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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
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Hypersonic rarefied flow over sharp slender cones

Drag, heat transfer, and number flux were measured on sharp cones in the near free, molecule flow regime, and the results were compared with available Monte Carlo calculations. In general, the calculations predicted the magnitude of the data; however, the heat transfer and drag increased with increasing Knudsen number at a faster rate than predicted. Also the drag coefficients measured for the slender cones at high Knudsen number were higher than predicted for free molecule flow. These disagreements between theory and experiment could possibly be attributed to the simplicity of the surface interaction laws assumed in the theory. Reynolds analogy factors obtained from the experimental measurements agreed with free-molecule values and also with that obtained by the Monte Carlo technique.

Kussoy, M. I.↗
NASA NTRS1972

Effects of wall cooling and angle of attack on boundary layer transition on sharp cones at free stream Mach 7.4

Tests were conducted on 5 deg and 15 deg half-angle sharp cones at wall-to-total-temperature ratios of 0.08 to 0.4, and angles of attack from 0 deg to 20 deg. The results indicate that (1) transition Reynolds numbers decrease with decreasing temperature ratio, (2) local transition Reynolds numbers decrease from the windward to the leeward side of the model, and (3) transition data on the windward ray of cones can be correlated in terms of the crossflow velocity gradient, momentum thickness Reynolds number, local Mach number, and cone half-angle.

Mateer, G. G.↗
NASA NTRS1974

Experimental study of sharp and blunt nose streamwise corners at Mach 20

Extensive heat transfer and pressure distribution data and oil flow studies on sharp and blunt-nose streamwise corners at Mach 20 in helium are presented. The far corner boundary layers on the wedge surfaces forming the corners are laminar for most test conditions. Analysis of the data indicates that the corner flow field geometry can be described in terms of the inviscid shock pattern on the two dimensional surfaces forming the corner. Parameters used to correlate blunt shock growth can be used to correlate features of the flow field observed in oil flow photographs in addition to the measured pressure and heat transfer distributions on the models. The flow field structure is described from available experimental data. Regions of the flow in which the structure still is not known are discussed.

Watson, R. D.↗
NASA NTRS1974

Theoretical and experimental longitudinal aerodynamic characteristics of an aspect ratio 0.25 sharp-edge delta wing at subsonic, supersonic, and hypersonic speeds

The suction analogy concept of Polhamus for predicting vortex lift in conjunction with an appropriate potential-flow solution is called the present method. This method is applied to an aspect ratio 0.25 sharp-edge delta wing from a Mach number of 0.143 to 10.4 in free air and at 0.074 in ground effect, and also to an aspect ratio 0.35 triangular crosssectional body at a Mach number of 6.9. The models had subsonic leading edges at the test Mach numbers. Vortex-flow effects could be neither confirmed nor denied to exist at high speeds because of the lack of flow visualization above a Mach number of 0.143. The data, however, could be better predicted by including a vortex-flow effect, although not always to the extent predicted from the present method because of the presence of actual and hypothesized unmodeled flow situations. The method of Nenni and Tung (NASA CR-1860) tended to confirm the existence of vortex flow at hypersonic speeds. The hypersonic-tangent-cone method predicted best the delta-wing results over the test angle-of-attack range and hypersonic Mach number range and did equally as well as the present method for the triangular body.

Fox, C. H., Jr.↗
NASA NTRS1974

Aerodynamic characteristics of three slender sharp-edge 74 degrees swept wings at subsonic, transonic, and supersonic Mach numbers

Slender sharp-edge wings having leading-edge sweep angles of 74 deg have been studied at Mach numbers from 0.60 to 2.80, at angles of attack from about minus 4 deg to 22 deg, and at angles of sideslip from 0 deg to 5 deg. The wings had delta, arrow, and diamond planforms. The experimental tests were made in the Langley 8-foot transonic pressure tunnel and the Langley Unitary Plan wind tunnel test section number 1. The theoretical predictions were made using the theories of NASA TN D-3767 and NASA TN D-6243. The results of the study indicated that the lift and drag characteristics as affected by planform and Mach number could be reasonably well predicted for the delta wing in the subsonic and transonic Mach number range. In the supersonic range, the delta and diamond wings were about equally good in the degree of agreement between experiment and theory. In making drag-due-to-lift predictions the vortex lift effects must be taken into account if reasonable results are to be obtained at moderate or high lift coefficients.

Davenport, E. E.↗
NASA NTRS1975

Maximum two-phase flow rates of subcooled nitrogen through a sharp-edged orifice

Data are presented of an experiment in which subcooled liquid nitrogen was discharged through a sharp-edged orifice at flow rates near the maximum. The data covered a range of inlet stagnation pressures from slightly above saturation to twice the thermodynamic critical pressure. The data were taken along five separate inlet stagnation isotherms ranging from 0.75 to 1.035 times the thermodynamic critical temperature. The results indicate that subcooled liquids do not choke or approach maximum flow in an asymptotic manner even though the back pressure is well below saturation; and orifice flow coefficients are not constant as is frequently assumed. A metastable jet appears to exist which breaks down if the difference between back pressure and saturation pressure is large enough.

Simoneau, R. J.↗
NASA NTRS1974

Simple methods for determining the virtual origin of turbulent boundary layers in hypersonic flow on sharp-edged flat plates

Two methods for determining the virtual origin of turbulent boundary layers in hypersonic flow are evaluated. The results of the analyses are restricted to wind-tunnel models having sharp-edged surfaces with zero or small pressure gradients. Virtual origin and skin friction estimates from these two methods are compared with values from a base method for which the virtual origin is calculated from the measured momentum thickness at a station downstream of boundary layer transition.

Hopkins, E. J.↗
NASA NTRS1975

Maximum two-phase flow rates of subcooled nitrogen through a sharp-edged orifice

An experiment was conducted and data are presented in which subcooled liquid nitrogen was discharged through a sharp-edged orifice at flow rates near the maximum. The data covered a range of inlet stagnation pressure from slightly above saturation to twice the thermodynamic critical pressure. The data were taken along five separate inlet stagnation isotherms ranging from 0.75 to 1.035 times the thermodynamic critical temperature. The results indicate that: (1) subcooled liquids do not choke or approach maximum flow in an asymptotic manner even though the back pressure is well below saturation; (2) orifice flow coefficients are not constant as is frequently assumed. A metastable jet appears to exist which breaks down if the difference between back pressure and saturation pressure is large enough.

Simoneau, R. J.↗
NASA NTRS1975

Organization and use of a Software/Hardware Avionics Research Program (SHARP)

The organization and use is described of the software/hardware avionics research program (SHARP) developed to duplicate the automatic portion of the STOLAND simulator system, on a general-purpose computer system (i.e., IBM 360). The program's uses are: (1) to conduct comparative evaluation studies of current and proposed airborne and ground system concepts via single run or Monte Carlo simulation techniques, and (2) to provide a software tool for efficient algorithm evaluation and development for the STOLAND avionics computer.

Karmarkar, J. S.↗
NASA NTRS1976

Static force tests of a sharp leading edge delta-wing model at ambient and cryogenic temperatures with a description of the apparatus employed

A sharp leading edge delta-wing model was tested through an angle-of-attack range at Mach numbers of 0.75, 0.80, and 0.85 at both ambient and cryogenic temperatures in the Langley 1/3-meter transonic cryogenic tunnel. Total pressure was varied with total temperature in order to hold test Reynolds number constant at a given Mach number. Agreement between the aerodynamic data obtained at ambient and cryogenic temperatures indicates that flows with leading-edge vortex effects are duplicated properly at cryogenic temperatures. The test results demonstrate that accurate aerodynamic data can be obtained by using conventional force-testing techniques if suitable measures are taken to minimize temperature gradients across the balance and to keep the balance at ambient (warm) temperatures during cryogenic operation of the tunnel.

Kilgore, R. A.↗
NASA NTRS1976

Subsonic loads on wings having sharp leading edges and tips

A vortex-lattice method for predicting the aerodynamics of wings having separation at the sharp edges in incompressible flows is extended to compressible subsonic flows using a modified Prandtl-Glauert transformation. Numerical results showing the effect of freestream Mach number on the aerodynamic coefficients are compared with available experimental data for several planforms. It is shown that the proposed method is suitable for predicting the aerodynamic loads on low-aspect wings at moderate angles of attack for high subsonic freestream Mach number. The method is limited to angles of attack up to 12 deg for high subsonic freestream Mach number and to angles of attack up to 20 deg for Mach number not exceeding 0.5.

Kandil, O. A.↗
NASA NTRS1977

Effects of canard location on the aerodynamic characteristics of a sharp-nosed missile at Mach numbers of 1.5 and 2.0

A sharp-nosed missile model with nose-mounted canards and cruciform tail surfaces was tested in the Ames 6- by 6-foot wind tunnel to determine the contributions of the component aerodynamic surfaces on the static aerodynamic characteristics at Mach numbers of 1.5 and 2.0 and a Reynolds number of 1,000,000 based on body diameter. Effect of canard location (at three different axial positions) was investigaed. Data were obtained at angles of attack ranging from 3 deg to 12 deg, roll angles of 0 deg and 45 deg, and canard-deflection angles from 3 deg to 15 deg for various stages of model build-up (i.e., with and without canard and/or tail surfaces). The canard in the most aft position was least effective in trimming the model. With movement of the canard to the most forward position, the model was trimmable at angles of attack up to about 5 deg or 6 deg with panel deflections of 9 deg.

Kassner, D. L.↗
NASA NTRS1978

Computation of hypersonic laminar viscous flow past spinning sharp and blunt cones at high angle of attack

Computational results, obtained with a parabolic Navier-Stokes marching code, are presented for hypersonic viscous flow past spinning sharp and blunt cones at angle of attack. The code takes into account the asymmetries in the flow field resulting from spinning motion and computes the asymmetric shock shape, crossflow and streamwise shear, heat transfer, crossflow separation, and vortex structure. The Magnus force and moments are also computed. Comparisons are made with other theoretical analyses based on boundary-layer and boundary-region equations, and an anomaly is discovered in the displacement thickness contribution to the Magnus force when compared with boundary-layer results. In addition, a new criterion for defining crossflow separation behind spinning bodies is introduced which generalizes the Moore-Rott-Sears criterion for two-dimensional unsteady separation. A condition which characterizes the onset of separation in the flow field is defined.

Agarwal, R.↗
NASA NTRS1982

Report of subpanel on image sharpness

Factors effecting the sharpness of images acquired by multispectral scanners, synthetic aperture radar, thermal infrared sensors, and multispectral linear arrays are defined. Factors associated with the sensor include the atmospheric blur/scatter function, the point spread function of the sensor, the sensor aperture, the filter characteristics, and the sampling rate and quatization effects. Several research tasks are proposed which include investigating the use of optical prefilters which include investigating the use of optical prefilters and the relationships of the instantaneous field of view (aperture width) on the performance of geocorrelation systems.

Source record↗
NASA NTRS1982

A discussion of image sharpness

The image sharpness problem is discussed in terms of a scene which is viewed by a sensor. The sensor has some sort of function which is a nonpoint observing function, and it's a function that gathers energy from some region around a point in the scene. That energy is integrated and is contributed to each point or each sample that is taken of the scene. The samples become the pixels, and the pixels are assembled together into the digital image. Each one has some blurr or some of what is called the point's spread function creating the value of information or data that is seen in each pixel. Then the sensor and electronic part of the system acts on that signal out of the sensor and perhaps adds more blurring, more loss of resolution to the system. Finally, sampling and quantization of the data produce their effects. The signal is sampled at some rate and the digital image is created from that. The sampling or digitizing process puts the continuous voltage into a number of discrete binary levels, and another error is introduced there.

Anuta, P.↗
NASA NTRS1982

Sharp flat plate heat transfer in helium at Mach numbers of 22.8 to 86.8

Surface heat transfer rates were measured on a sharp flat plate at zero angle of attack with helium over a Mach number range of 22.8 to 86.8 in a hypersonic shock tunnel. The density and leading edge Knudsen numbers were varied to span the continuum to near free molecule regimes. The strong interaction parameter varied from 11 to 16,000 with leading edge Knudsen numbers from 0.56 to 17.1, respectively. For high unit Reynolds number the rate of change of the heat transfer coefficient with the strong interaction parameter agreed well with the strong interaction theory of Li and Nagamatsu (1953, 1955).

Nagamatsu, H. T.↗
NASA NTRS1982

Sharp edges of planetary rings

The ring systems of Saturn and Uranus exhibit several sharp edges, across which the optical depth drops from order unity to essentially zero. At least two and perhaps all of these features are associated with the location of orbital resonances between a satellite and the ring particles. It is remarkable that the optical depth varies on a distance scale which is much finer than that over which angular momentum can be transferred between a satellite and the ring material. The important features of this phenomenon are: (1) a perturbed band of width Delta a/a of about (satellite mass/planetary mass) to the 1/2 power adjacent to the edge within which the angular momentum transfer occurs, (2) streamlines perturbed such that the angular momentum luminosity decreases smoothly across the band to zero at the edge even though the optical depth remains constant, and (3) dynamical equilibrium requires a relation between the random velocity, the rate of deformation and the optical depth.

Borderies, N.↗