【作者】 何雪松；

【导师】 黄其柏；

【作者基本信息】 华中科技大学 ， 车辆工程， 2008， 博士

【摘要】 研究空腔内部噪声问题是一个具有极强实际意义的问题,其应用对象包括汽车驾驶室、飞机机舱和舰船船舱,而在结构-声学耦合振动分析基础上进行声场优化是一个正在发展的方向。本文在分析了国内外现有研究结构-声学耦合方法有缺点的基础上,基于间接Trefftz理论,发展了一种新的结构-声学耦合分析方法——波函数法,详细推导了板结构、声学空腔和结构-声学耦合系统的波函数模型,并针对该方法中的两个关键问题,波函数序列与多域问题,提出了有效的解决方法;在此基础上,提出了一种基于波函数法的结构-声学灵敏度计算方法;然后应用波函数法,建立了相干双激励下的结构-声学耦合系统波函数模型,从理论上研究了相干激励下的声场分布规律;最后对所提出方法的有效性和可靠性进行了实验验证。基于间接Trefftz理论,详细推导了用波函数法求解平板与空腔耦合系统在外力作用下的三维结构-声学耦合系统的理论计算模型。论文利用任意边界条件的长方体空腔,推导并证明了新的声学波函数系列。通过一些计算实例,将该方法的数值仿真结果与精确解及有限元数值解进行对比,验证了波函数法的有效性,同时证明该方法在收敛速度、计算精度和计算时间上都有很大的优势,能将计算频率覆盖到中频区域。针对现有表征结构-声学耦合强度参数的缺陷,提出了新的耦合强度计算公式,使其更加全面和合理。针对波函数法的多域问题,提出了一种基于边界连续性条件的域分解方法,分别建立了平板结构、声学空腔和结构-声学耦合系统的多域计算模型,从而扩展了该方法的应用范围。数值仿真结果表明,这种域分解技术是正确而有效的,对收敛速度和计算时间没有太大的影响。基于波函数法理论,对结构-声学灵敏度进行了探讨,通过对结构与声学响应的波函数展开式直接相对于设计变量求导,便得到了结构-声学灵敏度表达式,然后对系统模型方程求导,求得灵敏度表达式中的未知参数,从而得到结构-声学灵敏度的最终计算公式。通过这种方法,分别建立了平板结构、声学空腔以及结构-声学耦合系统的灵敏度计算模型。通过实例研究,讨论了结构及声学响应相对于设计变量的灵敏度变化规律。应用波函数法,利用平板和空腔波函数模型以及它们的耦合关系,建立了相干双激励下的结构-声学耦合系统波函数模型。并针对一个长方体实例,从理论上验证了该模型的正确性,并讨论了激励之间的相位差、板结构的阻尼以及腔体表面上的吸声材料对空腔声场分布的影响,从仿真结果可以看出:激励之间的相位差对声场分布有较大的影响;抑制板结构的振动,能有效降低其近场声压,但对于远场分布影响很小;而吸声材料的使用导致声场能量的重新分配,材料附近的声压降低,而其相对的那一边声压却有升高。利用一个梯形体结构-声学耦合系统,以及一个实际轿车的内部声场实例,通过实验对所提出的方法进行了验证。最后对全文进行了总结和展望。更多还原

【Abstract】 It’s very important to study the noise problem inside a cavity. The objects studied in this field include driving cabs of automobile, passenger compartments of a plane and cabins of a ship. The optimization of sound field based on the structure-acoustic analysis is developing rapidly. Based on the analysis about the advantages and disadvantages of the existing researches on structure-acoustic problems and indirect Trefftz method, a new method, wave based method (WBM), is brought forward for structure-acoustic studies in this paper. The WBM model of plate, cavity and structure-acoustic coupled system are deduced in detail, and the two key problems of WBM, namely wave function series and muti-domain calculation, are effectively handled. Then, a new structure-acoustic sensitivity calculation method is presented based on WBM. The WBM model of structure-acoustic coupled system under two coherent excitations is established and the principle of sound field distribution is studied in theory. Lastly, the validity of the proposed method is proved by experiments.Based on indirect Trefftz theory, the 3D structure-acoustic coupled system calculation model is deduced in detail using WBM, which is applied to palte and cavity coupled system under point force excitation. Using a cuboid cavity with random boundary conditions, deduced and proved a new wave function series. The validity of the WBM is confirmed by comparing the simulation results with the analytical and FEM results. At the same time, the great advantage of the method in convergence rate, calculation precision and calculation speed are proved and the method can extend the calculation range to mid-frequency. Focused on the flaw of the existing parameter indicating the strength of structure-acoustic coupling interaction, a new formulation is presented, which is more comprehensive and reasonable.Based on the continuity of boundary conditions, the method of domain decomposition is presented and the multi-domain calculation model of plate, acoustic cavity and structure-acoustic coupled system are established, which extend the application range of the method. The simulation result shows that the domain decomposition technique is valid and has negletable influence on convergence rate and calculation speed.The structure-acoustic sensitivity is discussed based on WBM. The structure-acoustic sensitivity formula is obtained by directly derivate on the structural and acoustic response expansion formula. Then, derivating on the system model gets the unknown parameter and forms the final structure-acoustic sensitivity expression. The sensitivity calculation model of plate, acoustic cavity and structure-acoustic coupled system are established. The principle of structural and acoustic response sensitivity comparing with design parameters are discussed through some examples.The WBM model of the structure-acoustic coupled system excited by two coherent inputs is established using plate, cavity WBM model and its coupling relationship. Based on a cuboid cavity example, the validity of the model is proved in theory. The influence of phase difference between inputs, damping of plate and absorption material of cavity surfaces on sound field distribution are discussed. The simulation result shows that the phase difference between inputs influence the sound field very much; suppressing the vibration of the plate can effectively reduce nearfield sound pressure, however, the influence on farfield sound pressure is very tiny; the using of absorption material can lead to the redistribution of sound power, in other words, the pressure near the absorption material decreased and the pressure of the opposite side increased.The proposed theory in this dissertation is tested by examples of a trapezoid structure-acoustic coupled system and the interior sound field of a real car.Lastly, the summarization and expectation are given.更多还原