螺旋桨空化噪声源匹配场反演及实验验证

Propeller cavitation noise is an important noise source of the ship. The existing numerical and experimental methods can hardly evaluate the ship sound field change induced by propeller cavitation under maneuver condition, efficiently and dynamically. This research couples the near-field sound measurement technology with sound source inversion model of propeller, and the transfer function of the sound source strength to near-field sound is obtained via Helmholtz equation, so as to realize the dynamical inversion and far-field sound directivity prediction of the propeller cavitation noise. Firstly, the propeller is artificially equivalent to the combination of monopoles, dipoles and quadrupoles, based on which the point source model is built. Then, numerical simulation, model test and ship noise trial are carried out, to check and improve the point source model above mentioned. Followed by the nonlinear inversion problem of the propeller sound source is translated into a multi-parameters optimization problem with the assistance of the fast matched field inversion (MFI) algorithm, of which a special experiment is designed to validate the stability. Finally, the equivalent source strength of propeller is inverted and compared by the inversion samples and compare samples, respectively, measured in the propeller near-field, and the far-field sound directivity is predicted. Additionally, the visualization technology is applied to visualize the source location, strength and sound directivity change pattern of propeller. This research is expect to realize the acceptable prediction of the propeller cavitation noise in real time.

螺旋桨空化噪声是舰船重要噪声源，现有的数值预报及实验方法难以快速有效评估舰船变工况航行时螺旋桨空化引起的舰船水下辐射声场的动态变化。本项目拟将近场噪声测量技术与螺旋桨空化噪声反演模型有机结合，通过Helmholtz方程建立空化噪声源强度与近场噪声的传递函数，实现螺旋桨空化噪声源动态反演及远场声指向性的实时预报。1.将螺旋桨等效为单极子、偶极子、四极子组合声源，建立螺旋桨点源模型；2.采用数值仿真、螺旋桨消声水池噪声实验及实船试验检验并修正点源模型；3.将螺旋桨噪声源非线性反演问题转化为多参数优化问题，采用匹配场技术设计高效优化算法并对算法的稳健性进行专项实验验证；4.实验测量螺旋桨近场水声，用有限个反演样本与比较样本分别来反演、确认螺旋桨声源强度，基于此预报远场声指向性，并采用可视化技术动态显示螺旋桨噪声源位置、强度及声指向性的变化。本研究方法有望实现舰船螺旋桨空化噪声的实时、准确预报。

本研究围绕螺旋桨空化噪声源反演问题，开展了螺旋桨典型声源模型的建模与验证，并通过匹配场反演算法将螺旋桨噪声源反演问题转换为多参数优化问题，最后联合螺旋桨噪声实测与反演技术实现了螺旋桨声场的快速准确预报，具体如下：.一、建立了基本静止点声源（单极子、偶极子、纵向四极子）的辐射噪声解析模型，并以频域格林函数的球谐函数展开式为基础，推导了点声源旋转状态下的声压解析解，实现了源点与场点位置参数的解耦，在此基础上获得了任意场点处声压的解析解。采用等效源法（ESM）预报的声压对旋转声源声场解析解进行了验证，解析解与ESM解吻合较好。.二、将自适应模拟退火算法（ASSA）应用于螺旋桨噪声反演，开展了各类型点声源的位置参数、源强参数、相位参数的反演，且基于反演参数重构的声场与理论声场吻合较好，验证了反演算法的适用性。.三、开展了螺旋桨自由场和非自由场环境下辐射声场的时域预报。提出了基于螺旋桨单叶片流场信息来预报螺旋桨噪声的快速预报方法，并以均匀流与潜艇伴流场中螺旋桨辐射噪声为例对方法的可信性进行了验证。基于螺旋桨辐射噪声仿真数据，开展了潜艇伴流场中螺旋桨非空化噪声源的参数反演及声场重构。结果表明，螺旋桨非空化噪声具有典型的偶极子特性，并且用两个静止偶极子来等效螺旋桨噪声源具有较好的精度，而旋转单极子或旋转偶极子的等效效果较差。.四、基于消声水池噪声测试平台，开展了某四叶可调距模型桨的空化噪声和某七叶大侧斜模型桨非空化噪声的测量与分析，并以ASSA算法对螺旋桨噪声源进行了多参数反演与声场重构。实测及反演结果表明：在消声水池环境下，所选用的四叶桨空化噪声源可以等效为一个静止的偶极子或两个幅值相当、相位相反、但位置不重合的静止单极子，而所选用的七叶桨非空化噪声可以等效为两个静止偶极子。.本研究所提供的研究方法与结论，可为螺旋桨噪声预报与动态监测提供一定参考，而关于实船环境下螺旋桨噪声特性尚需要后续深入开展实船噪声测试与反演。