Hydrostatic equilibrium

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

Numerical and Experimental Modelling of a Wave Energy Converter Pitching in Close Proximity to a Fixed Structure

Abstract: Free-floating bodies are commonly modelled using Cummins’ equation based on linear potential flow theory and including non-linear forces when necessary. In this paper, this methodology is applied to a body pitching around a fixed hinge (not free-floating) located close to a second bottom-fixed body. Due to the configuration of the setup, strong hydrodynamic interactions occur between the two bodies. An investigation is made into which non-linear forces need to be included in the model in order to accurately represent reality without losing computational efficiency. The non-linear forces investigated include hydrostatic restoring stiffness and different formulations of excitation forces and quadratic drag forces. Based on a numerical comparison, it is concluded that the different non-linear forces, except for the quadratic drag force, have a minor influence on the calculated motion of the pitching body. Two formulations of the quadratic drag force are shown to result in similar motions, hence the most efficient one is preferred. Comparisons to wave basin experiments show that this model is, to a large extent, representative of reality. At the wave periods where the hydrodynamic interactions between the bodies are largest, however, the amplitudes of motion measured in the wave basin are lower than those calculated numerically.

The Black-Hole Accretion Disk in NGC 4258: One of Nature’s Most Beautiful Dynamical Systems

Abstract: In this talk I will summarize some of the work that the CfA group has done to study the structure of the water masers in the accretion disk of NGC 4258. A series of 18 epochs of VLBA data taken from 1997.3 to 2000.8 were used for this study. The vertical distribution of maser features in the systemic group was found to have a Gaussian distribution, as expected for hydrostatic equilibrium, with a $\sigma$-width of 5.1 $\mu$as. If the disk is in hydrostatic equilibrium, its temperature is about 600K. The systemic features exhibit a small, but persistent, gradient in acceleration versus impact parameter. This characteristic may indicate the presence of a spiral density wave rotating at sub-Keplerian speed. A more precise understanding of the dynamical properties of the disk is expected to lead to a more refined estimate of the distance to the galaxy.

Research on Influence of Cavity Depth on Load Capacity of Heavy Hydrostatic Bearing in Variable Viscosity Condition

Abstract: Owing to setting viscosity of lubrication oil as a constant value will lead errors in hydrostatic bearing calculation, the influence of cavity depth on load capacity of heavy static bearing is analyzed in variable viscosity condition. Firstly, viscosity-temperature equations of oil film are established; secondly, viscosity-temperature curve is fitted by B-Spline; finally, using finite volume method, hydrostatic pressure field and dynamic pressure field of heavy hydrostatic bearing is calculated with different cavity depth at the same velocity, and influence of cavity depth on load capacity is revealed. The results show that, were the cavity depth shallow enough(≤2mm), hydrostatic pressure and dynamic pressure of cavity would decline rapidly with the cavity depth increasing; whereas, were cavity deep enough(≥2mm), hydrostatic pressure and dynamic pressure of cavity would change little with the cavity depth extending. This numerical simulation reflects real distribution of bearing pressure appropriately, and provides a theoretical basis for hydrostatic bearing design and lectotype.

Device for measuring the quantity of fluid contained in a tank

Abstract: Device for measuring the quantity of fluid 3 contained in a tank 1 disposed in a vehicle According to the invention, this device is noteworthy in that hydrostatic measurement means 5 deliver at least one output signal 12 representing the hydrostatic pressure difference between an upper measurement point 9 and a lower measurement point 8 provided in the tank 1, in that the means 15 generating the signal connected to the attitude of the vehicle deliver at least the vertical component of the acceleration to which the said tank 1 is subjected and in that the said computer 18 calculates a magnitude equal to the ratio between the hydrostatic pressure difference and the product of the density of the fluid with the vertical component of the acceleration Gauging liquids