Averaged Dynamics of Fluids near the Oscillating Interface in a Hele-Shaw Cell

The steady flow in a Hele-Shaw cell filled with fluids with a high viscosity contrast in the presence of fluid oscillations is experimentally studied.The control of oscillatory dynamics of multiphase systems with interfaces is a challenging technological problem.We consider miscible(water and glycerol)and immiscible(water and high-viscosity silicone oil PMS-1000)fluids under subsonic oscillations perpendicular to the interface.Observations show that the interface shape depends on the amplitude and frequency of oscillations.The interface is undisturbed only in the absence of oscillations.Under small amplitudes,the interface between water and glycerol widens due to mixing.When the critical amplitude is reached,the interface becomes unstable to the fingering instability:Aqueous fingers penetrate the high-viscosity glycerol and induce intensive mixing of miscible fluids and associated decay of the instability.After the disappearance of the fingers,the interface takes a U-shape in the central part of the cell.A similar effect is observed for immiscible fluids:The oscillating interface tends to bend to the side of a high-viscosity fluid.Again,when the critical amplitude is reached,the fingering instability arises at the convex interface.This paper focuses on the causes of bending of the initially undisturbed interface between miscible or immiscible fluids.For this purpose,we measure the steady flow velocity near the interface and in the bulk of a high-viscosity fluid using Particle Image Velocimetry(PIV).

The Solely Use of the “Hydraulic-Diameter” Concept Is Not Sufficient to Describe Correctly Non-Symmetric Flow in Conduits

A well-known cornerstone in fluid mechanics is the equations that relate the friction factor to the Reynolds number obtained from the measurements in cylindrical cross-sectional tubes. The extension of these equations to different geometries failed to give reliable results. The introduction of the Hydraulic Diameter has fixed this issue particularly for the square ducts. However, for non-symmetric flows, as in concentric annuli, the discrepancies were unacceptable. Several attempts have been made to fix these problems with finally the introduction of a new concept like, “Laminar Equivalent Hydraulic Diameter” or “Efficient Hydraulic Diameter” provided satisfactory results. This approach seems to have fixed the problem and hence has been widely accepted. Nevertheless, it is based on a non-robust theoretical argument. In the present paper, it has been demonstrated that the solely use of the “Hydraulic Diameter” concept is insufficient to describe non-symmetric flows as in concentric annuli. It appears the need to use the Z axis component of the skew driving force for the laminar flow and the parameter λ for the turbulent one. At the same time, instead, it has been shown that in the case of flow in square and rectangular ducts, the “Hydraulic Diameter” is sufficient to describe it. In this case, the flow is practically symmetric. Moreover, several new straightforward equations are provided, which simplify a lot dealing with non-cylindrical cross-sectional conduits. In doing so, the concept of “Eigenvectors-Eigenvalues” has been implemented. This theoretical approach could help to simplify other non-symmetric cases in fluid dynamics. To mention, “Flow past immersed non-symmetric bodies”, “Flow in curved conduits” etc.

Liquid–liquid two-phase mass transfer characteristics in a rotating helical microchannel

In this work,the mass transfer characteristics of two immiscible fluids were investigated in a rotating helical microchannel with hydraulic diameter of 932μm.Aqueous phosphoric acid solution and 80%tri-n-butyl phosphate(TBP)in kerosene were selected for the investigation of mass transfer performance in quartz glass/high density polyethylene(HDPE)microchannel.High dispersion between the two immiscible fluids can be obtained in the microchannel due to the intensifying action of centrifugal force,and the majority of the droplets with average diameter of 20–100μm were produced in the microchannel.The flow rate and rotation speed were found to have great effects on the extraction efficiency and average residence time.The empirical correlation of average residence time based on experimental data was developed by theoretical analysis and data fitting method,and a mathematical model of the mass transfer coefficient in dispersed phase was proposed.

有机烃在预测隐伏金矿床中的应用及其成因探索

在国内外许多热液矿床的成矿作用研究中都发现有烃类组分的存在,这一现象已越来越受到矿床学家的关注。有机质、有机烃与金属成矿作用之间存在着直接或者间接的成因关系。有机烃指标应用于金属矿产勘查和深部隐伏矿体的预测是一个尚处于试验阶段的新的研究领域,其基础理论还不十分成熟。本文从有机烃预测隐伏金矿床的应用实例着手,归纳出金矿体上有机烃异常特征和模式,并对异常来源以及异常模式成因进行探讨,结果表明有机烃异常特征和有机烃组分间相关特性能有效反映深部隐伏金矿体的赋存空间和成矿规模,为利用有机烃预测隐伏金矿寻求更坚实的理论基础。

油水两相渗流多孔介质弹性波传播动力学模型研究

弹性波在储层渗流场中的传播与衰减规律是研究波场强化采油动力学机理的重要基础.基于等效流体理论和饱和静态流体弹性波传播Biot理论,建立油水两非混相流体渗流条件下储层多孔介质中弹性波传播的动力学模型,通过算例求解与分析,发现含油水两相渗流储层多孔介质中同时存在着3种纵波P1、P2、P3和1种横波S;受频率和含水饱和度的影响,各波波速和品质因子呈现出不同变化规律,4种体波波速与频率、饱和度正相关,P1、P2波品质因子与饱和度正相关,P3和S波品质因子与饱和度负相关;最后,通过与传统静态弹性波模型结果对比,进一步分析了宏观渗流场对弹性波传播特征的影响规律,为揭示低频人工地震波辅助强化采油技术的动力学机理和工艺参数优化提供了重要理论依据.

包含幂律流体的驱替过程的理论研究

建立了牛顿流体和非牛顿幂律流体两相渗流的微分方程。认为幂律流体的视粘度是势梯度和饱和度的函数，将ＢｕｃｋｌｅｙＬｅｖｅｒｅｔ的前缘驱替理论推广到包含幂律流体的驱替过程，得到一维非混驱替的饱和度分布。在此基础上研究了驱替机理，结合算例讨论了幂律流体的流变参数、驱替速度、重力对驱替过程的影响。图４参４（陈志宏摘）

CO2与原油混相及非混相条件下渗流机理差异

在CO_2的资源化利用获得广泛认识的同时,CO_2提高采收率技术得到深入发展。研究CO_2驱替过程中气、液组分变化有利于发现CO_2-原油混相或非混相状态对渗流特征影响的原因。采出程度、含水及气油比等变化规律显示CO_2在孔隙中具有独特的渗流特征。相同驱替量的情况下,非混相状态较早进入含水快速上升期,采出程度平缓增长,而混相状态的采出程度则保持较长时间的线性增长。组分分析结果显示,CO_2驱替过程中油、气组分变化具有相似的变化规律。除此之外,混相状态的CO_2易于与油相组分作用,而非混相状态的CO_2则偏向于与气相组分作用,说明混相或非混相状态时CO_2与原油的作用方式不同。

格子Boltzmann方程模拟不相溶二相流体运动理论

在碰撞项中引入了异类粒子的排斥势，用它取代着色粒子密度重新分布过程，完全克服了人为因素．理论推导表面张力系数的表达式，用以比较模拟的结果，为格子Ｂｏｌｔｚｍａｎｎ方法模拟不相溶二相流体运动提供了理论依据．

基于相场法的多孔介质三相相对渗透率的研究

本文基于相场模型研究了多孔介质内的三相流动过程,得到了三相相对渗透率曲线。通过模拟研究了润湿性、黏性比和毛细数对三相相对渗透率的影响。研究结果表明:润湿性对相对渗透率的影响很小;非润湿性流体的相对渗透率随黏性比的增加而增加,中性流体和润湿性流体的相对渗透率随黏性比的增加而降低;非润湿性流体的相对渗透率随毛细数的增加而减小,润湿性流体的相对渗透率随毛细数的增加而增加,中性流体的相对渗透率不随毛细数单调变化。