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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

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NASA NTRS1986

Forward-swept wing configuration designed for high maneuverability by use of a transonic computational method

A transonic computational analysis method and a transonic design procedure have been used to design the wing and the canard of a forward-swept-wing fighter configuration for good transonic maneuver performance. A model of this configuration was tested in the Langley 16-Foot Transonic Tunnel. Oil-flow photographs were obtained to examine the wind flow patterns at Mach numbers from 0.60 to 0.90. The transonic theory gave a reasonably good estimate of the wing pressure distributions at transonic maneuver conditions. Comparison of the forward-swept-wing configuration with an equivalent aft-swept-wing-configuration showed that, at a Mach number of 0.90 and a lift coefficient of 0.9, the two configurations have the same trimmed drag. The forward-swept wing configuration was also found to have trimmed drag levels at transonic maneuver conditions which are comparable to those of the HiMAT (highly maneuverable aircraft technology) configuration and the X-29 forward-swept-wing research configuration. The configuration of this study was also tested with a forebody strake.

Mann, M. J.↗

NASA NTRS1984

PIAS: A program for an iterative aeroelastic solution

A Program for an Iterative Aeroelastic Solution (PIAS) is discussed. This will be a modular computer program that combines the use of a finite-element structural analysis code with any linear or nonlinear aerodynamic code. At this point in time, PIAS has been designed but the software has not been written. The idea for this development originated with P. J. (Bud) Bobbitt of the NASA Langley Research Center. There was initial interest in an aeroelastic solution for a separation-induced leading-edge vortex. Some examples of the flow patterns for a low aspect ratio wing are shown. The Leading-Edge Vortex Program, which calculates pressure distributions including the effects of a separation-induced leading-edge vortex, uses an iterative solution method. This led to the concept of an iteration cycle on configuration shape external to the aerodynamic code.

Manro, M. E.↗

NASA NTRS1984

Vortex Flap Technology: a Stability and Control Assessment

A comprehensive low-speed wind tunnel investigation was performed of leading edge vortex flaps applied to representative aircraft configurations. A determination was made of the effects of analytically- and empirically-designed vortex flaps on the static longitudinal and lateral-directional aerodynamics, stability, and control characteristics of fighter wings having leading-edge sweep angles of 45 to 76.5 degrees. The sensitivity to several configuration modifications was assessed, which included the effects of flap planform, leading- and trailing-edge flap deflection angles, wing location on the fuselage, forebody strakes, canards, and centerline and outboard vertical tails. Six-component forces and moments, wing surface static pressure distributions, and surface flow patterns were obtained using the Northrop 21- by 30-inch low-speed wind tunnel.

Carey, K. M.↗

NASA NTRS1987

Automating the parallel processing of fluid and structural dynamics calculations

The NASA Lewis Research Center is actively involved in the development of expert system technology to assist users in applying parallel processing to computational fluid and structural dynamic analysis. The goal of this effort is to eliminate the necessity for the physical scientist to become a computer scientist in order to effectively use the computer as a research tool. Programming and operating software utilities have previously been developed to solve systems of ordinary nonlinear differential equations on parallel scalar processors. Current efforts are aimed at extending these capabilities to systems of partial differential equations, that describe the complex behavior of fluids and structures within aerospace propulsion systems. This paper presents some important considerations in the redesign, in particular, the need for algorithms and software utilities that can automatically identify data flow patterns in the application program and partition and allocate calculations to the parallel processors. A library-oriented multiprocessing concept for integrating the hardware and software functions is described.

Arpasi, Dale J.↗

NASA NTRS1987

Time-partitioning simulation models for calculation on parallel computers

A technique allowing time-staggered solution of partial differential equations is presented in this report. Using this technique, called time-partitioning, simulation execution speedup is proportional to the number of processors used because all processors operate simultaneously, with each updating of the solution grid at a different time point. The technique is limited by neither the number of processors available nor by the dimension of the solution grid. Time-partitioning was used to obtain the flow pattern through a cascade of airfoils, modeled by the Euler partial differential equations. An execution speedup factor of 1.77 was achieved using a two processor Cray X-MP/24 computer.

Milner, Edward J.↗

NASA NTRS1987

Protein crystal growth in low gravity

The solubility and growth mechanism of canavalin were studied, and the applicability of the Schlieren technique to protein crystal growth was investigated. Canavalin which may be crystallized from a basic solution by the addition of hydrogen (H+) ions was shown to have normal solubility characteristics over the range of temperatures (5 to 25 C) and pH (5 to 7.5) studied. The solubility data combined with growth rate data gathered from the seeded growth of canavalin crystals indicated that the growth mechanism at high supersaturation ratios (>1.28) is screw dislocation like. A Schlieren apparatus was constructed and flow patterns were observed in Rochelle salt (sodium potassium tartrate), lysozyme, and canavalin. The critical parameters were identified as the change in density with concentration (dp/dc) and the change in index of refraction with concentration (dn/dc). Some of these values were measured for the materials listed.

Feigelson, Robert S.↗

NASA NTRS1987

Performance and aerodynamic braking of a horizontal-axis wind turbine from small-scale wind tunnel tests

Wind tunnel tests of three 20" diameter, zero twist, zero pitch wind turbine rotor models were conducted in a 7' x 10' wind tunnel to determine the performance of such rotors with NACA 23024 and NACA 64 sub 3-621 airfoil sections. Aerodynamic braking characteristics of a 38% span, 30% chord, vented aileron configuration were measured on the NACA 23024 rotor. Surface flow patterns were observed using fluorescent mini-tufts attached to the suction side of the rotor blades. Experimental results with and without ailerons are compared to predictions using airfoil section data and a momentum performance code. Results of the performance studies show that the 64 sub 3-621 rotor produces higher peak power than the 23024 rotor for a given rotor speed. Analytical studies, however, indicate that the 23024 should produce higher power. Transition strip experiments show that the 23024 rotor is much more sensitive to roughness than the 64 sub 3-621 rotor. These trends agree with analytical predictions. Results of the aileron test show that this aileron, when deflected, produces a braking torque at all tip speed ratios. In free wheeling coastdowns the rotor blade stopped, then rotated backward at a tip speed ratio of -0.6.

Cao, H. V.↗

NASA NTRS1986

Large volume water sprays for dispersing warm fogs

A new method for dispersing of warm fogs which impede visibility and alter schedules is described. The method uses large volume recycled water sprays to create curtains of falling drops through which the fog is processed by the ambient wind and spray-induced air flow; the fog droplets are removed by coalescence/rainout. The efficiency of this fog droplet removal process depends on the size spectra of the spray drops and optimum spray drop size is calculated as between 0.3-1.0 mm in diameter. Water spray tests were conducted in order to determine the drop size spectra and temperature response of sprays produced by commercially available fire-fighting nozzles, and nozzle array tests were utilized to study air flow patterns and the thermal properties of the overall system. The initial test data reveal that the fog-dispersal procedure is effective.

Keller, V. W.↗

NASA NTRS1986

The global evolution of the primordial solar nebula

Complete radial, time-dependent calculations of the structure and evolution of the primordial solar nebula during the viscous diffusion stage are presented. The viscous stress is derived from analytic one-zone models of the vertical nebular structure based on detailed grain opacities. Comparisons with full numerical integrations indicate that the effective viscous alpha parameter is about 0.01. The evolution time of a minimum mass nebula is one-million yr or less. The flow pattern of fluid elements in the disk is examined and the implications the results have on the theory of the formation of the solar system are discussed.

Ruden, S. P.↗

NASA NTRS1987

Modeling free convective gravitational effects in chemical vapor deposition

In this paper, a combined fluid-mechanics, mass-transport, and chemistry model describing CVD in an open-tube atmospheric-pressure flow reactor is developed. The model allows gas-phase reactions to proceed to equilibrium and accounts for finite reaction rates at the surface of the deposition substrate. This model is a useful intermediate step toward a model employing fully rate-limited chemistry. The model is used to predict the effects of free convection on flow patterns, temperature and species-concentration profiles, and local deposition rates for silicon deposited by silane pyrolysis. These results are discussed in terms of implications for CVD of silicon and other compounds, microgravity studies, and techniques for testing and validating the model.

Stinespring, C. D.↗

NASA NTRS1987

Turbulent heat transfer in corrugated-wall channels with and without fins

A numerical study is performed examining flow and heat transfer characteristics in a channel with periodically corrugated walls. The complexity of the flow in this type of channel is demonstrated by such phenomena as flow impingement on the walls, separation at the bend corners, flow reattachment, and flow recirculation. Because of the strong nonisotropic nature of the turbulent flow in the channel, the full Reynolds-stress model was employed for the evaluation of turbulence quantities. Computations are made for several different corrugation periods and for different Reynolds numbers. The results computed by using the present model show excellent agreement with experimental data for mean velocities, the Reynolds stresses, and average Nusselt numbers. The study was further extended to a channel flow where fins are inserted at bends in the channel. It was observed that the insertion of fins in the flow passage has a visible effect on flow patterns and skin friction along the channel wall.

Amano, R. S.↗

NASA NTRS1986

A two-dimensional numerical study of the flow inside the combustion chamber of a motored rotary engine

A numerical study was performed to investigate the unsteady, multidimensional flow inside the combustion chambers of an idealized, two-dimensional, rotary engine under motored conditions. The numerical study was based on the time-dependent, two-dimensional, density-weighted, ensemble-averaged conservation equations of mass, species, momentum, and total energy valid for two-component ideal gas mixtures. The ensemble-averaged conservation equations were closed by a K-epsilon model of turbulence. This K-epsilon model of turbulence was modified to account for some of the effects of compressibility, streamline curvature, low-Reynolds number, and preferential stress dissipation. Numerical solutions to the conservation equations were obtained by the highly efficient implicit-factored method of Beam and Warming. The grid system needed to obtain solutions were generated by an algebraic grid generation technique based on transfinite interpolation. Results of the numerical study are presented in graphical form illustrating the flow patterns during intake, compression, gaseous fuel injection, expansion, and exhaust.

Shih, T. I-P.↗

NASA NTRS1987

A study of a circulation control airfoil with leading/trailing edge blowing

An experimental study of the flow past a two-dimensional circulation control airfoil under steady leading/trailing edge blowing was conducted. The effect of varying jet momentum on the flow field was determined through the use of flow visualization and airfoil force measurements. The flow patterns associated with leading edge blowing, alone and simultaneously with trailing edge blowing, are described and correlated with the lift measurements.

Mclachlan, B. G.↗

NASA NTRS1986

Quantitative model of magnetic coupling between solar wind and magnetosphere

Preliminary results are presented of a quantitative three-dimensional model of an open steady-state magnetosphere configuration incorporating a normal-component distribution corresponding to the subsolar merging-line hypothesis. The distribution of the normal magnetic-field component at the magnetopause is used as input and is used to calculate an interconnection magnetic field that links the internal and external fields. The interconnected field is then used to map the solar-wind electric field onto the polar cap. The resulting polar-cap flow patterns are found to be in agreement with observations.

Toffoletto, F. R.↗

NASA NTRS1987

The radiation impedance of an electrodynamic tether with end connectors

Electrodynamic tethers are wires deployed across the earth's geomagnetic field through which a current is flowing. The radiation impedance of a tether with end connectors carrying an ac current is computed from classical antenna theory. This simulates the use of a tether on a space structure. It is shown that the current flow pattern at the tether connector is critical to determining the overall radiation impedance. If the tether makes direct electrical contact with the ionosphere then radiation impedances of the order of several thousand Ohms can be expected. If the only electrical contact is through the end connectors then the impedance is only a few Ohms for a dc current rising to several tens of Ohms for an ac current with frequencies in the whistler range.

Hastings, Daniel E.↗

NASA NTRS1986

White-light movies of the solar photosphere from the SOUP instrument on Spacelab

Initial results are presented on solar granulation, pores and sunspots from the white-light films obtained by the Solar Optical Universal Polarimeter (SOUP) instrument in Spacelab 2. Several hours of movies were taken at various disk and limb positions in quiet and active regions. The images are diffraction-limited at 0.5 arcsec resolution and are, of course, free of atmospheric seeing and distortion. Properties of the granulation in magnetic and nonmagnetic regions are compared and are found to differ significantly in size, rate of intensity variation, and lifetime. In quiet sun, on the order of fifty-percent of the area has at least one 'exploding granule' occurring in it during a 25-min period. Local correlation tracking has detected several types of transverse flows, including systematic outflow from the penumbral boundary of a spot, motion of penumbral filaments, and cellular flow patterns of supergranular and mesogranular size. Feature tracking has shown that, in the quiet sun, the average granule fragment has a velocity of about one kilometer/second.

Title, A. M.↗

NASA NTRS1988

Photochromic Polyaphrons For Visualization Of Flow

Drops of ultraviolet-activated dyes encapsulated in liquid films reveal flow patterns. Method based on visualization material composed of polyaphrons containing photochromic dye. Polyaphrons are droplets of organic liquid encapsulated in thin layer of another liquid, which holds droplets stably by surface tension. Photochromic dye within a polyaphron acquires color temporarily after exposure to strong ultraviolet light.

Subbaraman, M. R.↗

NASA NTRS1988

Test Apparatus For Oversize Ball-Bearing Models

See-through machine enables direct observation and indirect measurements at moderate speeds. Model of ball bearing, six times larger than real bearing, rotated in test machine. Transparency of walls and simulated lubricant reveal flow patterns and allow visible-light and infrared photographs to be made.

Wagner, William R.↗