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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
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NASA NTRS1981

Magnetohydrodynamics of atmospheric transients. III - Basic results of nonplane two-dimensional analysis

The dynamic response of a stratified atmosphere permeated by a magnetic field to a sudden localized energy release (e.g., the onset of a flare) is examined in a physically self-consistent manner within the approximation of axisymmetric two-dimensional magnetohydrodynamics. In contrast to the previous plane analyses, with the inclusion of out-of-plane components of magnetic and velocity fields, it is shown that the presence of transverse waves leads to spiraling material motions and formation of ring current with open (mostly radial) magnetic field configuration. In the closed (mostly azimuthal) magnetic field, the evolutionary response of a magnetic field is shown to follow the typical sequence observed with a flare, namely, the relaxations of magnetic shear toward the potential configuration. The details of the results are described with discussions on their physical significance.

Nakagawa, Y.↗
NASA NTRS1981

Magnetohydrodynamic interaction of high-speed streams

Numerical solutions of a magnetohydrodynamic model are carried out to describe the nonlinear interaction of corotating high-speed streams near the solar equatorial plane. Two problems are studied. The first problem is to simulate the evolution of an idealized high-speed stream. Numerical solutions are obtained to represent the variations of flow velocity, magnetic field, plasma density, temperature, and conduction heat flux in the interaction region. They demonstrate that the dynamical interaction and heat conduction process are responsible for the thermal structure of a high-speed stream. The second problem deals with the formation of corotating shock waves near the leading edge of a broad stream resulting from the merging of characteristic curves. Corotating shocks do not necessarily occur in pairs; a reverse shock can be formed without a forward shock nearby.

Whang, Y. C.↗
NASA NTRS1981

Stellar chromospheric and coronal heating by magnetohydrodynamic waves

An investigation is presented on the way in which the generation of magnetohydrodynamic waves by turbulent motions in stellar convection zones depends on the star's effective temperature, surface gravity, and magnetic field strength. It is shown that the emitted Alfven wave flux (and acoustic slow wave flux in a very strong magnetic field) is in reasonable agreement with the general trend of observed chromospheric radiative losses in stars, and with the observations of three stars for which magnetic field strength, surface area covered by strong fields, and radiative losses have all been measured.

Stein, R. F.↗
NASA NTRS1981

Magnetohydrodynamics MHD Engineering Test Facility ETF 200 MWe power plant. Conceptual Design Engineering Report CDER. Volume 3: Costs and schedules

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.

Source record↗
NASA NTRS1981

Magnetohydrodynamics (MHD) Engineering Test Facility (ETF) 200 MWe power plant Conceptual Design Engineering Report (CDER)

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

Source record↗
NASA NTRS1981

Magnetohydrodynamics (MHD) Engineering Test Facility (ETF) 200 MWe power plant. Conceptual Design Engineering Report (CDER). Volume 4: Supplementary engineering data

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.

Source record↗
NASA NTRS1982

Two-and-a-half-dimensional magnetohydrodynamic turbulence

The homogeneous turbulence for which fluctuating magnetic fields and velocity fields are independent of one spatial coordinate but still possess all three components are studied to form a generalized two-and-half dimensional geometry. The integral of the z-vector potential and the magnetic helicity are shown to be ideal invariants, and the basic dynamical variables and the equations of uniform-density incompressible magnetohydrodynamics are defined. The possibility of simultaneous inverse cascades is considered, and Kolmogoroff dimensional analysis is employed to infer omnidirectional inverse cascade spectra. Implications of a selective decay hypothesis, where a tendency exists in the initial value problem for the ideal invariants directly cascaded to higher wavenumbers to be selectively dissipated, and the possibility of a dynamo action in the considered geometry, are examined.

Montgomery, D.↗
NASA NTRS1982

Electron heating by fast mode magnetohydrodynamic waves in the solar wind emanating from coronal holes

It is shown that fast mode magnetohydrodynamic waves, propagating outwards from the sun in coronal hole regions, will dissipate primarily through collisionless interaction with electrons rather than with protons. This dissipation can lead to higher electron than proton temperatures in the accelerating region of the solar wind, provided the waves carry a sufficiently large energy flux.

Habbal, S. R.↗
NASA NTRS1982

Numerical model of a two-dimensional, non-plane transient magnetohydrodynamic flow

The equations describing two-dimensional three-component magnetohydrodynamic (MHD) transient flows are formulated for a system of spherical coordinates. With the numerical code based on Implicit Continuous Fluid Eulerian (ICE) scheme, MHD flows resulting from a sudden energy release in a stratified medium are examined. Because of the inclusion of out-of-plane components of velocity and magnetic fields, MHD transverse waves are observed in addition to fast, slow and entropy waves. Numerical results for compressible MHD shocks are found in satisfactory agreement with the theoretical predictions.

Han, S. M.↗
NASA NTRS1982

Interaction of small-amplitude fluctuations with a strong magnetohydrodynamic shock

The interaction of small fluctuations with a strong magnetohydrodynamic shock is considered theoretically in the most general situation using an ideal model. An analytical treatment of the cutoff conditions for penetration of the upstream fluctuation through the bow shock is presented. The situation in which there exist unique solutions of the interaction is investigated quantitatively. Numerical examples of the interaction of waves in the solar wind with the terrestrial bow shock are given to illustrate the refracted waves to be found in the earth's magnetosheath.

Zhuang, H.-C.↗
NASA NTRS1982

Numerical experimentation on spherically symmetric one-dimensional magnetohydrodynamic /MHD/ wave propagation

Radial propagation of one-dimensional magnetohydrodynamic (MHD) waves are analyzed numerically on the basis of the Implicit-Continuous-Fluid-Eulerian (ICE) scheme. Accuracy of the numerical method and other properties are tested through the study of MHD wave propagation. The three different modes of MHD waves (i.e., fast-, slow- and Alfven (transverse) mode) are generated by applying physically consistent boundary perturbations derived from MHD compatibility relations. It is shown that the resulting flow following these waves depend upon the relative configurations of the initial magnetic field and boundary perturbations.

Han, S. M.↗
NASA NTRS1982

Magnetohydrodynamic equilibrium. III - Helically symmetric fields. IV - Nonequilibrium of nonsymmetric hydrodynamic topologies

It is pointed out that plasma confinement in stable equilibrium states constitutes a fundamental and still unresolved question in plasma astrophysics and thermonuclear fusion research. The problem has two parts related to the equilibrium states themselves and their mechanical stability. The question of the existence of general solutions of the field and fluid equations for the steady dynamical interaction of inviscid compressible fluids of high electrical conductivity with magnetic and gravity fields is considered. In the absence of fluid motions, the presented equations become the familiar equations of magnetostatics supplemented by an equation of state. Starting from this simplest case of magnetostatic equilibrium, the investigation proceeds to the more complex case of magnetohydrodynamic equilibrium. Examples of helically symmetric fields are presented to illustrate the use of the formulation for treating the dynamics of helically symmetric hydromagnetic flows.

Tsinganos, K. C.↗
NASA NTRS1982

Numerical simulation of magnetohydrodynamic shock propagation in the corona

Recent developments in the field of numerical simulation models for the study of shock wave propagation in the corona are presented. These models are based on gasdynamic (GD) and ideal (that is, dissipationless, except at shocks) magnetohydrodynamic (MHD) theories. The characteristics and physical interpretations of the results derived from these models are discussed in some detail. The most significant physical results obtained to date are provided by the two-dimensional non-planar, time-dependent, MHD numerical simulation model. In this model, the non-linear interaction among the three essential MHD waves, i.e., fast-, slow-, and Alfven waves are demonstrated. Finally, the physical relevance of these numerical simulation models in relation to observed solar activity is presented.

Wu, S. T.↗
NASA NTRS1982

Magnetohydrodynamics of atmospheric transients. IV - Nonplane two-dimensional analyses of energy conversion and magnetic field evolution

The evolution of the magnetic field and the manner of conversion of thermal energy into different forms in the corona following a solar flare are investigated by means of a nonplane magnetohydrodynamic (MHD) analysis. All three components of magnetic field and velocity are treated in a physically self-consistent manner, with all physical variables as functions of time (t) and two spatial coordinates (r, theta). The difference arising from the initial magnetic field, either twisted (force-free) or non-twisted (potential), is demonstrated. Consideration is given to two initial field topologies (open vs. closed). The results demonstrate that the conversion of magnetic energy is faster for the case of the initially twisted (force-free) field than for the initially untwisted (potential) field. In addition, the twisted field is found to produce a complex structure of the density enhancements.

Wu, S. T.↗
NASA NTRS1984

Magnetohydrodynamic power generation

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.↗
NASA NTRS1983

Viscous, resistive magnetohydrodynamic stability computed by spectral techniques

Expansions in Chebyshev polynomials are used to study the linear stability of one-dimensional magnetohydrodynamic quasi-equilibria, in the presence of finite resistivity and viscosity. The method is modeled on the one used by Orszag in accurate computation of solutions of the Orr-Sommerfeld equation. Two Reynolds-like numbers involving Alfven speeds, length scales, kinematic viscosity, and magnetic diffusivity govern the stability boundaries, which are determined by the geometric mean of the two Reynolds-like numbers. Marginal stability curves, growth rates versus Reynolds-like numbers, and growth rates versus parallel wave numbers are exhibited. A numerical result that appears general is that instability has been found to be associated with inflection points in the current profile, though no general analytical proof has emerged. It is possible that nonlinear subcritical three-dimensional instabilities may exist, similar to those in Poiseuille and Couette flow.

Dahlburg, R. B.↗
NASA NTRS1984

A magnetohydrodynamic model of whistler duct structure in the magnetosphere

In this study, the physical structure for the propagation of whistler waves within a duct in the earth's magnetosphere is investigated by means of magnetohydrodynamic (MHD) theory. Expressions for the current density and induced magnetic field are determined analytically and evaluated in terms of two models for the duct plasma density distribution. It is found that once the duct is formed, forces associated with the current structure will maintain it. MHD instabilities are examined briefly and found to be unlikely to threaten duct maintenance in regions where whistlers are typically observed. Examination of some effects of field-aligned currents suggest that this may be a viable mechanism for duct formation.

Wang, S.↗
NASA NTRS1985

Development of a Global 3-D magnetohydrodynamic computational model for solar wind-cometary and planetary studies

The development of a global, 3-D magnetohydrodynamic computational model is described. This model is used to quantitatively describe the detailed continuum field and plasma interaction process of the solar wind with cometary and planetary magneto/ionopause shapes. The present solar wind/terrestrial planet interaction (Level 1) model (which is based on an axisymmetric gas dynamic plus frozen field approximation to the full MHD equations) is extended to a full 3-D gas dynamic (Level 2) approximation. A mass loading capability in the Level 1 interaction model is implemented.

Stahara, S. S.↗