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Hydrostatic equilibrium

About: Hydrostatic equilibrium is a research topic. Over the lifetime, 2451 publications have been published within this topic receiving 62172 citations.


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Posted ContentDOI
27 Mar 2022
TL;DR: In this paper , the authors used a Bayesian Inversion of geophysical measurements of the moon Europa to explore the properties of its interior, composition, and habitability, and used the Love number to constrain internal structure models.
Abstract: <p>The NASA mission Europa Clipper is designed to conduct multi-disciplinary investigations of the interior, composition, and habitability of the Galilean moon Europa. The measurement of Europa’s gravity field, tides, orientation, and moment of inertia (MoI) will enable an accurate characterization of the moon’s interior by constraining internal structure models through the inversion of geophysical measurements. The refined knowledge of Europa’s interior will provide a better understanding of its thermal evolution and of the processes that formed and maintained the liquid water ocean underneath the moon’s outer icy shell. The accurate estimation of the tidal Love number <em>k<sub>2</sub></em> is expected to provide geodetic evidence of the existence of the ocean, and its combination with the Love number <em>h<sub>2 </sub></em>will enable the estimation of the icy shell mean global thickness.</p><p>The determination of the MoI, obtained either through measurements of the degree-2 gravity field with the hydrostatic equilibrium assumption or by also measuring Europa’s orientation and obliquity, will provide information on the deep interior of the moon, possibly constraining the size and the composition of the solid interior. Numerical simulations are performed to assess the expected accuracy of the key geophysical quantities from the analysis of Europa Clipper radiometric data. These measurements are used in a Bayesian Inversion (<em>e.g.</em>, Monte Carlo Markov chain) to explore the properties of Europa’s hydrosphere and deep interior.</p>

1 citations

Journal Article
TL;DR: In this article, it was shown that the ratio of the two length scales relates to the axis ratio of a velocity ellipsoid only through the Toomre parameter Q and in particular does not require a choice of the mass-to-light ratio or a distance scale.
Abstract: The spatial distribution of stars in a disk of a galaxy can be described by a radial scale length and a vertical scale height. The ratio of these two scale parameters contains infor- mation on the axis ratio of the velocity ellipsoid, i.e. the ratio of the vertical to radial stellar velocity dispersions of the stars, at least at some fiducial distance from the center. The radial veloc- ity dispersion correlates well with the amplitude of the rotation curve and with the disk integrated magnitude, as was found by Bottema (1993). These relations can be understood as the re- sult of the stellar disk being (marginally) stable against local instabilities at all length scales. This is expressed by Toomre's well-known criterion, which relates the sheer in the rotation to a minimum value that the radial stellar velocity dispersion should have for stability for a given surface density. Via the Tully-Fisher (1977) relation, the velocity dispersion then becomes related to the integrated magnitude and hence to the scale length. The vertical velocity dispersion relates directly to the scale height through hydrostatic equilibrium. It can be shown that the ratio of the two length scales relates to the axis ratio of the velocity ellipsoid only through the Toomre parameter Q and in particular does not require a choice of the mass-to-light ratio or a distance scale. We have applied this to the statistically complete sample of edge-on galaxies, for which de Grijs (1997) has performed surface photometry and has determined the length scales in the stellar light distribution.

1 citations

05 Mar 2013
TL;DR: In this paper, the authors studied the well-posedness of cap models with unbounded elasticity sets in dynamical and quasi-static regimes, where the elasticity domain is cut in the direction of hydrostatic stresses by means of a strain-hardening yield surface.
Abstract: This work is devoted to the analysis of elasto-plasticity models arising in soil mechanics. Contrary to the typical models mainly used for metals, it is required here to take into account plastic dilatancy due to the sensitivity of granular materials to hydrostatic pressure. The yield criterion thus depends on the mean stress and the elasticity domain is unbounded and not invariant in the direction of hydrostatic matrices. In the mechanical literature, so-called cap models have been introduced, where the elasticity domain is cut in the direction of hydrostatic stresses by means of a strain-hardening yield surface, called a cap. The purpose of this article is to study the well-posedness of plasticity models with unbounded elasticity sets in dynamical and quasi-static regimes. An asymptotic analysis as the cap is moved to infinity is also performed, which enables one to recover solutions to the uncapped model of perfect elasto-plasticity.

1 citations

Proceedings ArticleDOI
01 Jan 2003
TL;DR: In this paper, the authors developed a new type of ocean model for multi-scale analysis, which conducts hydrostatic analysis for phenomena in wide area and FULL-3D analysis for the detail flow around the interesting object simultaneously.
Abstract: Ohmura bay is a typical enclosed estuary located in Kyushu, Japan. In the summer season, strong stratification is formed which brings oxygen-dificient water mass in the bottom layer. For the purpose of restoring water quality in the bay, field experiment of an artificial purification system was carried out. In the experiment, a diffusion pump was installed on the bottom of the bay. The instrument draws in the surface water of lower density and rich oxygen, mixes it with the bottom water of higher density and poor oxygen, and diffuses the mixed water upward. The mixed water is expected to spread along the isopycnic as density current, which will cause resolution of anoxic water in the bottom layer and promote the circulation of nutrients. However, it cannot be said the experiment was successful, and detail analysis by numerical simulation should be necessary in order to design more effective purification system. Most of ocean models employ the hydrostatic approximation because the horizontal scale is usually much larger than the vertical scale in oceanic phenomena. In the hydrostatic approximation, dynamic pressure is neglected and momentum equation of vertical direction need not to be solved. But in the present case, around the purification system, hydrodynamic pressure is not negligible and momentum equation of vertical direction must to be solved (called FULL-3D here). In FULL-3D calculation the time of calculation is much longer compared with using hydrostatic approximation. It is almost impossible to calculate the flow of the whole Ohmura bay by FULL-3D approach. The authors developed a new type of ocean model for multi-scale analysis, which conducts hydrostatic analysis for phenomena in wide area and FULL-3D analysis for the detail flow around the interesting object simultaneously. In order to connect the hydrostatic region and FULL-3D region, nested grid system is employed. Using this combined system, the effect of purification system to the whole bay will be investigated accurately.© 2003 ASME

1 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023282
2022708
202167
202089
201998
201893