In this paper, the hydrodynamic characteristics and flow field around rectangular and delta hydrofoils, moving with a constant speed beneath the free surface are numerically studied by means of isoparametric boundary ...In this paper, the hydrodynamic characteristics and flow field around rectangular and delta hydrofoils, moving with a constant speed beneath the free surface are numerically studied by means of isoparametric boundary element method （IBEM）. The quantities （source and dipole strengths） and the geometry of the dements are represented by a linear distribution. Two types of three-dimensional hydrofoils （rectangular and delta） are selected with NACA4412 and symmetric Joukowski sections. Some numerical results of pressure distribution, lift, wave-making drag coefficients and velocity field around the hydrofoils are presented. Also, the wave pattern due to moving hydrofoil is predicted at different operational conditions. Comparisons are made between computational results obtained through this method and those from the experimental measurements and other numerical results which reveal good agreement.展开更多
On the basis of the recent geological surveys and the relevant studies of the Xianshuihe fault zone, this paper analyzes the seismogenic mechanism of some faults and characteristic morphology on the fault zone by the ...On the basis of the recent geological surveys and the relevant studies of the Xianshuihe fault zone, this paper analyzes the seismogenic mechanism of some faults and characteristic morphology on the fault zone by the boundary element method and discusses the fault segmentation and the related distribution of the earthquake ruptures. The main conclusions are: For the first order segmentation, the Xianshuihe fault zone can be divided into three major segments (the northwestern Luhuo-Qianning segment, the middle linking fracture region and the southeastern Kangding segment). Among them, the differences are not only in geometry and structure, but also in mechanical property and dynamics. Some of the characteristic morphologies on the Xianshuihe fault zone reflect the effects in cumulative deformation due to long-term fault movement, and reveal the fault segmentation in different orders. Such morphologies control, to some extent, the developments and the distributions of the earthquake ruptures on the fault zone.展开更多
A nonlinear multi zone boundary element method is applied to simulate the size effect of a series of geome trically similar three point bend specimens. The material in which particles are randomly dispersed in a relat...A nonlinear multi zone boundary element method is applied to simulate the size effect of a series of geome trically similar three point bend specimens. The material in which particles are randomly dispersed in a relatively hard matrix can be applicable to various aggregate materials as well as unidirectionally reinforced fiber composites in the transverse plane. A single edge macrocrack and interfacial microcracks randomly distributed between particles and matrix are prescribed as initial defects. The shape, size and location of the fracture process zone (FPZ) are realistically simulated and described. The nominal strength of the material is in agreement with the Bazant size effect law. In addition, the results show that microcracking is one of the most important micromechanisms for the size effect in aggregate materials.展开更多
Numerical methods can provide extremely powerful tools for analysis and design of engineering systems with complex factors that are not possible or very difficult with the use of the conventional methods. In this pape...Numerical methods can provide extremely powerful tools for analysis and design of engineering systems with complex factors that are not possible or very difficult with the use of the conventional methods. In this paper, we use the 2-D boundary element method (BEM) program to model elastic wave excited by a point explosive source propagating in cracked rocks. As an example, we consider the typical crack distributions in rocks, both models for the real crack structure are also talked about. The elastic wave propagating in rocks with aligned cracks and parallel fractures is assumed. Effects of different crack parameters, such as crack scale length and crack density are analyzed. Numerical results show that the BEM is a powerful interpretive tool for understanding the complicated wave propagation and interaction in cracked solids.展开更多
The fracture behavior of a series of geometrically similar three point bend specimens is simulated by a nonlinear multi zone boundary element computer program. The material is based on Al 2O 3 SiC (p) ceramic in which...The fracture behavior of a series of geometrically similar three point bend specimens is simulated by a nonlinear multi zone boundary element computer program. The material is based on Al 2O 3 SiC (p) ceramic in which particles are randomly dispersed in a relatively soft matrix. A single edge main crack and a large number of interfacial microcracks randomly distributed between particles and matrix are prescribed. The load deflection curve and the spread of the fracture process zone (FPZ) are observed with confidence. The computer simulated results show that the fracture toughness of the material increases with increasing specimen dimension and becomes constant when the specimen size exceeds a critical value. A practical specimen size for predicting the true fracture toughness of aggregate materials is proposed.展开更多
超声导波检测技术因其检测距离远、检测效率高,在工业管道的无损检测和健康监测中显示出良好的应用前景,但是目前对于广泛应用于工业领域的多层管的导波检测研究仍较少。应用半解析有限元法(Semi-analytical finite element method,SAF...超声导波检测技术因其检测距离远、检测效率高,在工业管道的无损检测和健康监测中显示出良好的应用前景,但是目前对于广泛应用于工业领域的多层管的导波检测研究仍较少。应用半解析有限元法(Semi-analytical finite element method,SAFE),基于虚功原理构建超声导波在多层管中传播的控制方程,求解导波在多层管中传播的特性,导出多层管中导波的频散特性,包括相速度、能量速度、衰减、波结构等,为导波检测多层管时选择模态和频率提供理论依据。讨论多层管中黏弹性介质引入的阻尼对导波传播的影响,求解多层管中的导波衰减频散曲线,用于指导多层管检测,并通过数值仿真以及利用MSGW磁致伸缩导波检测仪检测单层钢管和衬塑钢管试验验证部分理论结果。展开更多
文摘In this paper, the hydrodynamic characteristics and flow field around rectangular and delta hydrofoils, moving with a constant speed beneath the free surface are numerically studied by means of isoparametric boundary element method （IBEM）. The quantities （source and dipole strengths） and the geometry of the dements are represented by a linear distribution. Two types of three-dimensional hydrofoils （rectangular and delta） are selected with NACA4412 and symmetric Joukowski sections. Some numerical results of pressure distribution, lift, wave-making drag coefficients and velocity field around the hydrofoils are presented. Also, the wave pattern due to moving hydrofoil is predicted at different operational conditions. Comparisons are made between computational results obtained through this method and those from the experimental measurements and other numerical results which reveal good agreement.
文摘On the basis of the recent geological surveys and the relevant studies of the Xianshuihe fault zone, this paper analyzes the seismogenic mechanism of some faults and characteristic morphology on the fault zone by the boundary element method and discusses the fault segmentation and the related distribution of the earthquake ruptures. The main conclusions are: For the first order segmentation, the Xianshuihe fault zone can be divided into three major segments (the northwestern Luhuo-Qianning segment, the middle linking fracture region and the southeastern Kangding segment). Among them, the differences are not only in geometry and structure, but also in mechanical property and dynamics. Some of the characteristic morphologies on the Xianshuihe fault zone reflect the effects in cumulative deformation due to long-term fault movement, and reveal the fault segmentation in different orders. Such morphologies control, to some extent, the developments and the distributions of the earthquake ruptures on the fault zone.
文摘A nonlinear multi zone boundary element method is applied to simulate the size effect of a series of geome trically similar three point bend specimens. The material in which particles are randomly dispersed in a relatively hard matrix can be applicable to various aggregate materials as well as unidirectionally reinforced fiber composites in the transverse plane. A single edge macrocrack and interfacial microcracks randomly distributed between particles and matrix are prescribed as initial defects. The shape, size and location of the fracture process zone (FPZ) are realistically simulated and described. The nominal strength of the material is in agreement with the Bazant size effect law. In addition, the results show that microcracking is one of the most important micromechanisms for the size effect in aggregate materials.
文摘Numerical methods can provide extremely powerful tools for analysis and design of engineering systems with complex factors that are not possible or very difficult with the use of the conventional methods. In this paper, we use the 2-D boundary element method (BEM) program to model elastic wave excited by a point explosive source propagating in cracked rocks. As an example, we consider the typical crack distributions in rocks, both models for the real crack structure are also talked about. The elastic wave propagating in rocks with aligned cracks and parallel fractures is assumed. Effects of different crack parameters, such as crack scale length and crack density are analyzed. Numerical results show that the BEM is a powerful interpretive tool for understanding the complicated wave propagation and interaction in cracked solids.
文摘The fracture behavior of a series of geometrically similar three point bend specimens is simulated by a nonlinear multi zone boundary element computer program. The material is based on Al 2O 3 SiC (p) ceramic in which particles are randomly dispersed in a relatively soft matrix. A single edge main crack and a large number of interfacial microcracks randomly distributed between particles and matrix are prescribed. The load deflection curve and the spread of the fracture process zone (FPZ) are observed with confidence. The computer simulated results show that the fracture toughness of the material increases with increasing specimen dimension and becomes constant when the specimen size exceeds a critical value. A practical specimen size for predicting the true fracture toughness of aggregate materials is proposed.
文摘超声导波检测技术因其检测距离远、检测效率高,在工业管道的无损检测和健康监测中显示出良好的应用前景,但是目前对于广泛应用于工业领域的多层管的导波检测研究仍较少。应用半解析有限元法(Semi-analytical finite element method,SAFE),基于虚功原理构建超声导波在多层管中传播的控制方程,求解导波在多层管中传播的特性,导出多层管中导波的频散特性,包括相速度、能量速度、衰减、波结构等,为导波检测多层管时选择模态和频率提供理论依据。讨论多层管中黏弹性介质引入的阻尼对导波传播的影响,求解多层管中的导波衰减频散曲线,用于指导多层管检测,并通过数值仿真以及利用MSGW磁致伸缩导波检测仪检测单层钢管和衬塑钢管试验验证部分理论结果。
