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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 NTRS1976

Noise generated by impingement of turbulent flow on airfoils of varied chord, cylinders, and other flow obstructions

Noise spectra were measured in three dimensions for several surfaces immersed in turbulent flow from a jet and over a range of flow conditions. The data are free field and were corrected to remove the small contributions of jet noise, atmospheric attenuation and feedback tones. These broadband data were compared with the results of available theories which are only strictly applicable to simple geometries over a limited range of conditions. The available theories proved to be accurate over the range of flow, chord length, thickness, angle of attack, and surface geometries defined by the experiments. These results apply to the noise generated by fixed surfaces in engine passages, the lifting surfaces of aircraft and also to fan noise.

Olsen, W. A.↗
NASA NTRS1976

An experimental and computational investigation of the flow field about a transonic airfoil in supercritical flow with turbulent boundary-layer separation

A combined experimental and computational research program for testing and guiding turbulence modeling within regions of separation induced by shock waves incident on turbulent boundary layers is described. Specifically, studies are made of the separated flow over the rear portion of an 18%-thick circular-arc airfoil at zero angle of attack in high Reynolds number supercritical flow. The measurements include distributions of surface static pressure and local skin friction. The instruments employed include high-frequency response pressure cells and a large array of surface hot-wire skin-friction gages. Computations at the experimental flow conditions are made using time-dependent solutions of ensemble-averaged Navier-Stokes equations, plus additional equations for the turbulence modeling.

Rubesin, M. W.↗
NASA NTRS1977

Measurements of surface-pressure and wake-flow fluctuations in the flow field of a whitcomb supercritical airfoil

Measurements of surface pressure and wake flow fluctuations were made as part of a transonic wind tunnel investigation into the nature of a supercritical airfoil flow field. Emphasis was on a range of high subsonic Mach numbers and moderate lift coefficients corresponding to the development of drag divergence and buffeting. Fluctuation data were analyzed statistically for intensity, frequency content, and spatial coherence. Variations in these parameters were correlated with changes in the mean airfoil flow field.

Roos, F. W.↗
NASA NTRS1976

The scarcity of mappable flow lobes on the lunar maria - Unique morphology of the Imbrium flows

Unique features of Imbrium lava flows are their thickness (10-30 + m) and lengths (up to 400 km for phase-III, and up to 600 km for phase-II) when compared along later Imbrium and Eratosthenian units. They are distinct by virtue of their inferred short-lived (on the order of days) and extremely rapid rates of effusion. It is shown that there are numerous other basalt eruptives within the young blue western maria. The emplacement of these flows was by complex multilayering and intertonguing of individual flow units with thicknesses less than 10 m. They are generally restricted to the near vicinity of multiple vent sources.

Schaber, G. G.↗
NASA NTRS1978

Measurements in the turbulent boundary layer at constant pressure in subsonic and supersonic flow. Part 1: Mean flow

Experiments were carried out to test the accuracy of laser Doppler instrumentation for measurement of Reynolds stresses in turbulent boundary layers in supersonic flow. Two facilities were used to study flow at constant pressure. In one facility, data were obtained on a flat plate at M sub e = 0.1, with Re theta up to 8,000. In the other, data were obtained on an adiabatic nozzle wall at M sub e = 0.6, 0.8, 1.0, 1.3, and 2.2, with Re theta = 23,000 and 40,000. The mean flow as observed using Pitot tube, Preston tube, and floating element instrumentation is described. Emphasis is on the use of similarity laws with Van Driest scaling and on the inference of the shearing stress profile and the normal velocity component from the equations of mean motion. The experimental data are tabulated.

Collins, D. J.↗
NASA NTRS1978

Computational flow development for unsteady viscous flows: Foundation of the numerical method

A procedure is presented for effective consideration of viscous effects in computational development of high Reynolds number flows. The procedure is based on the interpretation of the Navier-Stokes equations as vorticity transport equations. The physics of the flow was represented in a form suitable for numerical analysis. Lighthill's concept for flow development for computational purposes was adapted. The vorticity transport equations were cast in a form convenient for computation. A statement for these equations was written using the method of weighted residuals and applying the Galerkin criterion. An integral representation of the induced velocity was applied on the basis of the Biot-Savart law. Distribution of new vorticity, produced at wing surfaces over small computational time intervals, was assumed to be confined to a thin region around the wing surfaces.

Bratanow, T.↗
NASA NTRS1978

Measurements of inlet flow distortions in an axial flow fan (6 and 9 blade rotor)

A large quantity of experimental data on inlet flow distortions in an axial flow fan were obtained. The purpose of the study was to determine the effects of design and operating variables and the type of distortion on the response of an axial flow turbomachinery rotor. Included are background information and overall trends observed in distortion attenuation and unsteady total pressure losses.

Barr, L. C.↗
NASA NTRS1978

The effects of design and operating variables on the response of an axial flow fan to inlet flow distortions

The results of a study of total pressure and velocity circumferential distortions in an axial-flow fan are presented. Some of the fundamental experimental data needed to understand distorted flow phenomena as affected by design and operating variables are provided. The flow through an isolated rotor was examined at various operating conditions with six different distortions and three different blade stagger angles. Circumferential surveys were conducted upstream and downstream of the rotor using five-hole probes in the nonnulling mode. The total pressure and axial velocity distortion data were analyzed to determine the degree of distortion attenuation as a function of blade stagger angle, mean incidence angle, and reduced frequency. The results indicate that, for the rotors tested, the mean incidence or loading has very little effect on the distortion attenuation.

Yocum, A. M., II↗
NASA NTRS1978

Mantle flow pressure and the angle of subduction - Non-Newtonian corner flows

Corner flows of Newtonian and non-Newtonian fluids are used to model the flow in a subduction zone which is viscously driven by the motions of the converging plates and the descending slab. The pressures induced by the flow tend to lift the slab up beneath the overriding plate thereby offsetting the tendency of gravity to align the slab with the vertical. The low angles of subduction observed in Peru and Central Chile may be the result of strong dynamic pressures forcing the slab up against the overriding plate. Viscous coupling between the overriding plate and the downgoing slab is essential if the nonvertical dips of slabs are a consequence of the balance between gravitational and pressure torques. For a Newtonian mantle, shear stresses and pressures on the top of the slab are comparable. If the mantle is non-Newtonian, however, the pressures greatly exceed the shear stresses, for most acute dip angles. Thus frictional forces on the top and bottom surfaces of slabs are less important in resisting slab descent into a non-Newtonian mantle than they are in resisting penetration into a Newtonian mantle.

Tovish, A.↗
NASA NTRS1979

Comparisons of the hydraulics of water flows in Martian outflow channels with flows of similar scale on earth

The hydraulics of channelized water flows on Mars and the resulting sediment transport rates are calculated, and similar computations are performed for such terrestrial analogs as the Mississippi River and the catastrophic Lake Missoula floods that formed the Channeled Scabland in eastern Washington State. The morphologies of deep-sea channels formed by catastrophic turbidity currents are compared with the Martian channels, many similarities are pointed out, and the hydraulics of the various flows are compared. The results indicate that the velocities, discharges, bottom shear stresses, and sediment-transport capacity of water flows along the Martian channels would be comparable to those of the oceanic turbidity currents and the Lake Missoula floods. It is suggested that the submarine canyons from which turbidity currents originate are the terrestrial counterparts to the chaotic-terrain areas or craters that serve as sources for many of the Martian channels.

Komar, P. D.↗
NASA NTRS1980

An axial flow research compressor facility designed for flow measurement in rotor passages

An axial flow research compressor facility, which is designed for relative flow measurement, is described in this paper. The facility has a rotating probe traverse mechanism which is capable of traversing hot wire, pitot and other probes at 0.09 deg intervals across the rotor blade passage. The data transmission system includes rotating transducers, pressure transfer device, ten-channel mercury slip ring unit, scanivalve, etc. The instrumentation includes on-line data processing capability. A brief description of probes used as well as some typical data on the rotor blade static pressure, rotor endwall flow and rotor wake characteristics are given in the paper.

Lakshminarayana, B.↗
NASA NTRS1980

Comparison between optical measurements and a numerical solution of the flow field within a transonic axial-flow compressor rotor

A comparison between numerical and experimental results is presented for the flowfield within a transonic axial-flow compressor rotor. The rotor was tested at design speed and a wide open throttle discharge condition. The relative tip Mach number was 1.4. A laser anemometer system was used to measure velocity and flow angle upstream, within, and downstream of the rotor. A holographic interferometer was used to visualize the rotor shock system near the tip. The computational procedure solves the full three-dimensional Euler equations using a time-marching technique. Shock location and shape determined from the two optical systems are compared. Calculated relative Mach number and flow angle contours, shock locations, and shock strength are compared to values measured with the laser anemometer.

Strazisar, A. J.↗
NASA NTRS1981

Effects of solid particles suspended in fluid flow through an axial flow compressor stage

An approximate method for calculating the flow properties of gas-particle mixture flowing over blades in a cascade is studied. Using an analytical method, the solid particle trajectory and location of collisions between the solid particles and the blade surfaces are determined. In addition an experimental investigation of the trajectories and velocities of solid particles suspended in a fluid passing through an axial flow compressor cascade was performed. The cascade blades were made of 2024 aluminum alloy and the solid particles used were quartz sand with average diameter of 165 microns. The following parameters were investigated: blade pressure distribution, and total pressure loss coefficient, both depending on the degree of erosion. In addition, a theoretical estimation of the blade erosion is compared with the experimental data.

Tabakoff, W.↗
NASA NTRS1982

Aerosound from corner flow and flap flow

Noise generation at the edge of a wing flap is analyzed. The phenomenon as a single vortex moving around a corner in an incompressible, potential flow is modelled. Vortex image retarding effects are proposed as an explanation for small Strouhal numbers. The model surface pressures, sound pressures (using Curle's theory), and Mach number dependencies agree with wind tunnel experiments. A double pressure peak is found in the model (credited to image action) which is qualitatively similar to measured sound correlations. Incompressible flow aerosound calculations are discussed. The effects of a series of vortices moving in the same idealized potential flow are also studied. The vortices are assumed to be statistically independent so their intensities can be added. The frequency of appearance of the vortices are determined from measurements. Diffraction effects caused by the presence of the wing near the dipole sound radiators on the flap surfaces are included.

Meecham, W. C.↗
NASA NTRS1982

Three dimensional flow field inside the passage of a low speed axial flow compressor rotor

Measurements of the subsonic flow in the rotor passage of a single stage axial flow compressor were made to study the nature of the flow field and to verify the existing numerical codes. The velocity and pressure fields were measured across the entire rotor passage at six axial locations and at five radial locations. A five-hole probe, rotating with the rotor, was used to measure the three components of velocity, the static and the total pressure. The experimental results are compared with the predictions from Katsanis and McNally's computer program. The agreement between the two is good for most of the cases.

Pouagare, M.↗
NASA NTRS1982

Evaluation of a wall-flow direction probe for measurements in separated flows

The upstream-downstream flow direction intermittency is an important parameter that can quantitatively describe the stages of flow separation. This paper gives an improved design for a wall-flow-direction probe. Intermittency measurements made using this modified probe show agreement within experimental uncertainties with direct measurements made using a LDV, although both the unmodified and modified probe designs produce results that are consistently higher than those for the LDV.

Shivaprasad, B. G.↗
NASA NTRS1982

Turbulent transport modeling of shear flows around an aerodynamic wing. Development of turbulent near-wall model and its application to recirculating flows

Progress in implementing and refining two near-wall turbulence models in which the near-wall region is divided into either two or three zones is outlined. These models were successfully applied to the computation of recirculating flows. The research was further extended to obtaining experimental results of two different recirculating flow conditions in order to check the validity of the present models. Two different experimental apparatuses were set up: axisymmetric turbulent impinging jets on a flat plate, and turbulent flows in a circular pipe with a abrupt pipe expansion. It is shown that generally better results are obtained by using the present near-wall models, and among the models the three-zone model is superior to the two-zone model.

Amano, R. S.↗