摘要
空腔作为舰船表面常见结构之一,其流动特征和声学特性近年已成为学术界研究的热点。该文以长深比L/D?2的空腔为原型,改变空腔底面坡度,用数值模拟方法考察空腔形状对空腔流涡结构和声辐射特性的影响。空腔非定常水流场数值模拟采用二维大涡模拟方法,分析了空腔底面坡度对空腔时均和瞬时流动特征的影响,比较了腔中瞬时涡量变化和壁面脉动压力特性。计算结果表明,底面坡度使空腔振荡模式从剪切层模式转变为尾流模式,振荡频率减小;计算结果与空腔流动流场PIV测量结果相比较吻合良好,验证了流场计算的有效性。同时采用LES-Lighthill声类比法混合方法,比较了不同形状空腔的噪声辐射特性;结合流动特征,分析了刚性壁面空腔的噪声机理和空腔底面坡度对声场的影响。分析结果表明,空腔流激振荡发声是主要噪声源,腔体的水动力噪声以低频噪声为主,总噪声级和低频纯声辐射具有指向性,上游辐射声压级较高;底面坡度使声压级增大,对声场指向性影响不大。
Cavity, is one of the common structures on the ship surface, and its study of flow and acoustic characteristics has become a research hotspot in recent years. Based on a cavity with a length depth ratio L/D =2, this study investigates the influence on the oscillating characteristics and hydrodynamic noise of a cavity shear layer by introducing a sloped bottom. The unsteady flow field in cavity is simulated by 2D large eddy simulation method to analyze the effect of bottom slope to the time-average and instantaneous flow characteristics. The instantaneous vorticity distribution and fluctuating pressure on wall are compared. It is shown that the oscillation mode of the prototype cavity is shear-layer mode while the bottom sloped cavity is of awake mode and the oscillation frequency is less. Calculation results of flow filed are compared with PIV measurement results to verify the effectiveness of the flow field simulation. At the same time, the LES-Lighthill acoustic analogy hybrid method is used to analyze noise radiation characteristics of these two cavities. The relationship between the feature of flow filed and acoustical filed provides possibility to analyze the noise mechanism of the rigid wall cavity and the role of bottom slope. The result shows that most of hydrodynamic noise is induced by the shear layer oscillation and the cavity acoustic energy mainly distributes in the low-frequency domain. The overall sound pressure level and the low-frequency pure tone have the radiation directivity, and the SPL is predominant in upstream of the cavity. Bottom slope make the SPL larger but has little influence on the acoustic field directivity.
出处
《水动力学研究与进展（A辑）》
CSCD
北大核心
2014年第2期218-224,共7页
Chinese Journal of Hydrodynamics
关键词
空腔流
振荡模式
大涡模拟
水动力噪声
声类比
cavity flow
oscillation mode
large eddy simulation
hydrodynamic noise
acoustic analogy
