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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Application of wave mechanics theory to fluid dynamics problems: Fundamentals

The application of the basic formalistic elements of wave mechanics theory is discussed. The theory is used to describe the physical phenomena on the microscopic level, the fluid dynamics of gases and liquids, and the analysis of physical phenomena on the macroscopic (visually observable) level. The practical advantages of relating the two fields of wave mechanics and fluid mechanics through the use of the Schroedinger equation constitute the approach to this relationship. Some of the subjects include: (1) fundamental aspects of wave mechanics theory, (2) laminarity of flow, (3) velocity potential, (4) disturbances in fluids, (5) introductory elements of the bifurcation theory, and (6) physiological aspects in fluid dynamics.

Krzywoblocki, M. Z. V.↗
NASA NTRS1974

Application of wave mechanics theory to fluid dynamics problems: Boundary layer on a circular cylinder including turbulence

The application of the elements of quantum (wave) mechanics to some special problems in the field of macroscopic fluid dynamics is discussed. Emphasis is placed on the flow of a viscous, incompressible fluid around a circular cylinder. The following subjects are considered: (1) the flow of a nonviscous fluid around a circular cylinder, (2) the restrictions imposed the stream function by the number of dimensions of space, and (3) the flow past three dimensional bodies in a viscous fluid, particularly past a circular cylinder in the symmetrical case.

Krzywoblocki, M. Z. V.↗
NASA NTRS1987

Dynamical modeling of a planetary wave mechanism for a Martian polar warming

The mechanisms involved in the global dust storm and polar warming seen in the Martian atmosphere by the Viking IRTM during the winter solstice of 1977 are investigated theoretically by means of numerical simulations. A two-component dynamical model (based on the combined action of a zonally symmetric 'Hadley' circulation at low and middle latitudes and a planetary-wave circulation at middle and high latitudes) is constructed by analogy to the model of Holton and Mass (1976) for terrestrial sudden stratospheric warmings. The Viking data and simulation results are presented in extensive graphs and characterized in detail. It is demonstrated that a planetary-wave mechanism, based primarily on wavenumber 1 and including a high degree of topographical or thermal wave forcing, can reproduce the observed polar warming. The roles of radiative damping, dissipation, and the transport of dust and water are explored.

Barnes, Jeffrey R.↗
NASA NTRS2012

Eurasian Heat Waves: Mechanisms and Predictability

This study uses the NASA MERRA reanalysis and GEOS 5 model simulations to examine the causes of Eurasian heat waves including the recent extreme events that occurred in Europe during 2003 and in Russia during 2010. The focus is on the warm season and the part of the Eurasian continent that extends north of about 40oN, or roughly to the north of the mean upper tropospheric jet stream. The results show that such extreme events are an amplification of natural patterns of atmospheric variability that develop over the Eurasian continent as a result of internal atmospheric forcing. The amplification occurs when the wave occasionally becomes locked in place for several weeks to months resulting in extreme heat and drying with the location depending on the phase of the upper atmospheric wave. An ensemble of very long GEOS-S model simulations (spanning the 20th century) forced with observed SST and greenhouse gases show that the model is capable of generating very similar heat waves, and that they have become more intense in the last thirty years as a result of the overall warming of the Asian continent. Sensitivity experiments with perturbed initial conditions indicate that these events have limited predictability.

Wang, Hailan↗
NASA NTRS1982

Free-electron laser from wave-mechanical beats of 2 electron beams

It is possible, though technically difficult, to produce beams of free electrons that exhibit beats of a quantum mechanical nature. (1) the generation of electromagnetic radiation, e.g., light, based on the fact that the beats give rise to alternating charge and current densities; and a frequency shifter, based on the fact that a beam with beats constitutes a moving grating. When such a grating is exposed to external radiation of suitable frequency and direction, the reflected rediation will be shifted in frequency, since the grating is moving. A twofold increase of the frequency is readily attainable. It is shown that it is impossible to generate radiation, because the alternating electromagnetic fields that accompany the beats cannot reform themselves into freely propagating waves. The frequency shifter is useless as a practical device, because its reflectance is extremely low for realizable beams.

Lichtenstein, R. M.↗
NASA NTRS1974

Application of wave mechanics theory to fluid dynamics problems: Flat plate flow

The characteristics of the flow in the laminar boundary layer along an infinitely long flat plate are discussed. The flow may be disturbed or not, depending on the situation. The physical, natural aspects of the flow, either a laminar flow free from disturbances or a flow which originally is a laminar one with disturbances superimposed upon it. Oscillograms of turbulence in wind tunnel tests and in the wake of a cylinder are presented.

Krzywoblocki, M. Z. V.↗
NASA NTRS1980

Mechanisms of wave transformation in finite-depth water

Mechanisms of wave transformation in finite-depth water are investigated. The linear mechanisms examined are percolation, bottom motion, shoaling, and refraction. The nonlinear mechanisms examined are wave-wave interaction and bottom friction. New exact computations of the nonlinear transfer for finite-depth waves are presented for some directional wave spectra. These mechanisms are found to explain satisfactorily wave decay observations obtained at several sites with different bottom sediment properties. The decay rates at these sites are found to be dominated by different mechanisms which are determined by the bottom conditions. As an example, detailed calculations are presented for data obtained at the Jonswap site.

Shemdin, O. H.↗
NASA NTRS1989

Interfacial wave theory for dendritic structure of a growing needle crystal. I - Local instability mechanism. II - Wave-emission mechanism at the turning point

The complicated dendritic structure of a growing needle crystal is studied on the basis of global interfacial wave theory. The local dispersion relation for normal modes is derived in a paraboloidal coordinate system using the multiple-variable-expansion method. It is shown that the global solution in a dendrite growth process incorporates the morphological instability factor and the traveling wave factor.

Xu, Jian-Jun↗
NASA NTRS1993

A comparison between numerically modelled and experimentally measured loss mechanisms in wave rotors

A numerical model has been developed which is capable of predicting the performance of a wave rotor (pressure exchanger) of specified geometry over a wide range of operating conditions. The model can account for the major loss mechanisms of leakage from the tube ends, fluid viscosity, heat transfer to the tube wails, finite tube opening time, shock waves, and non-uniform port flows. It is a one dimensional flow model which follows a single tube as it rotates past the various stationary ports. Since the model is relatively simple (i.e., one dimensional) it uses little computer time. This makes it suitable for design as well as analytical purposes. This paper will present a brief description of the model then discuss a comparison between the model predictions and several wave rotor experiments.

Paxson, Daniel E.↗
NASA NTRS1993

A Comparison Between Numerically Modelled and Experimentally Measured Loss Mechanisms in Wave Rotors

A numerical model has been developed which is capable of predicting the performance of a wave rotor (pressure exchanger) of specified geometry over a wide range of operating conditions. The model can account for the major loss mechanisms of leakage from the tube ends, fluid viscosity, heat transfer to the tube walls, finite tube opening time, shock waves, and non-uniform port flows. It is a one dimensional flow model which follows a single tube as it rotates past the various stationary ports. Since the model is relatively simple (i.e. one dimensional) it uses little computer time. This makes it suitable for design as well as analytical purposes. This paper will present a brief description of the model then discuss a comparison between the model predictions and several wave rotor experiments.

Paxson, Daniel E.↗
NASA NTRS1990

Re-forming supercritical quasi-parallel shocks. II - Mechanism for wave generation and front re-formation

This paper continues the study of Thomas et al. (1990) in which hybrid simulations of quasi-parallel shocks were performed in one and two spatial dimensions. To identify the wave generation processes, the electromagnetic structure of the shock is examined by performing a number of one-dimensional hybrid simulations of quasi-parallel shocks for various upstream conditions. In addition, numerical experiments were carried out in which the backstreaming ions were removed from calculations to show their fundamental importance in reformation process. The calculations show that the waves are excited before ions can propagate far enough upstream to generate resonant modes. At some later times, the waves are regenerated at the leading edge of the interface, with properties like those of their initial interactions.

Winske, D.↗
NASA NTRS1974

Implications of the Pioneer 10 measurements of the Jovian magnetic field for theories of Io-modulated decametric radiation

The configuration of the magnetic field of Jupiter imposes constraints upon theoretical models of decametric emission triggered by Io, with respect to such features as the frequency of the emission, the density of the inner plasmasphere, and the beaming pattern. Owing to the northern offset of the field model reported by Smith et al. (1974), the upper ranges of observed decametric frequencies can be equated to the electron gyrofrequency only in the northern hemisphere, in regions outside the trapping volume of radiation-belt particles. Emission mechanisms in which the frequency is at or very near the electron gyrofrequency must be stimulated by Io either through acceleration and precipitation of particles or through generation of MHD waves. Mechanisms invoking trapped particles are consistent with wave amplification in the southern hemisphere at the upper hybrid frequency, imposing a lower bound on the density of thermal plasma near the planet.

Smith, R. A.↗
NASA NTRS1994

The Large Impact Process Inferred from the Geology of Lunar Multiring Basins

The study of the geology of multiring impact basins on the Moon over the past ten years has given us a rudimentary understanding of how these large structures have formed and evolved on the Moon and other bodies. Two-ring basins on the Moon begin to form at diameters of about 300 km; the transition diameter at which more than two rings appear is uncertain, but it appears to be between 400 and 500 km in diameter. Inner rings tend to be made up of clusters or aligned segments of massifs and are arranged into a crudely concentric pattern; scarp-like elements may or may not be present. Outer rings are much more scarp-like and massifs are rare to absent. Basins display textured deposits, interpreted as ejecta, extending roughly an apparent basin radius exterior to the main topographic rim. Ejecta may have various morphologies, ranging from wormy and hummocky deposits to knobby surfaces; the causes of these variations are not known, but may be related to the energy regime in which the ejecta are deposited. Outside the limits of the textured ejecta are found both fields of satellitic craters (secondaries) and light plains deposits. Impact melt sheets are observed on the floors of relatively unflooded basins. Samples of impact melts from lunar basins have basaltic major-element chemistry, characterized by K, rare-earth elements (REE), P, and other trace elements of varying concentration (KREEP); ages are between 3.8 and 3.9 Ga. These lithologies cannot be produced through the fusion of known pristine (plutonic) rock types, suggesting the occurrence of unknown lithologies within the Moon. These melts were probably generated at middle to lower crustal levels. Ejecta compositions, preservation of pre-basin topography, and deposit morphologies all indicate that the excavation cavity of multiring basins is between about 0.4 and 0.6 times the diameter of the apparent crater diameter. Basin depths of excavation can be inferred from the composition of basin ejecta. A variety of mechanisms has been proposed to account for the formation of basin rings but none of them are entirely plausible. Mechanisms can be divided into two broad groups: (1) forcible uplift due to fluidization of the target; (2) concentric, brittle, fracturing and failure of the target, on regional (megaterraces) to global scales (lithospheric fracturing). Most basin rings are spaced at a constant factor on all planets. Evidence supports divergent ringforming models, so it may be that the ring-locating mechanism differs from the ring-forming mechanism. Thus, large-scale crustal foundering (megaterracing) could occur along concentric zones of weakness created by some type of resonant wave mechanism (fluidization and uplift); such immediate crustal adjustment could then be followed by long-term adjustment of the fractured lithosphere.

Spudis, Paul D.↗