Hydrostatic equilibrium

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

Calculating capillary pressure curve from single-speed centrifuge experiments

Abstract: We present a method for the calculation of the capillary pressure curve in porous media using centrifuge single-speed experimental data. The mathematical model is based on the hydrostatic equilibrium equation for capillary pressure and the inverse problem for finding the saturation distribution along the sample from the displaced fluid volume when all the flow has ceased. The capillary effects are interpreted as constraint forces which keep the oil trapped in the pores of the sample. We use the Lagrangian formulation to find the equilibrium configuration of the oil in the sample. The great advantage of this formulation is that the explicit inclusion of forces is not necessary. Mathematical properties of the capillary pressure curve and centrifuge data are used as constraints of the kinetic energy minimization procedure. The discretized problem is solved using a nonlinear programming procedure using only the single-speed experimental data. Numerical results are compared with calculations in the frequently used multi-speed centrifuge tests.

Estimation of the Possibility to Equalize the Fluid Temperature in a Hydrolevelling System by Mixing

Abstract: Measurement systems that are based on the hydrostatic leveling method under ideal conditions allow one to determine vertical displacements with accuracy on the order of a micron. Heterogeneous and time-varying environmental conditions have a significant effect on the measurement error. One method to increase the accuracy of results is to equalize the temperature of the fluid in the hydrostatic level by mixing the liquid inside it before taking measurements. In this paper, the possibility to perform this operation by forced circulation of the fluid is estimated. For this purpose, a model problem of the circulation flow created by a pump in a simplified analog of the hydrostatic level with allowance for the heat transfer through the hose wall is solved. The fluid dynamics is described by the Reynolds averaged Navier-Stokes equations which are closed by the Menter shear stress transport model. The analytically obtained estimates of heat transfer coefficients on the lateral surface of the hose are refined based on experiments at two values of the flow rate of water flowing through the pipe. The evolution of the temperature field is found from the numerical solution of the coupled heat transfer problem by the finite volume method. In a test example, in which two parts of the hydrostatic level are located in areas with markedly different temperature, the spatial inhomogeneity of the temperature field at different times is calculated. The mixing time sufficient to achieve a temperature distribution close to the homogeneous distribution of the flowing fluid in the hose at different volumes of the mixer joint with the hydrostatic level is determined. The proposed approach can be used under real external conditions for the selection of optimal operation parameters: the pump flow rate, mixing time, and mixing tank volume. The temperature field obtained in the calculation can serve as a basis for estimating the achievable accuracy of the measurement system.

On the partition of horizontal momentum between velocity and pressure components through the transition region of breaking waves

Abstract: When a water wave breaks, it undergoes a complicated interchange of total, depth integrated horizontal momentum between that part due to the velocity field and the part that can be assigned to the pressure distribution beneath the surface. This partition of total momentum for a strong, plunging breaker is described by a relatively crude model in which the horizontal velocity profile (over the vertical) is schematized in two layers and the pressure distribution is related to a hydrostatic distribution for the given water depth. An example calculation at four locations across the breaking transition region on a plane beach is utilized to demonstrate the principles of the model. The limitations of the approach which assumes momentum conservation in a reference frame moving with the wave celerity defined at the wave crest are presented, but await verification. The ultimate goal is a relatively simple model to predict the transition width of breaking waves (spillers, plungers and intermediate types) for plain and bar-trough beaches.

Simulation Research on Temperature Field of Circular Cavity Hydrostatic Thrust Bearing

Abstract: In order to solve the thermal deformation of the hydrostatic thrust bearing in the heavy equipment, a simulation research concerning temperature field of multi-pad hydrostatic thrust bearing having circular cavities was described. The Finite Volume Method of Fluent has been used to compute three-dimensional temperature field of gap fluid between the rotation worktable and base. This study theoretically analyzes the influence of cavity radius and cavity depth on the bearing temperature performance according to computational fluid dynamics and lubricating theory. It has revealed its temperature distribution law. The simulation results indicate that an improved characteristic can be gotten from a circular cavity hydrostatic thrust bearing, oil cavity temperature decreases by gradually with cavity radius enhancing, oil cavity temperature decreases by gradually with cavity depth. Through this method, the safety of a hydrostatic thrust bearing having circular cavities multi-pad can be forecasted, and the optimal design of such products can be achieved, so it can provide reasonable data for design and lubrication and experience and thermal deformation computation for hydrostatic thrust bearing in the heavy equipment.