不同外形声呐的水动力及流噪声数值模拟分析

Numerical simulation analysis on hydrodynamic characteristics and flow noise of different shape sonars

[目的]为降低传统圆形声呐外表面流噪声,设计3种不同外形(圆形、椭圆形以及方形)的声呐,并对其外表面的水动力特性和流噪声进行研究。[方法]基于Fluent中的标准k-ε湍流模型和Lighthill声类比方法,分析3种不同外形声呐外表面的流场和声场。[结果]结果显示:方形声呐的升力系数幅值和阻力系数均值最大,其次是圆形,椭圆形最小;各声呐方案的水动力特性之间的差异是因边界层分离点及尾涡的不同所致。对比流噪声结果发现,圆形声呐的总声压级最大,椭圆形声呐最小。圆形和方形声呐呈现了"正8字"的偶极子声源特性,声辐射最大值垂直于来流方向;而椭圆形声呐呈现"倒8字"的偶极子声源特性,最大值在水平来流方向。[结论]椭圆形声呐可以替代传统的圆形声呐,结果可作为声呐外形设计的参考。

[Objectives]In order to reduce the flow noise on the outer surface of the traditional circular sonar, three sonar shapes(circular, elliptical and square) are proposed, and the hydrodynamic characteristics and flow noise on their outer surfaces are studied.[Methods]Based on the standard k-ε turbulence model in Fluent and Lighthill’s acoustic analogy method, the flow field and sound field of the outer surfaces of three alternative sonars are analyzed.[Results]Comparing the hydrodynamic results of the three sonar shapes, it is found that the square has the largest lift coefficient amplitude and average drag coefficient, and the ellipse has the smallest. The hydrodynamic diversity is caused by the differences in the boundary layer separation points and wake vortex. Comparing the flow noise results, it is found that the total sound pressure level of the circle is the largest and that of the ellipse is the smallest. The circle and square show the characteristics of a "positive figure eight" dipole sound source, and the maximum sound radiation is perpendicular to the incoming flow direction, while the ellipse shows the characteristics of an "inverted figure eight" dipole sound source, and the maximum sound radiation is horizontal to the incoming flow direction.[Conclusions]This study can provide references for the shape design of sonar, e.g., replacing the traditional circular sonar with the elliptical sonar.