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Kinetic model for hydroisomerization reaction of C-aromatics

XU Ouguan, SU Hongye, JIN Xiaoming, CHU Jian

《化学科学与工程前沿（英文）》 2008年 第2卷 第1期   页码 10-16 doi: 10.1007/s11705-008-0015-2

摘要： Based on the reported reaction networks, a novel six-component hydroisomerization reaction network with a new lumped species including C-naphthenes and C-paraffins is proposed and a kinetic model for a commercial unit is also developed. An empirical catalyst deactivation function is incorporated into the model accounting for the loss in activity because of coke formation on the catalyst surface during the long-term operation. The Runge-Kutta method is used to solve the ordinary differential equations of the model. The reaction kinetic parameters are benchmarked with several sets of balanced plant data and estimated by the differential variable metric optimization method (BFGS). The kinetic model is validated by an industrial unit with sets of plant data under different operating conditions and simulation results show a good agreement between the model predictions and the plant observations.

关键词： ordinary differential     Runge-Kutta     catalyst deactivation     C-paraffins     optimization    

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Dynamics analysis of a cracked dual-disk over-hung rotor-bearing system

CHEN Hong, LI He, WEN Bang-chun, ZHANG Xiao-wei

《机械工程前沿（英文）》 2006年 第1卷 第2期   页码 204-208 doi: 10.1007/s11465-006-0002-6

摘要： A dynamic model of a dual-disk vertical over-hung rotor-bearing system is developed, taking into account nonlinear oil-film force. Its dynamic behaviors are investigated by numerical Runge-Kutta method. Its bifurcation and chaos characteristics are analyzed with crack fault and without crack fault. By analyzing the bifurcation plot, Poincare section plots and amplitude spectra, we found that the crack greatly influences the dynamic characteristics of the rotor-bearing system. Because of the strong effect of the nonlinear oil-film force and crack to the system, 1/2 times, 1/3 times frequency components appear in the response spectrum map. The results may bring up theoretical references for fault diagnosis of rotor-bearing systems.

关键词： nonlinear oil-film     diagnosis     bifurcation     dynamic     numerical Runge-Kutta    

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Chaotic behavior of LNG after stratification in main stream region of storage tank

WANG Jingjing, MA Xiaoqian

《能源前沿（英文）》 2008年 第2卷 第4期   页码 514-518 doi: 10.1007/s11708-008-0076-4

摘要： A study of the chaotic behavior of liquefied natural gas (LNG) after stratification in the main stream region of a storage tank was conducted. Based on non-linear dynamics, a 2-dimensional Rayleigh-Benard convection model was developed to simulate the convection, Lorenz equations of LNG convection were deduced from conservation equations, and the Runge-Kutta method was used to solve the equations. The results showed that when = 1.33, 106 < < 1470, chaos was obtained, which meant that the velocity field and the temperature field were highly unsteady. In addition, the influence of temperature and scale factor on the solutions and the corresponding range of parameters were studied. The results revealed that the chaos in LNG convection resulted from the interaction of buoyancy and viscid forces. A small quantity of heat impacting the storage tank would lead to a strong and unstable convection of LNG in the main stream region.

关键词： Runge-Kutta     non-linear     corresponding     temperature     addition    

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含空洞岩体微震定位的快速行进法——性能分析与工程应用 Article

蒋若辰, 戴峰, 刘燚, 李昂

《工程（英文）》 2021年 第7卷 第7期   页码 1023-1034 doi: 10.1016/j.eng.2020.10.019

摘要：

微震事件定位是微震监测技术的重要组成部分，用于圈定围岩损伤区。然而，复杂的地质条件会对最终的微震事件定位结果造成不利的影响。为实现含空洞复杂岩体中的高精度微震事件定位，本研究基于二阶差分形式的快速行进法，开发了微震事件定位方法。该方法基于建立的三维离散网格波速模型，通过搜索满足理论到时与实际到时之间残差最小的网格节点，实现对微震事件的定位。此外，基于二阶快速行进法的计算结果，微震破裂源到微震传感器的传播路径，可通过应用线性插值与龙格-库塔法获得。所用方法的合理性在一系列的数值仿真实验中得到了验证。提出的方法被应用于定位在猴子岩水电站地下洞室开挖过程中所记录的爆破与微震事件。爆破事件的定位结果表明，与采用均一岩体波速模型的定位结果相比，本方法能够有效减低微震事件定位误差。而对于微震事件的定位结果，通过现场的混凝土破裂与剥落，以及现场多点位移计的监测结果得到验证。本文提出的方法可提供相对更准确的岩体破裂位置，为圈定围岩损伤区工作提供便利。

关键词： 快速行进法     微震事件定位     含空洞复杂岩体     龙格-库塔法    

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GIS-based numerical simulation of Amamioshima debris flow in Japan

Jian WU, Guangqi CHEN, Lu ZHENG, Yingbin ZHANG

《结构与土木工程前沿（英文）》 2013年 第7卷 第2期   页码 206-214 doi: 10.1007/s11709-013-0198-6

摘要： Debris flow is a rapid flow which could lead to severe flooding with catastrophic consequences such as damage to properties and loss of human lives. It is important to study the movement of debris flow. Since during a debris flow process, the erosion and deposition processes are important, the no entrainment assumption is not acceptable. In this study, first we considered the debris flow as equivalent fluid and adopted the depth-averaged govern equations to simulate the movements and evolution of river bed. Secondly, the set of partial differential equations was solved numerically by means of explicit staggered leap-frog scheme that is accurate in space and time. The grid of difference scheme was derived from GIS raster data. Then the simulation results can be displayed by GIS and easily used to form the hazard maps. Finally, the numerical model coupled with GIS is applied to simulate the debris flow occurred on Oct. 20th, 2010, in Amamioshima City, Japan. The simulation reproduces the movement, erosion and deposition. The results are shown to be consistent with the field investigation.

关键词： debris flow     numerical simulation     GIS     movement     erosion     deposition    

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Experimental and numerical study on microcrack detection using contact nonlinear acoustics

Xiaojia CHEN, Yuanlin WANG

《结构与土木工程前沿（英文）》 2009年 第3卷 第2期   页码 137-141 doi: 10.1007/s11709-009-0028-z

摘要： This paper introduces a non-classical nonlinear acoustic theory for microcrack detection in materials, comparing contact nonlinearity with material nonlinearity. The paper’s main work concentrates on the experimental and numerical verification of the effectivity of contact nonlinear acoustic detection by using the contact nonlinear parameter , which can be represented by the ratio of the second-harmonic amplitude to the square of the first-harmonic amplitude. Both experiments and numerical tests are performed. The results show that is sensitive to the initiation of microcracks and varies with the development of the microcracks. The numerical test illustrates the decline of when microcracks penetrate each other.

关键词： microcrack detection     contact nonlinearity     numerical analysis    

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An investigation on prevalent strategies for XFEM-based numerical modeling of crack growth in porous

《结构与土木工程前沿（英文）》 2021年 第15卷 第4期   页码 914-936 doi: 10.1007/s11709-021-0750-8

摘要： Crack growth modeling has always been one of the major challenges in fracture mechanics. Among all numerical methods, the extended finite element method (XFEM) has recently attracted much attention due to its ability to estimate the discontinuous deformation field. However, XFEM modeling does not directly lead to reliable results, and choosing a strategy of implementation is inevitable, especially in porous media. In this study, two prevalent XFEM strategies are evaluated: a) applying reduced Young’s modulus to pores and b) using different partitions to the model and enriching each part individually. We mention the advantages and limitations of each strategy via both analytical and experimental validations. Finally, the crack growth is modeled in a natural porous media (Fontainebleau sandstone). Our investigations proved that although both strategies can identically predict the stress distribution in the sample, the first strategy simulates only the initial crack propagation, while the second strategy could model multiple cracks growths. Both strategies are reliable and highly accurate in calculating the stress intensity factor, but the second strategy can compute a more reliable reaction force. Experimental tests showed that the second strategy is a more accurate strategy in predicting the preferred crack growth path and determining the maximum strength of the sample.

关键词： numerical modeling     extended finite element method     porous media     crack growth     stress intensity factor    

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Simulation of viscoelastic behavior of defected rock by using numerical manifold method

Feng REN, Lifeng FAN, Guowei MA

《结构与土木工程前沿（英文）》 2011年 第5卷 第2期   页码 199-207 doi: 10.1007/s11709-011-0102-1

摘要： Numerical simulations of longitudinal wave propagation in a rock bar with microcracks are conducted by using the numerical manifold method which has great advantages in the simulation of discontinuities. Firstly, validation of the numerical manifold method is carried out by simulations of a longitudinal stress wave propagating through intact and cracked rock bars. The behavior of the stress wave traveling in a one-dimensional rock bar with randomly distributed microcracks is subsequently studied. It is revealed that the highly defected rock bar has significant viscoelasticity to the stress wave propagation. Wave attenuation as well as time delay is affected by the length, quantity, specific stiffness of the distributed microcracks as well as the incident stress wave frequency. The storage and loss moduli of the defected rock are also affected by the microcrack properties; however, they are independent of incident stress wave frequency.

关键词： stress wave propagation     defected rock     numerical manifold method     viscoelastic behavior     storage modulus     loss modulus    

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Numerical modeling and performance evaluation of passive convergence-permeable reactive barrier (PC-PRB

《环境科学与工程前沿（英文）》 2023年 第17卷 第11期 doi: 10.1007/s11783-023-1731-z

摘要：

● A 2D finite-element solute transport model, PRB-Trans, is developed.

关键词： Passive convergence-permeable reactive barrier     Numerical modeling     Hydraulic behavior assessment     Pollutant treatment performance evaluation     Influential factors analysis    

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Numerical analysis of hydrodynamic process of circular-translational-moving polishing (CTMP)

ZHAI Wenjie, LIU Changxiong, LIANG Yingchun

《机械工程前沿（英文）》 2008年 第3卷 第4期   页码 441-448 doi: 10.1007/s11465-008-0074-6

摘要： By keeping a pad moving relative to a wafer along a circular path without rotation, we developed a polishing technique called circular-translational-moving polishing (CTMP), which permits multidirectional polishing of the work piece and thus bears the advantage of isotropic polishing and a potential increase of material removal rate (MRR) on the wafer. To illuminate the mechanisms of CTMP and determine the optimum process variables in a CTMP process, a three-dimensional hydrodynamic lubrication model for CTMP with a smooth and rigid pad under a quasi-stable state is established in a polar coordinate system. The model equations are further calculated numerically by the finite difference method. The instantaneous distribution of fluid pressure is obtained, which shows that a negative pressure exists. The reason for negative pressure in CTMP and its effect on polishing is discussed. Moreover, the nominal clearance of the fluid film, roll, and pitch angles under different working conditions are obtained in terms of the applied load, moments, and polishing velocity. The obtained numerical analysis can be used as guidance for choosing operation parameters in a practical CTMP application.

关键词： numerical analysis     practical CTMP     circular-translational-moving polishing     CTMP     different    

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Vortex-induced vibration of stay cable under profile velocity using CFD numerical simulation method

Wenli CHEN, Hui LI,

《结构与土木工程前沿（英文）》 2009年 第3卷 第4期   页码 357-363 doi: 10.1007/s11709-009-0060-z

摘要： Vortex-induced vibration (VIV) of a stay cable subjected to a wind profile is numerically simulated through combining computational fluid dynamics (CFD) code CFX 10.0 and computational structural dynamics (CSD) code ANSYS 10.0. A stay cable with the inclined angle of 30° is used as the numerical model. Under a profile of mean wind speed, unsteady aerodynamic lift coefficients of the cable have been analyzed in both time domain and frequency domain when VIV occurs. The results indicate that the lift coefficient wave response of the stay cable under a wind profile is different from that of an infinitely long cable under a uniform flow in water (i.e., without consideration of profile) obtained by direct numerical simulation. Cable oscillations can severely affect the unsteady aerodynamic frequencies, change flow field distribution near the cable and affect the vortex shedding in the wake.

关键词： stay cable     fluid-structure interaction     numerical simulation     vortex-induced vibration    

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Analytical and numerical investigation into the longitudinal vibration of uniform nanotubes

null

《机械工程前沿（英文）》 2014年 第9卷 第2期   页码 142-149 doi: 10.1007/s11465-014-0292-z

摘要：

In recent years, prediction of the behaviors of micro and nanostructures is going to be a matter of increasing concern considering their developments and uses in various engineering fields. Since carbon nanotubes show the specific properties such as strength and special electrical behaviors, they have become the main subject in nanotechnology researches. On the grounds that the classical continuum theory cannot accurately predict the mechanical behavior of nanostructures, nonlocal elasticity theory is used to model the nanoscaled systems. In this paper, a nonlocal model for nanorods is developed, and it is used to model the carbon nanotubes with the aim of the investigating into their longitudinal vibration. Following the derivation of governing equation of nanorods and estimation of nondimensional frequencies, the effect of nonlocal parameter and the length of the nanotube on the obtained frequencies are studied. Furthermore, differential quadrature method, as a numerical solution technique, is used to study the effect of these parameters on estimated frequencies for both classical and nonlocal theories.

关键词： continuum theory     differential quadrature method     nanorod     longitudinal vibration    

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Digital representation of meso-geomaterial spatial distribution and associated numerical analysis of

YUE Zhongqi

《结构与土木工程前沿（英文）》 2007年 第1卷 第1期   页码 80-93 doi: 10.1007/s11709-007-0008-0

摘要： This paper presents the author's efforts in the past decade for the establishment of a practical approach of digital representation of the geomaterial distribution of different minerals, particulars, and components in the meso-scale range (0.1 to 500 mm). The primary goal of the approach is to provide a possible solution to solve the two intrinsic problems associated with the current main-stream methods for geomechanics. The problems are (1) the constitutive models and parameters of soils and rocks cannot be given accurately in geomechanical prediction; and (2) there are numerous constitutive models of soils and rocks in the literature. The problems are possibly caused by the homogenization or averaging method in analyzing laboratory test results for establishing the constitutive models and parameters. The averaging method employs an assumption that the test samples can be represented by a homogeneous medium. Such averaging method ignores the fact that the geomaterial samples are also consisted of a number of materials and components whose properties may have significant differences. In the proposed approach, digital image processing methods are used as measurement tools to construct a digital representation for the actual spatial distribution of the different materials and components in geomaterial samples. The digital data are further processed to automatically generate meshes or grids for numerical analysis. These meshes or grids can be easily incorporated into existing numerical software packages for further mechanical analysis and failure prediction of the geomaterials under external loading. The paper presents case studies to illustrate the proposed approach. Further discussions are also made on how to use the proposed approach to develop the geomechanics by taking into account the geomaterial behavior at micro-scale, meso-scale and macro-scale levels. A literature review of the related developments is given by examining the SCI papers in the database of Science Citation Index Expanded. The results of this review have shown that the proposed approach is one of the latest research and developments in geomechanics where actual spatial distribution and properties of materials and components at the meso-level are taken into account.

关键词： homogeneous     numerical analysis     Expanded     homogenization     meso-level    

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Numerical and experimental analyses of methane leakage in shield tunnel

《结构与土木工程前沿（英文）》   页码 1011-1020 doi: 10.1007/s11709-023-0956-z

摘要： Tunnels constructed in gas-bearing strata are affected by the potential leakage of harmful gases, such as methane gas. Based on the basic principles of computational fluid dynamics, a numerical analysis was performed to simulate the ventilation and diffusion of harmful gases in a shield tunnel, and the effect of ventilation airflow speed on the diffusion of harmful gases was evaluated. As the airflow speed increased from 1.8 to 5.4 m/s, the methane emission was diluted, and the methane accumulation was only observed in the area near the methane leakage channels. The influence of increased ventilation airflow velocity was dominant for the ventilation modes with two and four fans. In addition, laboratory tests on methane leakage through segment joints were performed. The results show that the leakage process can be divided into “rapid leakage” and “slight leakage”, depending on the leakage pressure and the state of joint deformation. Based on the numerical and experimental analysis results, a relationship between the safety level and the joint deformation is established, which can be used as guidelines for maintaining utility tunnels.

关键词： shield tunnel     harmful gas leakage     numerical analysis     laboratory test    

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Three-dimensional numerical simulation of the basic pulse tube refrigerator

DING Wenjing, GONG Liang, HE Yaling, TAO Wenquan

《能源前沿（英文）》 2008年 第2卷 第1期   页码 48-53 doi: 10.1007/s11708-008-0008-3

摘要： A three-dimensional physical and numerical model of the basic pulse tube refrigerator (PTR) was developed. The compressible and oscillating fluid flow and heat transfer phenomenon in the pulse tube were numerically investigated using a self-developed code. Some cross-section average parameter variations such as velocity, temperature and pressure wave during one cycle were revealed. The variations of velocity and temperature distributions in the pulse tube were also analyzed in detail for further understanding of the working process and refrigeration mechanism of PTRs.

关键词： refrigeration mechanism     three-dimensional     compressible     numerical     understanding    

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标题 作者 时间 类型 操作

Kinetic model for hydroisomerization reaction of C-aromatics

XU Ouguan, SU Hongye, JIN Xiaoming, CHU Jian

期刊论文

Dynamics analysis of a cracked dual-disk over-hung rotor-bearing system

CHEN Hong, LI He, WEN Bang-chun, ZHANG Xiao-wei

期刊论文

Chaotic behavior of LNG after stratification in main stream region of storage tank

WANG Jingjing, MA Xiaoqian

期刊论文

含空洞岩体微震定位的快速行进法——性能分析与工程应用

蒋若辰, 戴峰, 刘燚, 李昂

期刊论文

GIS-based numerical simulation of Amamioshima debris flow in Japan

Jian WU, Guangqi CHEN, Lu ZHENG, Yingbin ZHANG

期刊论文

Experimental and numerical study on microcrack detection using contact nonlinear acoustics

Xiaojia CHEN, Yuanlin WANG

期刊论文

An investigation on prevalent strategies for XFEM-based numerical modeling of crack growth in porous

期刊论文

Simulation of viscoelastic behavior of defected rock by using numerical manifold method

Feng REN, Lifeng FAN, Guowei MA

期刊论文

Numerical modeling and performance evaluation of passive convergence-permeable reactive barrier (PC-PRB

期刊论文

Numerical analysis of hydrodynamic process of circular-translational-moving polishing (CTMP)

ZHAI Wenjie, LIU Changxiong, LIANG Yingchun

期刊论文

Vortex-induced vibration of stay cable under profile velocity using CFD numerical simulation method

Wenli CHEN, Hui LI,

期刊论文

Analytical and numerical investigation into the longitudinal vibration of uniform nanotubes

null

期刊论文

Digital representation of meso-geomaterial spatial distribution and associated numerical analysis of

YUE Zhongqi

期刊论文

Numerical and experimental analyses of methane leakage in shield tunnel

期刊论文

Three-dimensional numerical simulation of the basic pulse tube refrigerator

DING Wenjing, GONG Liang, HE Yaling, TAO Wenquan

期刊论文