共查询到19条相似文献,搜索用时 389 毫秒
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有限元法(FEM)是广泛接受的分析耦合结构声(SA)系统动力响应的预报工具。由于随频率增加计算模型也增加导致基于单元的方法在实际中约束在低频段。一种替代方法是基于间接Trefftz法的基于波动方法(WBM)。但WBM的不足之处在于高计算效率只针对中度复杂的几何模型。为了利用两者的优势:FEM的广泛应用和WBM的高收敛特性,提出了混合FE-WB预报法(FEM-WBM)。基本原理是将FE模型中较大且几何简单的部分采用WBM代替。得到的耦合模型仍具有较少的自由度。简要描述了FEM、WBM以及混合FEM-WBM的理论基础。最后将该方法应用于一个简单的结构声模型,理论分析结果与数值仿真计算结果吻合较好,该混合方法有潜力覆盖中频段。 相似文献
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船舶超载防治是一个跨部门、跨水域、跨领域的社会公共问题,也是海事管理部门监管的重点和难点。在实践中,仅凭海事管理部门依靠行政管理手段,难以完全治理船舶超载。跨域治理理论的兴起和发展,为处理这类跨域公共问题提供了一种崭新的理论视角和有效的治理方式。本文从跨域治理理论的视角,分析船舶超载防治存在不足的原因,并提出船舶超载防治的对策建议。 相似文献
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匀速或匀加速运动目标的位置预测问题的分析 总被引:2,自引:0,他引:2
本文提出了一种计算匀速或匀速运动目标的空间位置分析预测的新理论。这种分析预测新理论与传统理论在预测方法的区别是改变了传统的观测方程和优化法则,增加了模拟方法阶的识别技术。它与传统理论在实际应用上的差别是对作出结论所需要的数据量没有要求,提供的运动目标位置预测值是有直接误差估计的,可提供一组满足不同时间需求的预测计算方法等。 相似文献
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针对航行船舶三维时域水动力分析问题,本文采用多域高阶边界元法(MDHOBEM, Multi-Domain Higher Order Boundary Element Method)开展研究,通过假设控制面,将计算域分为内域和外域两部分,内域采用Rankine面元法,外域使用自由面格林函数法,内外域联立求解。从内域、外域、波浪激励三个层面改进多域法的精度、计算效率,以适应不同工况需求。内域重新推导非线性边界条件,考虑入射波对绕辐射问题计算的影响,提高大幅波浪中运动计算精度;外域采用垂向积分形式自由面格林函数,提高格林函数积分计算的收敛性、稳定性及计算效率;波浪激励采用高阶谱(HOS, High Order Spectral)方法生成演化的波场,考虑波浪自身的非线性,提高对非线性现象的捕捉和模拟能力。以C11船为对象,研究内域非线性改进对船舶大幅运动计算精度的提高;以S175集装箱船为对象,验证外域垂向积分对运动及波阻增加计算效率和稳定性的提高;对比S175在线性波场和非线性波场中的运动,论证考虑非线性波场对运动计算的影响;以某内倾船为对象,研究不同层次改进对参数横摇现象捕捉的影响,验证非... 相似文献
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利用奇异函矩形域反平面剪切问题进行了位移与剪应力分析。主要考虑了局部线性分布载荷的3种形式,给出了矩形域在边界上作用纵向载荷时的级数解答。 相似文献
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对励磁电流精确控制是发电机励磁系统的重要要求,本文对具有H半桥结构的励磁电流功率放大电器工作原理进行分析和仿真。建立了以H半桥励磁电流功率放大器和感性负载为对象的电流闭环控制数学模型,并在对模型进行合理简化基础上,根据根轨迹和劳斯判据理论推导PI调节器参数的稳定域,通过试验验证了PI调节器参数对系统稳定性能的影响。根据分析和试验对控制器参数进行调整,确定合理的PI调节器参数,实现励磁电流以较小的超调量和较快的响应速度稳定输出。试验结果表明了理论推导的正确性,该方法简单有效,具有一定的工程应用价值。 相似文献
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This paper presents an algorithm for the frequency domain solution of dynamic linear “inverse” problems, that is for the processing of measurement data (strain, acceleration etc.) acquired on a mechanical structure, in order to estimate the loads acting on the structure and its corresponding response. The problem is formulated as a constrained (force equilibrium) optimization (small deviations from measurements, small loads) problem, which is transformed into an unconstrained problem, then into differential equations. The algorithm is applied to the estimation of hydrodynamic forces induced by the shedding of vortices from an offshore oil riser. 相似文献
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不连续问题的扩展有限元法分析 总被引:2,自引:0,他引:2
改进的扩展有限元不需要经过后处理可以直接求得应力强度因子,从而为动态不连续问题的分析提供了便利.研究表明:不连续区域附近的积分方案,特别是裂尖区域的积分方案,对结果精度影响很大.文中采用一种新的积分方案对裂尖和裂缝贯穿单元进行积分,既方便积分,又可以减少计算量.采用改进的扩展有限元模拟了裂纹扩展.对于闭合裂缝,必须考虑缝面间的接触条件;裂缝面间若采用完全接触,得到的结点加强自由度近似为零.由于避免了传统有限元方法中的网格重构,改进的扩展有限元在静态和动态不连续问题分析方面具有广阔的应用前景. 相似文献
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Underwater acoustic scattering echoes have time–space structures and are aliasing in time and frequency domains. Different series of echoes properties are not identified when incident angle is unknown. This article investigates variations in target echoes of monostatic sonar to address this problem. The mother wavelet with similar structures has been proposed on the basis of preprocessing signal waveform using matched filter, and the theoretical expressions between delay factor and incident angle are derived in the wavelet domain. Analysis of simulation data and experimental results in free-field pool show that this method can effectively separate geometrical scattering components of target echoes. The time delay estimation obtained from geometrical echoes at a single angle is consistent with target geometrical features, which provides a basis for object recognition without angle information. The findings provide valuable insights for analyzing elastic scattering echoes in actual ocean environment. 相似文献
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This paper considers the problem of ship hydroelasticity, which is an important technical issue in the design of ultra-large vessels. For the analysis of fluid-structure interaction problems, a partitioned method is applied. The fluid domain surrounding a flexible body is solved using a B-spline Rankine panel method, and the structural domain is handled with a three-dimensional finite element method. The two distinct methods are fully coupled in the time domain by using an implicit iterative scheme. The numerical results of natural frequency and the motion responses of simple and segmented barges are computed to validate the present method through comparisons with experimental and numerical results. This study extends to the application to two real ships, 6500 TEU and 10,000 TEU containerships, for more validation and also observation on the practicality of the present method. Based on this study, it is found that the present method provides reliable solutions to linear ship hydroelasticity problems. 相似文献
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CHEN Lu-yun WANG De-yu 《船舶与海洋工程学报》2007,6(4):55-61
For the structural-acoustic radiation optimization problem under external loading,acoustic radiation power was considered to be an objective function in the optimization method. The finite element method(FEM) and boundary element method(BEM) were adopted in numerical calculations,and structural response and the acoustic response were assumed to be de-coupled in the analysis. A genetic algorithm was used as the strategy in optimization. In order to build the relational expression of the pressure objective function and the power objective function,the enveloping surface model was used to evaluate pressure in the acoustic domain. By taking the stiffened panel structural-acoustic optimization problem as an example,the acoustic power and field pressure after optimized was compared. Optimization results prove that this method is reasonable and effective. 相似文献
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针对航道工程存在的离散地形数据或地形数据空值区域导致所创建地形曲面不够光滑、会出现深凹或凸起的问题,提出采用克里金插值法(Kriging)对航道区域离散的地形数据进行直接内插填补,再通过BIM技术构建航道地形曲面模型。结果表明,离散的地形数据经Kriging空间插值生成的地形曲面模型,更贴近实际效果及地形趋势走向,可真实显现航道现状三维地形。研究成果可为测绘单位开展BIM工作提供借鉴。 相似文献