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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Gravity gradient or gravity jitter induced viscous stress and moment fluctuations in microgravity

The dynamical behavior of fluids affected by the asymmetric gravity gradient and gravity jitter accelerations, in particular the effect of surface tension on partially-filled rotating fluids with a special example applicable to a full-scale Gravity Probe-B Spacecraft dewar tank, has been investigated. Results of slosh wave excitation along the liquid-vapor interface induced by gravity gradient acceleration indicated one-up one-down and one-down and one-up oscillations of two bubbles in the cross-section of doughnut profiles in the vertical r-z plane of a rotating dewar, and an eccentric contour of a bubble rotating around the axis of the dewar in the horizontal r-theta plane. Results of slosh wave excitation along the liquid-vapor interface induced by gravity jitter acceleration showed an equivalent to the time-dependent oscillatory force which pushes a bubble in the combined bubble motion of down-and-up and leftward-and-rightward as the bubble is rotating with respect to a rotating dewar axis. Fluctuations of fluid stress forces, fluid stress moments, and moment arm of fluid moment exerted on the dewar wall of the container due to slosh wave excitations driven by gravity gradient acceleration or gravity jitter acceleration are also investigated.

Hung, R. J.↗
NASA NTRS1984

Fluid signatures of rotational discontinuities at the earth's magnetopause

Fluid signatures in the MHD approximation at rotational discontinuities (RD) of finite width called rotational shear layers (RSL) are examined for general flow and magnetic geometries. Analytical and geometrical arguments illustrate that the fluid speed can either go up or down across an RSL for a fixed normal mass flux. The speed profile may or may not be monotonic depending on the boundary conditions. The flow velocity may or may not be field aligned or 'jetting' as a result of traversing the RSL. In general, significant 'convection' is expected in the layer. The observable signatures of (MHD) RSL's depend on 7 (boundary condition) parameters are (1) the mass density, (2 to 5) the incident normal and transverse components of the magnetic field and fluid velocity, (6) the angle epsilon between the incident tangential flow velocity and tangential magnetic field, and (7) the size of the magnetic angular rotation implemented by the layer delta phi.

Scudder, J. D.↗
NASA NTRS1993

Effect of the baffle on the spacecraft fluid propellant viscous stress and moment fluctuations

The dynamical behavior of fluids affected by asymmetric gravity jitter oscillations, in particular the effect of surface tension on rotating fluids in a partially filled dewar tank imposed by time-dependent directions of background gravity have been investigated. Results show that a lower frequency gravity jitter imposed on the time-dependent variations of the direction of background gravity induced a greater amplitude of oscillations and a stronger degree of asymmetry in liquid-vapor interface geometry than that caused by higher-frequency gravity jitter. As viscous force between liquid and solid interface greatly contributes to the damping effect of slosh wave excitation, a rotating dewar with installed baffle provides more areas of liquid-solid interface than a rotating dewar without baffle. Damping by baffle reduces the amplitude of slosh wave excitation, angular momentum, and fluid moment fluctuation and lowers the degree of asymmetry in the liquid-vapor distribution.

Hung, R. J.↗
NASA NTRS1991

Gravity jitter excited cryogenic liquid slosh waves in microgravity environment

The dynamical behavior of fluids, in particular the effect of surface tension on partially-filled rotating fluids (cryogenic liquid helium and helium vapor) in a full-scale Gravity Probe-B Spacecraft liquid helium container tank without probe imposed by various frequencies of gravity jitter have been investigated. Results disclose the conditions for the excitation of large amplitude slosh waves which should be avoided in the design of cryogenic liquid propellant system.

Hung, R. J.↗
NASA NTRS1994

Fluid System Angular Momentum and Moment Fluctuations Driven by Gravity Gradient or Gravity Jitter in Microgravity

The dynamical behaviour of fluids affected by the asymmetric gravity gradient acceleration and gravity jitter acceleration, in particular the effect of surface tension on partially-filled rotating fluids with special example applicable to a full-scale Gravity Probe-B Spacecraft dewar tank have been investigated. Results of slosh wave excitation along liquid-vapor interface induced by gravity gradient acceleration indicated that one-up one-down and one-down one-up oscillations of two bubbles in the cross-section of doughnut profiles in the vertical r-z plane of rotating dewar, and an eccentric contour of bubble rotating around the axis of dewar in horizontal r-Theta plane. Results of slosh wave excitation along liquid-vapor interface induced by gravity jitter acceleration indicated equivalent to time-dependent oscillatory forces which push bubble in the combined bubble motion of down-and-up and leftward-and-rightward as the bubble is rotating with respect to rotating dewar axis. Fluctuations of angular momentum, fluid moment and bubble mass center caused by slosh wave excitations driven by gravity gradient acceleration or gravity jitter acceleration are also investigated.

Hung, R. J.↗
NASA NTRS1979

Theoretical regime diagrams for thermally driven flows in a beta-plane channel

It is noted that thermally driven flows in rotating laboratory containers with cylindrical geometry can be axially symmetric or wavelike depending on the experimental parameters. In anticipation that rotating fluid experiments might soon be done in spherical shell geometry, Barcilon's model has been extended to a beta-plane channel in order to gain a rough understanding of the effects of rotating spherical geometry. An incompressible fluid version of the Charney (1947) model of baroclinic instability, modified to include Ekman pumping at rigid horizontal boundaries is used. With this model, stability boundaries are mapped out for individual zonal wavenumbers in the parameter space used by Barcilon.

Geisler, J. E.↗
NASA NTRS1976

Fluid mass sensor for a zero gravity environment

A sensor for measuring the mass of fluids, is described which includes a housing having an inlet and outlet for receiving and dumping the fluid, a rotary impeller within the housing for imparting centrifugal motion to the fluid and a pressure sensitive transducer attached to the housing to sense the rotating fluid pressure. The fluid may be drawn into the housing by entrainment within a gas stream. The resulting mixture is then separated into two phases: gas and liquid. The gas is removed from the housing and the pressure of the liquid, under centrifugal motion, is sensed and correlated with the mass of the fluid.

Fogal, G. L.↗
NASA NTRS1995

Sloshing dynamics modulated fluid angular momentum and moment fluctuations driven by orbital gravity gradient and jitter accelerations in microgravity

The dynamical behavior of spacecraft propellant affected by the asymmetric combined gravity gradient and jitter accelerations, in particular the effect of surface tension on partially-filled rotating fluids applicable to a full-scale Gravity Probe-B Spacecraft dewar tank has been investigated. Three different cases of orbital accelerations: (1) gravity gradient-dominated, (2) equally weighted between gravity gradient and jitter, and (3) gravity jitter-dominated accelerations are studied. The results of slosh wave excitation along the liquid-vapor interface induced by gravity gradient-dominated accelerations provide a torsional moment with tidal motion of bubble oscillations in the rotating dewar. The results are clearly seen from the twisting shape of the bubble oscillations driven by gravity gradient-dominated acceleration. The results of slosh wave excitation along the liquid-vapor interface induced by gravity jitter-dominated acceleration indicate the results of bubble motion in a manner of down-and-up and leftward-and-rightward movement of oscillation when the bubble is rotating with respect to rotating dewar axis. Fluctuations of angular momentum, fluid moment and bubble mass center caused by slosh wave excitations driven by gravity gradient acceleration or gravity jitter acceleration are also investigated.

Hung, R. J.↗
NASA NTRS1974

Analytic pulsar models

An analytical procedure is given for solving the Einstein equations of a rotating fluid body. It is demonstrated that an analytic model of uniform denisty, representing a slowly rotating neutron star, can describe both differentially and uniformly rotating stars.

Adams, R. C.↗
NASA NTRS1977

The calculation of the mass moment of inertia of a fluid in a rotating rectangular tank

This analysis calculated the mass moment of inertia of a nonviscous fluid in a slowly rotating rectangular tank. Given the dimensions of the tank in the x, y, and z coordinates, the axis of rotation, the percentage of the tank occupied by the fluid, and angle of rotation, an algorithm was written that could calculate the mass moment of inertia of the fluid. While not included in this paper, the change in the mass moment of inertia of the fluid could then be used to calculate the force exerted by the fluid on the container wall.

Source record↗
NASA NTRS1991

Gravity jitter response slosh wave excitation on the fluid in a rotating dewar

The present study investigates the dynamical behavior of fluids, in particular, the effect of surface tension on partially filled fluids in a rotating dewar in a microgravity environment. It is shown that there is a group of wave trains, both in longitudinal and transverse modes, with various frequencies and wavelengths of slosh waves generated by the restoring field force field of gravity jitters and centrifugal forces. The longest wave periods of slosh waves, either the longitudinal or transverse modes, are found to be responsible for the production of wave modes with the highest ratio of maximum wave amplitude to wavelength. The lower frequency slosh waves are the wave modes with higher wave energy than that of the higher frequency slosh waves.

Hung, R. J.↗
NASA NTRS1992

Three-dimensional spacecraft angular momentum fluctuations due to gravity jitter excited slosh waves in liquid propellant system

The paper investigates the dynamical behavior of fluids affected by asymmetric gravity jitter oscillations, in particular the effect of surface tension on partially filled rotating fluids (cryogenic liquid helium and helium vapor) in a subscale Gravity Probe-B spacecraft propellant dewar tank imposed by time-dependent variation in the direction of the background gravity environment. It is shown that lower frequency gravity jitter imposed on the time-dependent variation in the direction of background gravity induced a greater amplitude of oscillations and a stronger degree of asymmetry in liquid-vapor interface geometry than that made by the higher frequency gravity jitter. Fluctuations of angular momentum and spacecraft moment caused by slosh wave excitation are also studied. Slosh-wave-induced fluctuations in angular momentum and moment are important factors in spacecraft dynamics, guidance, and attitude controls.

Hung, R. J.↗
NASA NTRS1993

Effect of baffle on the asymmetric gravity jitter excited slosh waves in microgravity

The paper investigates the dynamical behavior of fluids affected by asymmetric gravity jitter oscillations, in particular, the effect of surface tension on partially filled rotating fluids in a full-scale Gravity Probe-B Spacecraft dewar tank, with and without the installation of the baffle-board, imposed by time-dependent directions of background gravity. The time-sequence evolution of the 3D behavior of the liquid-vapor interface oscillations resulting in the excitation of large amplitude slosh waves exerted by gravity jitter disturbances are examined. It is shown that the damping effect provided by baffle reduces the amplitude of slosh wave excitation and lowers the degree of asymmetry in the liquid-vapor distribution.

Hung, R. J.↗
NASA NTRS1995

Effect of Baffle on Gravity-Gradient-Excited Slosh Waves and Spacecraft Moment and Angular-Momentum Fluctuations in Microgravity

The dynamical behavior of fluids affected by the asymmetric gravity gradient acceleration has been investigated. In particular, the effects of surface tension on partially filled rotating fluids applicable to a full-scale Gravity Probe-B Spacecraft dewar tank with and without baffles are studied. Results of slosh wave excitation along the liquid-vapor interface induced by gravity gradient acceleration indicate that the gravity gradient acceleration is equivalent to the combined effect of a twisting force and a torsional moment acting on the spacecraft. The results are clearly seen from one-up one-down and one-down one-up oscillations in the cross-section profiles of two bubbles in the vertical (r, z)-plane of the rotating dewar, and from the eccentric contour of the bubble rotating around the axis of the dewar in a horizontal (r, theta)-plane. As the viscous force, between liquid and solid interface, greatly contributes to the damping of slosh wave excitation, a rotating dewar with baffles provides more areas of liquid-solid interface than that of a rotating dewar without baffles. Results show that the damping effect provided by the baffles reduces the amplitude of slosh wave excitation and lowers the degree of asymmetry in liquid-vapor distribution. Fluctuations of angular momentum and fluid moment caused by the slosh wave excited by gravity gradient acceleration with and without baffle boards are also investigated. It is also shown that the damping effect provided by the baffles greatly reduces the amplitudes of angular momentum and fluid moment fluctuations.

Hung, R. J.↗
NASA NTRS1995

Combined Gravity Gradient and Jitter Accelerations Acting on Liquid-Vapor Interface Oscillations in Reduced Gravity

The dynamical behavior of fluids affected by the asymmetric combined gravity gradient and jitter accelerations, in particular the effect of surface tension on partially-filled rotating fluids applicable to a full-scale Gravity Probe-B Spacecraft dewar tank, have been investigated. Three different cases of accelerations, one gravity gradient-dominated, one equally weighted between gravity gradient and jitter, and the others gravity jitter-dominated are studied. Results of slosh wave excitation along the liquid-vapor interface induced by gravity gradient-dominated acceleration indicate that the gravity gradient-dominated acceleration is equivalent to the combined effect of a twisting force and torsional moment acting on the spacecraft. Results of the slosh wave excitation along the liquid vapor interface induced by gravity jitter-dominated acceleration indicate that the gravity jitter-dominated acceleration is equivalent to time-dependent oscillatory forces which push the bubble in the combined directions of down-and-up and sideward -and-middleward as the bubble is rotating with respect to rotating dewar axis. This study discloses the slosh wave excitation along the liquid-vapor interface driven by the combined effects of gravity gradient and jitter accelerations which are two major driving forces affecting the stability of the fluid system in microgravity.

Hung, R. J.↗
NASA NTRS1991

Gravity Probe-B Spacecraft attitude control based on the dynamics of slosh wave-induced fluid stress distribution on rotating dewar container of cryogenic propellant

The dynamical behavior of fluids, in particular the effect of surface tension on partially-filled rotating fluids, in a full-scale Gravity Probe-B Spacecraft propellant dewar tank imposed by various frequencies of gravity jitters have been investigated. Results show that fluid stress distribution exerted on the outer and inner walls of rotating dewar are closely related to the characteristics of slosh waves excited on the liquid-vapor interface in the rotating dewar tank. This can provide a set of tool for the spacecraft dynamic control leading toward the control of spacecraft unbalance caused by the uneven fluid stress distribution due to slosh wave excitations.

Hung, R. J.↗
NASA NTRS1992

Effect of asymmetric gravity jitter excited slosh waves at liquid-vapor interface under microgravity

The dynamical behavior of fluids affected by the asymmetric gravity jitter oscillations, in particular the effect of surface tension on partially-filled rotating fluids (cryogenic liquid helium and helium vapor) in a sub-scale Gravity Probe-B Spacecraft propellant dewar tank imposed by time-dependent various directions of background gravity environment have been investigated. Results show that lower frequency gravity jitter imposed on the time-dependent variations of the direction of background gravity induced a greater amplitude of oscillations and a stronger degree of asymmetry in liquid-vapor interface geometry than that made by the higher frequency gravity jitter. Furthermore, the greater the components of background gravity in radial and circumferential directions will provide a greater contribution in driving more to the increasing amplitude and degrees of symmetry of liquid-vapor interface profiles which, in turn, modify the disturbance of moment of inertia and angular momentum of spacecraft.

Hung, R. J.↗