This study presents a new boundary element method(BEM)framework for the numerical solution of general time-dependent or transient problems.By reformulating the time derivative as a domain integral,the framework effect...This study presents a new boundary element method(BEM)framework for the numerical solution of general time-dependent or transient problems.By reformulating the time derivative as a domain integral,the framework effectively decouples the treatment of spatial and temporal variables,allowing for the independent application of specialized discretization methods.For the temporal domain,we introduce an innovative time-spectral integration technique,which is based on Gaussian-quadrature-based orthogonal polynomial expansions.This method not only achieves arbitrary orders of accuracy but also significantly enhances computational efficiency and stability,particularly for simulations involving rapid transients or long-time dynamic simulations.The domain integrals in the spatial domain are calculated using the scaled coordinate transformation BEM(SCT-BEM),a mathematically rigorous technique that converts domain integrals into equivalent boundary integrals,preserving the boundary-only discretization advantage inherent in BEM.Numerical experiments on transient heat conduction and dynamic wave propagation further demonstrate the framework’s performance and capabilities.These experiments show that the proposed framework outperforms traditional time-stepping BEM methods,particularly in terms of stability,convergence rates,and computational cost,making it a highly promising tool for practical engineering applications.展开更多
准确计算户内变电站大型、复杂的噪声场分布,进而评价可采用降噪措施的减噪效果,是解决户内变电站噪声污染的关键问题。为此,综合声学有限元法(finite element method,FEM)求解复杂声场收敛性好及精度高的优点,及声学边界元法(boundary ...准确计算户内变电站大型、复杂的噪声场分布,进而评价可采用降噪措施的减噪效果,是解决户内变电站噪声污染的关键问题。为此,综合声学有限元法(finite element method,FEM)求解复杂声场收敛性好及精度高的优点,及声学边界元法(boundary element method,BEM)降维求解大型声场的优势,提出了一种基于声学FEM-BEM的户内变电站噪声场求解算法。首先,建立变电站内部声源声固耦合模型,采用声学FEM求解混响噪声作用下的声固耦合响应;然后,基于声学FEM-BEM耦合理论,求解内、外耦合边界处结构单元受声固耦合激励产生的位移及应力载荷;最后,根据声压及应力载荷激发的外场声波扩散模型,基于常规Gauss数值积分法,建立外部空间声域2维BEM声学积分方程,求解外部声场。该算法在湖南某110 kV户内变电站噪声场的求解分析中得到了成功应用,与实测值的相对误差为3.61%~4.87%。展开更多
以对称层合板结构为对象,基于经典层合板理论,将其等效为单层各项异性板,采用FE-BEM法(hybrid finite element-boundary element method)分析了其在宽频噪声激励作用下的隔声特性。为验证等效方法的适用性,开展对称复合材料层合板模态...以对称层合板结构为对象,基于经典层合板理论,将其等效为单层各项异性板,采用FE-BEM法(hybrid finite element-boundary element method)分析了其在宽频噪声激励作用下的隔声特性。为验证等效方法的适用性,开展对称复合材料层合板模态测试和数值分析;为验证预估结论的正确性,将FE-BEM法结果与FE-SEA法(hybrid finite element-statistic energy analysis)结果、试验结果分别进行对比。结果表明:将等效方法用于对称层合板固有特性模拟是正确的,等效层合板的固有特性的仿真结果与试验值一致,误差在6.9%以内;等效方法和FE-BEM法结合进行对称层合板隔声预计是有效的,FE-BEM法预计结果与试验结果吻合良好;等效方法和FE-SEA法结合进行对称层合板隔声预计也是有效的,FE-BEM法比FE-SEA法所建模型计算耗时长,算例中计算耗时增大4.4%。展开更多
振动污染在国际上已被列入“七大环境公害”之一,填充沟是振动污染治理的一种常用隔振屏障。传统的填充沟受工程造价和施工工艺等限制工程中应用较困难;为克服上述问题,提出一种新型隔振屏障-内插预制芯墙的劲芯水泥土墙。对于饱和地基...振动污染在国际上已被列入“七大环境公害”之一,填充沟是振动污染治理的一种常用隔振屏障。传统的填充沟受工程造价和施工工艺等限制工程中应用较困难;为克服上述问题,提出一种新型隔振屏障-内插预制芯墙的劲芯水泥土墙。对于饱和地基中劲芯水泥土墙的隔振问题,饱和地基采用饱和土半解析边界元法(boundary element method,BEM)建模,劲芯水泥土墙采用有限元法(finite element method,FEM)建模,根据饱和地基-水泥土墙交界面的平衡和连续性条件,分别建立了劲芯水泥土墙对入射Rayleigh波(瑞利波)的远场被动隔振和对动力机器基础振动近场主动隔振的半解析BEM-FEM耦合分析方法,并对劲芯水泥土墙的隔振效果进行了计算分析。研究结果表明:饱和地基中设置劲芯水泥土墙能够起到较好的隔振作用,其隔振效果与混凝土墙基本相当且远优于纯水泥土墙;预制芯墙在劲芯水泥土墙隔振系统中起关键作用,为避免弹性波从芯墙底绕射而降低隔振效果,预制芯墙深度应与水泥土墙深度保持一致;增大芯墙厚度对隔振效果提升不大。在等深芯墙条件下,增大墙深能显著提高远场隔振效果,但对近场隔振效果提升较小;增大墙厚也可提高隔振效果,但提高幅度不大。实际工程中,建议结合工程造价和施工工艺,选择合适的水泥土墙和预制芯墙墙厚。此外,屏障距振源距离对主动隔振效果影响较小,建议根据被保护建筑与振源之间的实际情况,选择合适位置构建隔振屏障。展开更多
To design a propeller for ship power plant,the interaction between ship hull and propeller must be taken into account.The main concern is to apply the wake effect of ship stern on the propeller performance.In this pap...To design a propeller for ship power plant,the interaction between ship hull and propeller must be taken into account.The main concern is to apply the wake effect of ship stern on the propeller performance.In this paper,a coupled BEM(Boundary Element Method)/RANS(Renolds-Averaged Navier−Stokes)solver is used to simulate propeller behind the hull in the self-propulsion test.The motivation of this work is to develop a practical tool to design marine propulsion system without suffering long computational time.An unsteady boundary element method which is also known as panel method is chosen to estimate the propeller forces.Propeller wakes are treated using a time marching wake alignment method.Also,a RANS code coupled with VoF equation is developed to consider the ship motions and wake field effects in the problem.A coupling algorithm is developed to interchange ship wake field to the potential flow solver and propeller thrust to the RANS code.Based on the difference between hull resistance and the propeller thrust,a PI controller is developed to compute the propeller RPM in every time step.Verification of the solver is carried out using the towing tank test report of a 50 m oceanography research vessel.Wake factor and trust deduction coefficient are estimated numerically.Also,the wake rollup pattern of the propeller in open water is compared with the propeller in real wake field.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12372199,12422207,and W2431010)the Natural Science Foundation of Shandong Province of China(Grant No.ZR2021JQ02)the Ningbo Municipal Excellence Research Program(Zhejiang Province,China).
文摘This study presents a new boundary element method(BEM)framework for the numerical solution of general time-dependent or transient problems.By reformulating the time derivative as a domain integral,the framework effectively decouples the treatment of spatial and temporal variables,allowing for the independent application of specialized discretization methods.For the temporal domain,we introduce an innovative time-spectral integration technique,which is based on Gaussian-quadrature-based orthogonal polynomial expansions.This method not only achieves arbitrary orders of accuracy but also significantly enhances computational efficiency and stability,particularly for simulations involving rapid transients or long-time dynamic simulations.The domain integrals in the spatial domain are calculated using the scaled coordinate transformation BEM(SCT-BEM),a mathematically rigorous technique that converts domain integrals into equivalent boundary integrals,preserving the boundary-only discretization advantage inherent in BEM.Numerical experiments on transient heat conduction and dynamic wave propagation further demonstrate the framework’s performance and capabilities.These experiments show that the proposed framework outperforms traditional time-stepping BEM methods,particularly in terms of stability,convergence rates,and computational cost,making it a highly promising tool for practical engineering applications.
文摘准确计算户内变电站大型、复杂的噪声场分布,进而评价可采用降噪措施的减噪效果,是解决户内变电站噪声污染的关键问题。为此,综合声学有限元法(finite element method,FEM)求解复杂声场收敛性好及精度高的优点,及声学边界元法(boundary element method,BEM)降维求解大型声场的优势,提出了一种基于声学FEM-BEM的户内变电站噪声场求解算法。首先,建立变电站内部声源声固耦合模型,采用声学FEM求解混响噪声作用下的声固耦合响应;然后,基于声学FEM-BEM耦合理论,求解内、外耦合边界处结构单元受声固耦合激励产生的位移及应力载荷;最后,根据声压及应力载荷激发的外场声波扩散模型,基于常规Gauss数值积分法,建立外部空间声域2维BEM声学积分方程,求解外部声场。该算法在湖南某110 kV户内变电站噪声场的求解分析中得到了成功应用,与实测值的相对误差为3.61%~4.87%。
文摘以对称层合板结构为对象,基于经典层合板理论,将其等效为单层各项异性板,采用FE-BEM法(hybrid finite element-boundary element method)分析了其在宽频噪声激励作用下的隔声特性。为验证等效方法的适用性,开展对称复合材料层合板模态测试和数值分析;为验证预估结论的正确性,将FE-BEM法结果与FE-SEA法(hybrid finite element-statistic energy analysis)结果、试验结果分别进行对比。结果表明:将等效方法用于对称层合板固有特性模拟是正确的,等效层合板的固有特性的仿真结果与试验值一致,误差在6.9%以内;等效方法和FE-BEM法结合进行对称层合板隔声预计是有效的,FE-BEM法预计结果与试验结果吻合良好;等效方法和FE-SEA法结合进行对称层合板隔声预计也是有效的,FE-BEM法比FE-SEA法所建模型计算耗时长,算例中计算耗时增大4.4%。
文摘振动污染在国际上已被列入“七大环境公害”之一,填充沟是振动污染治理的一种常用隔振屏障。传统的填充沟受工程造价和施工工艺等限制工程中应用较困难;为克服上述问题,提出一种新型隔振屏障-内插预制芯墙的劲芯水泥土墙。对于饱和地基中劲芯水泥土墙的隔振问题,饱和地基采用饱和土半解析边界元法(boundary element method,BEM)建模,劲芯水泥土墙采用有限元法(finite element method,FEM)建模,根据饱和地基-水泥土墙交界面的平衡和连续性条件,分别建立了劲芯水泥土墙对入射Rayleigh波(瑞利波)的远场被动隔振和对动力机器基础振动近场主动隔振的半解析BEM-FEM耦合分析方法,并对劲芯水泥土墙的隔振效果进行了计算分析。研究结果表明:饱和地基中设置劲芯水泥土墙能够起到较好的隔振作用,其隔振效果与混凝土墙基本相当且远优于纯水泥土墙;预制芯墙在劲芯水泥土墙隔振系统中起关键作用,为避免弹性波从芯墙底绕射而降低隔振效果,预制芯墙深度应与水泥土墙深度保持一致;增大芯墙厚度对隔振效果提升不大。在等深芯墙条件下,增大墙深能显著提高远场隔振效果,但对近场隔振效果提升较小;增大墙厚也可提高隔振效果,但提高幅度不大。实际工程中,建议结合工程造价和施工工艺,选择合适的水泥土墙和预制芯墙墙厚。此外,屏障距振源距离对主动隔振效果影响较小,建议根据被保护建筑与振源之间的实际情况,选择合适位置构建隔振屏障。
文摘To design a propeller for ship power plant,the interaction between ship hull and propeller must be taken into account.The main concern is to apply the wake effect of ship stern on the propeller performance.In this paper,a coupled BEM(Boundary Element Method)/RANS(Renolds-Averaged Navier−Stokes)solver is used to simulate propeller behind the hull in the self-propulsion test.The motivation of this work is to develop a practical tool to design marine propulsion system without suffering long computational time.An unsteady boundary element method which is also known as panel method is chosen to estimate the propeller forces.Propeller wakes are treated using a time marching wake alignment method.Also,a RANS code coupled with VoF equation is developed to consider the ship motions and wake field effects in the problem.A coupling algorithm is developed to interchange ship wake field to the potential flow solver and propeller thrust to the RANS code.Based on the difference between hull resistance and the propeller thrust,a PI controller is developed to compute the propeller RPM in every time step.Verification of the solver is carried out using the towing tank test report of a 50 m oceanography research vessel.Wake factor and trust deduction coefficient are estimated numerically.Also,the wake rollup pattern of the propeller in open water is compared with the propeller in real wake field.
