﻿ 船体绕流场及流噪声的CFD模拟方法
 舰船科学技术  2019, Vol. 41 Issue (10): 63-69 PDF

CFD simulation analysis of flow field and flow-induced noise around ship hull
Liu Bo, Wu Guo-qi
Dalian Scientific Test and Control Technology Institute, Dalian 116013, China
Abstract: CFD numerical simulation technologies can provide highly accurate predictions for underwater noise level and noise propagation of ships, as well as giving insight into the changes ofhull flow field. In this paper, the VOF method and SSTκ-ω two-equation turbulence model were used to solve the unsteady viscous flow field of ships, and coupled with the FW-H equation for noise propagation. According to the Lighthill theory, the acoustic numerical calculation about different bulbous bow ship types was carried out, and the spatial directivity and near-far field distribution characteristics of hull flow noise were analyzed. The results showed that CFD technology could be used to simulate and analyze the flow field around the ships and problem of flow-induced noise, could provide reference for the design of low-noise hull lines.
Key words: flow field     Flow-induced noise     CFD technology     underwater noise     numerical simulation
0 引　言

1 数学计算模型 1.1 船舶绕流场模拟的湍流控制方程

 $\frac{\partial }{{\partial {{t}}}}\left( {\rm{\rho }} \right) + \frac{\partial }{{\partial {{{x}}_{{i}}}}}\left( {{\rm{\rho }}{{{u}}_{{i}}}} \right) = 0 {\text{，}}$ (1)
 $\begin{split} \frac{\partial }{{\partial {{t}}}}\left( {{\rm{\rho }}{{{u}}_{{i}}}} \right) + \frac{\partial }{{\partial {{{x}}_{{j}}}}}\left( {{\rm{\rho }}{{{u}}_{{i}}}{{{u}}_{{j}}}} \right) =\;& - \frac{{\partial {\rm{p}}}}{{\partial {{{x}}_{{i}}}}} + \frac{\partial }{{\partial {{{x}}_{{j}}}}}\left( { - {\rm{\rho }}\overline {{{u}}_i^{\rm{'}}{\rm{u}}_j^{\rm{'}}} } \right)+\\ & \frac{\partial }{{\partial {{{x}}_{{j}}}}}\left[ {{\rm{\mu }}\left( {\frac{{\partial {{{u}}_{{i}}}}}{{\partial {{{x}}_{{j}}}}} + \frac{{\partial {{{u}}_{{j}}}}}{{\partial {{{x}}_{{i}}}}}} \right)} \right] {\text{。}}\end{split}$ (2)

 $\frac{\partial }{{\partial {{t}}}}\left( {{{\rm \rho } {\textit{κ}}}} \right) + \frac{\partial }{{\partial {{{x}}_{{i}}}}}\left( {{\rm{\rho {\textit{κ}} }}{{{u}}_{{i}}}} \right) = \frac{\partial }{{\partial {{{x}}_{{j}}}}}\left( {{{\rm{\varGamma }}_{{k}}}\frac{{\partial {{k}}}}{{\partial {{{x}}_{{j}}}}}} \right) + {{{G}}_{{k}}} - {{{Y}}_{{k}}} + {{{S}}_{{\textit{κ}}}} {\text{，}}$ (3)
 $\frac{\partial }{{\partial {{t}}}}\left( {{\rm{\rho \omega }}} \right) + \frac{\partial }{{\partial {{{x}}_{{i}}}}}\left( {{\rm{\rho {\textit{ω}} }}{{{u}}_{{i}}}} \right) = \frac{\partial }{{\partial {{{x}}_{{j}}}}}\left( {{{\rm{\varGamma }}_{\rm{\omega }}}\frac{{\partial {\rm{\omega }}}}{{\partial {{{x}}_{{j}}}}}} \right) + {{{G}}_{\rm{\omega }}} - {{{Y}}_{\rm{\omega }}} + {{{D}}_{\rm{\omega }}} + {{{S}}_{\rm{\omega }}} {\text{。}}$ (4)

 ${{\rm{\sigma }}_{{k}}} = \frac{1}{{{{{F}}_1}/{{{\textit{σ}}}_{{{\textit{κ}}}1}} + \left( {1 - {{{F}}_1}} \right)/{{{\textit{σ}}}_{{{\textit{κ}}}2}}}} {\text{，}}$ (5)
 ${{\rm{\sigma }}_{\rm{\omega }}} = \frac{1}{{{{{F}}_1}/{{{\textit{σ}}}_{{\rm{\omega }}1}} + \left( {1 - {{{F}}_1}} \right)/{{{\textit{σ}}}_{{\rm{\omega }}2}}}} {\text{。}}$ (6)

 ${{\rm{\phi}} _1} = {\rm{min}}\left[ {\max \left( {\frac{{\sqrt {\rm{\kappa }} }}{{{{\rm{\beta }}^{\rm{*}}}{{\omega y}}}},\frac{{500{\rm{\nu }}}}{{{{{y}}^2}{\rm{\omega }}}}} \right),\frac{{4{\rm{\rho \kappa }}{{\rm{\sigma }}_{{\rm{\omega }}2}}}}{{{{D}}_{\rm{\omega }}^ + {{{y}}^2}}}} \right] {\text{，}}$ (7)
 ${{D}}_{\rm{\omega }}^ + = \max \left[ {2{\rm{\rho }}{{\rm{\sigma }}_{{\rm{\omega }}2}}\frac{1}{{\rm{\omega }}}\frac{{\partial {\rm{\kappa }}}}{{\partial {{{x}}_{{j}}}}}\frac{{\partial {\rm{\omega }}}}{{\partial {{{x}}_{{j}}}}},{{10}^{ - 10}}} \right] {\text{。}}$ (8)

1.2 声学方程

 $\frac{1}{{{{a}}_0^2}}\frac{{{\partial ^2}{{p'}}}}{{\partial {{{t}}^2}}} - {\nabla ^2}{{p'}} = \frac{\partial }{{\partial {{t}}}}\left[ {{{\rm{p}}_0}{{\rm{u}}_{{n}}}{\rm{\delta }}\left( {{f}} \right)} \right] + \frac{{{\partial ^2}}}{{\partial {{{x}}_{{i}}}\partial {{{x}}_{{j}}}}}{{{T}}_{{{ij}}}} - \frac{\partial }{{\partial {{{x}}_{{i}}}}}\left[ {{{{p}}_{{{ij}}}}{{{n}}_{{j}}}{\rm{\delta }}\left( {{f}} \right)} \right] {\text{，}}$ (9)

 ${{{T}}_{{{ij}}}} = {{\rho }}{{{u}}_{{i}}}{{{u}}_{{j}}} + {{{p}}_{{{ij}}}} - {{a}}_0^2\left( {{{\rho }} - {{{\rho }}_0}} \right){{{\delta }}_{{{ij}}}} {\text{，}}$ (10)
 ${{{p}}_{{{ij}}}} = {{p}}{{{\delta }}_{{{ij}}}} - {{\mu }}\left[ {\frac{{\partial {{{u}}_{{i}}}}}{{\partial {{{x}}_{{j}}}}} + \frac{{\partial {{{u}}_{{j}}}}}{{\partial {{{x}}_{{i}}}}} - \frac{2}{3}\frac{{\partial {{{u}}_{{k}}}}}{{\partial {{{x}}_{{k}}}}}{{\rm{\delta }}_{{{ij}}}}} \right] {\text{。}}$ (11)

2 船体模型建立及边界条件设置 2.1 某成品油船几何模型

 图 1 油船型线图 Fig. 1 Oil tanker lines

 图 2 船体模型示意图 Fig. 2 Schematic diagram of hull model
2.2 边界条件设置

 图 3 边界条件设置示意图 Fig. 3 Schematic diagram of boundary condition setting

3 船体绕流场和流噪声场的数值模拟 3.1 模型计算条件设置

 图 4 普通型（上）和上翘型（下）球艏的对比图 Fig. 4 Comparison of ordinary (Upper) and upwarping (Lower) bows

3.2 声接收点的选择

 图 5 船舶流噪声指向性示意图 Fig. 5 Directional diagram of ship flow noise

4 计算结果分析 4.1 船体绕流场结果分析

 图 6 上翘型球首船体静压力云图 Fig. 6 Static pressure contour of upwarping bow hull

 图 7 普通型球首船体静压力云图 Fig. 7 Static pressure contour of ordinary bow hull

 图 8 上翘型球首船首速度云图 Fig. 8 Head velocity contour of upwarping bow hull

 图 9 普通型球首船首速度云图 Fig. 9 Head velocity contour of ordinary bow hull

 图 10 上翘型球首船尾速度云图 Fig. 10 Stern velocity contour of upwarping bow hull

 图 11 普通型球首船尾速度云图 Fig. 11 Stern velocity contour of ordinary bow hull

 图 12 上翘型球首船波形分布图 Fig. 12 Waveform distribution of of upwarping bow hull

 图 13 普通型球首船波形分布图 Fig. 13 Waveform distribution of of ordinary bow hull

 图 14 船首自由液面分布情况 Fig. 14 Free surface distribution of bow

 图 15 船尾自由液面分布情况 Fig. 15 Free surface distribution of stern

 图 16 不同工况下阻力与弗劳德数的关系 Fig. 16 The relation between resistance and froude number under different working conditions

 图 17 不同工况下流噪声与弗劳德数的关系 Fig. 17 The relation between flow noise and froude number under different conditions
4.2 船舶流噪声空间指向性分析

 图 18 船舶流噪声水平指向性图 Fig. 18 Horizontal directivity diagram of ship flow noise

 图 19 船舶流噪声垂直指向性图 Fig. 19 Vertical directivity diagram of ship flow noise

4.3 不同球鼻首船型基本声场特性分析

 图 20 不同球首船型艏部特征点处的声压频响曲线对比 Fig. 20 Comparison of sound pressure frequency response curves at the bow characteristic points of different bows

 图 21 不同球首船型尾部特征点处的声压频响曲线对比 Fig. 21 Comparison of sound pressure frequency response curves at the stern characteristic points of different bows

 图 22 沿船舶首部Z方向特征点声压值变化曲线图 Fig. 22 Acoustic pressure curve of characteristic points along Z direction of ship bow

 图 23 沿船舶尾部Z方向特征点声压值变化曲线图 Fig. 23 Acoustic pressure curve of characteristic points along Z direction of ship stern

 图 24 沿船舶首部X方向特征点声压值变化曲线图 Fig. 24 Acoustic pressure curve of characteristic points along X direction of ship bow
5 结　语

1）在船舶首部区域，高压较集中，且集中点位于首部前缘；在船舶中线面处，船首部高速区域比较明显、船尾部出现较明显的低速带。

2）在相同工况下，上翘型球首船所受静压比普通型大，且上翘型球首因其形状特点，球鼻首最前端下方出现最大压力点，这样对延长球鼻首的使用寿命很有益处，并对内部结构起到保护作用。

3）不同工况下，上翘型球首船型比普通型所受船舶阻力略小，船舶流噪声总声级略低。

4）在船舶流噪声水平指向性图中，船舶纵轴沿船首方向左右30°方位角处，船舶流噪声水平指向性最强，在首尾方向流噪声向外辐射较弱；在船舶流噪声垂直指向性图中，从船舶舭部向外辐射的量级较高，船底处声辐射较弱，船舷两侧的声辐射强度最弱。由船舶的指向性分析能够很好地观察船舶的辐射噪声分布情况，并以此为船舶的型线优化设计提出改进措施。

5）在船舶流噪声分布特性方面，沿船舶首部Z方向上，上翘型球首船型在近壁区声压级高于普通型球首船，远场区则低于普通型球首船；沿船舶尾部Z方向上，上翘型球首船型在近壁区声压级先略低于普通型球首船，然后高于普通型球首船，之后缓慢下降低于普通型球首船；在沿船舶首部X方向上，上翘型球首船型在近壁区声压级高于普通型球首船，而在远场区则逐渐低于普通型球首船型。

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