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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Non Equilibrium Ionization in the Local Hot Bubble

The existence of a local hot bubble surrounding the solar system was shown by soft X-ray surveys. The spectrum of this hot interstellar medium was measured with solid state detectors during rocket flights between 300 and 1000 eV. The good resolution of the experiment permitted to measure C V, C VI and O VII line emissivities with good accuracy. These data are used to put some constraints on a model where the emission comes from a supernova remnant expanding in a finite pressure medium. The importance of nonequilibrium ionization phenomena is shown.

Arnaud, M.↗
NASA NTRS1984

Analysis of airfoil leading-edge separation bubbles

A local inviscid-viscous interaction technique was developed for the analysis of low speed airfoil leading edge transitional separation bubbles. In this analysis an inverse boundary layer finite difference analysis is solved iteratively with a Cauchy integral representation of the inviscid flow which is assumed to be a linear perturbation to a known global viscous airfoil analysis. Favorable comparisons with data indicate the overall validity of the present localized interaction approach. In addition numerical tests were performed to test the sensitivity of the computed results to the mesh size, limits on the Cauchy integral, and the location of the transition region.

Vatsa, V. N.↗
NASA NTRS1984

Velocity of a freely rising gas bubble in a soda-lime silicate glass melt

A comparison is conducted between measured velocities for the buoyant rise of single bubbles of varying size and composition, in a soda-lime silicate glass melt, with the steady state velocities predicted by the Stokes and Hadamard-Rybczynski formulas. In all cases, the data are noted to fit the Hadamard-Rybczynski expression for steady state rise speed considerably better than the Stokes formula.

Hornyak, E. J.↗
NASA NTRS1985

Variation of the temperature coefficient of collapse field in bismuth-based bubble garnets

An approximation to the collapse-field formula is used to show its dependence on magnetization and wall energy and the effect of additions of Gd, Sm, and Eu on 1-micron Bi:YIG bubble materials. The collapse field, magnetization, and wall energy are fitted to quadratic functions of temperature from -50 to 150 C. It is shown that the addition of the various classes of rare earths reduces the temperature derivative of the collapse field in Bi:YIG. Gd influences the collapse field through the magnetization, Sm affects it through the domain wall energy, and Eu does both. The singular magnetic properties of Eu result in the most nearly constant temperature dependence of the collapse field and the best match to a barium-ferrite bias magnite.

Fratello, V. J.↗
NASA NTRS1985

Separation bubble behavior for a NACA 23009 airfoil

Results are reported of experiments with smoke-wire flow visualization applied to characterizing the conditions conducive to formation of a separation bubble on an airfoil in low Re flow. An airfoil was used which spanned the test channel of the wind tunnel designed for low turbulence and noise. A wire coated with mineral oil was stretched across the channel upstream of the airfoil and heated. The smoke it gave off was flash-illuminated and photographed with ASA 3000 film. Extending the airfoil over the entire section yielded photographs that gave an essentially two-dimensional perspective. Angles of attack from 0-10 deg were investigated at Re of 33,000, 66,000, 100,000 and 133,000. Sample photographs illustrate the usefulness of the technique and apparatus in the flow regimes examined, particularly when used in conjunction with pressure tap data from the airfoil surface.

Fisher, S. S.↗
NASA NTRS1987

Self-Stabilizing Storage Loops for Magnetic-Bubble Memories

Adjacent, sinusoidal loops provide defect-tolerant, self-stabilizing structures. New technology consists of three components providing self-stabilizing structures. First, apertures positioned so bubbles propagate alternately into hexagonally related positions and directly opposed positions; addition of straight barriers by ion milling or implantation of garnet adds transverse stability but leaves longitudinally metastable postions. Second, modification of barrier to sinusoidal shape provides "energy wells" in longitudinal direction at opposed positions and eliminates metastability. Third, positioning and phasing of counterrotating storage loops, provide stable hexagonal support between adjacent loops.

Nelson, Gary L.↗
NASA NTRS1986

Rotating bubble membrane radiator for space applications

An advanced radiator concept for heat rejection in space is described which uses a two-phase working fluid to radiate waste heat. The development of advanced materials and the large surface area per mass makes the Bubble Membrane Radiator an attractive alternative to both conventional heat pipes and liquid droplet radiators for mid to high temperature applications. A system description, a discussion of design requirements, and a mass comparison with heat pipes and liquid droplet radiators are provided.

Webb, Brent J.↗
NASA NTRS1985

Six micrometer period wide-gap permalloy magnetic bubble devices

This report describes the progress made toward the goal of developing a 1 Mbit bubble memory chip, based on a 6 micron period wide-gap permalloy technology. Characterization of the functions showed that the guard-rail, generator, swap, write-line, read-line and after several revisions, the replicator and the expander-detector performed acceptably in preliminary testing. Several investigations were initiated to solve the problem of low minor loop yield. A dual-spacing process, which allows the minor loop propagation elements to be more tightly coupled to the garnet film was developed. Several new propagate structures, intended to be more tolerant of small defects were also conceived.

Chirovsky, L. M. F.↗
NASA NTRS1987

A unique measurement technique to study laminar-separation bubble characteristics on an airfoil

A 'nonintrusive', multielement heat-transfer sensor was designed to study laminar-separation bubble characteristics on a NASA LRN (1)-1010 low-Reynolds number airfoil. The sensor consists of 30 individual nickel films, vacuum-deposited on a thin substrate (0.05 mm) that was bonded to the airfoil model with the sensor array placed streamwise on the airfoil upper surface. Experiments were conducted on a 15-cm chord model in the 50,000-300,000 chord Reynolds number range. Time history as well as spectral analysis of signals from surface film gauges were simultaneously obtained to determine the location of laminar separation and the subsequent behavior of the separated shear layer. In addition to the successful determination of laminar separation, a new phenomenon involving a large phase shift in dynamic shear stresses across the separation and reattachment points was observed.

Stack, J. P.↗
NASA NTRS1987

Visualization of the laminar separation bubble on airfoils at low Reynolds numbers

The use of the smoke tube and titanium tetrachloride techniques in the study of low Reynolds number flow about two different airfoils is presented. Emphasis is placed on the problems of determining the characteristics of laminar separation bubbles occurring on the Wortmann FX63-137 airfoil and the NACA 66(3)-018 airfoil. Comparisons are made with the hot-wire technique and the use of kerosene vapor.

Mueller, T. J.↗
NASA NTRS1988

Experimental measurements in a large separation bubble due to a simulated glaze ice shape

The effect of a simulated glaze ice accretion on the aerodynamic performance of a NACA 0012 airfoil was studied experimentally. Two ice shapes were tested, one from an experimentally measured accretion and one from an accretion predicted using a computer model given the same icing conditions. Lift, drag and moment coefficients were measured for the airfoil with both ice shapes, smooth and rough. The aerodynamic performance of the two shapes compared well at positive, but not negative, angles of attack. Split hot-film probe velocity data were presented in the upper surface boundary layer and in the wake. Boundary layer parameters were presented for the separation bubble and in the reattached turbulent boundary layer.

Bragg, M. B.↗
NASA NTRS1989

Measuring Laminar-Separation Bubbles On Airfoils

Nonintrusive multielement heat-transfer sensor overcomes limitations of previous methods. New technique determines simultaneously extent of laminar boundary layer and locations of laminar separation, transition in separated layer, and turbulent reattachment. In tests, only small amounts of heat introduced, and heated thin films caused little disturbance to shear layer or to each other. Promising tool for measurements of stability of laminar boundary layers, separated shear layers, and transitional separation bubbles. Simple and capable of providing comprehensive picture of state of shear flow along entire surface. Significant savings in tunnel (or flight) test time with corresponding savings in cost.

Stack, John P.↗
NASA NTRS1989

Bubble behaviors in a slowly rotating helium dewar in a Gravity Probe-B spacecraft experiment

Potential problems for the Gravity Probe-B (GP-B) spacecraft design requirements and the operational considerations could arise because of the free surface configurations between liquid helium and helium vapor in the rotating dewar. This free surface is present in the partially filled liquid helium dewar. The liquid helium in the dewar is depleted as it is consumed as propellant for the spacecraft. In this study, the doughnut-shaped helium bubble equilibrium profiles in the rotating dewar have been numerically calculated. These calculations were performed under the conditions imposed during the period of the GP-B experiment instrument calibration (gyro spinup period) and also during the normal operational stages of the GP-B spacecraft.

Hung, R. J.↗
NASA NTRS1989

Axisymmetric bubble profiles in a slowly rotating helium dewar under low and microgravity environments

The Gravity Probe-B (GP-B) Spacecraft is designed to test the General Theory of Relativity through long-term monitoring the precession of a set of gyros in free-fall around the earth. The potential problems for GP-B Spacecraft design requirements could be due to asymmetry in the static liquid helium distribution, or to perturbations in free surface which is present in the partially-filled liquid helium dewar. In this study, doughnut-shaped helium bubble equilibrium profiles in rotating dewar, under the conditions during the period of GP-B experiment instrument calibration and also during the period of normal operation stages of GP-B Spacecraft, have been numerically calculated. For academic interest, the range of coverage has been extended beyond the conditions assigned by the GP-B Spacecraft experiment.

Hung, R. J.↗
NASA NTRS1990

Electrolysis Bubbles Make Waterflow Visible

Technique for visualization of three-dimensional flow uses tiny tracer bubbles of hydrogen and oxygen made by electrolysis of water. Strobe-light photography used to capture flow patterns, yielding permanent record that is measured to obtain velocities of particles. Used to measure simulated mixing turbulence in proposed gas-turbine combustor and also used in other water-table flow tests.

Schultz, Donald F.↗
NASA NTRS1990

Experimental measurements of the laminar separation bubble on an Eppler 387 airfoil at low Reynolds numbers

An experimental investigation was conducted to measure the flow velocity in the boundary layer of an Eppler 387 airfoil. In particular, the laminar separation bubble that this airfoil exhibits at low Reynolds numbers was the focus. Single component laser Doppler velocimetry data were obtained at a Reynolds number of 100,000 at an angle of attack of 2.0 degree. Static Pressure and flow visualization data for the Eppler 387 airfoil were also obtained. The difficulty in obtaining accurate experimental measurements at low Reynolds numbers is addressed. Laser Doppler velocimetry boundary layer data for the NACA 663-018 airfoil at a Reynolds number of 160,000 and angle of attack of 12 degree is also presented.

Cole, Gregory M.↗
NASA NTRS1990

Design considerations for honeycomb double-bubble tanks utilized in aerospace vehicles

Future earth-to-orbit vehicles will utilize reusable internal fuel tanks requiring most of the vehicle volume. Because weight reduction and volumetric efficiency are essential, these tanks will be integral to the vehicle structure, and the vehicle cross section will dictate the size and shape of the tank. For a fuselage with a noncircular cross section, a multibubble tank configuration may be employed. Multibubble tanks offer a reduction in tank weight over a single-lobe tank or several cylindrical tanks in a noncircular cross section but sacrifice the efficiency of utilizing the entire fuselage cross section. This paper includes a general configuration analysis of a double-bubble tank, a materials and efficiency study, and a complete mission design analysis centers on sizing the tank to withstand ascent and reentry loads while minimizing the structural weight.

Lentz, Christopher A.↗
NASA NTRS1990

Optical scattering methods applicable to drops and bubbles

An overview of optical scattering properties of drops and bubbles is presented. The properties lead to unconventional methods for optically monitoring the size or shape of a scatterer and are applicable to acoustically levitated objects. Several of the methods are applicable to the detection and measurement of small amplitude oscillations. Relevant optical phenomena include: (1) rainbows; (2) diffraction catastrophes from spheroids; (3) critical angle scattering; (4) effects of coatings; (5) glory scattering; and (6) optical levitation.

Marston, Philip L.↗