空气噪声和结构噪声及声辐射热区识别研究

发布时间：2018-05-10 12:21

本文选题：舰船噪声 + 结构噪声　；参考：《大连理工大学》2016年硕士论文

【摘要】：噪声问题关系着舰船的舒适性、安全性和隐身性,是舰船工程中重点关注的问题。在舰船的众多噪声源中,机械和设备噪声是舱室中的主要噪声,也是水下低频段的主要噪声。一直以来,对于机械和设备噪声的研究多将其当成一个整体。这样的研究忽视了构成机械和设备噪声总声场中各部分声场的差异,不利于制定针对性的降噪策略。基于这种认识,本文对一300吨巡逻艇的主机噪声进行研究,建立了区分机舱内部主机空气噪声声场和主机诱导船体结构振动辐射噪声声场的数值方法,并分析了主机空气噪声声场和主机结构噪声声场对总声场的贡献度。结果表明机舱内部主机空气噪声对总声场的贡献远远小于主机结构噪声对于总声场的贡献。说明对于机舱内部的降噪处理,对主机进行隔振比隔声更加重要。舰船水下噪声和舱室噪声有着密切的联系,主要表现在舱室内部设备的空气噪声会透过船壳向水下辐射,以及设备工作时的结构噪声激励船壳向水中辐射噪声。因此,对于水下由设备振动诱导的声场,也可以细分成设备空气噪声激发的声场以及设备结构噪声激发的声场。其本质是船体结构在声激励和力激励作用下在水下的声辐射。遵循这样的分离规则,本文对一300吨巡逻艇的水下主机诱导声场进行细分,并分析了主机空气噪声激发声场和主机结构噪声激发声场的特征,包括声场强度、声场指向性、辐射效率等。分析结果表明主机空气噪声所激发水下声场的强度远小于主机结构噪声所激发水下声场的强度。此外,从声场的特性上看,前者的指向性弱于后者的指向性,而辐射效率高于后者。舰船的水下远场声场和隐身性能密切相关,并对海洋生物有不利影响。对远场声场的声辐射热区进行识别有着重要意义和价值。舰船外壳是不同位置之间具有复杂相位关系的不规则几何体,其近场声场和远场声场有很大的不同。近场声场中以倏逝波形式存在的能量流只能沿着船壳表面切向传播,对远场声场没有贡献。然而,这股能量流包含于近场有功声强里面,导致使用近场有功声强进行远场声辐射热区定位不够准确。鉴于此,本文尝试使用远场声辐射的表面贡献方法对300吨巡逻艇船壳表面的远场声辐射热区进行定位。表面贡献方法不同于边界元中的板块贡献方法,该方法在振动结构表面构造了一个和位置相关的正值,意味着对应小块面积对声场的贡献恒为正,构造该正值的过程也就是获取表面非负声强的过程,而表面非负声强表达的就是对远场有贡献的声强。使用表面贡献方法,本文准确地标示出巡逻艇船壳表面的远场声辐射热区,这一尝试展现了表面贡献方法在舰船降噪中的应用前景。
[Abstract]:The noise problem, which concerns the comfort, safety and stealth of ships, is a key issue in warship engineering. Among the many noise sources of ships, the noise of machinery and equipment is the main noise in the cabin and also the main noise in the underwater low frequency band. All the time, the research on the noise of machinery and equipment regards it as a whole. This study ignores the difference of sound fields in the total sound field of mechanical and equipment noise, and is not conducive to the formulation of targeted noise reduction strategies. Based on this understanding, the main engine noise of a 300-ton patrol boat is studied in this paper, and a numerical method is established to distinguish the sound field of the main engine from the noise field of the main engine and the noise field of the hull structure induced by the engine. The contribution of the host air noise field and the host structure noise field to the total sound field is analyzed. The results show that the contribution of the main engine air noise to the total sound field is much smaller than that of the main engine structure noise to the total sound field. It shows that the vibration isolation of the main engine is more important than the sound insulation for the noise reduction within the engine room. The underwater noise of ship is closely related to the cabin noise, which is mainly reflected in the fact that the air noise in the cabin interior will radiate through the hull of the ship and the structural noise when the equipment is working is excited by the radiated noise from the hull to the water. Therefore, the underwater acoustic field induced by the equipment vibration can also be subdivided into the sound field excited by the equipment air noise and the sound field induced by the equipment structure noise. Its essence is the underwater acoustic radiation of the hull structure under the action of acoustic excitation and force excitation. Following this separation rule, the underwater mainframe induced sound field of a 300 ton patrol boat is subdivided, and the characteristics of the main engine air noise induced sound field and the host structure noise excitation sound field are analyzed, including the sound field intensity, the sound field directivity, Radiation efficiency, etc. The results show that the intensity of underwater sound field excited by host air noise is much less than that of underwater sound field excited by host structure noise. In addition, the directivity of the former is weaker than that of the latter, and the radiation efficiency is higher than that of the latter. The underwater far-field sound field of ships is closely related to their stealth performance and has adverse effects on marine life. It is of great significance and value to identify the radiation heat region of far field sound field. The hull of a ship is an irregular geometric body with complex phase relationship between different positions, and its near-field sound field is very different from that of far-field sound field. The energy flow in the near-field acoustic field in the form of evanescent wave can only propagate tangentially along the surface of the ship's shell and has no contribution to the far-field sound field. However, the energy flow is contained in the near-field active sound intensity, which leads to inaccurate location of far-field acoustic radiation heat region using near-field active power sound intensity. In view of this, this paper attempts to use the surface contribution method of far-field acoustic radiation to locate the far-field acoustic radiation heat zone on the surface of 300 ton patrol boat hull. The surface contribution method is different from the plate contribution method in the boundary element. This method constructs a position-dependent positive value on the surface of the vibrating structure, which means that the contribution of the corresponding small area to the sound field is always positive. The process of constructing the positive value is the process of obtaining the non-negative sound intensity on the surface, and the non-negative sound intensity on the surface represents the sound intensity that contributes to the far field. Using the surface contribution method, the far-field acoustic radiation heat region on the surface of the cruiser hull is accurately marked. This attempt shows the application prospect of the surface contribution method in the ship noise reduction.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U661.44;U674.70

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