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Process, mechanism and impacts of scale formation in alkaline flooding by a variable porosity and permeability model

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Acta Mechanica Sinica 2016年第3期32卷 406-421页

作者： Zhen Zhang Jiachun Li Key Laboratory of mechanics in fluid solid Coupling Systems Institute of Mechanics Chinese Academy of Sciences

In spite of the role of alkali in enhancing oil recovery（EOR）, the formation of precipitation during alkaline-surfactant-polymer（ASP） flooding can severely do harm to the stratum of oil reservoirs, which has been observed in situ tests of oil fields such as scale deposits found in oil stratum and at the bottom of oil wells. On the other hand,remarkable variation of stratum parameters, e.g., pore radius,porosity, and permeability due to scale formation considerably affects seepage flow and alkaline flooding process in return. The objective of this study is to firstly examine these mutual influential phenomena and corresponding mechanisms along with EOR during alkaline flooding when the effects of precipitation are no longer negligible. The chemical kinetic theory is applied for the specific fundamental reactions to describe the process of rock dissolution in silicabased reservoirs. The solubility product principle is used to analyze the mechanism of alkali scale formation in *** a 3D alkaline flooding coupling model accounting for the variation of porosity and permeability is established to quantitatively estimate the impact of alkali scales on reservoir stratum. The reliability of the present model is verified in comparison with indoor experiments and field tests of the Daqing oil field. Then, the numerical simulations on a 1/4well group in a 5-spot pattern show that the precipitation grows with alkali concentration, temperature, and injection pressure and, thus, reduces reservoir permeability and oil recovery correspondingly. As a result, the selection of alkaliwith a weak base is preferable in ASP flooding by tradeoff strategy.

关键词： Alkali Precipitation Chemical flood Permeability Oil recovery

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Hydrodynamic interactions of water waves with a group of independently oscillating truncated circular cylinders

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Acta Mechanica Sinica 2016年第5期32卷 773-791页

作者： Xiaohui Zeng Min Shi Shanlin Huang Key Laboratory for mechanics in fluid solid Coupling Systems Institute of Mechanics Chinese Academy of Sciences

In this study, we examine the water wave radiation by arrays of truncated circular cylinders. Each cylinder can oscillate independently in any rigid oscillation mode with a prescribed amplitude, including translational and rotational modes such as surge, sway, heave, pitch, roll, and their combinations. Based on the eigenfunction expansion and Graf＇s addition theorem for Bessel functions, we developed an analytical method that includes the effects of evanescent modes in order to analyze such arrays of cylinders. To investigate the effects of several influential factors on convergence,our objective is to dramatically reduce the number of tests required and determine the influencing relationships between truncation number and convergence behavior for different factor combinations. We use the orthogonal test method to fulfill the objective. Lastly, we present our results regarding the effects of evanescent modes on hydrodynamic coefficients.

关键词： Radiation Water wave Arrays of truncated circular cylinders oscillating independently Translational oscillation Rotational oscillation

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Frame-invariance in finite element formulations of geometrically exact rods

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Applied Mathematics and mechanics(English Edition) 2016年第12期37卷 1669-1688页

作者： Peinan ZHONG Guojun HUANG Guowei YANG Key Laboratory for mechanics in fluid solid Coupling Systems Institute of MechanicsChinese Academy of Sciences

This article is concerned with finite element implementations of the three- dimensional geometrically exact rod. The special attention is paid to identifying the con- dition that ensures the frame invariance of the resulting discrete approximations. From the perspective of symmetry, this requirement is equivalent to the commutativity of the employed interpolation operator I with the action of the special Euclidean group SE（3）, or I is SE（3）-equivariant. This geometric criterion helps to clarify several subtle issues about the interpolation of finite rotation. It leads us to reexamine the finite element for- mulation first proposed by Simo in his work on energy-momentum conserving algorithms. That formulation is often mistakenly regarded as non-objective. However, we show that the obtained approximation is invariant under the superposed rigid body motions, and as a corollary, the objectivity of the continuum model is preserved. The key of this proof comes from the observation that since the numerical quadrature is used to compute the integrals, by storing the rotation field and its derivative at the Gauss points, the equiv- ariant conditions can be relaxed only at these points. Several numerical examples are presented to confirm the theoretical results and demonstrate the performance of this al- gorithm.

关键词： geometrically exact rod finite element method interpolation equivariance frame invariance

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Investigation on transonic flutter active auppression with CFD-Based ROMs

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Science China(Physics,mechanics & Astronomy) 2015年第1期58卷 107-116页

作者： NIE XueYuan YANG GuoWei ZHANG MingFeng Key Laboratory for mechanics in fluid solid Coupling Systems Institute of Mechanics Chinese Academy of Sciences

The calculation of accurate unsteady aerodynamic forces is critical in the analysis of aeroelastic problems,however the efficiency is low because of high computational costs of the computational fluid dynamics(CFD)***,direct integrated CFD and computational structural dynamics(CSD)technique is unsuitable for the analysis of ASE and the flutter active suppression in state-space form.A reduced-order model(ROM)based on Volterra series was developed using CFD calculation and used to predict the flutter coupled with the *** closed-loop control systems designed by the sliding mode control(SMC)and linear quadratic Gaussian(LQG)control were constructed with ROM/CSD to suppress the AGARD 445.6wing *** detailed implementation of the two control approaches is presented,and the flutter suppression effectiveness is discussed and *** results indicate that SMC method can make the controlled object response decay to the stable equilibrium more rapidly and has better control effects than the LQG control.

关键词： reduced order model aeroelasticity linear quadratic Gaussian control sliding mode control active flutter suppression

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Equilibrium scour depth at offshore monopile foundation in combined waves and current

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Science China(Technological Sciences) 2014年第5期57卷 1030-1039页

作者： QI WenGang GAO FuPing Key Laboratory for mechanics in fluid solid Coupling Systems Institute of Mechanics Chinese Academy of Sciences

Unlike the pier scour in bridge waterways,the local scour at offshore monopile foundations should take into account the effect of wave-current *** the condition of wave-current coexistence,the water-soil interfacial scouring is usually coupled with the pore-pressure dynamics inside of the *** aforementioned wave/current-pile-soil coupling process was physically modeled with a specially designed flow-structure-soil interaction *** results indicate that superimposing a current onto the waves obviously changes the pore-pressure and the flow velocity at the bed around the *** concomitance of horseshoe vortex and local scour hole around a monopile proves that the horseshoe vortex is one of the main controlling mechanisms for scouring development under the combined waves and *** on similarity analyses,an average-velocity based Froude number(Fra)is proposed to correlate with the equilibrium scour depth(S/D)at offshore monopile foundation in the combined waves and *** empirical expression for the correlation between S/D and Fra is given for predicting equilibrium scour depth,which may provide a guide for offshore engineering practice.

关键词： monopile pore-pressure scour depth combined waves and current Froude number

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NUMERICAL AND EXPERIMENTAL STUDY ON LIQUID-solid FLOW IN A HYDROCYCLONE

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Journal of Hydrodynamics 2009年第3期21卷 408-414页

作者： WANG Li-yang ZHENG Zhi-chu WU Ying-xiang GUO Jun ZHANG Jun TANG Chi Laboratory of Applied fluid dynamics Division of Engineering Sciences Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

Hydrocyclones are widely used in industry, of which the geometrical design using CFD techniques is gaining more popularity in recent years. In this study, the Euler-Euler approach and the Reynolds stress model are applied to simulate the liquid-solid flowfield in a hydrocyclone. The methodology is validated by a good agreement between experimental data and numerical results. Within the research range, the simulation indicates that the liquid-solid separation mainly occurs in the conical segment, and increasing conical height or decreasing cylindrical height helps to improve the grade efficiencies of solid particles. Based on these results, two of the same hydrocyclones are designed and installed in series to establish a liquid-solid separation system. Many experiments are then conducted under different conditions, in which the effects of the water cut and the second hydrocyclone on the separation are investigated. The results also confirm that smaller solid particles are more susceptible to the inlet conditions, and the second hydrocyclone plays a more important role as the water cut reduces.

关键词： hydrocyclone liquid-solid flow model efficiency

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On the geometric phase in the spatial equilibria of nonlinear rods

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Acta Mechanica Sinica 2017年第2期33卷 457-471页

作者： Peinan Zhong Guojun Huang Guowei Yang Key Laboratory for mechanics in fluid solid Coupling Systems Institute of MechanicsChinese Academy of Sciences School of Engineering Science University of Chinese Academy of Science

Geometric phases have natural manifestations in large deformations of geometrically exact rods. The primary concerns of this article are the physical implications and observable consequences of geometric phases arising from the deformed patterns exhibited by a rod subjected to end moments. This mechanical problem is classical and has a long tradition dating back to Kirchhoff. However, the perspective from geometric phases seems to go more deeply into relations between local strain states and global geometry of shapes, and infuses genuinely new insights and better understanding, which enable one to describe this kind of deformation in a neat and elegant way. On the other hand, visual representations of these deformations provide beautiful illustrations of geometric phases and render the meaning of the abstract concept of holonomy more direct and transparent.

关键词： Geometric exact rod Geometric phase Rotation group Kirchhoff analogy

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Applicability of discrete element method with spherical and clumped particles for constitutive study of granular materials

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Journal of Rock mechanics and Geotechnical Engineering 2022年第1期14卷 240-251页

作者： Tongming Qu Min Wang Yuntian Feng Zienkiewicz Centre for Computational Engineering College of EngineeringSwansea UniversitySwanseaWales SA18EPUK T-3 fluid dynamics and solid mechanics group Theoretical DivisionLos Alamos National LaboratoryLos AlamosNM87545USA

Discrete element method(DEM)has been intensively used to study the constitutive behaviour of granular ***,to what extent a real granular material can be reproduced by virtual DEM simulations remains *** study attempts to answer this question by comparing DEM simulations with typical features of experimental granular *** groups of models with spherical and clumped particles are investigated from four perspectives:(i)deviatoric stress and volumetric behaviour;(ii)critical state behaviour;(iii)stress-dilatancy relationship;and(iv)the evolution of principal stress ratio against axial *** results demonstrate that DEM with spherical or clumped particles is capable of qualitatively describing macroscopic deviatoric stress responses,volumetric behaviour,and critical state behaviour observed in experiments for granular *** the other hand,some qualitative deviations between experiments and the investigated DEM simulations are also observed,in terms of the stress-dilatancy behaviour and principal stress ratio against axial strain,which are proven to be critical for constitutive *** results demonstrate that DEM with spherical or clumped particles may not necessarily fully capture experimental features of granular materials even from a qualitative *** is thus encouraged to thoroughly validate DEM with experiments when developing constitutive models based on DEM observations.

关键词： Discrete element method(DEM) Granular materials Constitutive behaviour Deviatoric hardening model Rolling resistance model Irregular particles

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Coupled hydroelastic vibrations of an elliptical cylindrical tank with an elastic bottom

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Journal of Hydrodynamics 2014年第2期26卷 264-276页

作者： HASHEMINEJAD Seyyed M. TAFANI Mostafa Acoustics Research Laboratory Center of Excellence in Experimental Solid Mechanics and Dynamics School of Mechanical Engineering Iran University of Science and Technology

An exact three-dimensional analysis based on the linear potential theory and the elaborated method of eigenfunction expansion in elliptic coordinates are presented to study the free coupled elasto-hyrodynamic characteristics of an upright non-deformable cylindrical container of elliptical planform with a flexible bottom plate, filled to an arbitrary depth with an inviscid incompressible liquid. Extensive numerical data are presented in an orderly fashion for the first few symmetric/anti-symmetric coupled hydroelastic natural frequencies as a function of fluid depth parameter for two plate aspect ratios. Also, selected hydrodynamic and structural deformation modes shapes are presented in graphical form. The effects of liquid level, bottom plate elasticity, and cross sectional aspect ratio on the sloshing frequencies and hydrodynamic pressure modes are examined. The validity of the results is examined through computations using a commercial finite element package as well as by comparison with the data available in literature.

关键词： exact solution fluid-structure interaction free surface oscillations vertical elliptical vessel Mathieu functions

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Effect of perforation on flow past a conic cylinder at Re =100: wavy vortex and sign laws

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Acta Mechanica Sinica 2018年第5期34卷 812-829页

作者： L.M.Lin X.F.Zhong Y.X.Wu Key Laboratory for mechanics in fluid solid Coupling Systems Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Sciences University of Chinese Academy of SciencesBeijing 100049China

In order to find the intrinsic physical mechanism of the original Kármán vortex wavily distorted across the span due to the introduction of three-dimensional (3-D) geometric disturbances,a flow past a peak-perforated conic shroud is numerically simulated at a Reynolds number of *** on previous work by Meiburg and Lasheras (1988),the streamwise and vertical interactions with spanwise vortices are introduced and *** vortex-shedding patterns in the near wake for different flow regimes are reinspected and illustrated from the view of these two ***,in regime Ⅰ,spanwise vortices are a little distorted due to the weak *** in regime Ⅱ,spanwise vortices,even though curved obviously,are still shed synchronously with moderate streamwise and vertical *** in regime Ⅲ,violently wavy spanwise vortices in some vortex-shedding patterns,typically an Ω-type vortex,are mainly attributed to the strong vertical interactions,while other cases,such as multiple vortex-shedding patterns in sub-regime Ⅲ-D,are resulted from complex streamwise and vertical interactions.A special phenomenon,spacial distribution of streamwise and vertical components of vorticity with specific signs in the near wake,is analyzed based on two models of streamwise and vertical vortices in explaining physical reasons of top and bottom shear layers wavily varied across the *** these two models and above two interactions are *** two sign laws are summarized:the first sign law for streamwise and vertical components of vorticity is positive in the upper shear layer,but negative in the lower shear layer,while the second sign law for three vorticity components is always negative in the wake.

关键词： Vortex-shedding pattern Flow control Vortex dynamics Conic disturbance Perforation Sign law

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