﻿ 大型客滚船首部砰击引发舱室噪声的数值模拟
 舰船科学技术  2023, Vol. 45 Issue (20): 25-31    DOI: 10.3404/j.issn.1672-7649.2023.20.005 PDF

Numerical simulation of the bow slamming induced cabin noise of a large RO-RO passenger ship
HE Li-si, WANG De-yu
School of Naval Architecture, Ocean & Civil Engineering, Shanghai Jiaotong University, Shanghai 200240, China
Abstract: The existing regulation of cabin noise is the noise of this focus due to the mechanical vibration. Since the periodical interaction between the high amplitude slamming forces at the ship bow may be an important noise source of the cabins, numerical investigations on the bow slamming induced cabin noise were conducted. Taking a large RO-RO ship as a computational example, numerical studies were performed by combing the computational fluid dynamics (CFD) and acoustic simulation. The slamming phenomena were simulated using the CFD code STAR-CCM+. The computed time-domain slamming forces were then converted into the frequency-domain using the self-developed signal converter before being substituted into the acoustic analysis as the external excitations. The acoustic simulation yielded finally the noise level of the overall ship hull and some typical cabins. Numerical results show that the sound pressure level caused by the slamming increases about 3 dB with each increment of the sea state level.A numerical prediction method for cabin noise caused by slamming is presented, which provides a useful tool for noise performance analysis of large passenger ships. The presented numerical results are of reference values to the design of related ship types.
Key words: slamming     acoustic analysis     computational fluid dynamics     time domain - frequency domain transform     noise rating
0 引　言

1 计算方法及船型选择 1.1 砰击引发舱室噪声的计算方法

 图 1 数值波浪水池立体示意图 Fig. 1 Schematic diagram of the numerical wave tank

CFD计算得到的是砰击力的时域信号，而目前常用的噪声分析数值工具多采用频域方法，两者之间存在数据转换的障碍。砰击噪声主要考虑的是船舶在高海况下，由于波浪诱导的大幅度运动而导致的首部砰击问题，尽管该物理过程存在强烈的非线性效应，但船体收到的砰击力本质上仍属于周期性激励。基于此，采用离散傅里叶变换算法，自主开发船舶入水砰击力信号的时域-频域转化软件。以船舶的砰击激励力时域信号为输入，通过内置数值计算和转换工具，实现时域信号到频域信号的快速计算。

1.2 目标船型的选取

 图 2 目标船型的布置情况 Fig. 2 General arrangement of the subject ship
2 模型的建立 2.1 CFD计算模型的建立

 图 3 简化后用于CFD计算的三维模型 Fig. 3 Simplified ship model for the CFD computation

 图 4 砰击压力监测点的布置情况 Fig. 4 Arrangement of pressure monitoring point
2.2 声学模型的建立

 图 5 VA One中建立的全船SEA模型分解视图 Fig. 5 Shrink view of the SEA model built in VA One

 图 6 VA One中建立的全船声腔模型分解视图 Fig. 6 Shrink view of the SEA cavities built in VA One

 图 7 船体首部砰击压力的计算单元分布 Fig. 7 Computation panels for slamming pressure at the bow

3 计算流程和目标区域 3.1 时域-频域转化软件

 图 8 软件功能界面 Fig. 8 The functional interface of the software
3.2 噪声监测位置的确定

 图 9 舱室噪声监测位置选择情况 Fig. 9 Selected cabin for noise monitoring
4 计算结果分析 4.1 砰击问题的数值模拟结果

 图 10 八级海况(S.S.8)下典型位置压力监测点监测到的压力变化时历结果 Fig. 10 Time history of the monitored pressure under Sea State 8
4.2 砰击引发舱室内噪声的数值结果

 图 11 八级海况(S.S.8)第2个单元上的砰击力频谱 Fig. 11 Computed slamming force spectrum for the panel No.2 under sea state 8

 图 12 各海况下船体总体声压分布计算结果 Fig. 12 Computed overall sound level of the ship at different Sea State

 图 13 目标舱室的NR曲线评定结果 Fig. 13 Evaluated NR-Level of the target cabin

8级海况下，各舱室内的噪声水平均发生显著提升。这是由于此海况下船体首部已出现了大范围的入水现象，此时船体首部所受的激励力与5～7级海况下相比已出现明显变化。在8级海况下，目标舱室1～舱室3的NR等级在50左右，目标舱室4内的噪声等级NR-45，目标舱室5内则为NR-20。对标表2中给出的噪声参考标准可以看出，此时目标舱室1～舱室4中的噪声已值得关注，特别是在目标舱室4内，对于人员活动的区域，较高的噪声等级可能影响旅客的乘坐舒适度，并可能导致一定的安全隐患。

5 结　语

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