A new DRBEM model for wave refraction and diffraction

A numerical model using the dual reciprocity boundary element method (DRBEM) is developed to study the combined refraction and diffraction of water waves propagating around islands or solid offshore structures over a seabed with a variable depth. Based on the well-known mild-slope equation, the model has been validated by comparison with both analytical solutions and standard numerical solutions available in the literature. The results show that a considerable improvement in terms of numerical efficiency has been achieved with the adoption of the DRBEM and the model has a great potential to be used in engineering practice to solve wave refraction and diffraction problems.     

A boundary element method for analysis of thermoelastic deformations in materials with temperature dependent properties

In this paper, the boundary element method (BEM) for solving quasi‐static uncoupled thermoelasticity problems in materials with temperature dependent properties is presented. The domain integral term, in the integral representation of the governing equation, is transformed to an equivalent boundary integral by means of the dual reciprocity method (DRM). The required particular solutions are derived and outlined. The method ensures numerically efficient analysis of thermoelastic deformations in an arbitrary geometry and loading conditions. The validity and the high accuracy of the formulation is demonstrated considering a series of examples. In all numerical tests, calculation results are compared with analytical and/or finite element method (FEM) solutions. Copyright © 2005 John Wiley & Sons, Ltd.     

A time-stepping DRBEM for the transient magneto-thermo-visco-elastic stresses in a rotating non-homogeneous anisotropic solid

The main objective of this paper is to study the transient magneto-thermo-visco-elastic stresses in a non-homogeneous anisotropic solid placed in a constant primary magnetic field acting in the direction of the z-axis and rotating about it with a constant angular velocity. The system of fundamental equations is solved by means of a dual-reciprocity boundary element method (DRBEM). In the case of plane deformation, a numerical scheme for the implementation of the method is presented and the numerical computations are carried out for the temperature, displacement components and thermal stress components. The validity of DRBEM is examined by considering a magneto-thermo-visco-elastic solid occupies a rectangular region and good agreement is obtained with the results obtained by other methods. The results obtained are presented graphically to show the effect of inhomogeneity on the displacement components and thermal stress components.     

Pressure correction DRBEM solution for heat transfer and fluid flow in incompressible viscous fluids

The Dual Reciprocity Boundary Element Method (DRBEM) is used to solve incompressible laminar viscous fluid flows and heat transfer. The DRBEM is extended to develop a pressure correction scheme to solve the incompressible Navier-Stokes equations. The velocity field is then used as input to the DRBEM solution of the energy transport equation, thereby retaining the boundary only discretization feature of the BEM for the solution of this problem. Numerical results for the proposed DRBEM solution for laminar flow and heat transfer in a channel are obtained for several Reynolds numbers and compare well with previously published data.     

A new application of an improved DRBEM model for water wave propagation over a frictional uneven bottom

This paper presents a numerical scheme to approximate water wave diffraction, refraction and frictional dissipation over an axi-symmetric pit. Based on an improved extended mild-slope equation (EMSE) including bottom friction effect, as the elliptic governing differential equation, dual reciprocity boundary element method (DRBEM) is employed to model water wave propagation over an axi-symmetric pit. To the authors' knowledge, this is the first application of DRBEM for water wave scattering over a pit. In order to promote accuracy of the model, not only effects of the bottom curvature and the slope-squared terms which are neglected in the mild-slope equation (MSE), are considered, but also effect of the bottom friction is measured by the improved EMSE. Numerical results are compared with existing analytical or numerical solutions or with experimental data by several examples. Through these numerical experiments reliability and efficiency of present DRBEM model for determining the total wave field over an uneven bottom is approved.     

振动荷载下路基的能量耗散率空间分布规律的研究

为研究振动荷载作用下的路基内部的能量状态分布,基于Parseval定理,分别以动应变/加速度为变量,推导建立了周期性和非周期性的路基内振动信号的能量耗散率计算公式;根据土体的动力互易性原理,进行了振动荷载下路基动力响应现场试验,利用试验测试结果,分析研究了该路基的能量耗散率空间分布规律.研究结果表明:①能量耗散率沿深度...     

Earthquake‐induced hydrodynamic pressures on a 3D rigid dam–reservoir system using DRBEM and a radiation matrix

The dual reciprocity method is applied to determine the hydrodynamic pressure distribution in a three‐dimensional dam–reservoir system subjected to earthquake excitation. The reservoir domain is idealized as a finite region of irregular geometry adjacent to the dam followed by an infinite domain of uniform cross‐section in the upstream direction. The reservoir hydrodynamic pressure response is governed by the Helmholtz equation subject to free surface, dam–reservoir interface, absorbing bottom/banks and radiation boundary conditions. A three‐dimensional (3D) dual reciprocity model is developed to determine the hydrodynamic pressure in the finite reservoir domain. A radiation matrix is developed and introduced to relate the hydrodynamic pressure and its normal derivative on the interface between the finite and infinite domains. The three‐dimensional radiation model used is developed by applying a two‐dimensional dual reciprocity formulation along the interface of the finite and infinite reservoirs together with a continuum solution in the upstream direction of the infinite domain. The model is compared for the hydrodynamic response of a three‐dimensional rectangular reservoir and found to be in excellent agreement with results obtained from a model based on the analytical formulation existing in the literature. Copyright © 2003 John Wiley & Sons, Ltd.     

A comparison of domain integral evaluation techniques for boundary element methods

In many cases, boundary integral equations contain a domain integral. This can be evaluated by discretization of the domain into domain elements. Historically, this was seen as going against the spirit of boundary element methods, and several methods were developed to avoid this discretization, notably dual and multiple reciprocity methods and particular solution methods. These involved the representation of the interior function with a set of basis functions, generally of the radial type. In this study, meshless methods (dual reciprocity and particular solution) are compared to the direct domain integration methods. The domain integrals are evaluated using traditional methods and also with multipole acceleration. It is found that the direct integration always results in better accuracy, as well as smaller computation times. In addition, the multipole method further improves on the computation times, in particular where multiple evaluations of the integral are required, as when iterative solvers are used. The additional error produced by the multipole acceleration is negligible. Copyright © 2001 John Wiley & Sons, Ltd.     

Solution for wave propagation through a circular cylinder mounted on different topography ripple-bed profile shoals using DRBEM

In this paper, the dual reciprocity boundary element method wave model that is governed by a modified mild-slope equation is developed. Instead of addressing the infinite boundary condition, the model automatically satisfies the Sommerfeld radiation condition. This work examines the effects of both the bottom curvature and the slope-squared terms. The conducted numerical experiments have a topography that is composed of a cylinder mounted on two kinds of basic shoal: types 1 and 2 cubic. In addition, numerical experiments that combine two cubic type islands with ripple-beds are performed.The results show that the curvature term dominates the calculation of the sinusoidal-varying topography; even a disturbance in the topography is insignificant. In contrast to smooth topographies, the bottom curvature and the slope-squared terms are not dominant. Thus, the extended terms can be neglected if the seabed is smooth and gentle. When the topographies are combined with ripple-beds, the difference in the dimensionless wave amplitudes along the sidewall of the types 1 and 2 cubic islands is found to be 2.9 and 3.02, respectively. According to our study of cubic islands that are combined with ripple-beds, we can conclude with certainty that even though the variation of the seabed is very slight, the curvature and the slope-squared terms cannot be neglected for an uneven bottom.     

A three-dimensional boundary element formulation for the elastoplastic analysis of cracked bodies

In this paper a general boundary element formulation for the three-dimensional elastoplastic analysis of cracked bodies is presented. The non-linear formulation is based on the Dual Boundary Element Method. The continuity requirements of the field variables are fulfilled by a discretization strategy that incorporates continuous, semi-discontinuous and discontinuous boundary elements as well as continuous and semi-discontinuous domain cells. Suitable integration procedures are used for the accurate integration of the Cauchy surface and volume integrals. The explicit version of the initial strain formulation is used to satisfy the non-linearity. Several examples are presented to demonstrate the application of the proposed method. © 1998 John Wiley & Sons, Ltd.     

Plane stress and plate bending coupling in BEM analysis of shallow shells

In this paper the shear deformable shallow shells are analysed by boundary element method. New boundary integral equations are derived utilizing the Betti's reciprocity principle and coupling boundary element formulation of shear deformable plate and two‐dimensional plane stress elasticity. Two techniques, direct integral method (DIM) and dual reciprocity method (DRM), are developed to transform domain integrals to boundary integrals. The force term is approximted by a set of radial basis functions. Several examples are presented to demonstrate the accuracy of the two methods. The accuracy of results obtained by using boundary element method are compared with exact solutions and the finite element method. Copyright © 2000 John Wiley & Sons, Ltd.     

A semi-analytic boundary element method for parabolic problems

A new semi-analytic solution method is proposed for solving linear parabolic problems using the boundary element method. This method constructs a solution as an eigenfunction expansion using separation of variables. The eigenfunctions are determined using the dual reciprocity boundary element method. This separation of variables-dual reciprocity method (SOV-DRM) allows a solution to be determined without requiring either time-stepping or domain discretisation. The accuracy and computational efficiency of the SOV-DRM is found to improve as time increases. These properties make the SOV-DRM an attractive technique for solving parabolic problems.     

耗能减振层对某超高层结构的减振控制研究

本文以某288m超高层框架－核心筒结构的减振控制为研究对象,针对该工程的自身特点提出了设置非线性粘滞阻尼器、铅粘弹性阻尼器耗能减振层的六种控制方案。在10年一遇风振作用下,利用改进的自回归AR模型模拟了结构Y方向的脉动风荷载时程,并对该结构进行了不同控制方案下的风振控制研究,同时针对该结构进行了7度小震和中震作用下的阻尼减震控制研究。对比分析了不同控制方案下耗能减振层对结构地震与风振作用的减振效果,结果表明本文提出的六种控制方案不仅能有效抑制结构的风致振动,显著改善结构的风振舒适度,对结构顶层峰值加速度响应的最大降幅达40％,而且还能提高结构在地震作用下的可靠性,进一步证明了耗能减振层对于超高层结构抗风与抗震的有效性和可行性,提出了风振与地震作用下设置耗能减振层超高层结构的分析与设计建议。     

芯轴式摩擦支撑滞回能量耗散模型及热效应影响参数研究EI北大核心CSCD

针对所提出的芯轴式摩擦支撑的构造特点,建立了滑动摩擦动热转换的滞回能量耗散模型,研究了摩擦生热对芯轴式摩擦支撑性能的影响,分析了初始摩擦力、摩擦片厚度、摩擦芯轴比热容和摩擦系数等因素对芯轴式摩擦支撑的力学性能和温度场的影响规律,给出了摩擦支撑在摩擦生热影响下的摩擦力增长值理论计算公式,并通过数值分析结果进行了验证。分析结果表明芯轴式摩擦支撑在摩擦过程中温度不断上升,高温区主要集中在摩擦芯轴和摩擦片的摩擦接触面上,并且随着摩擦片厚度、初始摩擦力和摩擦系数的增加,摩擦热效应越明显,随着材料比热容的增加,摩擦热效应下降。     

带加强层高层建筑地震作用分析与减震研究

带加强层的高层建筑在地震作用下侧移和内力有特有的规律。针对带加强层高层建筑分析其动力特性和地震作用下的侧移规律,并进行减震效果研究和优化设计,提出设计建议。以某高烈度区一座带加强层高层建筑为例的分析结果表明,带加强层的高层建筑在地震荷载作用下侧移有突变,楼板缺失导致整个结构变形规律发生改变,附加粘滞流体阻尼器后层间位移角和底部剪力都有所减小,减震方案优化后减震效果良好。     

A boundary element model for a partially piston-type porous wave energy converter in gravity waves

The present paper applies the multi-domain boundary element method (BEM) to investigate the performance of a partially piston-type porous wave energy converter (WEC), which consists of a solid wall, a vertical porous plate, a transmission bar, a rigid block constrained by rollers, a spring, and a damper. This WEC is subjected to a dynamic loading external source from a wave attack. For this wave-body interaction problem, a single-degree-of-freedom (SDOF) system is developed to describe the response of the present WEC. Linear wave theory governs the entire fluid domain, which is divided into three regions by a pseudo boundary and the vertical porous plate. Darcy's law applies to the porous plate. Examples are shown to illustrate the wave reflection from the WEC, the response to wave loading, and the instantaneous mechanical power from the wave.     

The evaluation of domain integrals in complex multiply-connected three-dimensional geometries for boundary element methods

The treatment of domain integrals has been a topic of interest almost since the inception of the boundary element method (BEM). Proponents of meshless methods such as the dual reciprocity method (DRM) and the multiple reciprocity method (MRM) have typically pointed out that these meshless methods obviate the need for an interior discretization. Hence, the DRM and MRM maintain one of the biggest advantages of the BEM, namely, the boundary-only discretization. On the other hand, other researchers maintain that classical domain integration with an interior discretization is more robust. However, the discretization of the domain in complex multiply-connected geometries remains problematic. In this research, three methods for evaluating the domain integrals associated with the boundary element analysis of the three-dimensional Poisson and nonhomogeneous Helmholtz equations in complex multiply-connected geometries are compared. The methods include the DRM, classical cell-based domain integration, and a novel auxiliary domain method. The auxiliary domain method allows the evaluation of the domain integral by constructing an approximately C ¹ extension of the domain integrand into the complement of the multiply-connected domain. This approach combines the robustness and accuracy of direct domain integral evaluation while, at the same time, allowing for a relatively simple interior discretization. Comparisons are made between these three methods of domain integral evaluation in terms of speed and accuracy. This work was partially supported by the United States Department of Energy (DOE) grants DE-FG03-97ER14778 and DE-FG03-97ER25332. This financial support does not constitute an endorsement by the DOE of the views expressed in this paper.     

两种不同组合形式的环形网耗能性能的对比分析

通过对单个R0CCO圆环的静力试验和理论分析,推导了圆环等效半径的计算方法。建立了两种组合形式环形网的计算模型：第一种组合形式（模型1）中1个R0CCO圆环与4个R0CCO圆环相连接;第二种组合形式（模型2）中1个R0CCO圆环与6个R0CCO圆环相连接,采用数值分析方法对模型1、2的静动力耗能性能进行了研究。结果表明：①当采用相同的ROCCO圆环组成模型1、2时,模型2中单个ROCCO圆环的耗能能力高于模型1;②当采用相等的材料组成模型1、2时,在相同动能的落石冲击作用下,模型2的变形距离低于模型1,且模型1受到的落石冲击荷载开始时低于模型2,随着落石直径的增大,逐渐高于模型2;③模型1、模型2在落石冲击作用下的极限耗能能力随着落石直径的增大而逐渐增大,且模型1的极限耗能能力开始时高于模型2,当落石直径达到一定程度后,模型2的耗能能力逐渐高于模型1。因此,当实际工程中需要考虑防护系统变形距离时,选择第二种组合形式的环形网可以节约工程造价,而当需要考虑系统极限耗能能力时,可以根据落石特征选择经济合理的环形网结构形式。     

Modal analysis of plates using the dual reciprocity boundary element method

This paper presents a new method for determining the natural frequencies and mode shapes for the free vibration of thin elastic plates using the boundary element and dual reciprocity methods. The solution to the plate's equation of motion is assumed to be of separable form. The problem is further simplified by using the fundamental solution of an infinite plate in the reciprocity theorem. Except for the inertia term, all domain integrals are transformed into boundary integrals using the reciprocity theorem. However, the inertia domain integral is evaluated in terms of the boundary nodes by using the dual reciprocity method. In this method, a set of interior points is selected and the deflection at these points is assumed to be a series of approximating functions. The reciprocity theorem is applied to reduce the domain integrals to a boundary integral. To evaluate the boundary integrals, the displacements and rotations are assumed to vary linearly along the boundary. The boundary integrals are discretized and evaluated numerically. The resulting matrix equations are significantly smaller than the finite element formulation for an equivalent problem. Mode shapes for the free vibration of circular and rectangular plates are obtained and compared with analytical and finite element results.     

贴壁射流形态对跌坎消能的水力特性影响试验研究

贴壁射流形态是影响跌坎型消力池消能效果和水力特性的重要因素之一。为研究贴壁射流形态对输水工程跌坎消能效果和水流特性的影响,通过１：２０的水工模型试验对反弧贴壁射流和平抛贴壁射流情况下的跌坎消力特性进行试验观察和测试。获得不同射流形态下的主流形态、消力池底板脉动压力过程及水面波动时程曲线。试验结果表明：平抛型贴壁射流通过增加射流入水的俯角,使射流进入消力池后产生强烈紊动和翻滚,导致消力池底板的时均压力和脉动压力比反弧贴壁射流大,但平抛贴壁射流减小了消力池和稳水区的水面波动,能更好地满足输水工程下游隧洞稳定输水要求。