Hydrostatic equilibrium

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

Modeling Long-Term Photometric Data of Trans-Neptunian Objects and Centaurs

Abstract: Trans-Neptunian objects and Centaurs are small Solar System bodies that reside in the outer parts of the Solar System. These objects present photometric behaviors that are influenced due to a change in their aspect angle. Using absolute photometric measurements and rotational light-curves at different locations on their orbits allows to model their photometric behavior and obtain physical properties such as pole orientation, shape, density, and even detecting different peculiarities as departure from hydrostatic equilibrium or rings. This work presents how these models are performed to extract different physical properties. A summary of the objects for which their long-term photometric behavior has been modeled is also given.

Small-Scale Modeling of Flexible Barriers. II: Interactions with Large Wood

Abstract: During strong floods, rivers often carry significant amounts of sediment and pieces of large wood (LW). When bridges and hydraulic structures are unable to allow LW to pass through, it becomes necessary to trap LW through specific wood retention structures (e.g., flexible barriers). This paper presents a comprehensive analysis of the interactions between LW and flexible barriers using small scale models. A dimensionless criterion is first proposed to compute blockage probability of single logs. It is based on experiments varying log size and shape, channel slope (2%, 4%, and 6%), water discharge, and barrier bottom clearance. Based on runs using six mixtures of hundreds of logs, an equation is secondly provided to compute flow depth at a barrier accounting for the head losses related to large numbers of logs. Conditions leading to the release of LW when the barrier is severely overwhelmed are also studied. The deformation measured on the barrier proves to be lower with LW-laden flows than under full hydrostatic loading of a barrier obstructed by a plastic sheet. Overall, we demonstrate that flexible barriers are very relevant structures to trap LW. A companion paper shows how to design and manufacture a small scale flexible barrier in mechanical similitude with the prototype scale.

Hybrid Topography of Lotus Leaf under Hydrostatic/Hydrodynamic Pressure

Abstract: The superhydrophobic characteristics and functional durability of the lotus leaf are determined by its surface flexible multistage topography. In this study, it is found that the hybrid arrangement of sub‐millimeter (sub‐mm) and micron papillae arrays on the edge of lotus leaves is more conducive to its resistance to hydrostatic and hydrodynamic water pressure, which provides a guarantee for the survival of lotus leaves. Inspired by this special design, a flexible hybrid structure is prepared by the template method, whose surface contains sub‐mm pillars, micropillars, and nanostructures. It has obvious advantages in resisting the continuous impact of water droplets. This systematic study reveals why the surface of the lotus leaf can withstand the fluid impact, and it provides a theoretical and experimental basis for improving the durability of artificial superhydrophobic function.

On the Structure and Long-term Evolution of Ice-rich Bodies

Abstract: The interest in the structure of ice-rich planetary bodies, in particular the differentiation between ice and rock, has grown due to the discovery of Kuiper Belt objects and exoplanets. We thus carry out a parameter study for a range of planetary masses M, yielding radii 50 ≲ R ≲ 3000 km, and for rock to ice mass ratios between 0.25 and 4, evolving them for 4.5 Gyr in a cold environment, to obtain the present structure. We use a thermal evolution model that allows for liquid and vapor flow in a porous medium, solving mass and energy conservation equations under hydrostatic equilibrium for a spherical body in orbit around a central star. The model includes the effect of pressure on porosity and on the melting temperature, heating by long-lived radioactive isotopes, and temperature-dependent serpentinization and dehydration. We obtain the boundary in parameter space (size, rock content) between bodies that differentiate, forming a rocky core, and those which remain undifferentiated: small bodies, bodies with a low rock content, and the largest bodies considered, which develop high internal pressures and barely attain the melting temperature. The final differentiated structure comprises a rocky core, an ice-rich mantle, and a thin dense crust below the surface. We obtain and discuss the bulk density–radius relationship. The effect of a very cold environment is investigated, and we find that at an ambient temperature of ∼20 K, small bodies preserve the ice in amorphous form to the present.

Cosmic Rays and a Stable Hydrostatic Equilibrium of the Galaxy

Abstract: It is argued that the stellar, gaseous, magnetic-field, and cosmic-ray components in the Galaxy may currently be in a large-scale hydrostatic equilibrium that is stable against Parker type instabilities. Equilibrium configurations considered in the past were found to be unstable as a consequence of simplifying assumptions, which are inconsistent with recent observations.