Three-Dimensional Finite Element Numerical Simulation and Physical Experiment for Magnetism-Stress Detecting in Oil Casing

The casing damage has been a big problem in oilfield production. The current detection methods mostly are used after casing damage, which is not very effective. With the rapid development of China's offshore oil industry, the number of offshore oil wells is becoming larger and larger. Because the cost of offshore oil well is very high, the casing damage will cause huge economic losses. What's more, it can also bring serious pollution to marine environment. So the effective methods of detecting casing damage are required badly. The accumulation of stress is the main reason for the casing damage. Magnetic anisotropy technique based on counter magnetostriction effect can detect the stress of casing in real time and help us to find out the hidden dangers in time. It is essential for us to prevent the casing damage from occurring. However, such technique is still in the development stage. Previous studies mostly got the relationship between stress and magnetic signals by physical experiment, and the study of physical mechanism in relative magnetic permeability connecting the stress and magnetic signals is rarely reported. The present paper uses the ANSYS to do the three-dimensional finite element numerical simulation to study how the relative magnetic permeability works for the oil casing model. We find that the quantitative relationship between the stress' s variation and magnetic induction intensity's variation is: Δδ =K* ΔB, K = 8.04×109, which is proved correct by physical experiment.

Analysis on nasal airway by using scale-adaptive simulation combined with standard κ-ω model and 3D printing modeling physical experiment

The physiological structure of the upper respiratory tract is complex and varies with each individual,and the circulating air has turbulent performance.In this paper,based on computed tomography(CT)medical images published online and the three-dimensional(3D)printing technology,a 3D model of the human upper respiratory tract was reconstructed and an experimental device of the upper respiratory tract was made.We implemented the respiratory experiment and measured the flow rate,and a scale-adaptive κ-ω model is applied for numerical simulation,the results are in good agreement.The flow field during respiratory was analyzed by coronal velocity cross section,vortex line and particle tracks.We found that the relatively strong shear effect happens at the areas of nasal valve and nasopharynx.In the middle and upper nasal tract,vortex line separation occurs and there is significant passage effect.The results indicate that SAS method is effective in studying upper respiratory airflow.

Simulation Experiments of Land Surface Physical Processes and Ecological Effect over Different Underlying Surface

Based on the existing Land Surface Physical Process Models(Deardorff, Dickinson, LIU, Noilhan, Seller, ZHAO), a Comprehensive Land Surface Physical Process Model (CLSPPM) is developed by considering the different physical processes of the earth's surface-vegetation-atmosphere system more completely. Compared with SiB and BATS, which are famous for their detailed parameterizations of physical variables, this simplified model is more convenient and saves much more computation time. Though simple, the feas...

Numerical simulation of non-Archie electrophysical property of saturated rock with lattice Boltzmann method

The electrophysical property of saturated rocks is very important for reservoir identification and evaluation. In this paper, the lattice Boltzmann method （LBM） was used to study the electrophysical property of rock saturated with fluid because of its advantages over conventional numerical approaches in handling complex pore geometry and boundary conditions. The digital core model was constructed through the accumulation of matrix grains based on their radius distribution obtained by the measurements of core samples. The flow of electrical current through the core model saturated with oil and water was simulated on the mesoscopic scale to reveal the non-Archie relationship between resistivity index and water saturation （I-Sw）. The results from LBM simulation and laboratory measurements demonstrated that the I-Sw relation in the range of low water saturation was generally not a straight line in the log-log coordinates as described by the Archie equation. We thus developed a new equation based on numerical simulation and physical experiments. This new equation was used to fit the data from laboratory core measurements and previously published data. Determination of fluid saturation and reservoir evaluation could be significantly improved by using the new equation.

Overlying strata movement of recovering standing pillars with solid backfilling by physical simulation

To analyze the overlying strata movement law of recovering room mining standing pillars with solid backfilling.Physical simulation experiments with sponge and wood as the backfilling simulation material were tested.The results show that:(i) The covering-rock mechanics of the overly strata comes from "two-arch structures + hinged girder + bend beam" to "backfilling material + hinged girder + bent beam" by increasing the fill ratio from 0%to 85%,the beginning of overlying strata movement appears later and the total duration of subsidence velocity increased from zero to the highest value increases.The trend of "single polarization" of the subsidence velocity curves becomes noticeable and the velocity variation trend becomes stable,(ii) The equiponderate aeolian sand was added to improve the anti-pressure ability of the loess,and the corresponding ground processing & transportation system was designed.

PHYSICAL SIMULATION BASED INTELLIGENT SYSTEM FOR THE PREDICTION OF SHEET METAL DRAWING CAPABILITY

With the combination of a new theoretical formula, physical simulation experiments, the technology of artificial neural network and database, an intelligent system for the prediction of sheet metal drawing capability is constructed for the first time. A modified criterion for sheet metal drawing capability is proposed in this paper, namely, the Technological Limiting Drawing Ratio, TLDR = f(R, n, s, t, F, μ,r_d,r_p…). Based on the studies of other scholars, a new formula is derived to predict the TLDR in this paper. Then a series of orthogonal physical simulation experiments are designed to investigate the effect of technological parameters on the TLDR, and the results are analyzed in the paper. Then the predicting system is constructed with the combination of the theoretical formula, orthogonal experiments, the technology of artifocial neural network and database. The predicted results show good agreements with experimental data, so it can be used to avoid the blindness in the selection of sheet metal before stamping. The system operates under the Windows operating system, and it supports the mechanism of Client/Server as well as Intranet, so the system has high engineering value.

Determination of the coefficient of rolling friction of an irregularly shaped maize particle group using physical experiment and simulations

The coefficient of rolling friction is an important physical property of a maize particle. It is difficult to obtain the value of this coefficient because of the irregular shape of maize particles. This paper describes an approach that combines the discrete-element method （DEM） and a physical test to determine the coefficient of rolling friction of irregularly shaped maize particles. A novel test platform was used to obtain the maize particle＇s coefficient of restitution and the coefficient of static friction. EDEM software （DEM- Solutions, United Kingdom） was used to simulate the accumulation of maize particles on particles and on a zincified plate. The golden-section method was used to determine the range of the maize particle＇s coefficient of roiling friction. A single-factor test was used to determine the relationship between the maize particle＇s coefficient of rolling friction and their angle of repose. The results obtained from the EDEM simulation were compared with physical test results to determine the intergranular coefficient of rolling friction and the coefficient of roiling friction between maize particles and the zincified plate. Our study demonstrates that the angle of repose increases linearly with the coefficient of rolling friction of maize particles. The effect of the coefficient of rolling friction on the particle movement is studied. The physical verification test indicates that the obtained rolling friction of the maize particles is accurate. The findings of this paper provide a theoretical basis for maize-processing machine design and a discrete-element studv of the motion of maize particles inside such machines.

Numerical Simulation Experiment of Land Surface Physical Processes and Local Climate Effect in Forest Underlying Surface

Based on the basic principles of atmospheric boundary layer and plant canopy micrometeorology, a forest underlying surface land surface physical process model and a two-dimensional atmospheric boundary layer numerical model are developed and numerical simulation experiments of biosphere and physiological processes of vegetation and soil volumetric water content have been done on land surface processes with local climate effect. The numerical simulation results are in good agreement with realistic observations, which can be used to obtain reasonable simulations for diurnal variations of canopy temperature, air temperature in canopy, ground surface temperature, and temporal and spatial distributions of potential temperature and vertical wind velocity as well as relative humidity and turbulence exchange coefficient over non-homogeneous underlying surfaces. It indicates that the model developed can be used to study the interaction between land surface process and atmospheric boundary layer over various underlying surfaces and can be extended to local climate studies. This work will settle a solid foundation for coupling climate models with the biosphere.

Physical simulation experiment and numerical inversion of the full life cycle of shale gas well

The ultra-low porosity and permeability,as well as complex occurrence and transport state of shale reservoir make it possess special L-type production characteristic curve and complicated shale gas flow mechanism.To solve the difficulty of collecting complete production data due to short production time and operation discontinuity,a full-diameter core physical simulation experiment on the full lifecycle production process of shale gas well depletion is conducted with the purpose of obtaining many important production data including complete pressure and daily gas output in the simulated production process of shale gas well.The experimental results show the production characteristic from simulation is consistent with those from gas well.Based on the simulation data,the critical desorption pressure(12 MPa)of core,free gas production(3820.8 mL),adsorbed gas production(2151.2 mL),the proportion of the daily gas production between free and absorbed gas under different time and formation pressure,as well as the production time and final recovery rate corresponding to abandoned pressure,can be determined accurately.Numerical inversion is carried out to calculate the production performance curve of shale gas well and predict the development effect of gas well based on well testing and similarity analysis of the dimensionless time between core experiment and gas well production.Finally,the permeability and the fracturing effect(fracture network density)as the keys to the effective development of shale gas reservoirs are proposed.The permeability is the fundamental factor and the fracturing technology is the major means.

基于Three.js的大学物理在线仿真实验开发

Three.js是用JavaScript编写的基于WebGL的在线三维场景和动画的开发引擎。为了使学生能在线开展虚拟仿真实验,探索学生线上自主学习和线下课堂学习相结合的实验教学模式,提升学生实操实验课时的有效利用,采用Three.js提供的JavaScript库函数来开发分光计实验和密立根油滴实验等在线虚拟仿真实验。通过该仿真实验,学生能在实验课之前对实验的原理和操作细节有具体了解,从而对实验中遇到的问题进行深入探究,提高实验教学效果。这些仿真实验也可以作为由于其他原因无法实现线下实验的一种替代教学实验方案。以Three.js为开源开发的物理在线仿真实验平台可推广。

裂隙中煤粉运移及解堵可视化物理模拟实验

煤粉在煤储层裂隙中沉积会降低裂隙导流能力,制约煤层气井高效稳产开发。设计了裂隙中煤粉运移及解堵可视化物理模拟实验方案,通过裂隙中煤粉运移可视化物理模拟实验,分析了裂隙不同位置煤粉颗粒沉积面积的变化和沉积形态特征,揭示了煤粉运移、沉积的动态规律;通过裂隙中煤粉解堵可视化物理模拟实验,分析了解堵时间和流速对裂隙中沉积煤粉解堵面积的影响,揭示了煤粉启动、解堵的动态规律。实验结果表明:煤粉颗粒在裂隙不同方向和位置聚集状态不同,裂隙喉道由入口向垂直主运移方向的两端及主运移方向煤粉颗粒沉积面积逐渐减少,支路通道沿主运移方向煤粉颗粒沉积面积逐渐增加。裂隙喉道、支路通道和主路通道处煤粉沉积的形态分别呈鹰嘴状、层状和流线型,其原因是裂隙不同位置对含煤粉流体的阻力不同,导致煤粉在不同位置的沉积形态不同。在相同流速下,随解堵时间增长,煤粉解堵效果越好,但前期解堵面积大,后期解堵面积小,裂隙喉道处煤粉解堵效果明显优于支路通道,其原因是松散、易于解堵的煤粉颗粒会被首先解堵,随时间进行,剩余未被解堵的煤粉颗粒需要更大的启动流速。流速越大,裂隙喉道处和支路通道处的煤粉解堵面积越大,其原因是提升流速能增强煤粉颗粒的流动性。

尾闾河道形态演变特征的模拟试验研究

尾闾河道是河流与海洋交互的关键地带,对其形态演变研究具有生态环境意义。采用物理试验方法对常见的喇叭状和蜿蜒状(河口左偏与右偏)尾闾河道演变过程进行模拟,研究不同水沙条件下河道演变规律,并以河相系数和相对粗糙度为基准对不同河型稳定性进行评估。试验发现:河道平面形态会经历一个“稳定—微变—强变”阶段;河床平均高程和比降随时间的增加而增大,模型河道上游和河口段变化最大,中游段变化最小;加沙时上游河岸侵蚀、河床淤积,加沙停止后下游与河口段河岸侵蚀大于河床侵蚀,河口分汊、摆动。平面形态不稳定区域:蜿蜒状为下游段,最大与最小河相系数相差6.51倍以上;喇叭状为河口段,最大与最小河相系数相差3.32倍以上。断面形态不稳定区域:左偏蜿蜒状为下游段,最大与最小相对粗糙度相差3倍以上;右偏蜿蜒状为上游段,最大与最小相对粗糙度相差2.03倍以上;喇叭状为下游段,最大与最小相对粗糙度相差4.09倍以上。

电磁无损检测实验设计与教学方法

电磁感应法是一种重要的无损检测方法,尤其在对混凝土钢筋的定量检测和评估时,该方法发挥了重要的作用。为了进一步提高无损检测相关课程的教学质量、优化教学体系,提出了一种基于物理实验和数值模拟的教学实验模式。通过设计的一款用于室内测量和标定实验的钢筋无损检测实验箱开展对混凝土钢筋无损检测的定量实验;采用COMSOL有限元仿真软件进行基于电磁感应原理和检测新方法的数值模拟研究。这种物理实验与数值模拟相结合的教学实验和检测方法,可以将抽象的电磁理论和探测机理转化为直观的数据图像,并将难以开展的现场测试引入教学过程中。

重离子加速器中的原子核碰撞虚拟仿真实验的建设与应用

利用虚拟仿真技术,结合教学团队的科研成果,设计开发了重离子加速器中的原子核碰撞等一系列实验教学项目.这些实验项目能够在电脑上再现真实的实验场景,解除了实验场地、费用、防护等方面的限制,为培养学生的实验探究设计能力、开拓学生视野提供了重要支撑.结合虚拟仿真技术的特点,教师团队采用适应的教学方法进行授课,建立了完善的评价体系.经过3年的课程建设,该课程在学生培养、教师教学质量、推广应用方面取得了良好的效果.

基于电机的“自动控制原理”实验教学

针对ACCT-Ⅲ实验箱开展“自动控制原理”实验教学缺乏具体的被控对象的问题,设计以电机为被控对象的实验教学,内容包括建立电机电流和速度数学模型,设计电流、速度闭环PID控制系统,控制系统Matlab仿真,实际伺服电机平台实验等。该实验教学从实物建模、模型仿真、控制器设计到控制系统仿真与实物验证,以项目设计理念为指导,让学生更好地理论与实际相结合,达到知识的内化,提高了教学质量。

永磁同步电机直接转矩控制系统实验教学设计与实现

为加深学生对电气传动控制技术和永磁同步电机(PMSM)直接转矩控制(DTC)系统理论知识的理解,培养学生的团队合作能力和综合实践能力,搭建了直接转矩控制系统的实验平台,在课程教学中引入了HiGale半实物仿真系统和MATLAB软件。学生基于MATLAB软件对永磁同步电机的直接转矩控制系统进行仿真建模、参数调试、运行和分析,并进一步在HiGale中进行半实物仿真实验,对主要实验过程及结果加以分析,使得教学形式更加多样化。该平台帮助学生加深对直接转矩控制系统的理解和认识,提高学生理论联系实际的能力,激发学生对电机控制技术的学习兴趣。

磁悬浮小球虚拟实验系统设计与开发

为了解决“动力控制原理与技术”课程内容抽象、学生缺乏对实际工程控制案例直观认识的问题,设计开发了一种基于半物理仿真的磁悬浮小球虚拟实验系统。建立了磁悬浮小球的仿真模型,设计了自定义目标软硬件实现方案,完成了虚拟磁悬浮小球与嵌入式目标之间的通信。通过所设计的实验系统,可以开展系统建模、PID串级悬浮控制、嵌入式控制器设计等各类开放性实验,弥补了传统实验的各种限制,达到寓教于乐,提升教学效果的目的。

面向电气工程实际的多物理场数值仿真开放实验教学

在电气工程专业本科生电磁场实验教学中,开展面向电气工程实际的多物理场数值仿真开放实验教学,对培养学生的工程观念、综合应用多学科专业知识解决实际电气工程问题的能力具有重要的意义。以电力系统中广泛应用的电力设备——干式空心电抗器为研究对象,阐述了开设干式空心电抗器电、磁、热以及力场等多物理场数值仿真开放实验的目的、内容及实施过程。这些开放实验取得了良好的教学效果。

天然气开发基础实验与应用研究进展

中国天然气开发实验技术取得了重要进展,已建设形成岩心样品制备、储层物性与岩石孔喉结构测试、储层敏感性评价、流体赋存状态及气水渗流特征研究、气藏开采物理模拟等5类技术序列,研发了一维、二维、三维系统配套的物理模拟实验方法及其装置,实现了在室内重构气藏地质条件、再现气藏开采方式和气藏开发全过程仿真模拟评价,为气藏开发基础研究提供了条件和保障;历时近20年持续坚持基础实验与理论研究,完成中国陆上五大盆地十余个气田基础实验测试上万组次,形成了较为系统的低渗透致密含水砂岩气藏储量动用机理和有水气藏控水开发机理认识体系,为鄂尔多斯盆地、四川盆地、松辽盆地等盆地气田高效开发奠定了理论基础;当前,中国天然气开发面临新区优质资源发现难度大和普遍产水储量动用难度大的双重困境,提高采收率是持续上产或保持稳产的重要保障,需要在现有天然气开发实验技术基础上进一步加快研发天然气提高采收率实验新技术,加强室内实验与矿场试验结合推动基础理论研究走向现场应用实践。

基于物理实验的典型透水铺装水文效应研究

为了研究典型透水铺装水文效应,设计研制了一套人工模拟降雨实验系统,经过降雨特性检验,对透水混凝土铺装和植草砖铺装进行了定雨强下渗实验和设计暴雨情景下降雨径流实验。结果表明,本实验系统可实现雨强自动连续变化,人工降雨与设计暴雨在降雨峰值、降雨总量和降雨过程上接近,模拟降雨效果较好。透水混凝土铺装初始下渗率较大,相比于植草砖铺装更早进入稳定下渗阶段,稳定下渗率也更小;植草砖铺装在充分供水条件下也可一定程度控制径流;Horton模型对于透水铺装下渗特性有较好的描述能力。透水混凝土铺装产流过程与降雨过程呈现较高相关性,相同重现期下透水混凝土铺装产流时间均早于植草砖铺装,且产流量大;在削减径流总量和径流峰值、延后径流峰值方面,植草砖铺装都表现更好。