油水两相渗流压力脉动的实验及数值分析

本文用高精度的压差传感器和高速度的数据采集设备同时测量出油水两相流体在多孔介质流动时产生的较大压力降和微小压力脉动,应用自行研制的大型数据处理软件对恒流速水驱油的两相渗流压力脉动实验数据进行了分析,发现不同阶段压力脉动具有明显的频谱特性和时间相关特性的不同,在第三阶段（油为主,水增加阶段）谱能增加最大,时间正相关程度最强。     

等熵轻质活塞风洞中活塞质量对匹配压力振荡的影响

等熵轻质活塞风洞的管道中被压缩的气体是作为实验段的气源，在实验阶段，要求其压力维持恒值，称此压力为匹配压力，这一条件只有在忽略活塞质量的理想情况下才可实现，本文研究在实际情况下，即考虑活塞质量时，质量对匹配压力振荡的影响，从而得出活塞质量的选择范围。     

A single-surface yield function for geomaterials

Summary The article outlines a seven-parametric yield function for geomaterials such as soils and rocks. Proceeding from a geometric representation in the principal stress space, the yield surface exhibits a closed shape, thus reflecting the sensitivity of the plastic response of this type of media to hydrostatic stresses. The yield function is able to describe the effects of primary yielding, as well as of isotropic and kinematic hardening. In addition the failure envelope contains an open cone when the number of material parameters is reduced from seven to five.Dedicated to F. G. Kollmann on the occasion of his 60th birthday     

Pressure-dependent viscosity of powder injection moulding compounds

A single piston capillary rheometer was modified by the addition of a second chamber with a restricting valve (developed at the Polymer Centre, Zlín, Czech Republic), which provides backpressure and increasing the pressure in the melted material during the flow through the die. The Carreau–Yasuda model was employed to fit the measured viscosity data and determine the temperature and pressure coefficients for polyolefin based binder and its compounds with carbide powder. Both temperature and pressure sensitivity coefficients are largely dependent on the structure of a polymer, which should be taken into account for binder-formation’s development. Increasing the loading level of the powder in the compound diminishes the pressure sensitivity of their flow properties.     

Regime diagram of the development of long-wave near-wall disturbances in a hypersonic boundary layer

A regime diagram of the development of slow near-wall disturbances induced by an unsteady self-induced pressure perturbation in a hypersonic boundary layer is constructed for a disturbance wavelength greater than the boundary layer thickness. It is shown that the main factors shaping the perturbed flow are the gas enthalpy near the body surface, the intensity of the viscous-inviscid interaction, and the nature (sub- or supersonic) of the main part of the boundary layer. Nonlinear boundary-value problems are formulated for regimes in which the near-wall boundary layer region plays a decisive role. Numerical and analytical solutions are obtained in the linear approximation. It is shown that intensification of the viscous-inviscid interaction or an increase in the role of the supersonic main region of the boundary layer impart generally supersonic properties to the main part of the boundary layer, i.e. the upstream propagation of the disturbances is damped and the disturbance growth downstream becomes more intense. Damping of the viscous-inviscid interaction and an increase in the role of the subsonic main part of the boundary layer have the opposite effect. Surface cooling increases the effect of the main part of the boundary layer on the formation of pressure disturbances and surface heating leads to an increase in the effect of the near-wall boundary layer region. It is also shown that for the regimes considered disturbances propagate in a direction opposite to that of the free stream from the turbulent flow region located downstream of the local disturbance development region.Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, 2004, pp. 59–71. Original Russian Text Copyright © 2004 by Bogolepov and Neiland.     

Numerical Solution and Sensitivity Analysis of Pore Liquid Pressure and Cake Porosity to Model Parameters

Filter cake formation is important in groundwater and oil wells where drilling contains suspended mud particles. The accumulation of these mud particles on the borehole wall creates a pressure drop in the well. Furthermore, the migration of colloidal particles into adjacent porous rock could damage the formation and cause productivity decline. In this study, numerical solutions for pore liquid pressure variation across the cake with variable total stress and associated porosity variation are obtained. Mass equations for captured and suspended particles are averaged along the mud cake thickness, taking into account conditions on the cake surface and at the filter septum. The variability of total stress in soil consolidations problem is considered to determine the pore liquid pressure along the mud cake thickness. Then, the relation between porosity and pressure is studied to determine the mud cake porosity. Experimental data obtained by various researchers is used to compare and test the validity of numerical solutions to develop guidelines for model applications. Results show that the pore liquid pressure increases with the decrease of membrane impedance value (i.e. less pervious membrane). Also, the pressure profile has a cubic function of dimensionless cake thickness. The conclusions from the sensitivity analysis conducted in this study agree with earlier conclusions.     

A New Model for Immiscible Displacement in Porous Media

Immiscible displacement is regarded as the superposition of forward flows of both water and oil, due to injection of water into the medium, and of additional forward flow of water coupled with reverse flow of oil, caused by the existence of capillary pressure gradients. The model has been evaluated numerically for the prediction of the evolution of saturation profiles in waterfloods covering a wide range of water injection rates. In agreement with experimentation, saturation profiles ranging from a completely flat shape to piston-shape, depending on the injection rate, have been obtained. Also in agreement with experimentation, numerical evaluation of the model for the case of a closed system with an initial step-function saturation profile has predicted a gradual spreading of the piston front into S-shaped profiles with an increasing variance. The final profile corresponds to uniform saturation everywhere in the medium.     

可聚合添加剂和极压添加剂对矿物油极压抗磨和抗疲劳性能的影响

选用重极压齿轮油和二聚酸 /司本 - 80添加剂制备了多种不同配比的油样 ,进行了疲劳和胶合试验 ,同时分析了磨损表面形貌和抗磨机理 .结果表明 :聚合添加剂的耐疲劳性能较好 ,其与极压添加剂经合理复配可以更好地提高油样的耐疲劳及抗胶合综合性能 .这是两类添加剂协同作用的结果     

Similarity Solutions for Thawing Processes with a Heat Flux Condition at the Fixed Boundary

Similarity solutions for a mathematical model for thawing in a saturated semi-infinite porous medium is considered when change of phase induces a density jump and a heat flux condition of the type is imposed on the fixed face x=0. Different cases depending on physical parameters are analysed and the explicit solution is obtained if and only if an inequality for the thermal coefficient q ₀ is verified. An improvement for the existence of a similarity solution for the same free boundary problem with a constant temperature on the fixed face x=0 is also obtained. Sommario. Vengono considerate soluzioni di similarità per un modello matematico di disgelo di un mezzo poroso saturo semi-infinito allorquando il cambiamento di fase induce un salto di densità ed una condizione di flusso di calore del tipo viene imposta sulla faccia fissa x=0. Si analizzano differenti casi dipendenti da parametri fisici e la soluzione esplicita viene ottenuta se e solo se risulta verificata una diseguaglianzo per il coefficiente termico q ₀. Si ottiene altresi un miglioramento della condizione di esistenza di una soluzione di similarità per lo stesso problema al contorno libero con temperatura costante sulla faccia fissa x=0.