流场中周期复合圆柱壳振动与能量传递带隙衰减特性研究

Vibration and radiation noise of underwater vehicle are the key indexes for evaluating its performance, engineers and scholars (military power) do all they can to reduce the vibration and radiation noise. Periodic structures with band gap attenuation characteristics designed based on photonic crystals provide a new approach for vibration and noise control, and will be great potential applications in reducing vibration and noise of underwater vehicle. But at present, research on vibration band gap attenuation characteristics of periodic compound cylindrical shell is mainly focused on the periodic compound cylindrical shell in air or filled with fluid in the published work. For the finite periodic compound cylindrical shell in fluid, the band gap attenuation characteristics of vibration transmission(velocity transmissibility and frequency response function) and energy transmission(input power flow, propagation power flow and radiation sound power) are lack of research, seriously restricting its applications in underwater vehicle. In the present work, the fluid-solid coupling model and the method of predicting radiation noise of the periodic compound cylindrical shell are established, through comprehensive use of wave propagation method and transfer matrix method, the mechanism of band gap attenuation characteristics of vibration transmission and energy transmission is investigated systematically with different boundary conditions, excitations and period numbers. And then the result is verified experimentally. It is hoped that the research will lay a theoretical foundation for engineering applications of periodic compound cylindrical shell in fluid.

水下航行器的振动和辐射噪声是其性能的主要指标，各军事强国极尽所能降低振动和噪声的数值。基于声子晶体理论设计的具有带隙衰减特性的周期结构，开创了全新的振动和噪声控制手段，在水下航行器上具有十分重要的应用潜力。然而目前对航行器主体结构—圆柱壳带隙衰减特性研究的主要研究对象是空气中或充液周期复合圆柱壳，对于浸没在流场中有限长周期复合圆柱壳振动传递（速度传递率和频响函数）和能量传递（输入功率流、传播功率流和辐射声功率）带隙衰减特性缺少必要研究，严重制约着周期复合圆柱壳在水下航行器中的应用。本项目以有限长周期复合圆柱壳为研究对象，突破流场中周期复合圆柱壳流固耦合建模方法和辐射噪声预报方法，建立其振动和辐射噪声数学模型，综合运用波传播法和传递矩阵法，对其在不同边界条件、不同激励和不同周期数目的振动传递和能量传递带隙衰减特性机理进行研究，并进行试验验证，为周期复合圆柱壳在流场中的工程应用奠定理论基础。

水下航行器的振动和辐射噪声是其性能的主要指标，为控制或降低其振动与噪声的数值，国内外学者对此进行了长期的研究，提出了从振源、传递途径和辐射面等三方面的减振降噪措施。针对在辐射面控制振动噪声的需求，通过结合20多年来提出的减振降噪新技术——基于声子晶体的振动衰减技术，开展了周期复合圆柱壳（水下航行器的主体结构）振动带隙衰减特性建模方法、周期复合圆柱壳带隙衰减特性影响规律、振动传递和能量传递带隙衰减特性关联关系等研究，提出了周期复合圆柱壳的振动与能量（辐射声功率）的带隙衰减机理。主要成果和结论有：①周期复合结构的振动带隙频率范围与激励是相关的，若周期复合结构按某阶模态进行线激励，则该激励下的振动带隙与该阶模态下的振动带隙是一致的；若周期复合结构在点激励（可以分解为各阶模态组合激励）作用，则该激励下的振动带隙是参与振动的各阶模态振动带隙的交集；②对比分析了周期复合圆柱壳的振动带隙与辐射声功率带隙的频率分布特征，其带隙频率分布是一致的；③建立了周期结构带隙的有限元计算方法，可以用于复杂结构振动带隙特性的计算，弥补了解析解只能计算简单规则结构带隙特性的不足。.周期复合圆柱壳的带隙频率分布是可设计的，针对工程实际中振动频段的控制要求，根据建立的理论方法或有限元计算方法，设计对应的结构形式，让待控制振动的频段处于带隙频率的范围，利用声子晶体带隙的特性极大的衰减振动，进而降低振动与噪声，科学意义和工程意义显著。