Influence of gravity on the performance of a conical vortex separator
Gravity effect on conical vortex separator, predicting body force effect on heavy fluid boundary layer flow for limiting condition determination
Burton, K. R.↗
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Class of asymptotic solutions of relativistic gas
Relativistic high temperature gas asymptotic solutions with or without body force, comparing flow field with photon gas
Chiu, H. H.↗
Convection in the tanks of a rotating spacecraft
A general study of convection and mixing of a stratified fluid in a rotating container is described, with application to the special problem of fluid heating and convection in a spacecraft tank. The analysis was based on a set of approximate equations for the Navier-Stokes description of fluid convection with small density variations in a rotating system, including effects of body forces due to temperature stratification (caused by a heater) and arbitrary time-dependent rotation of the tank about a noncentral axis. An efficient numerical finite difference scheme and computational method are described for the convection of vorticity and energy in a two-dimensional tank. Special procedures were developed for analysis of the thermodynamic states resulting from the approximate flow equations derived for small density variations. Results of the numerical simulation are presented for studying the effectiveness of rotation maneuvers in mixing stratified oxygen in the tanks of an Apollo spacecraft. Significant effects of the rotation maneuvers are discussed, including the reduction of the potential for pressure collapse.
Source record↗
Response of a semi-infinite elastic solid to an arbitrary line load along the axis.
The axisymmetric problem of a line load acting along the axis of a semiinfinite elastic solid is solved using Hankel transforms. In this solution the line load is interpreted as a body force loading and by assuming the line load to be of the form of a Dirac delta function the solution of Mindlin's problem of a point load within the interior of the half space is obtained. Solutions of this problem presented in the literature have been obtained using semiinverse techniques whereas the solution given here is obtained in a systematic step-by-step manner.
Agrawal, G. L.↗
The responses of rising or falling spherical wind sensors to atmospheric wind perturbations.
Analysis of the responses of rising or falling spherical wind sensors to atmospheric wind perturbations on the wind profile in the vertical, using Fourier transform techniques. The linearized equations of motion of a sensor that is subject to drag and gravitational body forces are developed by perturbing a sensor about an equilibrium uniform motion with wind fluctuations which have vertical variations. The wind environment and sensor velocities are decomposed with stochastic Fourier-Stieltjes integrals, and the linearized equations of motion are used to derive the response functions and phase angles of the sensor motions. The results of the analysis are used to analyze the response properties of the Jimsphere balloon wind sensor. It is shown that, in general, the transfer functions associated with the horizontal sensor motions are smaller than the transfer functions associated with the vertical sensor motions in the omega times T product range from zero to infinity, omega being the wind perturbation frequency and T a time constant of the system. Thus, the sensor is more responsive to vertical than to horizontal air motions.
Fichtl, G. H.↗
A half plane and a strip with an arbitrarily located crack
A technique is presented for dealing with the problem of an elastic domain containing an arbitrarily oriented internal crack. The problem is formulated as a system of integral equations for a fictitious layer of body forces imbedded in the plane along a closed smooth curve encircling the original domain. The problems of a half plane with a crack in the neighborhood of its free boundary and of an infinite strip containing a symmetrically located internal crack with an arbitrary orientation are considered as examples. In each case the stress intensity factors are computed and are given as functions of the crack angle.
Erdogan, F.↗
Energy distribution in parallel plate plasma accelerators
A parallel plate accelerator operated in the quasi-steady regime of argon mass flow discharges permits, on account of its geometry, the appraisal of the initial ratio of energy disposition into the kinetic and thermal modes of the plasma while retaining the essential features of coaxial high power self-field MPD accelerators. The energy disposition ratio, calculated as the ratio of kinetic energy to enthalpy in the exhaust flow, shows reasonable agreement with the ratio of the induced emf in the accelerator to resistive voltage drop. Both these ratios indicate that the discharge imparts more energy to the flow by resistive heating than by direct body force acceleration. This is turn suggests that other acceleration mechanisms must be responsible for the high performance of conventional MPD arcs.
Dicapua, M. S.↗
Transient boiling heat transfer in saturated liquid nitrogen and F113 at standard and zero gravity
Transient and steady state nucleate boiling in saturated LN2 and F113 at standard and near zero gravity conditions were investigated for the horizontal up, vertical and horizontal down orientations of the heating surface. Two distinct regimes of heat transfer mechanisms were observed during the interval from the step increase of power input to the onset of nucleate boiling: the conduction and convection dominated regimes. The time duration in each regime was considerably shorter with LN2 than with F113, and decreased as heat flux increased, as gravity was reduced, and as the orientation was changed from horizontal up to horizontal down. In transient boiling, boiling initiates at a single point following the step increase in power, and then spreads over the surface. The delay time for the inception of boiling at the first site, and the velocity of spread of boiling varies depending upon the heat flux, orientation, body force, surface roughness and liquid properties, and are a consequence of changes in boundary layer temperature levels associated with changes in natural convection. Following the step increase in power input, surface temperature overshoot and undershoot occur before the steady state boiling temperature level is established.
Oker, E.↗
Development of the program SPECEL: A special element for elasto-plastic crack tip analysis
Theory is stated in terms of increments of displacement and stress, and of instantaneous or accumulated values of stress. The equilibrium equations, in the absence of body forces, are written, along with constitutive relations for plane strain.
Swedlow, J. L.↗
A half plane and a strip with an arbitrarily located crack
The paper introduces a technique to deal with the problem of an elastic domain containing an arbitrarily oriented internal crack. The problem is formulated as a system of integral equations for a fictitious layer of body forces imbedded in the plane along a closed smooth curve encircling the original domain. The problems of a half plane with a crack in the neighborhood of its free boundary and of an infinite strip containing a symmetrically located internal crack with an arbitrary orientation are considered as examples. In each case the stress intensity factors are computed and are given as functions of the crack angle.
Erdogan, F.↗
Pressure- and buoyancy-driven thermal convection in a rectangular enclosure
Results are presented for unsteady laminar thermal convection in compressible fluids at various reduced levels of gravity in a rectangular enclosure which is heated on one side and cooled on the opposite side. The results were obtained by solving numerically the equations of conservation for a viscous, compressible, heat-conducting, ideal gas in the presence of a gravitational body force. The formulation differs from the Boussinesq simplification in that the effects of variable density are completely retained. A conservative, explicit, time-dependent, finite-difference technique was used and good agreement was found for the limited cases where direct comparison with previous investigations was possible. The solutions show that the thermally induced motion is acoustic in nature at low levels of gravity and that the unsteady-state rate of heat transfer is thereby greatly enhanced relative to pure conduction. The nonlinear variable density profile skews the streamlines towards the cooler walls but is shown to have little effect on the steady-state isotherms.
Spradley, L. W.↗
Convection measurement package for space processing sounding rocket flights
The effects on heated fluids of nonconstant accelerations, rocket vibrations, and spin rates, was studied. A system is discussed which can determine the influence of the convective effects on fluid experiments. The general suitability of sounding rockets for performing these experiments is treated. An analytical investigation of convection in an enclosure which is heated in low gravity is examined. The gravitational body force was taken as a time-varying function using anticipated sounding rocket accelerations, since accelerometer flight data were not available. A computer program was used to calculate the flow rates and heat transfer in fluids with geometries and boundary conditions typical of space processing configurations. Results of the analytical investigation identify the configurations, fluids and boundary values which are most suitable for measuring the convective environment of sounding rockets. A short description of fabricated fluid cells and the convection measurement package is given. Photographs are included.
Spradley, L. W.↗
Zero-G processing of magnets experiment MA-070
Solidification of magnetic materials in the low gravity orbital environment was studied. The magnetic compounds under study, manganese bismuth and copper cobalt cerium ((Cu, Co)5Ce), both have the potential for the development of high coercive strength. Preliminary results indicate that static fluid configurations, in the absence of the gravitational body force, differ substantially from the documented terrestrial behavior. Chemical homogeneity is substantially enhanced on a macroscopic and microscopic level. Single crystal matrices have been grown in the coordinated growth regions of the flight samples. Primary crystals one order of magnitude greater than those grown terrestrially have been noted and are limited in size by the ampoule dimensions.
Larson, D. J., Jr.↗
Studies of earth simulation experiments
The low gravity environment of earth orbit offers the potential for performing experiments involving baroclinic Geophysical Fluid Dynamics (GFD) on spherical surfaces. These experiments in turn have the potential for providing deeper understanding of large scale planetary and solar circulations. However, to perform these experiments, one requires an experimental technique whereby a radially directed body force can be generated to simulate a radial gravitational force field. One viable technique is the use of dielectric fluids with temperature dependent dielectric permittivity in a radially directed electric field. Application of the Boussinesq approximation to the equations of motion for this system and restrictions on the size of certain electrodynamic terms in the energy equations yields a set of equations which are analogous to the equations of motions of geophysical systems like the earth's atmosphere on term by term basis. The theoretical design of GFD experiments for performance in earth orbit are described along with results of preliminary tests of a prototype.
Hart, J. E.↗
Zero-G processing of magnets. Experiment MA-070
The magnetic compounds under study, manganese-bismuth (MnBi) copper-cobalt-cerium (Cu,Co)5Ce, are representative of magnetic alloy systems that have the potential for the development of high coercive strength and a high energy product. The samples of 50 at. % bismuth and 50 at. % manganese solidified in the low-g environment demonstrated a substantial improvement in the macroscopic chemical homogeneity. The bismuth/manganese-bismuth directionally solidified eutectic flight samples exhibited marked superior magnetic properties. Intrinsic coercive strengths in excess of 185 Koe have been measured in the low-g processed samples at 77 K. The average value of inductance was improved by 76 percent, and the energy product was improved by 57 percent. Additional results indicate that, in the near-absence of the gravitational body force, contained fluids will assume a lowest energy configuration that differs significantly from that found terrestrially.
Larson, D. J., Jr.↗
On the role of constant-stress surfaces in the problem of minimizing elastic stress concentration
Cases involving antiplane shear deformation, axisymmetric torsion, and plane strain theory, with surfaces of constant stress magnitude optimal in terms of minimizing stress, are investigated. Results for the plane theory refer to exterior doubly connected domains. Stresses generated by torsion of an elastic solid lying within a radially convex region of revolution with plane ends, body force absent, and lateral surface traction-free, are examined. The unknown portion of the boundary of such domains may involve a hole, fillet, or notch.
Wheeler, L.↗
The effects of curvature and viscosity on baroclinic instability: A two-layer model
A linear stability analysis of a baroclinic zonal current contained between two parallel rigid boundaries is presented. Curvature is included by performing the analysis on a beta b-plane and viscosity by allowing for the effects of Ekman layers on the rigid boundaries. A two-layer model is used. This calculation was carried out to assist in the design of a spherical model of the general circulation of the earth's atmosphere for Spacelab. In the low-gravity environment on an orbiting vehicle, a dominant radial dielectric body force, analogous to planetary gravity, can be achieved over a volume of liquid held between two concentric spheres. The results show the Eady short wavelength cutoff, and long wavelength cutoffs due to Ekman damping and curvature.
Fowlis, W. W.↗
Stellar magnetic fields. 1: The role of a magnetic field in the peculiar M giant, HD 4174
Coronal heating by resonant absorption of Alfvenic surface waves (quiescent), and magnetic tearing instabilities (impulsive), is discussed with emphasis on three principles which may have application to late-type evolved stars. (1) If sq B/8 pi greater than sq. rho V is observed 2 in a stellar atmosphere, then the observed magnetic field must originate in an interior dynamo. (2) Low mass loss rates could imply the presence of closed magnetic flux loops within the outer atmosphere which constrain hydrodynamic flows when the magnetic body forces exceed the driving forces. (3) given that such magnetic loops effect an enhancement of the local heating rate, a positive correlation is predicted between the existence of a corona and low mass loss rates. These principles are applied to the M giant star HD 4174, which is purported to have a kilogauss magnetic field. Several of its spectroscopic peculiarities are shown to be consistent with the above principles, and further observational checks are suggested.
Stencel, R. E.↗