Pressure Calculation Model Research Articles

Calculation of Earth Pressure on Straight Ditch Buried Rigid Pipe

Based on the unified twin shear strength theory, a new earth pressure formula is deduced for the straight groove buried rigid pipes, with a straight slip plane soil pressure calculation model established. Compared with traditional earth pressure calculation method, the new formula which considers influence of intermediate principal stress on the pipeline earth pressure can obtain the result which is much closer to the actual pipeline stress situation. The results determined from the proposed formula with an engineering example show the influence law of slot width and the thickness of the overburden on tube top soil pressure. The conclusions have some guidance significance for optimization design of pipeline engineering.

Prediction model of casing annulus pressure for deepwater well drilling and completion operation

Casing collapse and fracture may be caused by the rise of casing annulus temperature and pressure in the initial stage of production and testing of deepwater wells. Based on the casing program and wellbore heat transfer process, a pressure calculation model for casing annulus was established, which provides basis for annulus pressure control. With the annulus between testing string and production casing as an example, a casing annulus temperature calculation method was derived according to the principle of conservation of energy and wellbore heat transfer analysis. The casing annulus pressure prediction model was established for typical deepwater wells according to the volume change of casing annulus fluid with temperature and pressure, and in combination of the casing annulus PVT equation and annulus temperature equation. The casing annulus temperature and pressure calculation methods were successfully applied in the casing annulus temperature and pressure management operation in 7 deepwater wells in West Africa, and the predicted temperature and pressure were compared with the actual ones, which indicates that casing annulus temperature and pressure prediction methods have good accuracy, with the relative error below 10%.

Discussion on the Calculation and Analytic Method of the Surrounding Rock of Tunnel on the ADINA

Space of surrounding rock pressure is caused by underground excavation surrounding rock mass and the supporting force of deformation or destruction. Weight model, reduction weight model, tunnel specification and finite element model are four commonly surrounding rock pressure calculation methods. This paper put forward a more reasonable tunnel surrounding rock pressure calculation model by using the finite element analysis software, numerical simulation of tunnel excavation and comparison and analysis of the four calculations results.

Study of Fluid Phase Behavior and Pressure Calculation Methods of a Condensate Gas Well

To date, researchers are still using the method used for conventional gas wells to calculate the wellbore flowing pressure of condensate gas wells, while the calculating accuracy cannot meet the demands of performance analysis and production management. From the analysis of wellbore phase behavior transition in the production process, combined with wellbore temperature distribution change, the pressure calculation model is established based on gas-liquid equilibrium calculation and solved with the four-point implicit difference scheme. The calculated result agrees well with the actual situation and can solve the problem that the pressure gauge could neither be put in the middle part of layer nor operate normally, in order to save a great deal of manpower and material resources.

The Influence of Collar on Surge Pressure Caused by the Drill String Inertia Force Under Closed Pipe Condition

The study of surge pressure is of significant importance for the safety of drilling process. However, the existing surge pressure models rarely take the impact of the collar into consideration and thus will inevitably affect the precision of the surge pressure calculation. In this paper, based on closed pipe condition, a steady-state calculation model for surge pressure caused by drill string inertia force is developed considering the presence of collar. In the end a case study is presented to demonstrate the importance of collar during the calculation of surge pressure.

The Influence of Collar on Surge Pressure Caused by the Drilling Fluid Viscous Force under Pumping Condition

The study of surge pressure is of significant importance for the safety of drilling process because field practice shows that the surge pressure caused by fluid viscous force can cause a great damage to the drilling operation. The accurate calculation of surge pressure is directly related to the safety of the drilling process. However, the existing surge pressure models rarely take the impact of the collar into consideration and thus will inevitably affect the precision of the surge pressure calculation. In this study, based on the pumping condition, a steady-state calculation model for surge pressure caused by drilling fluid viscous force is developed considering the presence of collar. In the end a case study is presented to demonstrate the importance of collar during the calculation of surge pressure.

The Pressure Design of Wet Shift Clutch Based on Thermoelastic Instability Analysis

This paper investigated the dynamic pressure distribution on the plates within a wet shift clutch in hydrodynamic machineries for one engagement. The perturbation pressure model, heat conduction model and pressure calculation model excited by thermoealstic instability was developed. And wrote calculation programs with Maple 15 to analyze the influence of two kinds of typical friction materials, different thermal conductivity, different initial engagement speed on perturbation pressure amplitude and its impact on the pressure design margin and design radius. The results show that the margin can be decreased and design radius can be reduced, so power density increased. When the slipping speed is controlled within 16m /s, the radius can be reduced to about 1/2 of the original value.

Theoretical Analysis and Experimental Research on Cluster Bomb Warhead Built Pressure Device Based on Mechanical Mechanics

This paper according to a certain type of cluster bomb warhead built pressure chamber technical index requirements, design process a set of gas pressure device built principle prototype, and experimental study was carried out. Based on gas build pressure device working process research has determined its three working section: pressure rise section, pressure balance segment and pressure drop section, and then according to the rocket engine interior ballistic principle for each work period respectively calculated, get gas build pressure device and build pressure chamber of the interior ballistic pressure curve, and finally use of principle prototype experimental study. The theoretical calculation curve and test the measured curve have very good consistency; prove this paper established pressure calculation model is reasonable and credible for future related problems research provides a basis.

Generalized Electrolyte-UNIQUAC-NRF model for calculation of solubility and vapor pressure of multicomponent electrolytes solutions

The Electrolyte-UNIQUAC-NRF model proposed by Haghtalab and Peyvandi, Fluid Phase Equilib., 281, 2009 is modified and extended to represent the excess Gibbs energy function of multicomponent electrolyte solutions. Using the experimental mean activity coefficient of aqueous binary electrolyte systems in the extensive domain of temperature and molality, the adjustable temperature dependent parameters are obtained for the several binary electrolyte systems. Furthermore, the osmotic coefficient and vapor pressure of some binary systems are predicted at the wide range of temperature and molality using the adjustable parameters. Having the binary interaction parameters, the solubility of electrolytes in ternary aqueous electrolyte solutions are predicted at 298 K and the higher temperatures so that the phase diagram of the salt solubility are obtained for the several ternary aqueous-salt systems. The results of the solubility, osmotic coefficient and vapor pressure for the electrolyte systems demonstrate that the generalized Electrolyte-UNIQUAC-NRF model can be successfully applied for prediction of the thermodynamic properties of multicomponent electrolyte systems with very good accuracy.

Analysis Again for Earth Pressure Calculation Theory Considering Displacement Effects

According to Moore-Coulomb strength theory, combined with the shear strength reduction method, assumed that the exerted value of the soil’s internal friction Angle and displacement were in nonlinear, and the exerted value of the soil’s cohesion and displacement were in linear, and then put forward a unified, continuous with displacement earth pressure calculation model, and this model could be used to calculate the active and passive earth pressure for cohesive soils and cohesionless soils in any nonlimited state and any movement mode. Through the analysis of the calculation model showed that: (1) The above assumptions were all reasonable from the two perspectives of the theoretical and the measuring; (2) The variation process of earth pressure acted on the retaining wall with displacement, could regard as the process of the soil’s shear strength parameters exerting gradually; (3) Given the physical meanings to the calculated parameters; (4) Analyzed the characteristics of the calculation model, and pointed out that there were calculation errors when the displacement of retaining wall was in (0, x0H) for the Rankine earth pressure theory.

The Laboratorial Study of Fracture Energy Release Rate of the Reservoir Ice Layer

The fracture energy release rate , which is the important parameter of ice pressure calculation model that is built on energy balance method, is the fracture mechanics performance of ice material. It is related with these factors such as ice material temperature T, which must be measured by experiment. It is the experimental method of fracture mechanics used in this paper. These ice specimens on the different thickness T were tested with fracture mechanics method at low-temperature testing machine, to obtain the fracture flexibility change rate of ice body which contains pre-crack and the values of under different conditions of T, which could determine fracture energy release rate of ice body during the ice pressure generated, which provide the necessary experimental data to establish ice layer pressure calculation model for the application of energy balance method.

Delamination of moisture saturated graphite/polyimide composites due to rapid heating

In this study, experimental methods and a theoretical model are developed with aim of understanding and predicting the onset of steam pressure-induced delamination. Experiments are performed by rapid heat-up of moisture saturated T650-35/HFPE-II-52 graphite/polyimide laminates, pre-implanted in the midplane with circular starter cracks. The deformation of these flaws and subsequent delamination growth is measured using custom designed, transverse extensometers. A theoretical model for calculation of internal steam pressure within a deforming circular cavity is derived and combined with a linear elastic fracture mechanics approach to predict the onset of delamination growth. The experimental results and theoretical calculations are used to highlight the effect of heating rate, initial flaw size, initial moisture content, and material toughness on steam-induced delamination. A parametric study is conducted and used to identify conditions required for transition between steam-induced delamination and steam-induced blistering damage.

Modelling bond strength of corroded plain bar reinforcement in concrete

In this paper, the corrosion influence on bond strength between plain bar and concrete without confinement is studied at the time of cracking and before cracking occurs, and causes of bond strength increment are analysed quantitatively. A new calculation model for corrosion pressure and corrosion depth at the time of cracking is proposed. Considering the change of bar surface and increment of corrosion pressure, a new calculation model for bond strength at the time of cracking and before cracking occurs is given. Additionally, the theoretical model is verified using different test results.

Reflections on cavitation nuclei in water

The origin of cavitation bubbles, cavitation nuclei, has been a subject of debate since the early years of cavitation research. This paper presents an analysis of a representative selection of experimental investigations of cavitation inception and the tensile strength of water. At atmospheric pressure, the possibility of stabilization of free gas bubbles by a skin has been documented, but only within a range of bubble sizes that makes them responsible for tensile strengths up to about 1.5bar, and values reaching almost 300bar have been measured. However, cavitation nuclei can also be harbored on the surface of particles and bounding walls. Such nuclei can be related to the full range of tensile strengths measured, when differences of experimental conditions are taken into consideration. The absence or presence of contamination on surfaces, as well as the structure of the surfaces, are central to explaining why the tensile strength of water varies so dramatically between the experiments reported. A model for calculation of the critical pressure of skin-covered free gas bubbles as well as that of interfacial gaseous nuclei covered by a skin is presented. This model is able to bridge the apparently conflicting results of the many scientists, who have been working in the field over the years.

A calculation model for the evaporation recoil pressure in lasermaterial processing

A physical model is proposed to calculate the recoil pressure actingon the surface of an evaporating material irradiated by a high-intensity laserbeam, such as encountered in laser material processing. Laser attenuation inthe laser-induced plasma plume, reflection at the material surface and theenergy consumption for material heating and melting are considered in thismodel. This evaporation model represents a revised form of that previouslyemployed by Chen Xi (1996, 1997, 1998) to calculate the evaporation-addedpressure acting on an evaporating particle exposed to a thermal plasma, buthere the special features associated with laser material processing areconsidered. The calculated recoil pressures compare favourably withavailable experimental data.

A model for calculation of pressure in the duct due to discharge of gas from a failed fuel pin

Abstract In this paper an anlytical model for the calculation of the pressure pulse in hexagonal ducts due to discharge of gas from a failed fuel pin is developed. The analysis yields the time history of the pressure pulse which can be used in the calculation of permanent deformation of the duct or in the assessment of the susceptibility of the duct to fracture. In this model the analysis is divided into two stages. In the first stage the gas expands as a spherical bubble, but the influence of duct wall is taken into account. At the end of the first stage the spherical shape of the bubble is assumed to be lost and the gas is assumed to expand axially as a column. The end conditions of stage 1 are the initial conditions for stage 2. The analysis involves solving the continuity and momentum equations for the liquid along with the energy balance equation for the gas. In the analysis the liquid is assumed to be incompressible.

Minimization of the drag of blunt edges of projecting elements of a hypersonic object

An approximate method is given for calculating the pressure on the critical line of a cylindrical edge of an element projecting above the surface of a hypersonic object. Correlations of the pressure distribution in the interference regions are proposed on the basis of the calculations and analysis of the experimental data. Variational problems of finding the form of a leading edge having minimum drag are set up and solved on the basis of the pressure calculation model obtained. The solutions are sought with the use of Pontryagin's maximum principle. The effect on the minimum drag profile of Mach numbers and blunting of the body is analyzed. The advantage of the optimal form of the edge in comparison with a corresponding rectilinear edge is shown.

A Theoretical Model for Calculation of Xylem Sap Pressure from Climatological Data

A theoretical model is presented for the calculation of stem-xylem sap pressure from climatological data in an open-grown stand of Abies procera and A. amabilis located at 1206 m elevation in the Washington Cascades. Stem-xylem sap pressure is divided into two components: (1) a base level which is a function of soil moisture, and (2) a diurnal depression in sap pressure from this base level which is a function of current atmospheric evaporative demand. Predicted values of stem-xylem sap pressure were compared to observed values and no sig- nificant difference was observed. Other plant processes such as stomatal aperture were predicted from the model. Specific deficiencies in the model were observed and are discussed. Substantial apparent nighttime transpiration occurred within these two species under laboratory and field conditions, leading to a discrepancy between base level sap pressure and soil moisture. I NTRODUCTION The integrated abiotic and biotic factors affecting plants contribute to their water status (Fritts, 1966). Since growth frequently is limited by even mild foliar desiccation (Slatyer, 1967), the understanding of plant water status is essential to evaluating plant-environment inter- actions and the resulting ecological distribution of plants. Our effort to understand plant water status has led to the formulation of a model which predicts water status of forest trees from climatological data.