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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Effect of Spacecraft Rotation on Fluid Convection Under Microgravity

The influence of the rotational effects on two-dimensional fluid convection in a rectangular enclosure with rigid walls during the orbital flight is considered. It is shown that the Coriolis force influence both on steady and oscillatory convection becomes significant at Ekman numbers which are quite attainable in the space orbital conditions. In the case of harmonic oscillations of the gravity force appearance of the resonance phenomena is demonstrated. Dependence of the height and shape of the resonance peak on aspect ratio of a rectangular domain and orientation of vectors of the gravity force and the angular rotation velocity is studied. Special attention is given to non-linear effects caused by convective terms of Navier-Stokes equations. The convection produced by variations of the angular rotation velocity of a spacecraft is also discussed. It is shown that in some cases the latter convection can be comparable with another kinds of convection.

Yuferev, Valentin S.↗
NASA NTRS1978

Turbulent convection within rapidly rotating superadiabatic fluids with horizontal temperature gradients

A model is developed for small scale thermally driven turbulent convection in rapidly rotating systems. The Boussinesq equations of adiabatic and inviscid flow are perturbed about a basic state which is superadiabatic and which contains a horizontal temperature gradient balanced by a geostrophic wind. The growth rates and length scales of the most unstable modes are determined. It is found that these modes are either zonally or latitudinally symmetric, depending on the latitude and the horizontal temperature gradient. The transports of heat and momentum by the modes are computed. The linear amplitudes are assumed to be limited by shear instability. The model predicts a latitude dependent eddy diffusivity. The applicability of the model to astrophysical and planetary bodies is briefly discussed.

Flasar, F. M.↗
NASA NTRS1981

Model verification studies using accurate measurements of spin up

The reliability and accuracy of the numerical code for spin up flows in a cylinder by comparing the numerical results against high resolution laser Doppler velocimeter (LDV) measurements of the azimuthal flows were checked. A computer code to generate numerical solution for axisymmetric rotating fluid in a cylinder was obtained and amended for routine use at MSFC. The numerical simulations used the Navier-Stokes equations in axisymmetric form and employed finite difference techniques on both constant and variable grids. The numerical solutions are analyzed to gain further insight into the fundamental questions analyzed in rotating fluid dynamics.

Hyun, J. M.↗
NASA NTRS1980

Axially symmetric motion of a rotating stratified fluid

The spherical modeling of geophysical fluid flow is examined. In particular the extension of some previous work done in spherical geometry to the specific case of interest in the Spacelab atmospheric circulation experiment is discussed. This involves changing the boundary conditions under which the basic equations are to be solved. For simplicity the linear, axially symmetric steady state solution is sought.

Martin, B. J.↗
NASA NTRS1971

On hydromagnetic precession in a cylinder

Rotating fluid cylinder in magnetic field parallel to rotation axis, discussing hydromagnetic precession rate, resonance phenomena and magnetic Reynolds number flows

Gans, R. F.↗
NASA NTRS1992

Gravity jitter induced slosh waves in liquid propellant and disturbances of fluid stresses on spacecraft

The paper investigates 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 propellant dewar tank imposed by various frequencies of gravity jitters. Fluid stress distribution caused by the excitation of slosh waves and their associated large amplitude disturbances on the liquid-vapor interface and exerted on the outer and inner walls of a rotating dewar container are also examined. It is shown that fluid stress distributions near the outer and inner walls of the rotating dewar are closely related to the characteristics of slosh waves excited in the liquid-vapor interface in the rotating dewar tank. This can be of utility in managing spacecraft dynamic control leading to control of spacecraft imbalance caused by the uneven fluid stress distribution due to slosh wave excitations at the interface between liquid and vapor propellants.

Hung, R. J.↗
NASA NTRS1992

Spacecraft dynamical distribution of fluid stresses activated by gravity-jitter-induced slosh waves

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 propellant Dewar tank imposed by various frequencies of gravity jitters, has been investigated. Fluid stress distribution, caused by the excitation of slosh waves and their associated large-amplitude disturbances on the liquid-vapor interface, exerted on the outer and inner walls of a rotating Dewar container also has been investigated. Results show that fluid stress distributions near the outer and inner walls of the 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 useful tool for managing spacecraft dynamic control leading toward the control of spacecraft imbalance caused by the uneven fluid stress distribution due to slosh wave excitations at the interface between liquid and vapor propellants.

Hung, R. J.↗
NASA NTRS1969

Wave motion and vortex breakdown.

Vortex breakdown in rotating fluids associated with wave motion along axis of rotation, considering effects of nonzero wave amplitude

Leibovich, S.↗
NASA NTRS1983

Fluid signatures of rotational discontinuities at 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 NTRS1991

Particle orbits in a rotating liquid

The motion of small spherical particles under gravity, in a viscous fluid rotating uniformly about a horizontal axis, is investigated. Formulations and solutions are obtained for the particle orbit problem and the rotation rate optimization problem. It was found that the rotation rate which maximizes the fraction of the reactor cross-section area containing particles that will not spiral out to the wall in the experimental time (for heavy particles), or that have spiraled inward without hitting the wall (for light particles) is close to 1 rpm.

Roberts, Glyn O.↗
NASA NTRS1980

Fluid forces on rotating centrifugal impeller with whirling motion

Fluid forces on a centrifugal impeller, whose rotating axis whirls with a constant speed, were calculated by using unsteady potential theory. Calculations were performed for various values of whirl speed, number of impeller blades and angle of blades. Specific examples as well as significant results are given.

Shoji, H.↗
NASA NTRS1992

Similarity rules in gravity jitter-related spacecraft liquid propellant slosh waves excitation

The dynamical behavior of fluids, in particular the effect of surface tension on partially filled rotating fluids in a full-scale prototype Gravity Probe-B Spacecraft propellant tank and various 10 percent subscale containers with identical values of similarity parameters such as Bond number, dynamical capillary number, rotational Reynolds number, and Weber number, as well as imposed gravity jitters have been investigated. It is shown that the Bond number can be used to simulate the wave characteristics of slosh wave excitation, whereas the Weber number can be used to simulate the wave amplitude of slosh-mode excitation. It is shown that a dynamical capillary number can be used to simulate the induced perturbation of the fluid stress distribution exerted on the wall. This distribution is governed by the interaction between surface tension (slosh-wave excitation along the liquid-vapor interface) and viscous (fluid stress exerted on the wall) forces.

Hung, R. J.↗
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.↗