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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1950

Turbulence and heat stratification

With applications to meteorology in view, the method of small oscillations is used to investigate the stability of a plane laminar boundary layer in which the density depends in a special way on the distance from the plate. It is found that for a constant Froude number the flow becomes more stable as the Richardson number increases until, at a critical value of the Richardson number that depends on the Froude number, the flow is stable for all disturbance wave lengths and Reynolds numbers. The calculated results are verified by experiment.

FLOW VELOCITY - DISTRIBUTION↗
NASA NTRS1980

Transonic Flow Past a Symmetrical Airfoil-- Inviscid and Turbulent Flow Properties

Flowfield measurements are presented for a symmetrical NACA 64A010 airfoil section at transonic conditions. Measurements were obtained for three angles of attack with the freestream Mach number fixed at O.S. The cases studied included a weak shock-wave/boundary-layer interaction, an interaction of medium strength with mild separation, and an interaction of sufficient strength to produce a shock-induced stall situation. Two nonintrusive optical techniques, lower velocimetry and holographic interferometry, were used to characterize the flows. The results include Mach number contours and flow angle distributions in the inviscid flow regions, and turbulent flow properties, including the turbulent Reynolds stresses, of the upper surface viscous layers, and of the near-wake. The turbulent flow measurements reveal that the turbulence fluctuations attain equilibrium with the local mean flow much faster than previously expected.

Johnson D. A.↗
NASA NTRS1990

Airflow Model Testing to Determine the Distribution of Hot Gas Flow and O/F Ratio Across the Space Shuttle Main Engine Main Injector Assembly

Engine 0209, the certification engine for the new Phase 2+ Hot Gas Manifold (HGM), showed severe deterioration of the Main Combustion Chamber (MCC) liner during hot fire tests. One theory on the cause of the damage held that uneven local distribution of the fuel rich hot gas flow through the main injector assembly was producing regions of high oxidizer/fuel (O/F) ratio near the wall of the MCC liner. Airflow testing was proposed to measure the local hot gas flow rates through individual injector elements. The airflow tests were conducted using full scale, geometrically correct models of both the current Phase 2 and the new Phase 2+ HGMs. Different main injector flow shield configurations were tested for each HGM to ascertain their effect on the pressure levels and distribution of hot gas flow. Instrumentation located on the primary faceplate of the main injector measured hot gas flow through selected injector elements. These data were combined with information from the current space shuttle main engine (SSME) power balances to produce maps of pressure, hot gas flow rate, and O/F ratio near the main injector primary plate. The O/F distributions were compared for the different injector and HGM configurations.

Mahorter, L.↗
NASA NTRS1973

Some observed effects of part-span dampers on rotating blade row performance near design point

Detailed measured radial distributions of flow parameters for eight rotors with part-span dampers are used to study the effects of dampers on rotor performance and flow parameters at near design operation. All rotors had a blade tip diameter of about 20 in. and operated at a blade tip speed of about 1400 ft/sec. Several examples demonstrate that, when the local loss variations in the damper flow region are included in an aerodynamic design or analysis procedure, the computed spanwise distributions of flow parameters compare closely with measured distributions.

Esgar, G. M.↗
NASA NTRS1929

Some Effects of Air Flow on the Penetration and Distribution of Oil Sprays

Tests were made to determine the effects of air flow on the characteristics of fuel sprays from fuel injection valves. Curves and photographs are presented showing the airflow throughout the chamber and the effects of the air flow on the fuel spray characteristics. It was found that the moving air had little effect on the spray penetration except with the 0.006 inch orifice. The moving air did, however, affect the oil particles on the outside of the spray cone. After spray cut-off, the air flow rapidly distributed the atomized fuel throughout the spray chamber.

Rothrock, A M↗
NASA NTRS2003

Statistical Distribution of Inflation on Lava Flows: Analysis of Flow Surfaces on Earth and Mars

The surface morphology of a lava flow results from processes that take place during the emplacement of the flow. Certain types of features, such as tumuli, lava rises and lava rise pits, are indicators of flow inflation or endogenous growth of a lava flow. Tumuli in particular have been identified as possible indicators of tube location, indicating that their distribution on the surface of a lava flow is a junction of the internal pathways of lava present during flow emplacement. However, the distribution of tumuli on lava flows has not been examined in a statistically thorough manner. In order to more rigorously examine the distribution of tumuli on a lava flow, we examined a discrete flow lobe with numerous lava rises and tumuli on the 1969 - 1974 Mauna Ulu flow at Kilauea, Hawaii. The lobe is located in the distal portion of the flow below Holei Pali, which is characterized by hummocky pahoehoe flows emplaced from tubes. We chose this flow due to its discrete nature allowing complete mapping of surface morphologies, well-defined boundaries, well-constrained emplacement parameters, and known flow thicknesses. In addition, tube locations for this Mauna Ulu flow were mapped by Holcomb (1976) during flow emplacement. We also examine the distribution of tumuli on the distal portion of the hummocky Thrainsskjoldur flow field provided by Rossi and Gudmundsson (1996). Analysis of the Mauna Ulu and Thrainsskjoldur flow lobes and the availability of high-resolution MOC images motivated us to look for possible tumuli-dominated flow lobes on the surface of Mars. We identified a MOC image of a lava flow south of Elysium Mons with features morphologically similar to tumuli. The flow is characterized by raised elliptical to circular mounds, some with axial cracks, that are similar in size to the tumuli measured on Earth. One potential avenue of determining whether they are tumuli is to look at the spatial distribution to see if any patterns similar to those of tumuli-dominated terrestrial flows can be identified. Since tumuli form by the injection of lava beneath a crust, the distribution of tumuli on a flow should represent the distribution of thermally preferred pathways beneath the surface of the crust. That distribution of thermally preferred pathways may be a function of the evolution of a basaltic lava flow. As a longer-lived flow evolves, initially broad thermally preferred pathways would evolve to narrower, more well-defined tube-like pathways. The final flow morphology clearly preserves the growth of the flow over time, with inflation features indicating pathways that were not necessarily contemporaneously active. Here, we test using statistical analysis whether this final flow morphology produces distinct distributions that can be used to readily determine the distribution of thermally preferred pathways beneath the surface of the crust.

Glazel, L. S.↗
NASA NTRS1988

Flow visualization and pressure distributions for an all-body hypersonic aircraft

A CFD code-validation effort has been conducted at the NASA-Ames 3.5-ft hypersonic wind tunnel, using a generic, 'all-body' hypersonic aircraft configuration model. The CFD methods to be validated encompass approximate inviscid ones and the upwind parabolized Navier-Stokes solver code. Flow visualizations and pressure distributions are obtained for the cases of zero and 15 deg angles of attack. A complex leeward flow is observed at angle-of-attack with crossflow separation and vortices, and significant changes are noted in the transition from the forebody's conical to the afterbody's nonconical flows.

Lockman, William K.↗
NASA NTRS1950

Method of designing cascade blades with prescribed velocity distributions in compressible potential flows

By use of the assumption that the pressure-volume relation is linear, a solution to the problem of designing a cascade for a given turning and with a prescribed velocity distribution along the blade in a potential flow of a compressible perfect fluid was obtained by a method of correspondence between potential flows of compressible and incompressible fluids. The designing of an isolated airfoil with a prescribed velocity distribution along the airfoil is considered as a special case of cascade. If the prescribed velocity distribution is not theoretically attainable, the method provides a means of modifying the distribution so as to obtain a physically significant blade shape. Numerical examples are included.

Costello, George R↗
NASA NTRS1952

Detailed computational procedure for design of cascade blades with prescribed velocity distributions in compressible potential flows

A detailed step-by-step computational outline is presented for the design of two-dimensional cascade blades having a prescribed velocity distribution on the blade in a potential flow of the usual compressible fluid. The outline is based on the assumption that the magnitude of the velocity in the flow of the usual compressible nonviscous fluid is proportional to the magnitude of the velocity in the flow of a compressible nonviscous fluid with linear pressure-volume relation.

Costello, George R↗
NASA NTRS1976

A wind tunnel investigation of circular and straked cylinders in transonic cross flow

Pressure distributions around circular and circular/strake cylinders were measured in a wind tunnel at Mach numbers from 0.6 to 1.2 with Reynolds number independently variable from 10,000 to 100,000. The local pressures are integrated over the cylinder surface to determine the variation of drag coefficient with both Mach number and Reynolds number. Effects of tunnel blockage are evaluated by comparing results from circular cylinders of various diameters at common Mach and Reynolds number conditions. Compressibility effects are concluded to be responsible for a flight reduction of the drag coefficient near Mach 0.7. Drag increases with strake height, presumably approaching a maximum drag corresponding to a flat plate configuration.

Macha, J.↗
NASA NTRS1980

The hydrodynamic role of fish squamosal integument as an analog of surfaces directly formed by turbulent flow. Report 1: Similarity between irregularities in squamosal integument and those on surfaces formed by river bed flow

The distribution of squamae on the fish body and that of the deposits in the bed of the river can be described by the same equation. The curves reflecting the relative elongation and stability of the body shape of the fish continue the curves showing the elongation of bank spit and stability of the bed of the river.

Kudryashov, A. F.↗
NASA NTRS2014

Global Distribution of Lunar Impact Melt Flows

In this study, we analyzed the distribution and properties of 146 craters with impact melt deposits exterior to their rims. Many of these craters were only recently discovered due to their unusual radar properties in the near-global Mini-RF data set. We find that most craters with exterior deposits of impact melt are small, less than 20 kilometers, and that the smallest craters have the longest melt flows relative to their size. In addition, exterior deposits of impact melt are more common in the highlands than the mare. This may be the result of differing target properties in the highlands and mare, the difference in titanium content, or the greater variation of topography in the highlands. We find that 80 percent of complex craters and 60 percent of simple craters have melt directions that are coincident or nearly coincident with the lowest point in their rim, implying that pre-existing topography plays a dominant role in melt emplacement. This is likely due to movement during crater modification (complex craters) or breached crater rims (simple craters). We also find that impact melt flows have very high circular polarization ratios compared to other features on the Moon. This suggests that their surfaces are some of the roughest material on the Moon at the centimeter to decimeter scale, even though they appear smooth at the meter scale.

Cratering↗
NASA NTRS1992

Distributed acoustic receptivity in laminar flow control configurations

A model problem related to distributed receptivity to free-stream acoustic waves in laminar flow control (LFC) configurations is studied, within the Orr-Sommerfield framework, by a suitable extension of the Goldstein-Ruban theory for receptivity due to localized disturbances on the airfoil surface. The results, thus, complement the earlier work on the receptivity produced by local variations in the surface suction and/or surface admittance. In particular, we show that the cumulative effect of the distributed receptivity can be substantially larger than that of a single, isolated suction strip or slot. Furthermore, even if the receptivity is spread out over very large distances, the most effective contributions come from a relatively short region in vicinity of the lower branch of the neutral stability curve. The length scale of this region is intermediate to that of the mean of these two length scales. Finally, it is found that the receptivity is effectively dominated by a narrow band of Fourier components from the wall-suction and admittance distributions, roughly corresponding to a detuning of less than ten percent with respect to the neutral instability wavenumber at the frequency under consideration. The results suggest that the drop-off in receptivity magnitudes away from the resonant wavenumber is nearly independent of the frequency parameter.

Choudhari, Meelan↗
NASA NTRS1955

Calculated spanwise lift distributions, influence functions, and influence coefficients for unswept wings in subsonic flow

Spanwise lift distributions have been calculated for nineteen unswept wings with various aspect ratios and taper ratios and with a variety of angle-of-attack or twist distributions, including flap and aileron deflections, by means of the Weissinger method with eight control points on the semispan. Also calculated were aerodynamic influence coefficients which pertain to a certain definite set of stations along the span, and several methods are presented for calculating aerodynamic influence functions and coefficients for stations other than those stipulated. The information presented in this report can be used in the analysis of untwisted wings or wings with known twist distributions, as well as in aeroelastic calculations involving initially unknown twist distributions.

Diederich, Franklin W↗
NASA NTRS1971

Vibrational population distributions in nonequilibrium nozzle expansion flows

Experimental measurements and theoretical calculations of the vibrational population distribution in nonequilibrium nozzle expansion flows of gas mixtures are reported. These studies were directed toward determining whether vibrational energy exchange pumping could lead to laser action on the vibrational bands of a diatomic molecule. Three different types of experiments were conducted. These showed (1) that vibrational energy was preferentially transferred from N2 to CO in supersonic nozzle flows containing these gases; (2) that under some conditions this vibrational energy exchange pumping mechanism created population inversions in the vibrational levels of CO; and (3) that at large expansion ratios the magnitude of these population inversions was sufficient to sustain lasing in the nozzle. A theoretical model was developed to calculate vibrational state population distributions in gas dynamic expansions of a mixture of diatomic gases. Although only isothermal calculations have been completed, these data indicate that population inversions are predicted for conditions similar to those obtained in the nozzle expansion flows.

Watt, W. S.↗