舰船管路系统的低频声振控制研究

Ships always have a large and complex piping system. However, as the piping system begins to work, undesired vibration and noise are produced inevitably, especially the low-frequency vibration and noise. Control of low-frequency vibration and noise has become one of the key problems to be solved in ships since most of the vibration and noise are focus in low-frequency range. Low-frequency vibration and noise possess characters of easily transmitting, clear spectral with strong energy and always mutual coupling during the propagation, such that it is quite difficult to control them. Luckily, in front of the sound physical development, the presence of "acoustic metamaterials" concept may provide a new solution for the urgently control problem for ship piping system. By adjusting the structure design and parameters, acoustic metamaterials can obtain wave band gaps in the low frequency range, thereby the transmission of vibration and noise may be controlled. Detailedly, the current project plans to introduce the acoustic metamaterials theory into the structure design of ship piping system. By modeling the pipe wall to be some particular periodic structure, the system could be equipped with such a character that both of the acoustic and the elastic band gaps are existed in it. Through the optimization and design of low-frequency and broadband band gaps, the propagation of low-frequency vibration and noise can be manipulated, such that the low-frequency vibration and noise problem in ships may be solved. Further, a systemical analysis on the sound and vibration propagation characteristics under the fluid-structure coupling effects, engineering boundaries and complex excitation conditions will be carried out, as well as a consider of relevant parameters on the sound and vibration propagation characteristics. The eventual purpose of this project is to realize the reduction of noise and vibration simultaneously.

舰船内部有着庞大的管路系统。管路系统在工作过程中不可避免地产生振动和噪声，特别是低频振动和噪声。低频振动和噪声由于其能量大、传播距离远、特征谱线明显、控制难度大，且传播中相互耦合，声振综合控制困难，成为舰船设计和制造中亟待解决的关键问题之一。在声物理发展的前沿，“声学超材料”概念的提出为当前急需解决的舰船管路系统声振控制提供新的解决思路。通过结构设计和参数调节，声学超材料可以在较低频率范围内获得弹性波带隙，实现振动和噪声的传播操控。本项目拟针对目前舰船中亟待解决的管路系统低频减振降噪问题，以声学超材料理论为基础，对舰船管路系统进行周期设计，使系统同时具有声波和结构弹性波带隙，并进行带隙低频、宽带设计，以改变系统低频段的声振传播特性。考虑固液耦合效应、工程边界条件和复杂激励工况，系统分析管路周期化后的声振传播特性和相关影响规律，并优化结构设计，最终实现舰船管路系统低频振动和噪声的综合控制。

舰船管路系统具有动力系统冷却、重量补偿和二氧化碳吸收等功用，它犹如舰船的“血管系统”，维系着舰船的生命力。舰船管路系统在工作过程中不可避免地产生振动和噪声，特别是低频振动和噪声。由于低频振动和噪声能量大、传播距离远、特征谱线明显，且在舰船有限空间严格限制条件下，管路系统的传统减振降噪技术难以在低频段取得有效效果，成为舰船设计和制造中亟待解决的关键问题之一。. 凝聚态物理领域新兴的声学超材料理论为舰船管路系统的低频振动与噪声控制治理带来新的契机。声学超材料特有的带隙特性可以利用“小尺寸”实现“弹性波大长波的人为操控”，有望打破舰船管路系统低频声振控制的技术瓶颈。. 项目受声学超材料理论启发，将其周期结构设计思想引入舰船管路系统的结构设计，通过对管路结构的周期性设计获得可以抑制低频振动传递的弹性波带隙和控制低频噪声传播的声波带隙，以衰减抑制管路系统的低频振动和噪声传播。项目建立了周期管路声振传播理论与分析方法，可准确计算和分析舰船管路系统的振动传递和噪声传播特性；深入分析了周期管路的振动带隙及流体流速、轴向载荷及压力载荷等外部载荷对振动传递特性的影响规律，分析了定常流和脉动流条件下周期管路的流致振动特性；设计了消声器周期管路结构，分析了消声器周期布置声波带隙特性和参数影响规律，获得了低频宽带强衰减的声波带隙，实现了“小尺寸”控制大长波噪声的有效治理；开展了周期管路振动与噪声控制的实验测试，验证了消声器周期管路的振动传递和声波传播控制性能，有力地验证了项目的理论预测。. 总之，项目研究有望为舰船管路系统的低频声振传播控制提供一条切实可行的技术途径。