A finite element solution for the Navier_Stokes equations for steady flow through a double branched two dimensional section of three dimensional model of canine aorta is obtained. The numerical technique involves tran...A finite element solution for the Navier_Stokes equations for steady flow through a double branched two dimensional section of three dimensional model of canine aorta is obtained. The numerical technique involves transformation of the physical coordinates to a curvilinear boundary fitted coordinate system. The shear stress at the wall is calculated for Reynolds number of 1000 with branch to main aortic flow rate ratio as a parameter. The results are compared with earlier works involving experimental data and it is observed that the results are very close to their solutions. This work in fact is an improvement of the work of Sharma and Kapoor (1995) in the sense that computations scheme is economic and Reynolds number is large.展开更多
The general meshless local Petrov-Galerkin (MLPG) weak forms of the displacement and trac- tion boundary integral equations (BIEs) are presented for solids undergoing small deformations. Using the directly der...The general meshless local Petrov-Galerkin (MLPG) weak forms of the displacement and trac- tion boundary integral equations (BIEs) are presented for solids undergoing small deformations. Using the directly derived non-hyper-singular integral equations for displacement gradients, simple and straight- forward derivations of weakly singular traction BIEs for solids undergoing small deformations are also pre- sented. As a framework for meshless approaches, the MLPG weak forms provide the most general basis for the numerical solution of the non-hyper-singular displacement and traction BIEs. By employing the various types of test functions, several types of MLPG/BIEs are formulated. Numerical examples show that the pre- sent methods are very promising, especially for solving the elastic problems in which the singularities in dis- placements, strains, and stresses are of primary concern.展开更多
对某些无穷维动力系统的研究现状及研究方法进行了总结与评述.考虑材料的粘性效应,建立了一类轴向载荷作用下的更一般的粘弹性梁方程,并利用G a lerk in方法,证明了该方程在非线性边界条件下整体解的存在性,解对初值的连续依赖性,整体...对某些无穷维动力系统的研究现状及研究方法进行了总结与评述.考虑材料的粘性效应,建立了一类轴向载荷作用下的更一般的粘弹性梁方程,并利用G a lerk in方法,证明了该方程在非线性边界条件下整体解的存在性,解对初值的连续依赖性,整体解的唯一性.展开更多
The interaction between an elastic structure and electrodynamic shakers commonly exists in Ground Flutter Simulation Tests(GFST)with multi-point excitations,causing a considerable discrepancy between the practical exc...The interaction between an elastic structure and electrodynamic shakers commonly exists in Ground Flutter Simulation Tests(GFST)with multi-point excitations,causing a considerable discrepancy between the practical excitation forces and desired ones.To investigate the excitation force characteristics on a cantilever beam excited by a voltage-sourced electrodynamic shaker,the coupled shaker-beam system is modeled to derive the excitation force formula using Hamilton’s principle and Galerkin’s approach.Simulation results using the multi-mode beam model coupled with the shaker model are in good agreement with experimental results,verifying that the proposed multi-mode method can accurately predict the excitation force.Furthermore,parametric studies show that the influence of system parameters on the excitation force is related to the shaker’s operating mode.Unlike in current mode of shaker,when the beam resonant frequency approaches the suspension frequency of shaker armature,the variation of excitation force amplitude in voltage mode is no longer minimal.Meanwhile,if the exciting point in the GFST is located far away from the modal node,it is essential to compensate the force because the accuracy of tests can be reduced dramatically.The coupled shaker-beam model proposed in this paper can provide the basis for compensation measures.展开更多
文摘A finite element solution for the Navier_Stokes equations for steady flow through a double branched two dimensional section of three dimensional model of canine aorta is obtained. The numerical technique involves transformation of the physical coordinates to a curvilinear boundary fitted coordinate system. The shear stress at the wall is calculated for Reynolds number of 1000 with branch to main aortic flow rate ratio as a parameter. The results are compared with earlier works involving experimental data and it is observed that the results are very close to their solutions. This work in fact is an improvement of the work of Sharma and Kapoor (1995) in the sense that computations scheme is economic and Reynolds number is large.
文摘The general meshless local Petrov-Galerkin (MLPG) weak forms of the displacement and trac- tion boundary integral equations (BIEs) are presented for solids undergoing small deformations. Using the directly derived non-hyper-singular integral equations for displacement gradients, simple and straight- forward derivations of weakly singular traction BIEs for solids undergoing small deformations are also pre- sented. As a framework for meshless approaches, the MLPG weak forms provide the most general basis for the numerical solution of the non-hyper-singular displacement and traction BIEs. By employing the various types of test functions, several types of MLPG/BIEs are formulated. Numerical examples show that the pre- sent methods are very promising, especially for solving the elastic problems in which the singularities in dis- placements, strains, and stresses are of primary concern.
基金co-supported by the Overseas Expertise Introduction Project for Discipline In-novation(111 Project,BP0719007)the National Natural Science Foundation of China(No.12002280)。
文摘The interaction between an elastic structure and electrodynamic shakers commonly exists in Ground Flutter Simulation Tests(GFST)with multi-point excitations,causing a considerable discrepancy between the practical excitation forces and desired ones.To investigate the excitation force characteristics on a cantilever beam excited by a voltage-sourced electrodynamic shaker,the coupled shaker-beam system is modeled to derive the excitation force formula using Hamilton’s principle and Galerkin’s approach.Simulation results using the multi-mode beam model coupled with the shaker model are in good agreement with experimental results,verifying that the proposed multi-mode method can accurately predict the excitation force.Furthermore,parametric studies show that the influence of system parameters on the excitation force is related to the shaker’s operating mode.Unlike in current mode of shaker,when the beam resonant frequency approaches the suspension frequency of shaker armature,the variation of excitation force amplitude in voltage mode is no longer minimal.Meanwhile,if the exciting point in the GFST is located far away from the modal node,it is essential to compensate the force because the accuracy of tests can be reduced dramatically.The coupled shaker-beam model proposed in this paper can provide the basis for compensation measures.
