﻿ 船舶声呐结构机械自噪声的传播分析
 舰船科学技术  2022, Vol. 44 Issue (15): 127-130    DOI: 10.3404/j.issn.1672-7649.2022.15.026 PDF

Propagation analysis of mechanical self noise in ship sonar structure
TIAN Zi-xin
College of Applied Engineering, Henan University of Science and Technology, Sanmenxia 472000, China
Abstract: Sonar is a very important ranging, navigation and target detection tool for ships. It is of great significance to improve its detection accuracy and efficiency. Due to the influence of ship mechanical noise, structural self noise and environmental noise, ship sonar signal is mixed with a variety of noise, which has an adverse impact on the detection accuracy of sonar. To solve this problem, this paper analyzes the noise source of ship sonar, establishes the acoustic model of ship sonar under the condition of fluid structure coupling, analyzes the propagation characteristics of mechanical self noise of sonar structure, and finally simulates the noise characteristics of sonar structure based on the finite element software Ansys Workbench.
Key words: sonar structure     self noise     fluid solid coupling     finite element     simulation
0 引　言

1 舰船声呐结构机械自噪声的来源与特性分析

 图 1 船舶声呐结构机械自噪声的来源示意图 Fig. 1 Source diagram of mechanical self noise of ship sonar structure

1）水动力噪声

2）螺旋桨噪声

 图 2 不同转速下螺旋桨噪声特性曲线图 Fig. 2 Noise characteristic curve of propeller at different speeds

3）机械振动噪声

2 船舶声呐结构机械自噪声的传播分析和仿真研究 2.1 建立考虑流固耦合作用的声呐部件声学模型

 图 3 船舶声呐导流罩位置处的数学模型 Fig. 3 Mathematical model of the position of sonar fairing

 $\left\{ {\begin{array}{*{20}{c}} {\dfrac{1}{{{c^2}}}\dfrac{{{\partial ^2}{P_0}}}{{\partial {t^2}}} = {\nabla ^2}{P_0}} \;，\\ {\dfrac{{\partial {P_0}}}{{\partial s}} = - {\rho _0}jw{V_0}} \; 。\end{array}} \right. \text{}$

 $\mathop {\lim }\limits_{t \to \infty } \left[ {d\left( {\frac{{\partial {P_0}}}{{\partial s}} + jk{P_0}} \right)} \right] = 0 。$

 $\iint {\left[ {P\left( {M,N} \right)\frac{{\partial G(M,N)}}{{\partial n}} + jwG(M,N)} \right]}{\rm{d}} s= \frac{1}{2}P\left( h \right) \text{。}$

 $\delta \left( t \right) = {e^{ - t}}\left( {\cos {w_0}t + k{\rm{sin}}{w_0}t} \right) \text{，}$

 图 4 声呐导流罩辐射噪声的功率谱 Fig. 4 Power spectrum of noise radiated by sonar dome
2.2 考虑流固耦合作用的声呐机械噪声传播分析

 ${D_0}\left( {\frac{{{\partial ^4}w}}{{\partial {x^4}}} + 2\frac{{{\partial ^4}w}}{{\partial {x^2}\partial {y^2}}} + \frac{{{\partial ^4}w}}{{\partial {y^4}}}} \right) + \rho h\frac{{{\partial ^2}w}}{{\partial {t^2}}} = p(x,y,t) \text{，}$

 ${D_0}{\nabla ^4}w + \rho h\frac{{{\partial ^2}w}}{{\partial {t^2}}} = p({\text{x}},y,t) \text{。}$

 ${\nabla ^4} = \left( {\frac{{{\partial ^2}}}{{\partial {x^2}}} + \frac{{{\partial ^2}}}{{\partial {y^2}}}} \right)\left( {\frac{{{\partial ^2}}}{{\partial {x^2}}} + \frac{{{\partial ^2}}}{{\partial {y^2}}}} \right) \text{。}$

 ${\nabla ^4}w + \frac{{\rho h}}{{{D_0}}}\frac{{{\partial ^2}w}}{{\partial {t^2}}} = 0 。$

 $w({{x}},y,t) = W({{x}},y)\sin (\omega t + \varphi ) \text{，}$

$W({{x}},y)$ 满足4个方向的边界条件如下：

 $\begin{gathered} {\left. W \right|_{x = 0}} = {\left. {\frac{{{\partial ^2}W}}{{\partial {x^2}}}} \right|_{x = 0}} = 0,{\left. W \right|_{x = d}} = {\left. {\frac{{{\partial ^2}W}}{{\partial {x^2}}}} \right|_{x = \infty }} = 0 ，\\ {\left. W \right|_{y = 0}} = {\left. {\frac{{{\partial ^2}W}}{{\partial {y^2}}}} \right|_{y = 0}} = 0,{\left. W \right|_{y = h}} = {\left. {\frac{{{\partial ^2}W}}{{\partial {y^2}}}} \right|_{y \to \infty }} = 0 。\\ \end{gathered}$

 图 5 流固耦合作用下声呐矩形腔体的数学模型 Fig. 5 Mathematical model of sonar rectangular cavity under fluid structure coupling

 ${F_r}(\sigma ) = \cos \left( {\frac{{l{\text{π}} x}}{a}} \right)\sin \left( {\frac{{m{\text{π}} y}}{b}} \right)\cos \left( {\frac{{n{\text{π}} z}}{d}} \right) \text{，}$

$l/m/n$ 为自然数，腔体的振动固有频率为：

 $\omega _r^{} = {c_0}\sqrt {{{\left( {\frac{{l{\text{π}} }}{{ax}}} \right)}^2} + {{\left( {\frac{{m{\text{π}} }}{{by}}} \right)}^2} + {{\left( {\frac{{n{\text{π}} }}{{dz}}} \right)}^2}} {\text{ }} 。$
2.3 基于有限元的声呐结构机械自噪声仿真

1）有限元模型的搭建

 图 6 声呐导流罩与舱壁结合部位的有限元模型 Fig. 6 Finite element model of the joint of sonar shroud and bulkhead

2）真求解

 图 7 基于Ansys的声呐机械自噪声声压仿真结果 Fig. 7 Simulation results of sonar mechanical self noise sound pressure based on Ansys
3 结　语

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