前缘扰流体对水中流激空腔振荡影响的数值研究

Numerical investigation on the influence of leading-edge spoilers on underwater flow-induced cavity oscillations

为抑制水中流激空腔振荡,提出一种基于“分流”原理的被动控制方法:在空腔前缘的后上方一定高度处放置一倒楔形块,该研究称其为前缘分流体(leading-flow division,LFD),前缘分流体可将一部分来流边界层内流体分流进腔内,改善腔内流场环境,进而抑制空腔振荡。采用大涡模拟(largeeddy simulation,LES)的数值计算方法,主要从脉动压力、流场速度特性和涡量特性三个方面,计算并分析了前缘分流体对水中流激空腔振荡的控制效果,并与圆柱扰流棒(rod spoiler,RS)和锯齿单元(saw-tooth spoiler,STS)这两种已被证明具有良好控制效果的前缘扰流体进行对比。结果表明:前缘分流体对流激空腔振荡的抑制效果最好,可降低腔底脉动压力线谱达17.4 dB;前缘分流体还具有最小的附加阻力,更适用于实际工程应用。研究工作为降低船舶水下开孔部位的流激空腔噪声奠定了良好的理论基础。

In order to suppress flow-induced cavity oscillations in water,a new kind of passive control method based on flow-separation mechanism was proposed,that is mounting an inverted wedge block at a certain height above the cavity leading-edge.This wedge block,called as leading-flow division(LFD)in this paper,can improve the flow field in the cavity and suppress the cavity oscillation by dividing part of incoming boundary layer fluid into cavity.The large eddy simulation(LES)method was used to the numerical investigation of the control effect of LFD on the underwater cavity oscillation from three aspects:pulsation pressure,velocity characteristics,and vorticity characteristics of flow field.The control effect of LFD on cavity oscillation was also compared with rod spoiler(RS)and saw-tooth spoiler(STS),which were proved having good effects on suppressing cavity oscillation.The results show that LFD has the best effect on suppressing cavity oscillation with reducing the line spectrum amplitude of the bottom pulsation pressure to 17.4 dB.Besides,the calculation results also show that LFD has the minimum additional resistance which is more suitable for practical engineering applications.This study lays a good theoretical foundation for reducing flow-induced cavity noise at the underwater apertures of ships.