Hydrostatic equilibrium

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

Influence of Geometric Parameters of Conical Acrylic Portholes on Their Stress–Strain Behaviour

Abstract: Translucent elements in the form of truncated cones, which are made of organic glass, are widely used in the structures of portholes, submersible vessels, space vehicles, pressure chambers, teleboxes and other types of technical equipment. The decisive factor in designing portholes is to ensure the strength of their translucent elements. In order to reduce the weight of portholes and, accordingly, to increase the payload, it is necessary to optimise the geometric parameters of the translucent elements, which include the tapering angle and the ratio of thickness to radius of the smaller base. The paper deals with development of the applied (engineering) method for determining the stress–strain behaviour of the conical translucent elements of portholes made of organic glass under the action of a uniform hydrostatic pressure. Finite-element modelling of the translucent element of the conical porthole is performed, with the calculation of its stress–strain behaviour. External hydrostatic pressure of 10 MPa, absence of loads from the inside and continuous sliding of the translucent element with friction along the conical supporting surface of the porthole metal body are the boundary conditions for the computational model. Full-scale tests of translucent elements of portholes made of organic glass were performed under the action of uniform hydrostatic pressure. Analysis of the influence of geometric characteristics of the portholes on stress–strain behaviour showed that the increase in the tapering angle at the constant relative thickness of the translucent element reduced its axial displacement in all cases. Equivalent stresses acquire minimum values when the tapering angle is in the range from 75° to 105° (when the relative thickness increases, the optimal tapering angle becomes smaller). It is shown that the developed method for determination of the stress–strain behaviour of the conical translucent elements of portholes made of organic glass reflects the real picture of deformation and agrees with the results of full-scale tests. Results of the work allow us to choose the rational parameters of the translucent element for increasing the reliability of portholes through the creation of an effective distribution of stresses and strains in the translucent element, and improving its optical characteristics due to a relatively small deflection in operation.

Simulation of the lubricant flow in thin slot channels with a moving wall under slip boundary conditions

Abstract: The article presents the results of studying the flow of a Newtonian fluid in a narrow wedge-shaped slot with a moving wall. A solution to the problem with slip boundary conditions on the channel walls is obtained. The influence of the slip conditions on the walls on the flow parameters is shown. In diverging and converging sections of the channel, different types of flow take place. In the region of the diverging flow near the stationary wall, a reverse flow zone is formed, the width of which increases with an increase in the Knudsen number, which is due to an increase in the flow velocity on the stationary wall due to the slip condition. Calculations elucidated the effect of slippage on the variation of the hydrostatic lifting force and hydraulic resistance in the slot channel. The dependence of the relative hydrostatic lifting force on the Knudsen number and the opening angle of the channel were revealed. It has been determined that with an increase in the Knudsen number, the magnitude of the hydrostatic lifting force decreases, since in this case the influence of the flow on the wall weakens. With an increase in the opening angle of the channel, slip effect weakens.

Effects of changes in the Earth's rotation rate on sea level

Abstract: The decrease in the earth's angular velocity over the last 100 million years has had an effect on sea level. Comparison of the ellipticity of the earth, as calculated from artificial satellite observations, and the ellipticity of a hydrostatic model gives upper limits on the changes in sea level. These limits are 60 meters at the poles and –30 meters at the equator.

Two-temperature equations of state for d-band metals irradiated by femtosecond laser pulses

Abstract: The cold curves for energy and pressure of Copper, Iron, and Tantalum were obtained using methods of the density functional theory. We consider hydrostatic and uniaxial deformations in the range from double compression of the initial volume per atom to double stretching. The presence of allotropic transformation from $\alpha$ - phase of Iron to the hexaferrum with the growth of pressure is observed. In the case of hydrostatic deformations we also have obtained analogous cold curves, but with non-zero electronic temperatures in the range up to 5 eV. The similar volume and electronic temperature ranges have been considered recently. The behavior of electronic internal energy, pressure, and density of states was investigated in the volume and temperature ranges called above. The maximum hydrostatic strains and the types of lattice instabilities were theoretically predicted for the considered metals. The influence of high electronic temperature on the electronic heat conductivity and electric resistivity has been provided for d-band metals by the approach based on the solution of Boltzmann kinetic equation in $\tau$-approximation. This data is compared with the results of quantum molecular dynamics for Gold.