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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    

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    

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    

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    

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    

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    

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    

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    

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    

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    

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    

Three-dimensional numerical modeling of single geocell-reinforced sand

Xiaoming YANG, Jie HAN, Robert L. PARSONS, Dov LESHCHINSKY,

《结构与土木工程前沿(英文)》 2010年 第4卷 第2期   页码 233-240 doi: 10.1007/s11709-010-0020-7

摘要: This paper summarizes the development of a three-dimensional numerical model for analyzing single geocell-reinforced soil. In this model, the infill soil was modeled using the Duncan-Chang model, which can simulate non-linearity and stress-dependency of soil. Geocell was modeled using linearly elastic plate elements, which can carry both bending and membrane stresses. A linear interface stress-strain relationship with a Mohr-Coulomb yield criterion was adopted to model the interface friction between the geocell wall and the soil. By modeling the geocell and the soil separately, the interaction between the soil and the geocell can be accurately simulated. To verify this model, a plate load test was conducted in the laboratory, in which a 12-cm-thick sand layer reinforced by a single geocell was subjected to a vertical load from a circular steel plate. The load-displacement curves and the horizontal tensile strain of the geocell were recorded during the test. A numerical model was created according to the setup of the load test. The numerical results compared reasonably well with the test data.

关键词: geosynthetic reinforcement     geocell     numerical model     FLAC3D    

Numerical analysis of nonlinear dynamic behavior of earth dams

Babak EBRAHIMIAN

《结构与土木工程前沿(英文)》 2011年 第5卷 第1期   页码 24-40 doi: 10.1007/s11709-010-0082-6

摘要: A numerical study is conducted to investigate the dynamic behavior of earth dams. The numerical investigation employs a fully nonlinear dynamic finite difference analysis incorporating a simple elastic perfectly plastic constitutive model to describe the stress-strain response of the soil and the Rayleigh damping to increase the level of hysteretic damping. The extended Masing rules are implemented into the constitutive model to explain more accurately the soil response under general cyclic loading. The soil stiffness and hysteretic damping change with loading history. The procedures for calibrating the constructed numerical model with centrifuge test data and also a real case history are explained. For the latter, the Long Valley (LV) earth dam subjected to the 1980 Mammoth Lake earthquake as a real case-history is analyzed and the obtained numerical results are compared with the real measurements at the site in both the time and frequency domains. Relatively good agreement is observed between computed and measured quantities. It seems that the Masing rules combined with a simple elasto-plastic model gives reasonable numerical predictions. Afterwards, a comprehensive parametric study is carried out to identify the effects of dam height, input motion characteristics, soil behavior, strength of the shell materials and dam reservoir condition on the dynamic response of earth dams. Three real earthquake records with different levels and peak acceleration values (PGAs) are used as input motions. The results show that the crest acceleration decreases when the dam height increases and no amplification is observed. Further, more inelastic behavior and more earthquake energy absorption are observed in higher dams.

关键词: earth dam     numerical     nonlinear response     dynamic analysis     earthquake     dam height    

Improved numerical method for time domain dynamic structure-foundation interaction analysis based on

DU Jianguo, LIN Gao

《结构与土木工程前沿(英文)》 2008年 第2卷 第4期   页码 336-342 doi: 10.1007/s11709-008-0054-2

摘要: Based on the reduced set of base function in scaled boundary finite element method (SBFEM), an improved time domain numerical approach for the dynamic structure-foundation interaction analysis was proposed. With reasonable choice of the number of base functions, the degrees of freedom on the structure-foundation interface were reduced and the associated computation for the calculation of convolution integral was greatly reduced. The results of this proposed approach applied to the calculation of a gravity dam and an arch dam. The acceleration frequency response functions were calculated and the influences affected by different reduced set of base functions as well as full set were compared. It was found that a higher degree of reduced set of base functions resulted in a significant increase of computational efficiency but a little bit of loss in accuracy. When the reduced set was decreased by 60%, the efficiency may be increased to up to five times, while the loss of accuracy of peak value of response will be less than 4%. It may be concluded that the proposed approach is suitable for large-scale structure-foundation interaction analysis.

关键词: structure-foundation interface     computational efficiency     different     suitable     numerical approach    

Evaluation of potential failure of rock slope at the left abutment of Jinsha River Bridge by model test and numerical

Zhiming ZHAO, Xihua WANG

《结构与土木工程前沿(英文)》 2013年 第7卷 第3期   页码 332-340 doi: 10.1007/s11709-013-0206-x

摘要: Jinsha River Bridge is located on Tiger Leaping Gorge town, China. The left bank slope composes of moderately thick layer of slate overlain by schistose basalt, and where rocks are controlled by two sets of joint planes. To evaluate the stability of the rock slope under bridge foundation, model test and calculation model based on the geological parameters and the slope stability was simulated and analyzed using Universal Distinct Element Code (UDEC) and Finite Element Mehod (FEM). According to model test, failure mainly initiated at the toe with shear movement along the joint planes, eventually resulting in the sliding along the slope surface and formation of tension crack at the crest of the model. This result coincide with the UDEC model, which shows that slope surface will produce loosening damage and slipping expected along the joint planes under different loading conditions. Moreover, the result of FEM analysis indicates that the rock mass under the main pier has potential shear failure region. So, the bridge foundation should be strengthened to prevent the slope failure under external forces.

关键词: slope stability     strength properties     model test     numerical analysis    

标题 作者 时间 类型 操作

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

Three-dimensional numerical modeling of single geocell-reinforced sand

Xiaoming YANG, Jie HAN, Robert L. PARSONS, Dov LESHCHINSKY,

期刊论文

Numerical analysis of nonlinear dynamic behavior of earth dams

Babak EBRAHIMIAN

期刊论文

Improved numerical method for time domain dynamic structure-foundation interaction analysis based on

DU Jianguo, LIN Gao

期刊论文

Evaluation of potential failure of rock slope at the left abutment of Jinsha River Bridge by model test and numerical

Zhiming ZHAO, Xihua WANG

期刊论文