Hydrostatic equilibrium

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

Extension of Small-Strain Theory to Finite Deformation of Cylindrical Vessels by Internal Over-Pressure

Abstract: Calculations of the pressure distention of closed cylindrical vessels using classical infinitesimal-strain theory predict that, for isotropic materials, the length remains fixed while the diameter increases linearly with pressure. These predictions can be verified experimentally only if the radial deformation is less than 2–3%. This paper develops formulae applicable to deformations up to approximately 10 times the above, based on a modification of infinitesimal theory. The results predict significant lengthening of isotropic vessels, and ballooning or ‘blow-out’ above a certain pressure. It is shown that the classical stresses contain a common hydrostatic component which must be subtracted before the stresses can be integrated across the wall thickness to yield wall tensions. When the hydrostatic component is taken into account, Laplace’s law is found to hold for thick-walled vessels as well as for thin-walled vessels.

Simulation on Temperature Field of Gap Oil Film in Constant Flow Hydrostatic Center Frame

Abstract: In order to solve the thermal deformation of the hydrostatic center frame in the heavy type horizontal lathe, a simulation research concerning temperature field of hydrostatic center frame is described. The Finite Volume Method of CFX has been used to compute three-dimensional temperature field of gap fluid between workpiece and bearing pillow. This research theoretically analyzes the influence of angular velocity on the bearing temperature performance according to lubricating theory and computational fluid dynamics, and it has revealed its temperature distribution law of gap oil film. Results indicate that an improved characteristic will be affected by angular velocity easily, and oil cavity temperature increases by gradually with angular velocity enhancing. Through this method, the safety of a hydrostatic center frame can be forecasted, and the optimal design of such products can be achieved, so it can provide reasonable data for design, lubrication, experience and thermal deformation computation for hydrostatic center frame in the heavy type horizontal lathe.

Simulation and experimental study on lubrication characteristics of vertical hydrostatic guide rails

Abstract: In order to improve the cutting stiffness,the paper studies the vertical hydrostatic bearing in the slide when a ram is in feed process.The change of the oil film thickness on hydrostatic guide rail and the curve of the oil film thickness in various cutting forces are calculated and a relation model through theoretical analysis method is derived.The pressure field of the guide rail recess is simulated based on the finite volume method and demonstrated through experiments.The study is of vital theoretical significance for the improvement of machining accuracy of numerical control machines and the entire computer numerical control(CNC) equipment and provides valuable theoretical basis for the design of hydrostatic guide rail in engineering practice.

Thermal Instability in Clusters of Galaxies with Conduction

Abstract: We consider a model of galaxy clusters in which the hot gas is in hydrostatic equilibrium and maintains energy balance between radiative cooling and heating by thermal conduction. We analyze the thermal stability of the gas using a Lagrangian perturbation analysis. For thermal conductivity at the level of 20-40 % of Spitzer conductivity, consistent with previous estimates for cluster gas, we find that the growth rate of the most unstable global radial mode is ~ 6-9 times lower than the growth rate of local isobaric modes at the cluster center in the absence of conduction. The growth time in typical clusters is ~ 2-5 Gyr, which is comparable to the time since the last major merger episode, when the gas was presumably well mixed. Thus, we suggest that thermal instability is not dynamically significant in clusters, provided there is an adequate level of thermal conduction. On the other hand, if the heating of the gas is not the result of thermal conduction or any other diffusive process such as turbulent mixing, then the thermal instability has a growth time under a Gyr in the central regions of the cluster and is a serious threat to equilibrium. We also analyze local nonradial modes and show that the Lagrangian technique leads to the same dispersion relation as the Eulerian approach, provided that clusters are initially in strict thermal equilibrium. Because cluster gas is convectively stable, nonradial modes always have a smaller growth rate than equivalent radial modes.