Search NASA⌕ Search

SEARCH · Search NASA

Results for “EQUATIONS - DRAG, PROFILE - BICKNELL”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Effect of Solvent Motion on Ion Transport in Electrolytes

We use concentrated solution theory to derive an equation governing solvent velocity in a binary electrolyte when a current passes through it. This equation, in combination with the material balance equation, enables the prediction of electrolyte concentration profiles and species velocities as a function of space and time. This framework is used to predict ion velocities in Li-Li symmetric cells containing a mixture of lithium bis(trifluoromethanesulfonyl)imide and poly(ethylene oxide) (LiTFSI/PEO), for which the cation transference number relative to the solvent velocity, ${t}_{+}^{0},$ can be either positive or negative, depending on salt concentration. Accounting for the solvent motion is increasingly important at higher concentrations. Especially for negative ${t}_{+}^{0},$ if solvent velocity is set to zero, the cation velocity, based on the electrode-electrolyte interface reference frame, is pointed opposite to the current flow. However, when solvent motion is taken into account, the cation velocity, based on the same reference frame, is in the same direction as the current. This analysis demonstrates the importance of accounting for solvent velocity rigorously in seemingly simple systems such as symmetric cells.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1973

An integral turbulent kinetic energy analysis of free shear flows

Mixing of coaxial streams is analyzed by application of integral techniques. An integrated turbulent kinetic energy (TKE) equation is solved simultaneously with the integral equations for the mean flow. Normalized TKE profile shapes are obtained from incompressible jet and shear layer experiments and are assumed to be applicable to all free turbulent flows. The shear stress at the midpoint of the mixing zone is assumed to be directly proportional to the local TKE, and dissipation is treated with a generalization of the model developed for isotropic turbulence. Although the analysis was developed for ducted flows, constant-pressure flows were approximated with the duct much larger than the jet. The axisymmetric flows under consideration were predicted with reasonable accuracy. Fairly good results were also obtained for the fully developed two-dimensional shear layers, which were computed as thin layers at the boundary of a large circular jet.

Peters, C. E.↗
NASA NTRS1975

Rough-to-smooth transition of an equilibrium neutral constant stress layer

A model is proposed for low-level atmospheric flows over terrains of changing roughness length, such as those found at the windward end of landing strips adjoining rough terrain. The proposed model is used to develop a prediction technique for calculating transition wind and shear-stress profiles in the region following surface roughness discontinuity. The model for the transition region comprises two layers: a logarithmic layer and a buffer layer. The flow is assumed to be steady, two-dimensional, and incompressible, with neutral hydrostatic stability. A diagram is presented for a typical wind profile in the transition region, obtained from the logarithmic and velocity defect profiles using shear stress calculated by relevant equations.

Logan, E., Jr.↗
NASA NTRS1976

Evidence that pitch angle scattering is an important loss mechanism for energetic electrons in the inner radiation belt of Jupiter

Analysis of data from the Pioneer 10 flyby discloses that pitch angle scattering plays an important part in determining the distribution of energetic electrons in the inner magnetosphere of Jupiter. Angular distributions measured by a Cerenkov detector reveal that redistribution takes place in pitch angle. Additionally, the radial profile of phase space density along the equator demands simultaneous particle losses. The loss rates are too high to be accounted for by synchrotron radiation loss, but are reasonably attributed to pitch angle scattering into the planetary loss cone.

Fillius, W.↗
NASA NTRS1979

Radio science with Voyager 1 at Jupiter - Preliminary profiles of the atmosphere and ionosphere

A preliminary profile of the atmosphere of Jupiter in the South Equatorial Belt shows (1) the tropopause occurring at a pressure level of 100 millibars and temperature of about 113 K, (2) a higher warm inversion layer at about the 35-millibar level, and (3) a lower-altitude constant lapse rate matching the adiabatic value of about 2 K/km, with the temperature reaching 150 K at the 600-millibar level. Preliminary afternoon and predawn ionospheric profiles at 12 deg and near the equator, respectively, have topside plasma scale heights of 590 km changing to 960 km above an altitude of 3500 km for the dayside, and about 960 km at all measured heights above the peak for the nightside. The higher value of scale height corresponds to a plasma temperature of 1100 K under the assumption of a plasma of protons and electrons in ambipolar diffusive equilibrium. The peak electron concentration in the upper ionosphere is approximately 200,000/cu cm for the dayside and about a factor of 10 less for the nightside. These peaks occur at altitudes of 1600 and 2300 km, respectively. Continuing analyses are expected to extend and refine these results, and to be used to investigate other regions and phenomena.

Eshleman, V. R.↗
NASA NTRS1984

Segregation of Impurities in Directionally Solidified Silicon

Hall measurements and four-point probe resistivity measurements are used to determine the concentration profile of boron and iron in doped semi-conductor silicon ingots grown by the Bridgman technique. The concentration profiles are fitted to the normal segregation equation and the effective segregation coefficient, K sub eff, is calculated. The average value of K sub eff, is 0.803 for boron. For iron, K sub eff, is concentration dependent and is in the range 0.00008 to 0.00012.

Ravishankar, P. S.↗
NASA NTRS1984

The thermosphere of Titan

The vertical structure of Titan's thermosphere is calculated down to the mesopause as a function of local time based on Voyager 1 occultation data. The thermal time scales that characterize the diurnal behavior of the thermosphere are discussed, the input model atmosphere used to calculate the temperature profile is presented, and the dominant heating and cooling mechanisms in the thermosphere are examined. The temperature profiles obtained by integrating the heat transfer equation with and without electron heating are presented and discussed. The implications that derived exospheric temperatures have for the neutral hydrogen torus are investigated. The diurnal exospheric temperature is unlikely to exceed 225 K, averages between 187 and 197 K, and has a variational amplitude of 28 K or less. The vertical extent of the hydrogen cloud is too large to be explained in terms of simple thermal escape of hydrogen from the exosphere.

Friedson, A. J.↗
NASA NTRS1984

Surface roughness studies with DALLAS-detector array for laser light angular scattering

An attempt is made to develop a better mathematical description of optical scattering phenomena, in order to construct an optical scattering apparatus for reliable and routine measurements of roughness parameters without resorting to comparator standards. After a brief outline of optical scattering theory, a description is presented of an experimental instrument for measuring surface roughness which incorporates optical scattering principles. The instrument has a He-Ne laser which illuminates the test surface at a variable angle of incidence. Scattered light distribution is detected by an array of 87 fiber-optic sensors positioned in a rotating semicircular yoke. The output from the detector is digitized and analyzed in a laboratory computer. For a comparison with experimental data, theoretical distributions are calculated by substituting the roughness profiles into the operand of and integral equation for electromagnetic scattering developed by Beckmann and Spizzichino (1963). A schematic diagram of the instrument is provided and the general implications of the experimental results are discussed.

Vorburger, T. V.↗
NASA NTRS1987

On the spatial instability of piecewise linear free shear layers

The main goal of this paper is to clarify the spatial instability of a piecewise linear free shear flow. This is done by obtaining numerical solutions to the Orr-Sommerfeld equation of high Reynolds numbers. The velocity profile chosen is very much like a piecewise linear one, with the exception that the corners have been rounded so that the entire profile is infinitely differentiable. It is found that the (viscous) spatial instability of this modified profile is virtually identical to the inviscid spatial instability of the piecewise linear profile and agrees qwalitatively with the inviscid results for the tanh profile when the shear layers are convectively unstable. The unphysical features, previously identified for the piecewise linear velocity profile, arise only when the flow is absolutely unstable. It is concluded that there is nothing wrong with the inviscid spatial instability of piecewise linear shear flows.

Balsa, T. F.↗
NASA NTRS1990

Melt migration in a silicate liquid-olivine system - An experimental test of compaction theory

An experimentally derived melt migration profile is compared with those obtained from compaction theory. A couple is prepared in which a source-for-melt (a disk composed of a silicate glass and olivine) was placed in contact with a sink-for-melt (a disk of polycrystalline olivine) in order to induce melt migration under laboratory conditions. It is noted that melt infiltrates into the sink disk along triple junctions driven by capillary forces. In order to analyze the melt migration profile in terms of compaction theory, the equations developed by McKenzie (1984) to describe porous flow of a liquid in a deformable matrix were modified. The bouyancy force term is replaced with a capillary force term and governing equations are then solved numerically with the initial boundary conditions specified by the experimental design. Also, it is determined that compaction theory provides a good description of the experimental results provided that the permeability of these solid-liquid materials increases linearly with increasing liquid fraction.

Riley, G. N., Jr.↗
NASA NTRS1991

The symmetric turbulent plane wake downstream of a sharp trailing edge

The analysis and modeling of the symmetric turbulent plane wake downstream of a sharp trailing edge is addressed. A compact description of the flow near the trailing edge is formulated using the results of a previous asymptotic analysis. The new description retains the two-layered structure identified in the previous work, and it clarifies the principal dynamics of the flow in the near-wake outer layer, away from the wake centerline. For zero-pressure-gradient flow, the near-wake outer layer is shown to be represented to leading order by the similarity solution that governs the outer region of the surface boundary layer. The leading perturbation in the outer layer due to the developing near-wake inner-layer flow is identified, and this is shown to be asymptotically smaller than undetermined higher-order terms associated with the surface boundary-layer flow. Results of the new near-wake analysis are used to formulate an algebraic eddy viscosity model for wake flow predictions at arbitrary distances from the trailing edge. The model is used in a numerical solution of the boundary layer equations, and computed velocity and Reynolds stress profiles are shown to compare well with experimental data.

Bogucz, E. A.↗
NASA NTRS1992

Characterization of gaseous helium jet dispersion to atmosphere

A major ground-based experiment to be performed for the Superfluid Helium On Orbit Transfer (SHOOT) program is the accidental loss of the vacuum guard of the super-insulated dewar. The design of the dewar vent-path requires adequate mass removal after a preset pressure is reached due to external heat transfer. The existing helium creates a turbulent buoyant jet, expanding in air with entrainment of the jet interface to the surrounding. Transient analysis is performed for axial and radial jet temperature prediction using the self-similarity assumption applied to mass, momentum, and the energy-balance equations of helium. The predicted jet temperature profiles with vertical and radial expansion up to 1.6 and 1.0 m, respectively, demonstrate the low temperature core established by gaseous helium. For all time steps, the axial and radial temperature predictions are observed to be within 8 and 20 percent, respectively.

Khan, H. J.↗
NASA NTRS1993

Absorption heat pump for space applications

In the first part, the performance of the Absorption Heat Pump (AHP) with water-sulfuric acid and water-magnesium chloride as two new refrigerant-absorbent fluid pairs was investigated. A model was proposed for the analysis of the new working pairs in a heat pump system, subject to different temperature lifts. Computer codes were developed to calculate the Coefficient of Performance (COP) of the system with the thermodynamic properties of the working fluids obtained from the literature. The study shows the potential of water-sulfuric acid as a satisfactory replacement for water-lithium bromide in the targeted temperature range. The performance of the AHP using water-magnesium chloride as refrigerant-absorbent pair does not compare well with those obtained using water-lithium bromide. The second part concentrated on the design and testing of a simple ElectroHydrodynamic (EHD) Pump. A theoretical design model based on continuum electromechanics was analyzed to predict the performance characteristics of the EHD pump to circulate the fluid in the absorption heat pump. A numerical method of solving the governing equations was established to predict the velocity profile, pressure - flow rate relationship and efficiency of the pump. The predicted operational characteristics of the EHD pump is comparable to that of turbomachinery hardware; however, the overall efficiency of the electromagnetic pump is much lower. An experimental investigation to verify the numerical results was conducted. The pressure - flow rate performance characteristics and overall efficiency of the pump obtained experimentally agree well with the theoretical model.

Nguyen, Tuan↗
NASA NTRS1997

Spectral Density of Laser Beam Scintillation in Wind Turbulence: Theory - Part 1

The temporal spectral density of the log-amplitude scintillation of a laser beam wave due to a spatially dependent vector-valued crosswind (deterministic as well as random) is evaluated. The path weighting functions for normalized spectral moments are derived, and offer a potential new technique for estimating the wind velocity profile. The Tatarskii-Klyatskin stochastic propagation equation for the Markov turbulence model is used with the solution approximated by the Rytov method. The Taylor 'frozen-in' hypothesis is assumed for the dependence of the refractive index on the wind velocity, and the Kolmogorov spectral density is used for the refractive index field.

Balakrishnan, A. V.↗
NASA NTRS1999

Waves in the Martian Atmosphere: Results from MGS Radio Occultations

Temperatures retrieved from Mars Global Surveyor radio occultations have been searched for evidence of waves. Emphasis has been on the initial series of occultations between 29 deg N and 64 deg S, obtained during the early martian southern summer, L(sub s) = 264 deg - 308 deg. The profiles exhibit an undulatory behavior that is suggestive of vertically propagating waves. wavelengths approximately 10 km are often dominant, but structure on smaller scales is evident. The undulatory structure is most pronounced between latitudes 29 deg N and 10 deg S, usually in regions of "interesting" topography, e.g., in the Tharsis region and near the edge of Syrtis Major. Several temperature profiles, particularly within 30 deg of the equator, exhibit lapse rates that locally become superadiabatic near the 0.4-mbar level or at higher altitudes. This implies that the waves are "breaking" and depositing horizontal momentum into the atmosphere. Such a deposition may play an important role in modulating the atmospheric winds, and characterizing the spatial and temporal distribution of these momentum transfers can provide important clues to understanding how the global circulation is maintained.

Flasar, F. M.↗
NASA NTRS2000

Model Study of the Sources of Upper Tropospheric Ozone Over The Atlantic, with Emphasis on Interhemispheric Asymmetries

Measurements of ozone and aerosols from ships transecting the Atlantic Ocean reveal considerable interhemispheric asymmetries in the vertical structure of the ozone distribution. There is much more upper tropospheric ozone to the South of the Equator than in the northern hemisphere. These profiles suggest that the air in the southern hemispheric tropics and subtropics has a source in the stratosphere, while that in the northern hemisphere originates in the boundary layer. A model experiment designed to investigate this problem will be discussed. They are based on a new general circulation model, based on a Finite-Volume dynamical core and the physical parametrizations from the Community Climate Model at the National Center for Atmospheric Research (NCAR). The model simulates a climatological state in reasonable agreement with observations, comparable to other contemporary climate models, but has a much more accurate transport capability than most other present-day models. The experiment involves using a suite of tracers, designed to highlight air from different source regions. Some of these (water vapor and ozone) represent real atmospheric quantities, while others are markers which indicate whether the air originates in the stratosphere, the boundary layer, or has traversed regions of convection (for example). The experiments were run for periods of up to one month, initialized from snapshots from a long climate integration of the model. A sample of results will be presented, chosen to illustrate the different sources of air in the upper troposphere and the physical mechanisms by which these air parcels arrived there.

Pawson, Steven↗
NASA NTRS1995

Dependence of Convective Heat Flux Calculations on Roughness Lengths

The zero plane displacement height (d) and aerodynamic roughness length (z0) can be determined separately for momentum, heat, and humidity by using a procedure based on the Levenberg-Marquardt method for solving non-linear equations. This procedure is used to analyze profile data previously collected by Lo (1977) in a forested area in Canada and by Morgan et al (1971) on a field at the University of California at Davis (UCD) in the United States. The UCD data base is used to show the effects of allowing for different roughness lengths (zom,z0h,z0q) in calculating sensible and latent heat flux densities from bulk transfer coefficients.

Convective Heat↗