel.

Magnetohydrodynamic (MHD) principles may be used to decelerate the flow of arterial blood and hence be of potential value in the treatment of cardiovascular disorders associated with an accelerated circulation. We examine the non-steady flow of blood in a porous parallel plate channel under the influence of a transverse magnetic field and different pressure gradients. PMID:3392984

Rao, P S; Rao, J A

1988-05-01

333

MHD Integrated Topping Cycle Project

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.

Not Available

1992-01-01

334

A new matching method has been invented for linear stability analysis of magnetohydrodynamics (MHD) modes for plasmas marginally stable against ideal MHD. An inner region with a finite width is utilized as in our previous study [M. Furukawa, S. Tokuda, and L.-J. Zheng, Phys. Plasmas 17, 052502 (2010)]. An ordering scheme for the outer region has been newly developed, thereby it succeeds to include effects of small plasma inertia and resistivity perturbatively in the outer region. The corresponding boundary condition requires direct, not asymptotic, matching of the outer and inner solutions, which assumes nothing special for the behavior of parallel electric field across the matching points. The union of the ordering scheme and the boundary condition enables us to apply our matching method even for plasmas marginally stable against ideal MHD. Because our matching method is not asymptotic, it is easy to implement numerically. The stability analysis of resistive MHD modes, such as internal kink and tearing modes, is satisfactory.

Furukawa, M. [Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8561 (Japan); Tokuda, S. [Research Organization for Information Science and Technology, Shinagawa-ku, Tokyo 140-0001 (Japan)

2011-06-15

335

Magnetohydrodynamic simulations of massive gas injection into Alcator C-Mod and DIII-D plasmas

Disruption mitigation experiments using massive gas injection (MGI) on Alcator C-Mod [Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] and DIII-D [Luxon and Davis, Fusion Technol. 8, 441 (1985)] have shown that magnetohydrodynamics (MHD) plays an important role. The three-dimensional MHD code NIMROD [Sovinec et al., J. Comput. Phys. 195, 355 (2004)] has been extended to include atomic physics taken from the KPRAD code to perform simulations of MGI. Considerable benchmarking of the code has been done against Alcator C-Mod for neon and helium gas jet experiments. The code successfully captures the qualitative sequence of events observed in MGI experiments up to the end of the thermal quench. Neon jet simulations also show quantitative agreement with the experimental thermal quench onset time. For helium gas jets, we show that a small percent boron density can significantly alter the results even in the presence of a helium jet with three orders of magnitude higher density. The thermal quench onset time is considerably overpredicted unless boron radiation is included. A DIII-D helium jet simulation shows a faster rise time for total radiated power than the experiment, but comparable amplitude. Similar to the important role of boron in C-Mod, carbon radiation is a significant factor in DIII-D helium jet simulations and experiments.

Izzo, V. A.; Hollmann, E. M. [University of California-San Diego, La Jolla, California 92093 (United States); Whyte, D. G.; Granetz, R. S. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Parks, P. B.; Lao, L. L.; Wesley, J. C. [General Atomics, P.O. Box 85608, San Diego, California 92186-56088 (United States)

2008-05-15

336

NASA Technical Reports Server (NTRS)

Magnetohydrodynamic (MHD) perturbations in flat Robertson-Walker universes were analyzed, emphasizing their effects on galaxy formation. The Newtonian approximation is used. There is no increase in the growth rates beyond those of the usual perturbed Robertson-Walker models; the MHD modes extract as much energy as they contribute. Some global properties of fully MHD Bianchi I relativistic models are analyzed including vorticity, fluid accelerations, and dissipative effects. The time dependence of perturbations of a fully MHD diagonal Bianchi I cosmology is studied, with an enhanced growth rate of the density contrast of t found which is still not exponential Jeans-type growth. This indicates that a more detailed analysis is needed if a solution to the galaxy formation problem in MHD cosmologies is to be found.

Fennelly, A. J.; Evans, C. R.

1980-01-01

337

We generalize the method of A. M. Polyakov, [ Phys. Rev. E 52 6183 (1995)] for obtaining structure-function relations in turbulence in the stochastically forced Burgers equation, to develop structure-function hierarchies for turbulence in three models for magnetohydrodynamics (MHD). These are the Burgers analogs of MHD in one dimension [ Eur. Phys. J. B 9 725 (1999)], and in three dimensions (3DMHD and 3D Hall MHD). Our study provides a convenient and unified scheme for the development of structure-function hierarchies for turbulence in a variety of coupled hydrodynamical equations. For turbulence in the three sets of MHD equations mentioned above, we obtain exact relations for third-order structure functions and their derivatives; these expressions are the analogs of the von Kármán-Howarth relations for fluid turbulence. We compare our work with earlier studies of such relations in 3DMHD and 3D Hall MHD. PMID:24580182

Basu, Abhik; Naji, Ali; Pandit, Rahul

2014-01-01

338

On the Existence and Non-uniqueness of Solutions of Riemann Problems in Ideal Magnetohydrodynamics

NASA Astrophysics Data System (ADS)

We have built a new exact Riemann solver for ideal magnetohydrodynamics (MHD) that can handle all types of the non-regular waves, such as intermediate shocks and switch-on/off waves. This code can find all the exact solutions for a given MHD Riemann problem. Using the solver, we found that there are uncountably many non-regular solutions for the Brio & Wu problem, which is one of the best-known MHD Riemann problems as it is used as a test problem for numerical codes. This result has cast a question on the numerical MHD simulations: Why do most of the numerical MHD codes always produce a typical non-regular solution which consists of a compound wave?

Takahashi, K.; Yamada, S.

2014-09-01

339

NASA Astrophysics Data System (ADS)

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.

Globus, Noemie; Levinson, Amir

2014-11-01

340

Sub-Alfvenic Non-Ideal MHD Turbulence Simulations with Ambipolar Diffusion: I. Turbulence Statistics

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.

Klein, R I; Li, P S; McKee, C F; Fisher, R

2008-04-10

341

Sub-Alfvenic Non-Ideal MHD Turbulence Simulations with Ambipolar Diffusion: I. Turbulence Statistics

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 256^3 and 512^3 simulations on supersonic but sub-Alfvenic turbulent systems with AD using the Heavy-Ion Approximation developed in Li, McKee, & Klein (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.

Pak Shing Li; Christopher F. McKee; Richard I. Klein; Robert T. Fisher

2008-05-05

342

On the MHD Acceleration of Astrophysical Jets

NASA Astrophysics Data System (ADS)

We present a 2.5D magnetohydrodynamic (MHD) simulation of the acceleration of a collimated jet from a magnetized accretion disk. We employ a MHD Adaptive Mesh Refinement (AMR) code (FLASH—University of Chicago). Thanks to this tool we can follow the evolution of the system for many dynamical timescales with a high-spatial resolution. Assuming an initial condition in which a Keplerian disk, thus with no accretion motions, is threaded by a uniform poloidal magnetic field, we show how both the accretion flow and the acceleration of the outflow occur, and we present in detail which are the forces responsible for the jet launching and collimation. Our simulation also shows how the collimating forces due to the self-generated toroidal magnetic field can produce some peculiar knotty features.

Zanni, Claudio; Ferrari, Attilio; Massaglia, Silvano; Bodo, Gianluigi; Rossi, Paola

2004-09-01

343

MHD waves in stratified and dissipative plasmas

NASA Astrophysics Data System (ADS)

One of the most interesting processes in solar and astrophysical plasmas is the complicated interaction of plasma motions with magnetic fields. These media are highly non-uniform and as a consequence are a natural environment for magnetohydrodynamic (MHD) waves. The propagation of waves in vertical thin flux tubes.embedded in a vertically stratified plasma in the presence of viscosity is shown to be governed by the Klein-Gordon-Burgers (KGB) equation which is solved assuming an isothermal medium in hydrostatic equilibrium surrounded by a quiescent environment. The results presented here can be applied to, e.g. study the propagation of MHD waves generated by the granular buffeting motion in thin magnetic photospheric tubes or the propagation of impulsively generated waves in coronal loops.

Ballai, Istvan

2007-03-01

344

NASA Astrophysics Data System (ADS)

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.

Burke, B. J.; Kruger, S. E.; Hegna, C. C.; Zhu, P.; Snyder, P. B.; Sovinec, C. R.; Howell, E. C.

2010-03-01

345

A nuclear detonation at altitudes several hundred kilometers above the earth will severely distort the earth`s magnetic field and result in a strong magnetohyrodynamic electromagnetic pulse (MHD-EMP). The geomagnetic disturbance interacts with the soil to induce current and horizontal electric gradients. The geomagnetic disturbance interacts with the soil to induced current and horizontal electric gradients in the earth. MHD-EMP, also called E3 since it is the third component of the high-altitude EMP (HEMP), lasts over 100 s after the exoatmospheric burst. MHD-EMP is similar to solar geomagnetic storms in it`s global and low frequency (less than 1 Hz) nature except that E3 can be much more intense with a far shorter duration. When the MHD-EMP gradients are integrated over great distances by power lines, communication cables, or other long conductors, the induced voltages are significant. (The horizontal gradients in the soil are too small to induce major responses by local interactions with facilities.) The long pulse waveform for MHD-EMP-induced currents on long lines has a peak current of 200 A and a time-to-half-peak of 100 s. If this current flows through transformer windings, it can saturate the magnetic circuit and cause 60 Hz harmonic production. To mitigate the effects of MHD-EMP on a facility, long conductors must be isolated from the building and the commercial power harmonics and voltage swings must be addressed. The transfer switch would be expected to respond to the voltage fluctuations as long as the harmonics have not interfered with the switch control circuitry. The major sources of MHD-EMP induced currents are the commercial power lines and neutral; neutral current indirect coupling to the facility power or ground system via the metal fence, powered gate, parking lights, etc; metal water pipes; phone lines; and other long conductors that enter or come near the facility. The major source of harmonics is the commercial power system.

Barnes, P.R.; Vance, E.F.

1992-03-01

346

Contributions from space technology to central power generation

NASA Technical Reports Server (NTRS)

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.

Dicks, J. B., Jr.

1972-01-01

347

On the equations of thermally radiative magnetohydrodynamics

NASA Astrophysics Data System (ADS)

An initial-boundary value problem is considered for the viscous compressible thermally radiative magnetohydrodynamic (MHD) flows coupled to self-gravitation describing the dynamics of gaseous stars in a bounded domain of R3. The conservative boundary conditions are prescribed. Compared to Ducomet-Feireisl [13] (also see, for instance, Feireisl [18], Feireisl-Novotný [20]), a rather more general constitutive relationship is given in this paper. The analysis allows for the initial density with vacuum. Every transport coefficient admits a certain temperature scaling. The global existence of a variational (weak) solution with any finite energy and finite entropy data is established through a three-level approximation and methods of weak convergence.

Li, Xiaoli; Guo, Boling

2014-11-01

348

Rarefaction wave in relativistic steady magnetohydrodynamic flows

We construct and analyze a model of the relativistic steady-state magnetohydrodynamic (MHD) rarefaction that is induced when a planar symmetric flow (with one ignorable Cartesian coordinate) propagates under a steep drop of the external pressure profile. Using the method of self-similarity we derive a system of ordinary differential equations that describe the flow dynamics. In the specific limit of an initially homogeneous flow we also provide analytical results and accurate scaling laws. We consider that limit as a generalization of the previous Newtonian and hydrodynamic solutions already present in the literature. The model includes magnetic field and bulk flow speed having all components, whose role is explored with a parametric study.

Sapountzis, Konstantinos

2014-01-01

349

Athena: A New Code for Astrophysical MHD

A new code for astrophysical magnetohydrodynamics (MHD) is described. The code has been designed to be easily extensible for use with static and adaptive mesh refinement. It combines higher-order Godunov methods with the constrained transport (CT) technique to enforce the divergence-free constraint on the magnetic field. Discretization is based on cell-centered volume-averages for mass, momentum, and energy, and face-centered area-averages for the magnetic field. Novel features of the algorithm include (1) a consistent framework for computing the time- and edge-averaged electric fields used by CT to evolve the magnetic field from the time- and area-averaged Godunov fluxes, (2) the extension to MHD of spatial reconstruction schemes that involve a dimensionally-split time advance, and (3) the extension to MHD of two different dimensionally-unsplit integration methods. Implementation of the algorithm in both C and Fortran95 is detailed, including strategies for parallelization using domain decomposition. Results from a test suite which includes problems in one-, two-, and three-dimensions for both hydrodynamics and MHD are given, not only to demonstrate the fidelity of the algorithms, but also to enable comparisons to other methods. The source code is freely available for download on the web.

James M. Stone; Thomas A. Gardiner; Peter Teuben; John F. Hawley; Jacob B. Simon

2008-04-02

350

The acceleration of protons in a dynamically evolving magnetotail is investigated by tracing particles in the fields obtained from a three-dimensional resistive magnetohydrodynamic (MHD) simulation. The MHD simulation, representing plasmoid formation and ejection through a near-Earth reconnection process, leads to cross-tail electric fields of up to approximately 4 mV\\/m with integrated voltages across the tail of up to approximately 200

Joachim Birn; Michael Hesse

1994-01-01

351

Real-time Earth's magnetosphere simulator with 3-dimensional MHD code

Adopting the three-dimensional (3D) magneto-hydrodynamical (MHD) simulation code developed by Tanaka, we have constructed the real-time numerical simulator of interplanetary space-magnetosphere-ionosphere coupling system. By using the real-time one-minute solar wind data of a density, a flow speed and interplanetary magnetic field (IMF) from the ACE spacecraft as boundary conditions, this MHD simulation system reproduced numerically the global structure of magnetosphere

M. den; T. Tanaka; T. Obara; H. Shimazu; H. Amo; Y. Hayashi; Y. Seo; K. Suehiro; H. Takahara; T. Takei

2004-01-01

352

Relativistic radiation magnetohydrodynamics in dynamical spacetimes: Numerical methods and tests

Many systems of current interest in relativistic astrophysics require a knowledge of radiative transfer in a magnetized gas flowing in a strongly curved, dynamical spacetime. Such systems include coalescing compact binaries containing neutron stars or white dwarfs, disks around merging black holes, core-collapse supernovae, collapsars, and gamma-ray burst sources. To model these phenomena, all of which involve general relativity, radiation (photon and/or neutrino), and magnetohydrodynamics (MHD), we have developed a general relativistic code capable of evolving MHD fluids and radiation in dynamical spacetimes. Our code solves the coupled Einstein-Maxwell-MHD-radiation system of equations both in axisymmetry and in full 3+1 dimensions. We evolve the metric by integrating the BSSN (Baumgarte-Shapiro-Shibata-Nakamura) equations, and use a conservative, high-resolution shock-capturing scheme to evolve both the MHD and radiation moment equations. In this paper, we implement our scheme for optically thick gases and gray-body opacities. Our code gives accurate results in a suite of tests involving radiating shocks and nonlinear waves propagating in Minkowski spacetime. In addition, to test our code's ability to evolve the relativistic radiation-MHD equations in strong-field dynamical spacetimes, we study 'thermal Oppenheimer-Snyder collapse' to a black hole and find good agreement between analytic and numerical solutions.

Farris, Brian D.; Li, T.K.; Liu, Y.T.; Shapiro, Stuart L. [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

2008-07-15

353

A Meshless Method for Magnetohydrodynamics and Applications to Protoplanetary Disks

NASA Astrophysics Data System (ADS)

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 study. Nonetheless, how the test is posed circumvents the issues raised by tests starting from a sharp contact discontinuity yet it still shows the poor performance of Smoothed Particle Hydrodynamics. We then comment on the connection between this behavior and the underlying lack of zeroth-order consistency in Smoothed Particle Hydrodynamics interpolation. In astrophysical magnetohydrodynamics (MHD) and electrodynamics simulations, numerically enforcing the divergence free constraint on the magnetic field has been difficult. We observe that for point-based discretization, as used in finite-difference type and pseudo-spectral methods, the divergence free constraint can be satisfied entirely by a choice of interpolation used to define the derivatives of the magnetic field. As an example we demonstrate a new class of finite-difference type derivative operators on a regular grid which has the divergence free property. This principle clarifies the nature of magnetic monopole errors. The principles and techniques demonstrated in this chapter are particularly useful for the magnetic field, but can be applied to any vector field. Finally, we examine global zoom-in simulations of turbulent magnetorotationally unstable flow. We extract and analyze the high-current regions produced in the turbulent flow. Basic parameters of these regions are abstracted, and we build one dimensional models including non-ideal MHD, and radiative transfer. For sufficiently high temperatures, an instability resulting from the temperature dependence of the Ohmic resistivity is found. This instability concentrates current sheets, resulting in the possibility of rapid heating from temperatures on the order of 600 Kelvin to 2000 Kelvin in magnetorotationally turbulent regions of protoplanetary disks. This is a possible local mechanism for the melting of chondrules and the formation of other high-temperature materials in protoplanetary disks.

McNally, Colin P.

2012-08-01

354

Anisotropic scaling of magnetohydrodynamic turbulence.

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

Horbury, Timothy S; Forman, Miriam; Oughton, Sean

2008-10-24

355

Anisotropic Scaling of Magnetohydrodynamic Turbulence

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{sub parallel}{sup -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.

Horbury, Timothy S.; Forman, Miriam; Oughton, Sean [Blackett Laboratory, Imperial College London, London SW7 2AZ (United Kingdom); Stony Brook University, Stony Brook, New York 11794 (United States); Department of Mathematics, University of Waikato, Hamilton (New Zealand)

2008-10-24

356

Anisotropic scaling of magnetohydrodynamic turbulence

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 wavenumbers with a $k_{\\parallel}^{-2}$ 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 wavevectors at large angles to the local magnetic field and that this component of the turbulence has a spectral index of 5/3.

Horbury, T S; Oughton, S

2008-01-01

357

Electron magnetohydrodynamics: dynamics and turbulence.

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

Lyutikov, Maxim

2013-11-01

358

Helium refrigerator-liquefier system for MHD generator

MHD power generators have been investigated in the Electrotechnical Laboratory as one of the National Research and Development Programmes. A helium refrigerator-liquefier system has been developed to cool the superconducting magnet for a 1000 kW class MHD power generator. The turbo-expander with low temperature gas bearings and an alternator had been developed for the MHD project at the Electrotechnical Laboratory

Y. Akiyama; H. Ishii; M. Ando; Y. Mori; M. Yamamoto; R. Wada; K. Mendelssohn

1974-01-01

359

Analysis and design of an ultrahigh temperature hydrogen-fueled MHD generator

NASA Astrophysics Data System (ADS)

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.

Moder, Jeffrey P.; Myrabo, Leik N.; Kaminski, Deborah A.

1993-10-01

360

MHD Stability of Polar Caps of Accreting Neutron Stars

NASA Astrophysics Data System (ADS)

We assess the stability of magnetic Rayleigh-Taylor type modes driven by the overpressure of magnetically confined accreted matter on the surface of a neutron star. We employ the magnetohydrodynamic (MHD) energy principle to analyze the stability of short-wavelength (ballooning) modes subject to line-tying in the neutron star crust. Research supported by ASCI/Alliances Center for Astrophysical Thermonuclear Flashes at the University of Chicago.

Litwin, C.; Brown, E. F.; Rosner, R.

2000-12-01

361

MHD Stability of Polar Caps of Accreting Neutron Stars

We assess the stability of magnetic Rayleigh-Taylor type modes driven by the overpressure of magnetically confined accreted matter on the surface of a neutron star. We employ the magnetohydrodynamic (MHD) energy principle to analyze the stability of short-wavelength (ballooning) modes subject to line-tying in the neutron star crust. Research supported by ASCI\\/Alliances Center for Astrophysical Thermonuclear Flashes at the University

C. Litwin; E. F. Brown; R. Rosner

2000-01-01

362

Magnetic reversals in a simple model of MHD

We study a simple magnetohydrodynamical approach in which hydrodynamics and MHD turbulence are coupled in a shell model, with given dynamo constrains 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 non trivial evolution linked to the nature of the hydrodynamics turbulence.

Roberto Benzi; Jean-Francois Pinton

2009-06-02

363

Excitation of MHD waves in magnetized anisotropic cosmologies

The excitation of cosmological perturbations in an anisotropic cosmological model and in the presence of a homogeneous magnetic field was studied, using the resistive magnetohydrodynamic (MHD) equations. We have shown that fast-magnetosonic modes, propagating normal to the magnetic field grow exponentially and saturated at high values, due to the resistivity. We also demonstrate that the jeans-like instabilities are enhanced inside a resistive and the formation of condensations formed within an anisotropic fluid influence the growing magnetosonic waves.

A Kuiroukidis; K Kleidis; D B Papadopoulos; L Vlahos

2007-05-15

364

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 ?m/s range in redox-MHD-based microfluidic devices, from which 3D flow maps are obtained with a spatial resolution down to 2 ?m. The 2 ?m 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 ?m/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

365

Large Scale Quasi-geostrophic Magnetohydrodynamics

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 invariant. Its presence is shown to imply energy accumulation ...

Balk, Alexander M

2014-01-01

366

Large-Scale Quasi-geostrophic Magnetohydrodynamics

NASA Astrophysics Data System (ADS)

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.

Balk, Alexander M.

2014-12-01

367

Magneto-hydrodynamically stable axisymmetric mirrors

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.

Ryutov, D. D.; Cohen, B. I.; Molvik, A. W. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Berk, H. L. [University of Texas, Austin, Texas 78712 (United States); Simonen, T. C. [University of California, Berkeley, California 94720 (United States)

2011-09-15

368

Status of Magnetohydrodynamic Augmented Propulsion Experiment

NASA Technical Reports Server (NTRS)

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

Litchford, Ron J.; Lineberry, John T.

2007-01-01

369

Magnetohydrodynamic sea water propulsion

An experimental and theoretical investigation of a large scale MHD propulsor has been undertaken whose objectives are to (1) investigate the transient and steady state performance of the thruster over operating parameter ranges that are compatible with achievement of high efficiency, (2) to quantify the principal loss mechanisms within the thruster and (3) to obtain preliminary hydroacoustic data. The performance

M. Petrick; A. Thomas; L. Genens; J. Libera; R. Nietert; J. Bouillard; E. Pierson; D. Hill; B. Picologlou; O. Ohlsson; T. Kasprzyk; G. Berry

1991-01-01

370

AMR Simulations of Magnetohydrodynamic Problems by the CESE Method in Curvilinear Coordinates

NASA Astrophysics Data System (ADS)

The objective of this paper is to present new extensions of the space - time conservation element and solution element (CESE) method for simulations of magnetohydrodynamic (MHD) problems in general curvilinear coordinates by using an adaptive mesh refinement (AMR) grid system. By transforming the governing MHD equations from the physical space ( x, y, z) to the computational space ( ?, ?,?) while retaining the form of conservation, the CESE method is established for MHD in the curvilinear coordinates. Utilizing the parallel AMR package PARAMESH, we present the first implementation of applying the AMR CESE method for MHD (AMR-CESE-MHD) in both Cartesian and curvilinear coordinates. To show the validity and capabilities of the AMR-CESE-MHD code, a suite of numerical tests in two and three dimensions including ideal MHD and resistive MHD are carried out, with two of them in both Cartesian and curvilinear coordinates. Numerical tests show that our results are highly consistent with those obtained previously by other authors, and the results under both coordinate systems confirm each other very well.

Jiang, Chaowei; Feng, Xueshang; Zhang, Jian; Zhong, Dingkun

2010-12-01

371

Thermoacoustic magnetohydrodynamic electrical generator

A thermoacoustic magnetohydrodynamic electrical generator includes an intrinsically irreversible thermoacoustic heat engine coupled to a magnetohydrodynamic electrical generator. The heat engine includes an electrically conductive liquid metal as the working fluid and includes two heat exchange and thermoacoustic structure assemblies which drive the liquid in a push-pull arrangement to cause the liquid metal to oscillate at a resonant acoustic frequency on the order of 1000 Hz. The engine is positioned in the field of a magnet and is oriented such that the liquid metal oscillates in a direction orthogonal to the field of the magnet, whereby an alternating electrical potential is generated in the liquid metal. Low-loss, low-inductance electrical conductors electrically connected to opposite sides of the liquid metal conduct an output signal to a transformer adapted to convert the low-voltage, high-current output signal to a more usable higher voltage, lower current signal.

Wheatley, J.C.; Swift, G.W.; Migliori, A.

1984-11-16

372

Thermoacoustic magnetohydrodynamic electrical generator

A thermoacoustic magnetohydrodynamic electrical generator includes an intrinsically irreversible thermoacoustic heat engine coupled to a magnetohydrodynamic electrical generator. The heat engine includes an electrically conductive liquid metal as the working fluid and includes two heat exchange and thermoacoustic structure assemblies which drive the liquid in a push-pull arrangement to cause the liquid metal to oscillate at a resonant acoustic frequency on the order of 1,000 Hz. The engine is positioned in the field of a magnet and is oriented such that the liquid metal oscillates in a direction orthogonal to the field of the magnet, whereby an alternating electrical potential is generated in the liquid metal. Low-loss, low-inductance electrical conductors electrically connected to opposite sides of the liquid metal conduct an output signal to a transformer adapted to convert the low-voltage, high-current output signal to a more usable higher voltage, lower current signal.

Wheatley, John C. (Los Alamos, NM); Swift, Gregory W. (Los Alamos, NM); Migliori, Albert (Santa Fe, NM)

1986-01-01

373

High Resolution Simulations of Relativistic Hydrodynamic and MHD Turbulence

NASA Astrophysics Data System (ADS)

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 ? ? > 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 (? ˜ 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. Larger magnetic fields, as found in our high resolution local simulations, may have consequences for gravitational wave signals, GRB precursor events, radio afterglows, and optical afterglows due to emission from ejected radioactive r-process material.

Zrake, Jonathan; MacFadyen, A.

2013-01-01

374

Optimum performance of MHD-augumented chemical rocket thrusters for space propulsion applications

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.

Schulz, R.J.; Chapman, J.N. [Univ. of Tennessee Space Institute, Tullahoma, TN (United States)

1995-12-31

375

Large amplitude MHD waves upstream of the Jovian bow shock

NASA Technical Reports Server (NTRS)

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.

Goldstein, M. L.; Smith, C. W.; Matthaeus, W. H.

1983-01-01

376

The role of magnetohydrodynamics in heliospheric space plasma physics research

NASA Technical Reports Server (NTRS)

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.

Dryer, Murray; Smith, Zdenka Kopal; Wu, Shi Tsan

1988-01-01

377

Broken Ergodicity in MHD Turbulence in a Spherical Domain

NASA Technical Reports Server (NTRS)

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.

Shebalin, John V.; wang, Yifan

2011-01-01

378

On explicit analytic solution for MHD pipe flow of a fourth grade fluid

The goal of this work is the analytical solution of incompressible, magnetohydrodynamic (MHD) flow through a circular pipe for fourth grade fluids. HAM (homotopy analysis method) solution has been obtained for the governing non-linear problem. Results are presented graphically and discussed for the emerging parameters of interest.

T. Hayat; M. Sajid; M. Ayub

2008-01-01

379

A numerical algorithm for MHD of free surface flows at low magnetic Reynolds numbers

We have developed a numerical algorithm and computational software for the study of magnetohydrodynamics (MHD) of free surface flows at low magnetic Reynolds numbers. The governing system of equations is a coupled hyperbolic–elliptic system in moving and geometrically complex domains. The numerical algorithm employs the method of front tracking and the Riemann problem for material interfaces, second order Godunov-type hyperbolic

Roman Samulyak; Jian Du; James Glimm; Zhiliang Xu

2007-01-01

380

Diffusion coefficient of a passive contaminant in a local MHD model of a turbulent accretion disc

We calculate the radial diffusion coefficient for a passive contaminant in an accretion disc which is turbulent due to the action of the magnetorotational instability. Numerical magnetohydrodynamic (MHD) simulations are used to follow the evolution of a local patch of the disc using the shearing box formalism. A separate continuity equation for the mass fraction of contaminant is integrated along

Augusto Carballido; James M. Stone; James E. Pringle

2005-01-01

381

HYDRODYNAMIC AND MHD EQUATIONS ACROSS THE BOW SHOCK AND ALONG THE SURFACES OF PLANETARY OBSTACLES

Examinations of the magnetohydrodynamic (MHD) equations across a bow shock are presented. These equations are written in the familiar Rankine-Hugoniot set, and an exact solution to this set is given which involves the upstream magnetosonic Mach number, plasma , polytropic index, and , as a function of position along the shock surface. The asymptotic Mach cone angle of the shock

S. M. PETRINEC; C. T. RUSSELL

1997-01-01

382

Peristaltically induced motion of a MHD third grade fluid in a deformable tube

We consider incompressible, magnetohydrodynamic (MHD) third grade fluid confined in a circular cylindrical tube. The tube surfaces are electrically non-conducting. Travelling sinusoidal wave is imposed on the tube which induces peristaltic motion in the fluid. The stream function, axial velocity and pressure gradient are determined analytically for small Deborah number (?). The analysis consists of a perturbation expansion in terms

T. Hayat; N. Ali

2006-01-01

383

Homotopy analysis of MHD flows of an Oldroyd 8-constant fluid

Summary. This paper deals with some steady unidirectional flows of an Oldroyd 8-constant magnetohydrodynamic (MHD) fluid in bounded domains. The fluid is electrically conducting in the presence of a uniform magnetic field. Three nonlinear flows are produced by the motion of a boundary or by sudden application of a constant pressure gradient or by the motion of a boundary and

T. Hayat; M. Khan; S. Asghar

2004-01-01

384

The influence of thermal radiation on MHD flow of a second grade fluid

The present analysis deals with the steady magnetohydrodynamic (MHD) flow of a second grade fluid in the presence of radiation. By means of similarity transformation, the arising non-linear partial differential equations are reduced to a system of four coupled ordinary differential equations. The series solutions of coupled system of equations are constructed for velocity and temperature using homotopy analysis method

T. Hayat; Z. Abbas; M. Sajid; S. Asghar

2007-01-01

385

Complexities of a 3-D plasmoid flux rope as shown by an MHD simulation

The results of a global magnetohydrodynamic (MHD) simulation of a pair of magnetospheric substorms on 11 August 2002 are presented. Comparisons of data with simulation results reveal a good agreement regarding the sequence of events during substorm development. We give particular emphasis to results in the simulation of a flux rope formed during the second substorm. Unlike standard 2-D depictions

N. L. Farr; D. N. Baker; M. Wiltberger

2008-01-01

386

MHD boundary-layer flow of an upper-convected Maxwell fluid in a porous channel

Two-dimensional magnetohydrodynamic (MHD) boundary layer flow of an upper-convected Maxwell fluid is investigated in a channel. The walls of the channel are taken as porous. Using the similarity transformations and boundary layer approximations, the nonlinear partial differential equations are reduced to an ordinary differential equation. The developed nonlinear equation is solved analytically using the homotopy analysis method. An expression for

Z. Abbas; M. Sajid; T. Hayat

2006-01-01

387

We present the implementation of a radiative transfer solver with coherent scattering in the new BIFROST code for radiative magneto-hydrodynamical (MHD) simulations of stellar surface convection. The code is fully parallelized using MPI domain decomposition, which allows for large grid sizes and improved resolution of hydrodynamical structures. We apply the code to simulate the surface granulation in a solar-type star,

W. Hayek; M. Asplund; M. Carlsson; R. Trampedach; R. Collet; B. V. Gudiksen; V. H. Hansteen; J. Leenaarts

2010-01-01

388

Radiation effects on MHD flow of Maxwell fluid in a channel with porous medium

This paper describes the heat transfer analysis with thermal radiation on the two-dimensional magnetohydrodynamic (MHD) flow in a channel with porous walls. The upper-convected Maxwell (UCM) fluid fills the porous space between the channel walls. The corresponding boundary layer equations are transformed into ordinary differential equations by means of similarity transformations. The resulting problems are solved by employing homotopy analysis

T. Hayat; R. Sajjad; Z. Abbas; M. Sajid; Awatif A. Hendi

2011-01-01

389

Self-heating in kinematically complex magnetohydrodynamic flows

The non-modal self-heating mechanism driven by the velocity shear in kinematically complex magnetohydrodynamic (MHD) plasma flows is considered. The study is based on the full set of MHD equations including dissipative terms. The equations are linearized and unstable modes in the flow are looked for. Two different cases are specified and studied: (a) the instability related to an exponential evolution of the wave vector and (b) the parametric instability, which takes place when the components of the wave vector evolve in time periodically. By examining the dissipative terms, it is shown that the self-heating rate provided by viscous damping is of the same order of magnitude as that due to the magnetic resistivity. It is found that the heating efficiency of the exponential instability is higher than that of the parametric instability.

Osmanov, Zaza; Rogava, Andria [Centre for Theoretical Astrophysics, ITP, Ilia State University, 0162-Tbilisi (Georgia); Poedts, Stefaan [Centre for Plasma Astrophysics, Katholieke Universiteit Leuven, Celestijnenlaan 200B, Bus 2400 B-3001 (Belgium)

2012-01-15

390

Simulation of operation modes of a centrifugal conductive magnetohydrodynamic pump

NASA Astrophysics Data System (ADS)

A mathematical model of a centrifugal conductive magnetohydrodynamic (MHD) pump that calculates the distributions of velocity, current density, and pressure along the channel is developed. The viscous forces in the original system of MHD equations are taken into account on the basis of the known square law of the drag for a turbulent flow in a pipe, generalized for the case of plane flows in a channel. Dependences of the drag coefficient on the main governing parameters (metal flow rate, current intensity, and intensity of magnetic induction), which provide the agreement of the calculated and experimental data on the pressure at the pump outlet for different operation modes, are obtained. It is shown that these dependences have a universal character and the proposed model can be used to design pumps of this type and to manage their operation in production industry.

Katsnelson, S. S.; Pozdnyakov, G. A.

2013-09-01

391

Hamiltonian magnetohydrodynamics: Lagrangian, Eulerian, and dynamically accessible stability—Theory

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.

Andreussi, T. [Alta S.p.A., Pisa 56121 (Italy)] [Alta S.p.A., Pisa 56121 (Italy); Morrison, P. J. [Institute for Fusion Studies and Department of Physics, The University of Texas at Austin, Austin, Texas 78712-1060 (United States)] [Institute for Fusion Studies and Department of Physics, The University of Texas at Austin, Austin, Texas 78712-1060 (United States); Pegoraro, F. [Università di Pisa, Dipartimento di Fisica E. Fermi, Pisa 56127 (Italy)] [Università di Pisa, Dipartimento di Fisica E. Fermi, Pisa 56127 (Italy)

2013-09-15

392

MAGNETOHYDRODYNAMIC SIMULATION OF A SIGMOID ERUPTION OF ACTIVE REGION 11283

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.

Jiang Chaowei; Feng Xueshang [SIGMA Weather Group, State Key Laboratory for Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China); Wu, S. T.; Hu Qiang, E-mail: cwjiang@spaceweather.ac.cn, E-mail: fengx@spaceweather.ac.cn, E-mail: wus@uah.edu, E-mail: qh0001@uah.edu [Center for Space Plasma and Aeronomic Research, The University of Alabama in Huntsville, Huntsville, AL 35899 (United States)

2013-07-10

393

A Simple and Accurate Riemann Solver for Isothermal MHD

A new approximate Riemann solver for the equations of magnetohydrodynamics (MHD) with an isothermal equation of state is presented. The proposed method of solution draws on the recent work of Miyoshi and Kusano, in the context of adiabatic MHD, where an approximate solution to the Riemann problem is sought in terms of an average constant velocity and total pressure across the Riemann fan. This allows the formation of four intermediate states enclosed by two outermost fast discontinuities and separated by two rotational waves and an entropy mode. In the present work, a corresponding derivation for the isothermal MHD equations is presented. It is found that the absence of the entropy mode leads to a different formulation which is based on a three-state representation rather than four. Numerical tests in one and two dimensions demonstrates that the new solver is robust and comparable in accuracy to the more expensive linearized solver of Roe, although considerably faster.

A. Mignone

2007-01-28

394

Outline of fast analyzer for MHD equilibrium FAME

NASA Astrophysics Data System (ADS)

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.

Sakata, Shinya; Haginoya, Hirofumi; Tsuruoka, Takuya; Aoyagi, Tetsuo; Saito, Naoyuki; Harada, Hiroo; Tani, Keiji; Watanabe, Hideto

1994-02-01

395

An approximate Riemann solver for magnetohydrodynamics (that works in more than one dimension)

NASA Technical Reports Server (NTRS)

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.

Powell, Kenneth G.

1994-01-01

396

A description of the modifications made to improve the plasma parameters of the U-25B Facility is presented. The oxygen enrichment system was modified to allow oxygen enrichment of up to 50% (by volume) ahead of the preheaters. Optimum design and operating conditions of the seed injection system were defined as a result of experimental investigations. An account of the extensive diagnostic studies performed and a description of the measurement techniques and of the new submillimeter laser interferometer are given. The performance of the MHD generator is analyzed for different operating modes. Studies of fluctuations and nonuniformities, current take-off distributions, local electrical analysis, overall heat transfer history of the MHD channel, and an extensive parametric study of the generator are presented. A detailed account of the complete disassembly and inspection of channel No. 1 after more than 100 hours of operation with the combustor, and of the condition of its various elements is also given.

Picologlou, B F; Batenin, V M [eds.

1980-07-01

397

On the theory of MHD waves in a shear flow of a magnetized turbulent plasma

The set of equations for magnetohydrodynamic (MHD) waves in a shear flow is consecutively derived. 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 (Alfvenic) 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. The planned MC calculations can be incorporated in global models for accretion disks and also in all other physical conditions where there is a shear flow in a magnetized turbulent plasma. It is supposed that the heating mechanism by Alfven 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 numerical calculations and by exact solutions for the time dependence of the magnetic field given by the Heun function.

T. M. Mishonov; Y. G. Maneva; Z. D. Dimitrov; T. S. Hristov

2005-07-29

398

MHD Coal-Fired Flow Facility. Quarterly/annual technical progress report, October-December 1979

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.

Dicks, J. B.; Chapman, J. N.; Crawford, L. W.

1980-02-01

399

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.

Picologlou, B F; Batenin, V M

1981-01-01

400

NASA Technical Reports Server (NTRS)

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.

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

401

An analysis is presented to study the effects of viscous dissipation and Joule heating on MHD-free convection flow past a semi-infinite vertical flat plate in the presence of the combined effect of Hall and ion-slip currents for the case of power-law variation of the wall temperature. The fluid is permeated by a strong transverse magnetic field imposed perpendicularly to the

Emad M. Abo-Eldahab; Mohamed A. El Aziz

2005-01-01

402

An unsplit staggered mesh scheme for multidimensional magnetohydrodynamics

NASA Astrophysics Data System (ADS)

We introduce an unsplit staggered mesh scheme (USM) for multidimensional magnetohydrodynamics (MHD) that uses a constrained transport (CT) method with high-order Godunov fluxes and incorporates a new data reconstruction-evolution algorithm for second-order MHD interface states. In this new algorithm, the USM scheme includes so-called "multidimensional MHD terms", proportional to ?·B, in a dimensionally-unsplit way in a single update. This data reconstruction-evolution step, extended from the corner transport upwind (CTU) approach of Colella, maintains in-plane dynamics very well, as shown by the advection of a very weak magnetic field loop in 2D. This data reconstruction-evolution algorithm is also of advantage in its consistency and simplicity when extended to 3D. The scheme maintains the ?·B=0 constraint by solving a set of discrete induction equations using the standard CT approach, where the accuracy of the computed electric field directly influences the quality of the magnetic field solution. We address the lack of proper dissipative behavior in the simple electric field averaging scheme and present a new modified electric field construction (MEC) that includes multidimensional derivative information and enhances solution accuracy. A series of comparison studies demonstrates the excellent performance of the full USM-MEC scheme for many stringent multidimensional MHD test problems chosen from the literature. The scheme is implemented and currently freely available in the University of Chicago ASC FLASH Center's FLASH3 release.

Lee, Dongwook; Deane, Anil E.

2009-03-01

403

Hall magnetohydrodynamic reconnection in the plasmoid unstable regime

A set of reduced Hall magnetohydrodynamic (MHD) equations are used to evaluate the stability of large aspect ratio current sheets to the formation of plasmoids (secondary islands). Reconnection is driven by resistivity in this analysis, which occurs at the resistive skin depth d{sub {eta}}{identical_to}S{sub L}{sup -1/2}{radical}(L{nu}{sub A}/{gamma}), where S{sub L} is the Lundquist number, L, the length of the current sheet, {nu}{sub A,} the Alfven speed, and {gamma}, the growth rate. Modifications to a recent resistive MHD analysis [N. F. Loureiro et al., Phys. Plasmas 14, 100703 (2007)] arise when collisions are sufficiently weak that d{sub {eta}} is shorter than the ion skin depth d{sub i}{identical_to}c/{omega}{sub pi}. Secondary islands grow faster in this Hall MHD regime: the maximum growth rate scales as (d{sub i}/L){sup 6/13}S{sub L}{sup 7/13}{nu}{sub A}/L and the number of plasmoids as (d{sub i}/L){sup 1/13}S{sub L}{sup 11/26}, compared to S{sub L}{sup 1/4}{nu}{sub A}/L and S{sup 3/8}, respectively, in resistive MHD.

Baalrud, S. D.; Bhattacharjee, A.; Huang, Y.-M.; Germaschewski, K. [Center for Integrated Computation and Analysis of Reconnection and Turbulence, University of New Hampshire, Durham, New Hampshire 03824 (United States)

2011-09-15

404

Thermodynamic Cycle Analysis of Magnetohydrodynamic-Bypass Airbreathing Hypersonic Engines

NASA Technical Reports Server (NTRS)

Established analyses of conventional ramjet/scramjet performance characteristics indicate that a considerable decrease in efficiency can be expected at off-design flight conditions. This can be explained, in large part, by the deterioration of intake mass flow and limited inlet compression at low flight speeds and by the onset of thrust degradation effects associated with increased burner entry temperature at high flight speeds. In combination, these effects tend to impose lower and upper Mach number limits for practical flight. It has been noted, however, that Magnetohydrodynamic (MHD) energy management techniques represent a possible means for extending the flight Mach number envelope of conventional engines. By transferring enthalpy between different stages of the engine cycle, it appears that the onset of thrust degradation may be delayed to higher flight speeds. Obviously, the introduction of additional process inefficiencies is inevitable with this approach, but it is believed that these losses are more than compensated through optimization of the combustion process. The fundamental idea is to use MHD energy conversion processes to extract and bypass a portion of the intake kinetic energy around the burner. We refer to this general class of propulsion system as an MHD-bypass engine. In this paper, we quantitatively assess the performance potential and scientific feasibility of MHD-bypass airbreathing hypersonic engines using ideal gasdynamics and fundamental thermodynamic principles.

Litchford, Ron J.; Bityurin, Valentine A.; Lineberry, John T.

1999-01-01

405

We present global 3D MHD simulations of disks of gas and solids, aiming at developing models that can be used to study various scenarios of planet formation and planet-disk interaction in turbulent accretion disks. A second goal is to show that Cartesian codes are comparable to cylindrical and spherical ones in handling the magnetohydrodynamics of the disk simulations, as the disk-in-a-box models presented here develop and sustain MHD turbulence. We investigate the dependence of the magnetorotational instability on disk scale height, finding evidence that the turbulence generated by the magnetorotational instability grows with thermal pressure. The turbulent stresses depend on the thermal pressure obeying a power law of 0.24+/-0.03, compatible with the value of 0.25 found in shearing box calculations. The ratio of stresses decreased with increasing temperature. We also study the dynamics of boulders in the hydromagnetic turbulence. The vertical turbulent diffusion of the embedded boulders is comparable to the turbulent viscosity of the flow. Significant overdensities arise in the solid component as boulders concentrate in high pressure regions.

W. Lyra; A. Johansen; H. Klahr; N. Piskunov

2007-05-28

406

THE PARABOLIC JET STRUCTURE IN M87 AS A MAGNETOHYDRODYNAMIC NOZZLE

The structure and dynamics of the M87 jet from sub-milliarcsec to arcsecond scales are continuously examined. We analyzed the Very Long Baseline Array archival data taken at 43 and 86 GHz to measure the size of very long baseline interferometry (VLBI) cores. Millimeter/sub-millimeter VLBI cores are considered as innermost jet emissions, which has been originally suggested by Blandford and Königl. Those components fairly follow an extrapolated parabolic streamline in our previous study so that the jet has a single power-law structure with nearly 5 orders of magnitude in the distance starting from the vicinity of the supermassive black hole (SMBH), less than 10 Schwarzschild radius (r{sub s}). We further inspect the jet parabolic structure as a counterpart of the magnetohydrodynamic (MHD) nozzle in order to identify the property of a bulk acceleration. We interpret that the parabolic jet consists of Poynting-flux dominated flows, powered by large-amplitude, nonlinear torsional Alfvén waves. We examine the non-relativistic MHD nozzle equation in a parabolic shape. The nature of trans-fast magnetosonic flow is similar to the one of transonic solution of Parker's hydrodynamic solar wind; the jet becomes super-escape as well as super-fast magnetosonic at around ?10{sup 3} r{sub s}, while the upstream trans-Alfvénic flow speed increases linearly as a function of the distance at ?10{sup 2}-10{sup 3} r{sub s}. We here point out that this is the first evidence to identify these features in astrophysical jets. We propose that the M87 jet is magnetically accelerated, but thermally confined by the stratified interstellar medium inside the sphere of gravitational influence of the SMBH potential, which may be a norm in active galactic nucleus jets.

Nakamura, Masanori; Asada, Keiichi, E-mail: nakamura@asiaa.sinica.edu.tw, E-mail: asada@asiaa.sinica.edu.tw [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China)

2013-10-01

407

A pressure-based high resolution numerical method for resistive MHD

NASA Astrophysics Data System (ADS)

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.

Xisto, Carlos M.; Páscoa, José C.; Oliveira, Paulo J.

2014-10-01

408

Magnetohydrodynamics of fractal media

The fractal distribution of charged particles is considered. An example of this distribution is the charged particles that are distributed over the fractal. The fractional integrals are used to describe fractal distribution. These integrals are considered as approximations of integrals on fractals. Typical turbulent media could be of a fractal structure and the corresponding equations should be changed to include the fractal features of the media. The magnetohydrodynamics equations for fractal media are derived from the fractional generalization of integral Maxwell equations and integral hydrodynamics (balance) equations. Possible equilibrium states for these equations are considered.

Tarasov, Vasily E. [Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow 119992 (Russian Federation)

2006-05-15

409

Variational integration for ideal magnetohydrodynamics with built-in advection equations

NASA Astrophysics Data System (ADS)

Newcomb's Lagrangian for ideal magnetohydrodynamics (MHD) in Lagrangian labeling is discretized using discrete exterior calculus. Variational integrators for ideal MHD are derived thereafter. Besides being symplectic and momentum-preserving, the schemes inherit built-in advection equations from Newcomb's formulation, and therefore avoid solving them and the accompanying error and dissipation. We implement the method in 2D and show that numerical reconnection does not take place when singular current sheets are present. We then apply it to studying the dynamics of the ideal coalescence instability with multiple islands. The relaxed equilibrium state with embedded current sheets is obtained numerically.

Zhou, Yao; Qin, Hong; Burby, J. W.; Bhattacharjee, A.

2014-10-01

410

The third-order law for magnetohydrodynamic turbulence with shear: Numerical investigation

NASA Astrophysics Data System (ADS)

The scaling laws of third-order structure functions for isotropic, homogeneous, and incompressible magnetohydrodynamic (MHD) turbulence relate the observable structure function with the energy dissipation rate. Recently [Wan et al. Phys. Plasmas 16, 090703 (2009)], the theory was extended to the case in which a constant velocity shear is present, motivated by the application of the third-order law to the solar wind. We use direct numerical simulations of two-dimensional MHD with shear to confirm this new generalization of the theory. The presence of the shear effect broadens the circumstances in which the law can be applied. Important implications for laboratory and space plasmas are discussed.

Wan, M.; Servidio, S.; Oughton, S.; Matthaeus, W. H.

2010-05-01

411

NASA Astrophysics Data System (ADS)

Numerical procedures have been developed to analyze multidimensional flow and imposed electromagnetic fields associated with a marine magnetohydrodynamic (MHD) propulsion concept. Chorin's artificial compressibility treatment is applied to determine the incompressible flowfield both internal and external to the MHD thruster, using a zonal formulation. Both inviscid and viscous flow are considered. Determination of three-dimensional magnetic, electric, and Lorentz force fields is based on suitable idealizations. This provides indicative results without getting into detailed sytem design considerations. Among other conclusions, it is established that secondary flow induced by the nonuniform Lorentz force is not a key issue in the magnet end-turn regions.

Choi, D.; Knight, C. J.

1993-02-01

412

On the theory of MHD waves in a shear flow of a magnetized turbulent plasma

NASA Astrophysics Data System (ADS)

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.''

Mishonov, Todor M.; Maneva, Yana G.; Dimitrov, Zlatan D.; Hristov, Tihomir S.

413

Center for Extended Magnetohydrodynamic Modeling Cooperative Agreement

The Center for Extended Magnetohydrodynamic Modeling (CEMM) is developing computer simulation models for predicting the behavior of magnetically confined plasmas. Over the first phase of support from the Department of Energy’s Scientific Discovery through Advanced Computing (SciDAC) initiative, the focus has been on macroscopic dynamics that alter the confinement properties of magnetic field configurations. The ultimate objective is to provide computational capabilities to predict plasma behavior—not unlike computational weather prediction—to optimize performance and to increase the reliability of magnetic confinement for fusion energy. Numerical modeling aids theoretical research by solving complicated mathematical models of plasma behavior including strong nonlinear effects and the influences of geometrical shaping of actual experiments. The numerical modeling itself remains an area of active research, due to challenges associated with simulating multiple temporal and spatial scales. The research summarized in this report spans computational and physical topics associated with state of the art simulation of magnetized plasmas. The tasks performed for this grant are categorized according to whether they are primarily computational, algorithmic, or application-oriented in nature. All involve the development and use of the Non-Ideal Magnetohydrodynamics with Rotation, Open Discussion (NIMROD) code, which is described at http://nimrodteam.org. With respect to computation, we have tested and refined methods for solving the large algebraic systems of equations that result from our numerical approximations of the physical model. Collaboration with the Terascale Optimal PDE Solvers (TOPS) SciDAC center led us to the SuperLU_DIST software library [http://crd.lbl.gov/~xiaoye/SuperLU/] for solving large sparse matrices using direct methods on parallel computers. Switching to this solver library boosted NIMROD’s performance by a factor of five in typical large nonlinear simulations, which has been publicized as a success story of SciDAC-fostered collaboration. Furthermore, the SuperLU software does not assume any mathematical symmetry, and its generality provides an important capability for extending the physical model beyond magnetohydrodynamics (MHD). With respect to algorithmic and model development, our most significant accomplishment is the development of a new method for solving plasma models that treat electrons as an independent plasma component. These ‘two-fluid’ models encompass MHD and add temporal and spatial scales that are beyond the response of the ion species. Implementation and testing of a previously published algorithm did not prove successful for NIMROD, and the new algorithm has since been devised, analyzed, and implemented. Two-fluid modeling, an important objective of the original NIMROD project, is now routine in 2D applications. Algorithmic components for 3D modeling are in place and tested; though, further computational work is still needed for efficiency. Other algorithmic work extends the ion-fluid stress tensor to include models for parallel and gyroviscous stresses. In addition, our hot-particle simulation capability received important refinements that permitted completion of a benchmark with the M3D code. A highlight of our applications work is the edge-localized mode (ELM) modeling, which was part of the first-ever computational Performance Target for the DOE Office of Fusion Energy Science, see http://www.science.doe.gov/ofes/performancetargets.shtml. Our efforts allowed MHD simulations to progress late into the nonlinear stage, where energy is conducted to the wall location. They also produced a two-fluid ELM simulation starting from experimental information and demonstrating critical drift effects that are characteristic of two-fluid physics. Another important application is the internal kink mode in a tokamak. Here, the primary purpose of the study has been to benchmark the two main code development lines of CEMM, NIMROD and M3D, on a relevant nonlinear problem. Results from the two

Carl R. Sovinec

2008-02-15

414

We performed a series of high-resolution (up to 1024{sup 3}) direct numerical simulations of hydro and magnetohydrodynamic (MHD) turbulence. Our simulations correspond to the 'strong' MHD turbulence regime that cannot be treated perturbatively. We found that for simulations with normal viscosity the slopes for energy spectra of MHD are similar to ones in hydro, although slightly more shallower. However, for simulations with hyperviscosity the slopes were very different, for instance, the slopes for hydro simulations showed a pronounced and well defined bottleneck effect, while the MHD slopes were relatively much less affected. We believe that this is indicative of MHD strong turbulence being less local than the Kolmogorov turbulence. This calls for revision of MHD strong turbulence models that assume local 'as-in-hydro case' cascading. Nonlocality of MHD turbulence casts doubt on numerical determination of the slopes with currently available (512{sup 3}-1024{sup 3}) numerical resolutions, including simulations with normal viscosity. We also measure various so-called alignment effects and discuss their influence on the turbulent cascade.

Beresnyak, A.; Lazarian, A. [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States)], E-mail: andrey@astro.wisc.edu, E-mail: lazarian@astro.wisc.edu

2009-09-10

415

The numerical solution of resistive MHD equations, in order to show that some intermediate shocks are admissible, is described. A coplanar case with v(z) = Bz = 0, and a full MHD case with v(z) and Bz not equal to zero are studied. In the first cast no intermediate wave existed, but based on the solution of the equations intermediate

C. C. Wu

1987-01-01

416

A closed set of reduced equations describing low-frequency nonlinear flute magnetohydrodynamic (MHD) convection and the resulting nondiffusive processes of particle and energy transport in a weakly collisional cylindrical plasma with an anisotropic pressure is derived. The Chew-Goldberger-Low anisotropic magnetohydrodynamics is used as the basic dynamic model, because this model is applicable to describing flute convection in a cylindrical plasma column even in the low-frequency limit. The reduced set of equations was derived using the method of adiabatic separation of fast and slow motions. It is shown that the structure of the adiabatic transformation and the corresponding velocity field are identical to those obtained earlier in the isotropic MHD model. However, the derived heat transfer equations differ drastically from the isotropic pressure model. In particular, they indicate a tendency toward maintaining different radial profiles of the longitudinal and transverse pressures.

Nebogatov, V. A.; Pastukhov, V. P., E-mail: past@nfi.kiae.ru [National Research Centre Kurchatov Institute (Russian Federation)

2013-06-15

417

Statistical Theory of the Ideal MHD Geodynamo

NASA Technical Reports Server (NTRS)

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 rotation axis.

Shebalin, J. V.

2012-01-01

418

Anisotropic Scaling of Magnetohydrodynamic Turbulence Timothy S. Horbury*

of the anisotropic power and scaling of magnetic field fluctuations in inertial range magnetohydrodynamic turbulence of fluctuations in field-parallel wave numbers with a kÃ?2 k spectrum but is also consistent with the presence of the power is contained in wave vectors at large angles to the local magnetic field and that this component

Oughton, Sean

419

ELECTRON BEAM GENERATED PLASMAS IN HYPERSONIC MHD CHANNELS

The paper analyzes a novel concept of hypersonic cold-air MHD power generators and accelerators with ionization by electron beams. Ionization processes are considered in detail. Strong coupling between hypersonic boundary layers and electrode sheaths is demonstrated, and anode voltage fall in hypersonic MHD channels is shown to be very high. A potential anode sheath instability and ways to suppress it

Sergey O. Macheret; Mikhail N. Shneider; Richard B. Miles; Ronald J. Lipinski

420

NASA Astrophysics Data System (ADS)

During the passage of solar wind high-speed streams, normally characterized by a weak IMF, historic observations [e.g. Rostoker et al., JGR 1998] have shown that a peak of both ULF wave power and electron flux is formed at high L (5-6), measurable from geosynchronous orbit (6.6). Recurrence of the streams leads to a driven oscillation in the magnetospheric field and particle distributions between an excited and a quiet state, with a delay time of 2 days following the solar wind speed. Here we show that, in the presence of Southward IMF Bz, the new peak will form instead at low L (~3) and in some events within the slot L range (2-3). In addition to the change in the magnetospheric configuration resulting from a steady IMF BSouth, it is the fluctuations in the field power and therefore in the wave-particle interaction that are significant in changing the wave power and particle flux profiles. The timescale for those interactions is reduced from 2 days to several hours or tens of minutes. The effect is compared both to effects during low-IMF high-speed streams and to interplanetary coronal mass ejections (Vassiliadis et al., submitted to GRL).

Koepke, M.; Vassiliadis, D.; Baker, D.; Weigel, R.; Zhang, J.; Poomvises, W.

2007-12-01

421

Comparison of Several Finite Difference Methods for Magnetohydrodynamics in 1D and 2D

The comparison of several finite difference methods for ideal magnetohydrodynamics (MHD) is presented. Compared finite difference\\u000a methods include composite schemes, central scheme, WENO, component wise CWENO, and public freely available packages Nirvana\\u000a and Flash. 1D Cartesian tests concern smooth, Brio–Wu and intermediate shock formation problems. From 2D Cartesian tests we\\u000a shortly present Orszag–Tang vortex problem and shock–cloud interaction problem. As

P. Havlík; R. Liska

422

COMPARISON OF SEVERAL FINITE DIFFERENCE SCHEMES FOR MAGNETOHYDRODYNAMICS IN 1D AND 2D

In this paper we present comparison of several flnite difierence methods for ideal Magnetohydrodynamics (MHD) - the system of conservation laws obtained as extension the Euler equations for ideal gas dynamics by including equations for magnetic fleld evolution. We compare results of composite Lax-Friedrichs and Lax-Wendrofi scheme, central scheme of Nessayahu-Tadmor type, WENO and CWENO scheme. Additionally, results from public

PETR HAVLIK; RICHARD LISKA

2006-01-01

423

New exact solutions for magnetohydrodynamic flows of an Oldroyd-B fluid

. This paper presents the new exact analytical solutions for magnetohydrodynamic (MHD) flows of an Oldroyd-B fluid. The explicit\\u000a expressions for the velocity field and the associated tangential stress are established by using the Laplace transform method.\\u000a Three characteristic examples: (i) flow due to impulsive motion of plate, (ii) flow due to uniformly accelerated plate, and (iii) flow due to non-uniformly

M. Khan; Sidra Mahmood; C. Fetecau

2009-01-01

424

In the present paper we discuss the magnetohydrodynamic (MHD) peristaltic flow of a hyperbolic tangent fluid model in a vertical\\u000a asymmetric channel under a zero Reynolds number and long wavelength approximation. Exact solution of the temperature equation\\u000a in the absence of dissipation term has been computed and the analytical expression for stream function and axial pressure\\u000a gradient are established. The

Sohail Nadeem; Safia Akram

2011-01-01

425

Theory and Simulation of Real and Ideal Magnetohydrodynamic Turbulence

NASA Technical Reports Server (NTRS)

Incompressible, homogeneous magnetohydrodynamic (MHD) turbulence consists of fluctuating vorticity and magnetic fields, which are represented in terms of their Fourier coefficients. Here, a set of five Fourier spectral transform method numerical simulations of two-dimensional (2-D) MHD turbulence on a 512(sup 2) grid is described. Each simulation is a numerically realized dynamical system consisting of Fourier modes associated with wave vectors k, with integer components, such that k = |k| less than or equal to k(sub max). The simulation set consists of one ideal (non-dissipative) case and four real (dissipative) cases. All five runs had equivalent initial conditions. The dimensions of the dynamical systems associated with these cases are the numbers of independent real and imaginary parts of the Fourier modes. The ideal simulation has a dimension of 366104, while each real simulation has a dimension of 411712. The real runs vary in magnetic Prandtl number P(sub M), with P(sub M) is a member of {0.1, 0.25, 1, 4}. In the results presented here, all runs have been taken to a simulation time of t = 25. Although ideal and real Fourier spectra are quite different at high k, they are similar at low values of k. Their low k behavior indicates the existence of broken symmetry and coherent structure in real MHD turbulence, similar to what exists in ideal MHD turbulence. The value of PM strongly affects the ratio of kinetic to magnetic energy and energy dissipation (which is mostly ohmic). The relevance of these results to 3-D Navier-Stokes and MHD turbulence is discussed.

Shebalin, John V.

2004-01-01

426

Magnetohydrodynamic Modeling of Space Plasmas with Pressure Anisotropy

NASA Astrophysics Data System (ADS)

The present generation of global 3D magnetohydrodynamic (MHD) simulations of the Sun-Earth environment is based on the assumption that the plasma pressure is isotropic. This assumption, however, is an inadequate description of space plasmas, such as plasmas in the Earth's magnetosheath and inner magnetosphere, as well as in the solar corona, where strong magnetic fields give rise to highly anisotropic plasma pressures. Specifically, particle collisions are not frequent enough to balance the particle motions along and perpendicular to the magnetic field, thus the corresponding parallel and perpendicular pressure components are different. This dissertation research, therefore focuses on extending the University of Michigan MHD space physics code BATS-R-US to account for pressure anisotropy. The analytical model is developed by studying the formulation of anisotropic MHD under both classical and semirelativistic approximations, in particular, deriving the dispersion relation and characteristic wave speeds for semirelativistic anisotropic MHD. The software implementation of the new model, Anisotropic BATS-R-US, is verified through numerical tests. Several applications of Anisotropic BATS-R-US are considered in this work. The first application is to simulate the quiet time terrestrial magnetosphere and validate the results with satellite measurements. Pressure anisotropy is found to widen the magnetosheath, enhance the nightside plasma pressure, and reduce the flow speed in the magnetotail. In the second application, Anisotropic BATS-R-US is coupled with two ring current models, respectively, to conduct global magnetospheric simulations during geomagnetic disturbed times. The simulation results indicate the importance of pressure anisotropy in controlling the nightside magnetic field topology. Finally, Anisotropic BATS-R-US is applied to simulate the solar corona and heliosphere, in which pressure anisotropy results in faster solar wind speeds close to the Sun. This application has the potential to capture the anisotropic heating mechanism that has not been addressed by isotropic MHD models.

Meng, Xing

427

General Relativistic MHD Simulations of Jet Formation

NASA Technical Reports Server (NTRS)

We have performed 3-dimensional general relativistic magnetohydrodynamic (GRMHD) simulations of jet formation from an accretion disk with/without initial perturbation around a rotating black hole. We input a sinusoidal perturbation (m = 5 mode) in the rotation velocity of the accretion disk. The simulation results show the formation of a relativistic jet from the accretion disk. Although the initial perturbation becomes weakened by the coupling among different modes, it survives and triggers lower modes. As a result, complex non-axisymmetric density structure develops in the disk and the jet. Newtonian MHD simulations of jet formation with a non-axisymmetric mode show the growth of the m = 2 mode but GRMHD simulations cannot see the clear growth of the m = 2 mode.

Mizuno, Y.; Nishikawa, K.-I.; Hardee, P.; Koide, S.; Fishman, G. J.

2005-01-01

428

APPROXIMATE DECONVOLUTION MODELS FOR MAGNETOHYDRODYNAMICS

and engineering problems. The magnetic field induces currents in the fluid, which create Lorentz forces on the fluid and change the magnetic field itself. The dynamics of MHD flows is complex, with increased confinement, liquid-metal cooling of nuclear reactors, electromagnetic casting, MHD sea water propulsion (see

Trenchea, Catalin

429

Global and Local Magnetohydrodynamic Relaxations.

National Technical Information Service (NTIS)

Based on theoretical and computational considerations, magnetic reconnection driven nonlinearly by a kink instability is confirmed to play the key role in the magnetohydrodynamic relaxation. An important finding is that the relaxation takes either global ...

T. Sato, R. Horiuchi, K. Kusano

1987-01-01

430

Magnetohydrodynamic Origin of Jets from Accretion Disks

NASA Technical Reports Server (NTRS)

A review is made of magnetohydrodynamic (MHD) theory and simulation of outflows from disks for different distributions of magnetic field threading the disk. In one limit of a relatively weak, initially diverging magnetic field, both thermal and magnetic pressure gradients act to drive matter to an outflow, while a toroidal magnetic field develops which strongly collimates the outflow. The collimation greatly reduces the field divergence and the mass outflow rate decreases after an initial peak. In a second limit of a strong magnetic field, the initial field configuration was taken with the field strength on the disk decreasing outwards to small values so that collimation was reduced. As a result, a family of stationary solutions was discovered where matter is driven mainly by the strong magnetic pressure gradient force. The collimation in this case depends on the pressure of an external medium. These flows are qualitatively similar to the analytic solutions for magnetically driven outflows. The problem of the opening of a closed field line configuration linking a magnetized star and an accretion disk is also discussed.

Lovelace, R. V. E.; Romanova, M. M.

1998-01-01

431

Magnetohydrodynamics of Schwarzschild Plasmas near the Horizon

NASA Astrophysics Data System (ADS)

Very close to the horizon of a blackhole, the gravitational acceleration becomes so large that vacuum can begin to radiate (Hawking radiation). The temperature of this radiation can exceed (twice of) the rest mass of electrons at the position Delta r=lambda_P (M/m_e)(1/2) away from the horizon, where lambda_P is the Planck length, M and m_e are the mass of the blackhole and the electron. In this vicinity a electron-positron plasma is realized even within 3R_s (R_s is the Schwarzschild's radius). We study this plasma in the 3+1 paradigm of general relativistic magnetohydrodynamics. We present various equilibrium solutions of such a plasma in a local frame (co-moving Rindler's coordinates). We also carry out a dynamical study and present MHD results of 3D simulation. The plasma is subject to magnetic buoyancy (Parker) instability, shear (Balbus-Hawley) instability, and vertical slot convection, depending on the parameters adopted. We also find jet is formed in such a system according to our simulation.

Chou, W.; Tajima, T.

1997-05-01

432

Fully Implicit, Nonlinear 3D Extended Magnetohydrodynamics

NASA Astrophysics Data System (ADS)

Extended magnetohydrodynamics (XMHD) includes nonideal effects such as nonlinear, anisotropic transport and two-fluid (Hall) effects. XMHD supports multiple, separate time scales that make explicit time differencing approaches extremely inefficient. While a fully implicit implementation promises efficiency without sacrificing numerical accuracy,(D. A. Knoll et al., phJ. Comput. Phys.) 185 (2), 583-611 (2003) the nonlinear nature of the XMHD system and the numerical stiffness associated with the fast waves make this endeavor difficult. Newton-Krylov methods are, however, ideally suited for such a task. These synergistically combine Newton's method for nonlinear convergence, and Krylov techniques to solve the associated Jacobian (linear) systems. Krylov methods can be implemented Jacobian-free and can be preconditioned for efficiency. Successful preconditioning strategies have been developed for 2D incompressible resistive(L. Chacón et al., phJ. Comput. Phys). 178 (1), 15- 36 (2002) and Hall(L. Chacón and D. A. Knoll, phJ. Comput. Phys.), 188 (2), 573-592 (2003) MHD models. These are based on ``physics-based'' ideas, in which knowledge of the physics is exploited to derive well-conditioned (diagonally-dominant) approximations to the original system that are amenable to optimal solver technologies (multigrid). In this work, we will describe the status of the extension of the 2D preconditioning ideas for a 3D compressible, single-fluid XMHD model.

Chacon, Luis; Knoll, Dana

2003-10-01

433

The Classification of Magnetohydrodynamic Regimes of Thermonuclear Combustion

NASA Astrophysics Data System (ADS)

Physical properties of magnetohydrodynamic (MHD) reaction fronts are studied as functions of the thermodynamic conditions, and the strength and orientation of the magnetic field in the unburned matter through which the fronts propagate. We determine the conditions for the existence of the various types of MHD reaction fronts and the character of the changes in physical quantities across these reaction fronts. The analysis is carried out in general for a perfect gas equation of state and a constant energy release, and then extended to thermonuclear reaction fronts in degenerate carbon-oxygen mixtures and degenerate helium in conditions typical of Type Ia supernova explosions. We find that as unburned matter enters perpendicular to a reaction front, the release of energy through burning generates shear velocity in the reacting gas that, depending on the type of reaction front, strengthens or weakens the magnetic field. In addition, we find that the steady-state propagation of a reaction front is impossible for certain ranges of magnetic field direction. Our results provide insight into the phenomena of MHD thermonuclear combustion that is relevant to the interpretation of future simulations of SN Ia explosions that have magnetic fields systematically incorporated.

Remming, Ian S.; Khokhlov, Alexei M.

2014-10-01

434

Regularity criteria for incompressible magnetohydrodynamics equations in three dimensions

NASA Astrophysics Data System (ADS)

In this paper, we give some new global regularity criteria for three-dimensional incompressible magnetohydrodynamics (MHD) equations. More precisely, we provide some sufficient conditions in terms of the derivatives of the velocity or pressure, for the global regularity of strong solutions to 3D incompressible MHD equations in the whole space, as well as for periodic boundary conditions. Moreover, the regularity criterion involving three of the nine components of the velocity gradient tensor is also obtained. The main results generalize the recent work by Cao and Wu (2010 Two regularity criteria for the 3D MHD equations J. Diff. Eqns 248 2263-74) and the analysis in part is based on the works by Cao C and Titi E (2008 Regularity criteria for the three-dimensional Navier-Stokes equations Indiana Univ. Math. J. 57 2643-61 2011 Gobal regularity criterion for the 3D Navier-Stokes equations involving one entry of the velocity gradient tensor Arch. Rational Mech. Anal. 202 919-32) for 3D incompressible Navier-Stokes equations.

Lin, Hongxia; Du, Lili

2013-01-01

435

RADIATION MAGNETOHYDRODYNAMIC SIMULATIONS OF PROTOSTELLAR COLLAPSE: PROTOSTELLAR CORE FORMATION

We report the first three-dimensional radiation magnetohydrodynamic (RMHD) simulations of protostellar collapse with and without Ohmic dissipation. We take into account many physical processes required to study star formation processes, including a realistic equation of state. We follow the evolution from molecular cloud cores until protostellar cores are formed with sufficiently high resolutions without introducing a sink particle. The physical processes involved in the simulations and adopted numerical methods are described in detail. We can calculate only about one year after the formation of the protostellar cores with our direct three-dimensional RMHD simulations because of the extremely short timescale in the deep interior of the formed protostellar cores, but successfully describe the early phase of star formation processes. The thermal evolution and the structure of the first and second (protostellar) cores are consistent with previous one-dimensional simulations using full radiation transfer, but differ considerably from preceding multi-dimensional studies with the barotropic approximation. The protostellar cores evolve virtually spherically symmetric in the ideal MHD models because of efficient angular momentum transport by magnetic fields, but Ohmic dissipation enables the formation of the circumstellar disks in the vicinity of the protostellar cores as in previous MHD studies with the barotropic approximation. The formed disks are still small (less than 0.35 AU) because we simulate only the earliest evolution. We also confirm that two different types of outflows are naturally launched by magnetic fields from the first cores and protostellar cores in the resistive MHD models.

Tomida, Kengo [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)] [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Tomisaka, Kohji [Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), Osawa, Mitaka, Tokyo 181-8588 (Japan)] [Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), Osawa, Mitaka, Tokyo 181-8588 (Japan); Matsumoto, Tomoaki [Faculty of Humanity and Environment, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160 (Japan)] [Faculty of Humanity and Environment, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160 (Japan); Hori, Yasunori; Saigo, Kazuya [National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588 (Japan)] [National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588 (Japan); Okuzumi, Satoshi [Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan)] [Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan); Machida, Masahiro N., E-mail: tomida@astro.princeton.edu, E-mail: tomisaka@th.nao.ac.jp, E-mail: yasunori.hori@nao.ac.jp, E-mail: saigo.kazuya@nao.ac.jp, E-mail: matsu@hosei.ac.jp, E-mail: okuzumi@nagoya-u.jp, E-mail: machida.masahiro.018@m.kyushu-u.ac.jp [Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812-8581 (Japan)

2013-01-20

436

SHEAR-DRIVEN INSTABILITIES IN HALL-MAGNETOHYDRODYNAMIC PLASMAS

The large-scale dynamics of plasmas is well described within the framework of magnetohydrodynamics (MHD). However, whenever the ion density of the plasma becomes sufficiently low, the Hall effect is likely to become important. The role of the Hall effect has been studied in several astrophysical plasma processes, such as magnetic reconnection, magnetic dynamo, MHD turbulence, or MHD instabilities. In particular, the development of small-scale instabilities is essential to understand the transport properties in a number of astrophysical plasmas. The magneto-rotational instability (MRI), which takes place in differentially rotating accretion disks embedded in relatively weak magnetic fields, is just one example. The influence of the large-scale velocity flows on small-scale instabilities is often approximated by a linear shear flow. In this paper, we quantitatively study the role of the Hall effect on plasmas embedded in large-scale shear flows. More precisely, we show that an instability develops when the Hall effect is present, which we therefore term as the Hall magneto-shear instability. As a particular case, we recover the so-called MRI and quantitatively assess the role of the Hall effect on its development and evolution.

Bejarano, Cecilia; Gomez, Daniel O. [Instituto de Astronomia y Fisica del Espacio (Consejo Nacional de Investigaciones Cientificas y Tecnicas, Universidad de Buenos Aires), Ciudad Universitaria, 1428 C.A.B.A., Buenos Aires (Argentina); Brandenburg, Axel, E-mail: cbejarano@iafe.uba.ar, E-mail: gomez@iafe.uba.ar, E-mail: brandenb@nordita.org [NORDITA, AlbaNova University Center, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)

2011-08-20

437

Summary. Using the concept of simple Riemann solvers, we present entropic and positive Godunov-type schemes preserving contact discontinuities for both Lagrangian and Eulerian systems of gas dynamics and magnetohydrodynamics (MHD). On the one hand, for the Lagrangian form, we develop positive and entropic Riemann solvers which can be considered as a natural extension of Roe's solvers in which the sound

Gérard Gallice

2003-01-01

438

We present the results of global cylindrical disc simulations and local shearing box simulations of protoplanets interacting with a disc undergoing magnetohydrodynamic (MHD) turbulence. The specific emphasis of this paper is to examine and quantify the magnitude of the torque exerted by the disc on the embedded protoplanets as a function of the protoplanet mass, and thus to make a

Richard P. Nelson; John C. B. Papaloizou

2004-01-01

439

NASA Technical Reports Server (NTRS)

We use the global magnetohydrodynamic (MHD) code BATS-R-US to model multipoint observations of Flux Transfer Event (FTE) signatures. Simulations with high spatial and temporal resolution predict that cavities of weak magnetic field strength protruding into the magnetosphere trail FTEs. These predictions are consistent with recently reported multi-point Cluster observations of traveling magnetopause erosion regions (TMERs).

Kuznetsova, M. M.; Sibeck, D. G.; Hesse, M.; Wang, Y.; Rastaetter, L.; Toth, G.; Ridley, A.

2009-01-01

440

EFFECTS OF HALL CURRENT ON MHD FLOW IN A ROTATING CHANNEL PARTIALLY FILLED WITH A POROUS MEDIUM

In a rotating system, magnetohydrodynamic fully developed flow in a parallel-plate channel partially filled with a fluid-saturated porous medium and partially with a clear fluid is considered in the presence of an inclined magnetic field. Hall effects are taken into account and exact solutions of the governing MHD differential equations are obtained in a closed form. The effects of pertinent

Dileep Singh Chauhan; Rashmi Agrawal

2010-01-01

441

This article describes the effects of heat and mass transfer on the magnetohydrodynamic (MHD) peristaltic flow in a planar channel with compliant walls. An incompressible Maxwell fluid occupies a porous space. The mathematical formulation is based upon the modified Darcy’s law. The analytic treatment of the solution is given by choosing a small wave number. The expressions of stream function,

T. Hayat; S. Hina

2010-01-01

442

Heat transfer analysis on the MHD flow of a second grade fluid in a channel with porous medium

In this paper, the heat transfer analysis is investigated for magnetohydrodynamic (MHD) flow in a porous channel. The second grade fluid fills the porous space inside the channel. The governing non-linear problem is solved analytically. Homotopy analysis method (HAM) is employed to obtain the expressions for velocity and temperature fields. Convergence of the obtained solutions is properly analyzed. Graphs are

T. Hayat; Z. Abbas

2008-01-01

443

The development of z-pinch instabilities in the presence of the Hall term, finite Larmor radius effects (FLR), and axial magnetic field is being investigated. The linear stage of instability development is studied with linearized magnetohydrodynamic (MHD) equations based on the Hall fluid model. Results for linear growth rates as a function of axial sheared flow, axial magnetic field, and the

V. I. Sotnikov; L. Wanes; B. S. Bauer; I. Paraschiv; J. N. Leboeuf; P. Hellinger; P. Travnicek; V. Fiala

2003-01-01

444

An Upwind Slope Limiter for PPM that Preserves Monotonicity in Magnetohydrodynamics

NASA Astrophysics Data System (ADS)

We introduce a hybridized slope limiter for PPM that combines a new upwind biased slope limiter with a conventional TVD slope limiter. We demonstrate that this hybrid upwind limiter reduces spurious numerical oscillations near discontinuities, and therefore can compute sharp, monotonized profiles in compressible flows when using PPM, especially in Magnetohydrodynamics (MHD) slowly moving shock regions. Our proposed approach first detects a local, slowly moving shock, and considers an upwind direction to compute a monotonicity-preserving slope limiter. This new approach, in addition to improving the numerical solutions in MHD to levels that reduce (or eliminate) such oscillatory behaviors, while preserving sharp discontinuities in MHD, is also simple to implement. The method described in this paper has been verified against the results from other high-resolution shock-capturing (HRSC) methods such as MUSCL and WENO schemes in FLASH.

Lee, D.

2011-10-01

445

The statistics of a passive scalar in field-guided magnetohydrodynamic turbulence

A variety of studies of magnetised plasma turbulence invoke theories for the advection of a passive scalar by turbulent fluctuations. Examples include modelling the electron density fluctuations in the interstellar medium, understanding the chemical composition of galaxy clusters and the intergalactic medium, and testing the prevailing phenomenological theories of magnetohydrodynamic turbulence. While passive scalar turbulence has been extensively studied in the hydrodynamic case, its counterpart in MHD turbulence is significantly less well understood. Herein we conduct a series of high-resolution direct numerical simulations of incompressible, field-guided, MHD turbulence in order to establish the fundamental properties of passive scalar evolution. We study the scalar anisotropy, establish the scaling relation analogous to Yaglom's law, and measure the intermittency of the passive scalar statistics. We also assess to what extent the pseudo Alfven fluctuations in strong MHD turbulence can be modelled as a pas...

Mason, Joanne; Cattaneo, Fausto; Perez, Jean Carlos

2014-01-01

446

Steady and unsteady Hall magnetohydrodynamics near an X-type magnetic neutral line

NASA Astrophysics Data System (ADS)

Hall magnetohydrodynamics (MHD) properties near a two-dimensional (2D) X-type magnetic neutral line in the steady state are considered via heuristic and rigorous developments. The heuristic development turns out to be useful in providing insight into the lack of dependence of the reconnection rate on the mechanism breaking the frozen-in condition of the magnetic field lines in the electron fluid. The latter result can be understood in terms of the ability of the ions and electrons to transport equal amounts of magnetic flux per unit time out of the reconnection region. The Hall effects are shown via a rigorous development to be able to sustain the hyperbolicity of the magnetic field (and hence a more open X-point configuration) near the neutral line in the steady state. The time-dependent Hall MHD problem shows that the Hall effect, when sufficiently strong, can indeed quench the finite-time singularity exhibited in ideal MHD.

Shivamoggi, Bhimsen K.

2011-05-01

447

Steady and unsteady Hall magnetohydrodynamics near an X-type magnetic neutral line

Hall magnetohydrodynamics (MHD) properties near a two-dimensional (2D) X-type magnetic neutral line in the steady state are considered via heuristic and rigorous developments. The heuristic development turns out to be useful in providing insight into the lack of dependence of the reconnection rate on the mechanism breaking the frozen-in condition of the magnetic field lines in the electron fluid. The latter result can be understood in terms of the ability of the ions and electrons to transport equal amounts of magnetic flux per unit time out of the reconnection region. The Hall effects are shown via a rigorous development to be able to sustain the hyperbolicity of the magnetic field (and hence a more open X-point configuration) near the neutral line in the steady state. The time-dependent Hall MHD problem shows that the Hall effect, when sufficiently strong, can indeed quench the finite-time singularity exhibited in ideal MHD.

Shivamoggi, Bhimsen K. [University of Central Florida, Orlando, Florida 32816-1364 (United States)

2011-05-15

448

Liquid metal MHD research and development in Israel

NASA Astrophysics Data System (ADS)

The study and development of liquid-metal magnetohydrodynamics (MHD) in Israel, from 1973 to the present, are reviewed. Following extensive research and evaluation, it was established that the most promising concept for a relatively short development time was the gravitational system, using lead or lead alloys as the magnetohydrodynamic fluid and steam or gases as the working fluid. The Etgar Program, set up to investigate such systems, is comprised of seven segments, of which the first six have been completed; work on the last segment has been started. The segments are as follows: studies of the physical phenomena; development of a universal numerical code for parametric studies and optimization and design of the system; materials studies; development of engineering components; construction and testing of small-scale Etgar-type systems; economic evaluation and comparison with conventional technologies; and development of an industrial demonstration plant.

Branover, H.

1991-05-01

449

MHD Boundary Layer Flow of Dilatant Fluid in a Divergent Channel with Suction or Blowing

NASA Astrophysics Data System (ADS)

An analysis is carried out to study a steady magnetohydrodynamic (MHD) boundary layer flow of an electrically conducting incompressible power-law non-Newtonian fluid through a divergent channel. The channel walls are porous and subjected to either suction or blowing of equal magnitude of the same kind of fluid on both walls. The fluid is permeated by a magnetic field produced by electric current along the line of intersection of the channel walls. The governing partial differential equation is transformed into a self-similar nonlinear ordinary differential equation using similarity transformations. The possibility of boundary layer flow in a divergent channel is analyzed with the power-law fluid model. The analysis reveals that the boundary layer flow (without separation) is possible for the case of the dilatant fluid model subjected to suitable suction velocity applied through its porous walls, even in the absence of a magnetic field. Further, it is found that the boundary layer flow is possible even in the presence of blowing for a suitable value of the magnetic parameter. It is found that the velocity increases with increasing values of the power-law index for the case of dilatant fluid. The effects of suction/blowing and magnetic field on the velocity are shown graphically and discussed physically.

Krishnendu, Bhattacharyya; C. Layek, G.

2011-08-01

450

NASA Astrophysics Data System (ADS)

Physical models of the radiation belt seek to simulate and predict variations in the space radiation environment based on first-principles views of the particle dynamics, making necessary approximations to turn complex field and particle interactions into computationally tractable problems. For example, global magnetohydrodynamic (MHD) models of the magnetosphere provide large-scale views of the interactions of the solar wind with the geomagnetic environment; coupling these global models with test particle simulations provides one means of examining aspects of the evolution of the radiation belts under complex driving conditions. In this work we discuss how global MHD/particle models may be extended to predict the spatiotemporal and frequency characteristics of plasma waves precluded by the MHD approximation, (e.g. magnetospheric EMIC and chorus waves), and examine ways in which the impact of these non-MHD waves may be included in the MHD/particle approach.

Elkington, Scot; Chan, Anthony; McCollough, James

2012-07-01

451

MHD waves within Noncommutative Maxwell theory

In the presence of a strong uniform magnetic field, we study the influence of space noncommutativity on the electromagnetic waves propagating through a quasi-static homogeneous plasma. In this treatment, we have adopted a physical model which considers plasma as quasi-neutral single fluid. By using noncommutative Maxwell theory, the ideal magnetohydrodynamics (MHD) equations are established, in which new equilibrium conditions are extracted. As an empirical study, some attractive features of MHD waves behavior are investigated. Furthermore, it is shown that the presence of space noncommutativity enhances slightly the phase velocity of the incompressive shear Alfv\\'{e}n waves. In a compressible plasma, the noncommutativity plays the role of an additional compression on the medium, in which its relevant effect on the fast mode occurs for highly oblique branchs, while the low effect appears when the propagations are nearly parallel or anti-parallel. In addition, it turned out that the influence of space deformation on the slow modes is $\\sim 10^{3}$ times smaller than that on the fast modes. The space noncommutativity effect on the slow waves is negligible in low plasma $\\beta $ value, and could appear when $\\beta $ is higher than $0.1,$ thus the extreme modification occurs for oblique slow waves propagating with angles between $30^{\\circ}$ and $60^{\\circ}$. Finally, we comment on the possible effect of such waves on CMB spectrum in photon-baryon plasma.

S. Bourouaine; A. Benslama

2006-10-23

452

Solar Nebula Magnetohydrodynamics

The dynamical state of the solar nebula depends critically upon whether or not the gas is magnetically coupled. The presence of a subthermal field will cause laminar flow to break down into turbulence. Magnetic coupling, in turn, depends upon the ionization fraction of the gas. The inner most region of the nebula ($\\lesssim 0.1$ AU) is magnetically well-coupled, as is the outermost region ($\\gtrsim 10$ AU). The magnetic status of intermediate scales ($\\sim 1$ AU) is less certain. It is plausible that there is a zone adjacent to the inner disk in which turbulent heating self-consistently maintains the requisite ionization levels. But the region adjacent to the active outer disk is likely to be magnetically ``dead.'' Hall currents play a significant role in nebular magnetohydrodynamics. Though still occasionally argued in the literature, there is simply no evidence to support the once standard claim that differential rotation in a Keplerian disk is prone to break down into shear turbulence by nonlinear instabilities. There is abundant evidence---numerical, experimental, and analytic---in support of the stabilizing role of Coriolis forces. Hydrodynamical turbulence is almost certainly not a source of enhanced turbulence in the solar nebula, or in any other astrophysical accretion disk.

Steven A. Balbus; John F. Hawley

1999-06-18

453

JET Snake Magnetohydrodynamic Equilibria

NASA Astrophysics Data System (ADS)

A long-lived density perturbation labelled a ``snake'' has been observed in the JET tokamak with pellet injection for toroidal field Bt=3.1T and toroidal current It=3MA.ootnotetextR. D. Gill et al., Nucl. Fusion 32 (1992) 723. Spontaneous snakes triggered by core impurity accumulation have also been reported at Bt=2.8T and It=4.2MA.ootnotetextibid. We compute model magnetohydrodynamic equilibria with the 3D ANIMEC codeootnotetextW. A. Cooper et al., Comput. Phys. Commun. 180 (2009) 1524. that can recover snake-like conditions by prescribing peaked pressure and hollow toroidal current profiles which are consistent with those in the experimental discharges.ootnotetextM. Hugon et al., Nucl. Fusion 32 (1992) 33. The internal helical distortions that look like snake structures have been obtained with the following parameters: Bt˜2.65T, It=3.75MA, q0˜1.7, qmin˜1, qedge˜7.5, li˜1.2, ˜2.4%, ?N˜2.3.

Cooper, W. Anthony; Graves, J. P.; Sauter, O.; Pochelon, A.

2010-11-01

454

A Modern Astrophysical MHD Solver on CUDA-Capable GPUs

NASA Astrophysics Data System (ADS)

Current numerical simulations employed by the astrophysics simulation community typically require long times to complete, particularly for three-dimensional regions. The recently developed CUDA extensions for C allow existing code to be modified to run on modern graphics cards in an efficient and parallelizeable manner. Graphics cards, particularly those developed for scientific computation, have significant speed advantages over CPUs for highly-parallelizeable applications such as magnetohydrodynamics grid solvers. Athena, a grid-based MHD code for astrophysics (Stone et al. 2008), is retooled to run on CUDA capability 2.0 or greater NVIDIA graphics cards, with effort taken to maximize performance. Performance benchmarks between graphics cards and CPUs are presented.

Ryan, Ben

2012-01-01

455

Asymmetric and Moving-Frame Approaches to MHD Equations

The magnetohydrodynamic (MHD) equations of incompressible viscous fluids with finite electrical conductivity describe the motion of viscous electrically conducting fluids in a magnetic field. In this paper, we find twelve families of solutions of these equations by Xu's asymmetric and moving frame methods. A family of singular solutions may reflect basic characteristics of vortices. The other solutions are globally analytic with respect to the spacial variables. In particular, Bernoulli equation and Wronskian determinants play important roles in our approaches. Our solutions may also help engineers to develop more effective algorithms to find physical numeric solutions to practical models.

Bintao Cao

2009-08-25

456

On fan-shaped cold MHD winds from Keplerian accretion discs

NASA Astrophysics Data System (ADS)

We investigate under which conditions cold, fan-shaped winds can be steadily launched from thin (Keplerian) accretion discs. Such winds are magnetocentrifugal winds launched from a thin annulus in the disc along open magnetic field lines that fan out above the disc. In principle, such winds could be found in two situations: (1) at the interface between an inner jet emitting disc, which is itself powering magnetocentrifugally driven winds, and an outer standard accretion disc; (2) at the interface between an inner closed stellar magnetosphere and the outer standard accretion disc. We refer to terminal or T-winds as the former kind and to magnetospheric or M-winds as the latter. The full set of resistive and viscous steady-state magnetohydrodynamic (MHD) equations are analysed for the disc (the annulus), which allow us to derive general expressions valid for both configurations. We find that, under the framework of our analysis, the only source of energy able to power any kind of fan-shaped winds is the viscous transport of rotational energy coming below the inner radii. Using standard local ? prescriptions for the anomalous (turbulent) transport of angular momentum and magnetic fields in the disc, we derive the strength of the transport coefficients that are needed to steadily sustain the global configuration. It turns out that in order for these winds to be dynamically relevant and explain observed jets, the disc coefficients must be far much larger than values expected from current knowledge of turbulence occurring inside protostellar discs. Either the current view on MHD turbulence must be deeply reconsidered or steady-state fan-shaped winds are never realized in nature. The latter hypothesis seems to be consistent with current numerical simulations.

Ferreira, J.; Casse, F.

2013-01-01

457

An advanced implicit solver for MHD

NASA Astrophysics Data System (ADS)

A new implicit algorithm has been developed for the solution of the time-dependent, viscous and resistive single fluid magnetohydrodynamic (MHD) equations. The algorithm is based on an approximate Riemann solver for the hyperbolic fluxes and central differencing applied on a staggered grid for the parabolic fluxes. The algorithm employs a locally aligned coordinate system that allows the solution to the Riemann problems to be solved in a natural direction, normal to cell interfaces. The result is an original scheme that is robust and reduces the complexity of the flux formulas. The evaluation of the parabolic fluxes is also implemented using a locally aligned coordinate system, this time on the staggered grid. The implicit formulation employed by WARP3 is a two level scheme that was applied for the first time to the single fluid MHD model. The flux Jacobians that appear in the implicit scheme are evaluated numerically. The linear system that results from the implicit discretization is solved using a robust symmetric Gauss-Seidel method. The code has an explicit mode capability so that implementation and test of new algorithms or new physics can be performed in this simpler mode. Last but not least the code was designed and written to run on parallel computers so that complex, high resolution runs can be per formed in hours rather than days. The code has been benchmarked against analytical and experimental gas dynamics and MHD results. The benchmarks consisted of one-dimensional Riemann problems and diffusion dominated problems, two-dimensional supersonic flow over a wedge, axisymmetric magnetoplasmadynamic (MPD) thruster simulation and three-dimensional supersonic flow over intersecting wedges and spheromak stability simulation. The code has been proven to be robust and the results of the simulations showed excellent agreement with analytical and experimental results. Parallel performance studies showed that the code performs as expected when run on parallel computers and the speedups obtained were excellent.

Udrea, Bogdan

458

Performance optimization of an MHD generator with physical constraints

NASA Technical Reports Server (NTRS)

A method to optimize the Faraday MHD generator performance under a prescribed set of electrical and magnet constraints is described. The results of generator performance calculations using this technique are presented for a very large MHD/steam plant. The differences between the maximum power and maximum net power generators are described. The sensitivity of the generator performance to the various operational parameters are presented.

Pian, C. C. P.; Seikel, G. R.; Smith, J. M.

1979-01-01

459

Excitation Of MHD Modes With Gravitational Waves: A Testbed For Numerical Codes

We consider a gravitational wave oscillating in an initially homogeneous, magnetized fluid. The fluid is perfectly conducting and isentropic, and the magnetic field is initially uniform. We find analytic solutions for the case in which the gravitational wave is linear and unaffected by the background fluid and field. Our solutions show how gravitational waves can excite three magnetohydrodynamic (MHD) modes in the fluid: Alfven waves, and both fast and slow magnetosonic waves. Our analytic solutions are particularly useful for testing numerical codes designed to treat general relativistic MHD in dynamical spacetimes, as we demonstrate in a companion paper.

Matthew D. Duez; Yuk Tung Liu; Stuart L. Shapiro; Branson C. Stephens

2005-03-18

460

Experimental facility for studying MHD effects in liquid metal cooled blankets

NASA Astrophysics Data System (ADS)

The capabilities of a facility, brought into service to collect data on magnetohydrodynamic (MHD) effects, pertinent to liquid metal cooled fusion reactor blankets, are presented. The facility, design to extend significantly the existing data base on liquid metal MHD, employs eutectic NaK as the working fluid in a room temperature closed loop. The instrumentation system is capable of collecting detailed data on pressure, voltage, and velocity distributions at any axial position within the base of a 2 Tesla conventional magnet. The axial magnetic field distribution can be uniform or varying with either rapid or slow spatial variations.

Reed, C. B.; Picologlou, B. F.; Dauzvardis, P. V.