Showing papers on "Hydrostatic equilibrium published in 1977"
TL;DR: In this paper, the problem of the gravitational collapse of isothermal spheres by applying the similarity method to the gas-dynamic flow is considered, and two types of similarity solutions are obtained: one is the prototype for starting states which correspond to unstable hydrostatic equilibrium; the other, for states where the mass of the cloud slightly exceeds the maximum limit allowable for hydrostatic equilibria.
Abstract: We consider the problem of the gravitational collapse of isothermal spheres by applying the similarity method to the gas-dynamic flow. We argue that a previous solution obtained by Larson and Penston to describe the stages prior to core formation is physically artificial; however, we find that the flow following core formation does exhibit self-similar properties.The latter similarity solution shows that the inflow in the dense central regions proceeds virtually at free-fall before the material is arrested by a strong radiating shock upon impact with the surface of the core. Two types of similarity solutions are obtained: one is the prototype for starting states which correspond to unstable hydrostatic equilibrium; the other, for states where the mass of the cloud slightly exceeds the maximum limit allowable for hydrostatic equilibrium. In both cases, an r/sup -2/ law holds for the density distribution in the static or nearly static outer envelope, and an r/sup -3///sup 2/ law holds for the freely falling inner envelope. Rapid infall is initiated at the head of the expansion wave associated with the dropping of the central regions from beneath the envelope. A numerical example is presented which is shown to be in good agreement with the envelopemore » dynamics obtained in previous studies of star formation using hydrodynamic codes.« less
1,747 citations
TL;DR: In this article, the results of investigations into recessed hydrostatic bearings and slot-entry hydrostatic bearing are presented, and initial comparative results show that there are certain conditions under which slot entry bearings may have marked advantages.
47 citations
TL;DR: In this article, a sequence of one-dimensional fluid flow models of the transition zone and the inner corona is presented, and various physical effects are introduced, one at a time, observing the response of the model.
Abstract: A description is presented of a sequence of one-dimensional fluid flow models of the transition zone and the inner corona. A hydrostatic model atmosphere in reasonable agreement with observations of closed, large-scale coronal structures found in the quiet sun is considered and various physical effects are introduced, one at a time, observing the response of the model. As a result of the investigations, a model is developed of the plasma flow in a coronal hole. It is shown that the data severely circumscribe the allowable range of possible models.
31 citations
TL;DR: In this paper, the theoretical equilibrium for Phobos is a triaxial ellipsoid whose a and b axes differ by about 25% and this difference is less than 2% for Deimos.
30 citations
TL;DR: In this article, the wave velocity equations are deduced from Biot's theory of stress by assuming that the effects of gravity are equivalent to a type of initial stress of a hydrostatic nature.
Abstract: In this paper formulae are derived for surface waves in a viscoelastic medium of Voigt type under the influence of gravity. The wave velocity equations are deduced from Biot's theory of stress by assuming that the effects of gravity are equivalent to a type of initial stress of a hydrostatic nature. The resulting equations are used to briefly investigate the particular surface waves of Rayleigh, Love and Stoneley type. In all cases the final results are in agreement with the corresponding classical results when the effects of gravity and viscosity are neglected.
10 citations
TL;DR: In this article, the optimal configuration of the bearing restrictor system for optimal stiffness was provided by the steepest gradient method of optimization for both circular and rectangular pads in a bearing system.
9 citations
TL;DR: In this article, a general integral equation for the stream function is derived from which a special Fourier representation is shown to hold in a well-defined region of the atmosphere, leading to simple expressions for energy and momentum fluxes and to a useful form for the energy conservation law.
Abstract: The scattering of two-dimensional, hydrostatic, Boussinesq, internal gravity waves by orographic features is considered, with special attention paid to energy and momentum fluxes. A general integral equation for the streamfunction is derived from which a special Fourier representation is shown to hold in a well-defined region of the atmosphere. This leads to simple expressions for the energy and momentum fluxes and to a useful form for the energy conservation law. Scattering efficiency functions are defined. When the topography satisfies certain conditions, analytic approximations can be used to determine the scattering; it is found that the reflected momentum flux is larger than the incident flux. The manner in which viscosity affects this result is discussed. In the special case that the maximum topographic slope is less than that of the incident wave fronts, a simple integral equation is derived and used to calculate numerically the scattering from several different orographies. In every case,...
8 citations
TL;DR: In this paper, it is argued that this must be caused by convection in the solid interior rather than an initial distortion retained by the finite strength of the interior, and the presence of an iron core in Mercury poses an interesting question as to why a second degree harmonic convection pattern in the silicate mantle is present.
5 citations
01 Jan 1977
TL;DR: In this paper, models of the Jovian interiors based on theoretical equations of state of hydrogen and helium supported by a few experimental points and on observed parameters such as oblateness, gravitational coefficients, heat emission, magnetic fields, are discussed.
Abstract: Models of the Jovian interiors based on theoretical equations of state of hydrogen and helium supported by a few experimental points and on observed parameters such as oblateness, gravitational coefficients, heat emission, magnetic fields, are discussed. The models fall into three categories: (1) those that assume a uniform and rather low H2/He ratio throughout the planet; (2) those in which this ratio is solar and thus higher; and (3) those that take into account the lack of complete miscibility of the two elements in the condensed state. It appears now also that within the limits of error the planet is in a hydrostatic equilibrium. The large heat emission and the need for an efficient source of internal heat are confirmed, but the results do not indicate which one of the various possible mechanisms is favored, although new evolutionary models suggest that the primordial heat may be insufficient. A new red spot has been discovered. Finally, the presence of a highly eccentric and inclined magnetic field poses new problems related to the pattern of internal convection and to the possibility of a north-south asymmetry of the interior. Further analysis of the available data may throw additional light on these questions.
4 citations
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09 Dec 1977TL;DR: In this article, a hydrostatic seismic sensor including a sensing mass suspended on a defoble reservoir containing a sensing fluid and a differential pressure transducer was used to measure the pressure in the reservoir.
Abstract: A hydrostatic seismic sensor including a sensing mass suspended on a defoble reservoir containing a sensing fluid and a differential pressure transducer to measure the pressure in the reservoir.
3 citations
TL;DR: In this article, three types of stress waves were performed under atmospheric and hydrostatic pressures of 1000kg/cm2 at 270°C and the results showed that the time to rupture of the material under hydrostatic pressure was remarkably longer than that in atmosphere.
Abstract: Sheet test specimen of commercial pure copper was used and tests on three types of stress waves were performed under atmospheric and hydrostatic pressures of 1000kg/cm2 at 270°C. From the present experiments the following were concluded. At the same stress wave, time to rupture of the material under hydrostatic pressure was remarkably longer than that in atmosphere. In this connection, slower crack initiation and propagation rate were observed under hydrostatic pressure as compared to atmospheric pressure. From the calculation of both fatigue damage φf of the material and creep damage φc in the tests of fatigue with hold-time, the value of commulative damage, φc+φf, is larger than unity under both hydrostatic and atmospheric pressures. The fatigue damage of the material is predominant under hydrostatic pressure but the creep damage of the material is influential under atmospheric pressure.
TL;DR: In this article, the strength of a rhombic model of a defective polymer crystal in hydrostatic tension has been calculated for the set of configurations assumed by the model in the process of plastic deformation.
Abstract: The strength of a rhombic model of a defective polymer crystal in hydrostatic tension has been calculated for the set of configurations assumed by the model in the process of plastic deformation. The dislocation centers and twinning curves are calculated for models with one and two coordination polygons in hydrostatic tension. It is shown that in hydrostatic tension the twinning limit of the models is considerably reduced.
TL;DR: In this paper, a three-dimensional two-component model was used to model the distribution of argon in the upper atmosphere of the earth, and the effects of departures from hydrostatic equilibrium on the argon density distribution were examined.
Abstract: This report describes the application of a three-dimensional two-component model to the distribution of argon in the upper atmosphere of the earth. The Cira (1972) model is used to specify the background gas density and the temperature as functions of altitude, latitude, local time, and day of the year. Emphasis is placed on examining the effects of departures from hydrostatic equilibrium on the argon density distribution. Such effects are found to be significant, producing a strong summer argon bulge. Comparisons of the model results with observational data are discussed.
01 Jan 1977
TL;DR: In this article, the conditions for hydrostatic equilibrium in 3He-A and the equations that describe the non-linear orbital hydrodynamics are given, along with the equations for nonlinear orbital dynamics.
Abstract: The conditions for hydrostatic equilibrium in 3He-A and the equations that describe the non-linear orbital hydrodynamics are given.
TL;DR: In this paper, a perturbation expansion for the density distribution of a fluid in a steep field gradient is presented, which is a power series in the scale γ of an external potential ψ (γx), and is asymptotically valid as γ→0, although convergence is not proved.
Abstract: A new perturbation expansion for the hydrostatic density distribution of a fluid in a steep field gradient is presented. It is a power series in the scale γ of an external potential ψ (γx), and is asymptotically valid as γ→0, although convergence is not proved. Significant corrections to the conventional hydrostatic equations are found near the critical point of a fluid, even in the gravitational field.