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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Studies of the inner shelf and coastal sedimentation environment of the Beaufort Sea from ERTS-1

The author has identified the following significant results. Northward flowing rivers of Alaska inundate extensive areas of sea ice during spring breakup. This process has been studied under the ERTS-1 program. Drainage of large volumes of fresh water through the ice at holes and cracks (strudel) causes scour depressions, over 4 m deep, and up to 20 m across in the sea floor below. Strudel scours occur within 30 km of river mouths, generally in areas where ERTS-1 imagery shows less potential for drifting ice to scour the bottom than elsewhere. The shapes and distribution patterns of strudel scours correspond with those of strudel seen in the ice canopy. Densities of scours are highest in the inner areas of overlfow. But strudel scours also occur outside of overflow areas mapped during the last several years. These must be very old. One strudel scour investigated by diving is surrounded by a rim, has vertical walls exposing a tundra horizon, and terminates at a gravel layer 4 m below the lagoon floor. Another terminates at a semi-consolidated layer of silty clay. The gravel and silty clay are pre-Holocene deposits. Mixing of Holocene marine with older sediments by vertical strudel flow causes great variability in sediment types over small areas. These observations complicate interpretation of shallow water deposits of cold climates.

Reimnitz, E.↗
NASA NTRS1973

Buoyant plumes and wakes.

The problem of mixing of pollutants induced by vehicular motions is considered as an example of dispersion that is initially unaffected by atmospheric turbulence. Some models are discussed that have proven helpful in understanding certain aspects of the problem of dispersion of air pollutants in the atmosphere. However, the considerable variability of atmospheric flow, as compared with a laboratory flow, makes the application of these models, both experimental and theoretical, of limited scientific usefulness to the prediction of ambient air-pollutant levels.

Fay, J. A.↗
NASA NTRS1976

An Empirical Model for the Mixing of a Row of Dilution Jets with a Confined Crossflow

An empirical model was developed for predicting the temperature distribution downstream from a row of cool jets injected normally into a hot confined crossflow. The model is based on the assumption that all properly non-dimensionalized vertical temperature profiles can be expressed in a self-similar form. The scaling parameters in this form were correlated in terms of the independent flow and geometric variables. The effect of parametric variation of each of the independent variables on the experimental and predicted profiles are examined. The predicted distributions show excellent agreement with the data over a wide range of the independent variables.

Holdeman, J. D.↗
NASA NTRS1976

An empirical model for the mixing of a row of dilution jets with a confined crossflow

An empirical model has been developed for predicting the temperature distribution downstream of a row of cool jets injected normal to a hot confined crossflow. The model is based on the assumption that all properly non-dimensionalized vertical temperature profiles can be expressed in a self-similar form. The scaling parameters in this form have been correlated in terms of the independent flow and geometric variables. The effect of parametric variation of each of the independent variables on the experimental and predicted profiles are examined. The predicted distributions show excellent agreement with the data over a wide range of the independent variables.

Holdeman, J. D.↗
NASA NTRS1977

Simulation model of erosion and deposition on a barchan dune

Erosion and deposition over a barchan dune near the Salton Sea, California, are modeled by bookkeeping the quantity of sand in saltation following streamlines of transport. Field observations of near surface wind velocity and direction plus supplemental measurements of the velocity distribution over a scale model of the dune are combined as input to Bagnold type sand transport formulas corrected for slope effects. A unidirectional wind is assumed. The resulting patterns of erosion and deposition compare closely with those observed in the field and those predicted by the assumption of equilibrium (downwind translation of the dune without change in size or geometry). Discrepancies between the simulated results and the observed or predicted erosional patterns appear to be largely due to natural fluctuations in the wind direction. The shape of barchan dunes is a function of grain size, velocity, degree of saturation of the oncoming flow, and the variability in the direction of the oncoming wind. The size of the barchans may be controlled by natural atmospheric scales, by the age of the dunes, or by the upwind roughness. The upwind roughness can be controlled by fixed elements or by sand in the saltation. In the latter case, dune scale is determined by grain size and wind velocity.

Howard, A. D.↗
NASA NTRS1979

Space shuttle active-pogo-suppressor control design using linear quadratic regulator techniques

Two methods of active pogo suppression (stabilization) for the space shuttle vehicle were studied analytically. The basis for both approaches was the linear quadratic regulator, state space technique. The first approach minimized root-mean-square pump inlet pressure by using either fullstate feedback, partial-state feedback, or output feedback with a Kalman filter. The second approach increased the modal damping associated with the critical structural modes by using either full-state feedback or reconstructed state feedback. A number of implementable controls were found by both approaches. The designs were analyzed with respect to sensitivity, complexity, and controller energy requirements, as well as controller performance. Practical controllers resulting from the two design approaches tended to use pressure and flow as feedback variables for the minimum-rms method and structural accelerations or velocities for the modal control method. Both approaches are suitable for the design of active pogo-suppression controllers.

Lehtinen, B.↗
NASA NTRS1979

A prediction method for velocity and temperature profiles in a two-dimensional nominally steady turbulent boundary layer

This paper describes a recently developed boundary-layer prediction method for a variable property compressible flow, in which heat transfer takes place primarily by forced convection and for which the mainstream Mach number is small. The leading order terms, in asymptotic expansions for large Reynolds numbers, are obtained for the mean velocity and temperature distribution in both the inner and outer layer of the turbulent boundary layer. Closure in the inner layer is achieved using an analytical model for the mean profiles which is based on the observed coherent structure of the time-dependent inner layer flow. For the outer layer, simple eddy viscosity and conductivity models are developed without recourse to the Reynolds analogy. In the prediction method a numerical solution of the outer layer equations is matched to the analytical inner layer profiles as the computation procedes downstream. Calculations are presented for a range of adverse and favorable pressure gradient flows and the predicted results compare well with existing data.

Weigand, G. G.↗
NASA NTRS1980

Genesis of breath sounds-Preliminary verification of theory

Experimental results are presented which tend to validate a previously developed theory of sound production in the human lung over a particular Reynolds number range. In addition, a new, presently nonunderstood, phenomenon was observed at higher Reynolds number. These results, which show how sound generation in the lung depends upon the physiologically important variables of volume flow rate and bronchial diameter, have potentially important application in noninvasive lung examination and the diagnosis of lung disease.

Patterson, J. L.↗
NASA NTRS1981

Fully implicit shock tracking

A tracking method for solving hyperbolic free boundary problems arising in fluid dynamics is presented. The principal feature of the new approach is that the implicit form is used to simultaneously treat both interior points and boundary conditions. In particular, the location of the free boundary (shock) surface is treated implicitly and coupled with all other unknowns. The method is presented in the context of unsteady one-dimensional flow in a variable area duct with an internal shock wave. The fully implicit method and other strategies for advancing the shock are compared for computing a steady solution via a time asymptotic approach. Issues regarding extension of the method to multiple dimensions are also discussed.

Bell, J. B.↗
NASA NTRS1982

An implicit solution of the three-dimensional Navier-Stokes equations for an airfoil spanning a wind tunnel

An implicit finite-difference algorithm is developed for the numerical solution of the incompressible three dimensional Navier-Stokes equations in the non-conservative primitive-variable formulation. The flow field about an airfoil spanning a wind-tunnel is computed. The coordinate system is generated by an extension of the two dimensional body-fitted coordinate generation techniques of Thompson, as well as that of Sorenson, into three dimensions. Two dimensional grids are stacked along a spanwise coordinate defined by a simple analytical function. A Poisson pressure equation for advancing the pressure in time is arrived at by performing a divergence operation on the momentum equations. The pressure at each time-step is calculated on the assumption that continuity be unconditionally satisfied. An eddy viscosity coefficient, computed according to the algebraic turbulence formulation of Baldwin and Lomax, simulates the effects of turbulence.

Moitra, A.↗
NASA NTRS1983

An algorithm for using a laser anemometer to determine mean streamline patterns in a turbulent flow

The technique of tracing out a mean flow streamline with a three dimensional laser Doppler anemometer (LDA) is discussed with respect to cumulative, systematic errors that are inherent when the motion of the LDA test point is in the direction of the local measured velocity. Using simple potential flows that have variable curvature and inflection points to simulate an LDA experiment, a streamline tracing algorithm is developed that minimizes these errors. Also, the test point path remains close to the correct streamline even when simulated statistical measurement variations are included.

Orloff, K. L.↗
NASA NTRS1983

Perspectives on the mixing of a row of jets with a confined crossflow

An interactive computer code, written for a microcomputer, is presented which displays 2-D and 3-D oblique plots of the temperature distribution downstream of jets mixing with a confined crossflow, for either single-side or opposed jet injection. Temperature profiles calculated with this routine are presented to show the effects of flow and geometric variables on the mixing. Examples are shown to illustrate the different perspectives on the mixing available by exercising various view options. In addition, the program is used to calculate profiles for opposed rows of jets with their centerlines in-line, by assuming that the confining effect of an opposite wall is equivalent to that of a plane of symmetry between opposed jets.

Holdeman, J. D.↗
NASA NTRS1984

Modeling of dilution jet flowfields

The present paper will compare temperature field measurements from selected cases in these investigations with distributions calculated with an empirical model based on assumed vertical profile similarity and superposition and with a 3-D elliptic code using a standard K-E turbulence model. The results will show the capability (or lack thereof) of the models to predict the effects of the principle flow and geometric variables.

Holdeman, J. D.↗
NASA NTRS1984

On modeling dilution jet flowfields

This paper compares temperature field measurements from selected experiments on a single row, and opposed rows, of jets injected into a ducted crossflow with profiles calculated using an empirical model based on assumed vertical profile similarity and superposition, and distributions calculated with a 3-D elliptic code using a standard K-E turbulence model. The empirical model predictions are very good within the range of the generating experiments, and the numerical model resultings, although exhibiting too little mixing, correctly describe the effects of the principal flow and geometric variables.

Holdeman, J. D.↗
NASA NTRS1984

On modeling dilution jet flowfields

This paper compares temperature field measurements from selected experiments on a single row, and opposed rows, of jets injected into a ducted crossflow with profiles calculated using an empirical model based on assumed vertical profile similarity and superposition, and distributions calculated with a 3-D elliptic code using a standard K-E turbulence model. The empirical model predictions are very good within the range of the generating experiments, and the numerical model results, although exhibiting too little mixing, correctly describe the effects of the principal flow and geometric variables.

Holdeman, J. D.↗
NASA NTRS1985

Vapor-liquid phase separator studies

A study of porous plug use for vapor-liquid phase seperation in spaceborne cryogenic systems was conducted. The three main topics addressed were: (1) the usefulness of porous media in designs that call for variable areas and flow rates; (2) the possibility of prediction of main parameters of porous plugs for a given material; and (3) prediction of all parameters of the plug, including secondary parameters.

Yuan, S. W. K.↗
NASA NTRS1983

Suprathermal H(+) and He(2+) in the distant geomagnetic tail ISEE-3 observations

Preliminary ISEE 3 observations of suprathermal H(+) and He(2+) in the distant geomagnetic tail are summarized, with an emphasis on their energy spectra and composition. Regions found near earth are duplicated in the distant tail, but with various regions more intermixed and less distinct. The H(+) and He(2+) energy spectra in all regions and at all geocentric distances for which observations exist are on average not power laws but are well represented by a given expression. The He(2+)/H(+) ratio of 0.03 to 0.07 in the plasma sheet shows no systematic variation with geocentric distance and is two to three times lower than in the other regions. Well-directed, strong, tailward flows distinguish the near bow-shock/magnetosheath region from the geomagnetic tail and plasma sheet where anisotropies are generally smaller and the flow direction more variable although still tailward, indicating source locations at less than 60 earth radii most of the time.

Gloeckler, G.↗
NASA NTRS1984

Altitude testing of a flight weight, self-cooled, 2D thrust vectoring exhaust nozzle

The Augmented Deflector Exhaust Nozzle (ADEN) was tested in PSL-3 at NASA-Lewis Research Center using an F404 engine. The ADEN is a flight weight Single Expansion Ramp Nozzle with thrust vectoring, an internal cooling system utilizing the available engine fan flow, and a variable area throat controlled by the engine control system. Test conditions included dry and max A/B operation at nozzle pressure ratios from 2.0 to 15.0. High nozzle pressure loading was simulated to verify structural integrity at near maximum design pressure. Nozzle settings covered the full range in throat area and + or - 15 deg deflection angle. Test results demonstrated expected aerodynamic performance, cooling system effectiveness, control system stability, and mechanical integrity.

Wooten, W. H.↗