Conventional element based methods for modeling acoustic problems are limited to low-frequency applications due to the huge computational efforts. For high-frequency applications, probabilistic techniques, such as sta...Conventional element based methods for modeling acoustic problems are limited to low-frequency applications due to the huge computational efforts. For high-frequency applications, probabilistic techniques, such as statistical energy analysis （SEA）, are used. For mid-frequency range, currently no adequate and mature simulation methods exist. Recently, wave based method has been developed which is based on the indirect TREFFTZ approach and has shown to be able to tackle problems in the mid-frequency range. In contrast with the element based methods, no discretization is required. A sufficient, but not necessary, condition for convergence of this method is that the acoustic problem domain is convex. Non-convex domains have to be partitioned into a number of （convex） subdomains. At the interfaces between subdomains, specific coupling conditions have to be imposed. The considered two-dimensional coupled vibro-acoustic problem illustrates the beneficial convergence rate of the proposed wave based prediction technique with high accuracy. The results show the new technique can be applied up to much higher frequencies.展开更多
Sloshing-induced force and moment may affect the dynamic property of the liquid-contained system.Analytically presented linear Stokes-Joukowski potentials of fluid are usually needed for analytical study of sloshing i...Sloshing-induced force and moment may affect the dynamic property of the liquid-contained system.Analytically presented linear Stokes-Joukowski potentials of fluid are usually needed for analytical study of sloshing in liquid-filled tank under rotational(e.g.,pitching)excitations.To obtain the analytically approximate linear Stokes-Joukowski potentials of fluid in the rigid baffled tanks,a variational domain-decomposition scheme is proposed.This scheme includes three steps:(i)dividing the hydrostatic baffled fluid domain into simple sub-domains based on the positions of the baffles(i.e.,using the baffle as part of the boundaries of the sub-domain)by introducing artificial interfaces and densities of fluids in the different sub-domains or auxiliary normal fluid velocity functions on the artificial interfaces;(ii)expressing the solution for linear Stokes-Joukowski potential of each sub-domain as a linear combination of a class of harmonic functions with undetermined coefficients,and expressing the auxiliary normal fluid velocity functions on the artificial in terfaces as Fourier-type series with undetermined coefficients;(iii)solving the undetermined coefficients by the Trefftz method and the proposed variational formulations.The obtained semi-analytical linear Stokes-Joukowski potential agrees well with that published in literature or given by finite element method(FEM),and its applicability to study nonlinear sloshing problem is verified by applying it to a two-dimensional partially fluid-filled rectangular tank with a T-shaped baffle under pitching excitation.The present semi-analytical result is compared with that given by computational fluid dynamics(CFD)software or literature.展开更多
岩土工程规模大,加上岩土介质复杂的特性,使得当前有限元数值模拟在时间和精确度上很难达到工程要求。研究了在普通 PC 机群上实现的大规模并行有限元方法,以更好地发挥有限元在岩土工程中的应用。组建了Windows 下 PC 机群并行系统。...岩土工程规模大,加上岩土介质复杂的特性,使得当前有限元数值模拟在时间和精确度上很难达到工程要求。研究了在普通 PC 机群上实现的大规模并行有限元方法,以更好地发挥有限元在岩土工程中的应用。组建了Windows 下 PC 机群并行系统。采用“分而治之”的并行策略实现有限元并行,并实现了存储局部化。采用基于区域分解预处理技术的并行共轭梯度法来实现方程组的求解。集成以上方法,用 C++开发了并行有限元程序ParallelGeoFEM。对水布垭地下厂房进行了三维有限元并行模拟,得到了较好的加速比。结果表明,基于区域分解的并行有限元方法可以实现岩土工程大规模快速精细的模拟。展开更多
基金This project is supported by National Natural Science Foundation of China (No.10472035).
文摘Conventional element based methods for modeling acoustic problems are limited to low-frequency applications due to the huge computational efforts. For high-frequency applications, probabilistic techniques, such as statistical energy analysis （SEA）, are used. For mid-frequency range, currently no adequate and mature simulation methods exist. Recently, wave based method has been developed which is based on the indirect TREFFTZ approach and has shown to be able to tackle problems in the mid-frequency range. In contrast with the element based methods, no discretization is required. A sufficient, but not necessary, condition for convergence of this method is that the acoustic problem domain is convex. Non-convex domains have to be partitioned into a number of （convex） subdomains. At the interfaces between subdomains, specific coupling conditions have to be imposed. The considered two-dimensional coupled vibro-acoustic problem illustrates the beneficial convergence rate of the proposed wave based prediction technique with high accuracy. The results show the new technique can be applied up to much higher frequencies.
基金the National Natural Science Foundation of China(Grant Nos.11572018 and 11772020).
文摘Sloshing-induced force and moment may affect the dynamic property of the liquid-contained system.Analytically presented linear Stokes-Joukowski potentials of fluid are usually needed for analytical study of sloshing in liquid-filled tank under rotational(e.g.,pitching)excitations.To obtain the analytically approximate linear Stokes-Joukowski potentials of fluid in the rigid baffled tanks,a variational domain-decomposition scheme is proposed.This scheme includes three steps:(i)dividing the hydrostatic baffled fluid domain into simple sub-domains based on the positions of the baffles(i.e.,using the baffle as part of the boundaries of the sub-domain)by introducing artificial interfaces and densities of fluids in the different sub-domains or auxiliary normal fluid velocity functions on the artificial interfaces;(ii)expressing the solution for linear Stokes-Joukowski potential of each sub-domain as a linear combination of a class of harmonic functions with undetermined coefficients,and expressing the auxiliary normal fluid velocity functions on the artificial in terfaces as Fourier-type series with undetermined coefficients;(iii)solving the undetermined coefficients by the Trefftz method and the proposed variational formulations.The obtained semi-analytical linear Stokes-Joukowski potential agrees well with that published in literature or given by finite element method(FEM),and its applicability to study nonlinear sloshing problem is verified by applying it to a two-dimensional partially fluid-filled rectangular tank with a T-shaped baffle under pitching excitation.The present semi-analytical result is compared with that given by computational fluid dynamics(CFD)software or literature.
文摘岩土工程规模大,加上岩土介质复杂的特性,使得当前有限元数值模拟在时间和精确度上很难达到工程要求。研究了在普通 PC 机群上实现的大规模并行有限元方法,以更好地发挥有限元在岩土工程中的应用。组建了Windows 下 PC 机群并行系统。采用“分而治之”的并行策略实现有限元并行,并实现了存储局部化。采用基于区域分解预处理技术的并行共轭梯度法来实现方程组的求解。集成以上方法,用 C++开发了并行有限元程序ParallelGeoFEM。对水布垭地下厂房进行了三维有限元并行模拟,得到了较好的加速比。结果表明,基于区域分解的并行有限元方法可以实现岩土工程大规模快速精细的模拟。
