水下航行器水动力噪声分离预报

Separating prediction of the hydrodynamic noise of an underwater vehicle

近年来,水下航行器的声隐蔽性受到广泛关注,而有关其水动力噪声的研究却较少。将水动力噪声分为壳体流噪声、壳体流激振动噪声、螺旋桨流噪声和螺旋桨流激振动噪声4类,采用大涡模拟(LES)结合Light-hill声类比混合计算方法,对水下航行器的水动力噪声进行分离预报。首先,采用已有文献数据验证该混合声学计算方法的有效性。随后,对水下航行器壳体和螺旋桨三维流场的流噪声和流激振动噪声进行数值模拟和分析。结果表明,4类噪声均与速度呈非线性关系。在上游段,螺旋桨流激振动噪声为主要噪声;在下游段,壳体流噪声所占比例最大。在低速时,由壳体激发的水动力噪声是主要噪声;随着航速的增大,由螺旋桨激发的水动力噪声占总噪声的比例逐渐增加;总体水动力噪声能量随航速的增大而增大。

In recent years, acoustic stealthiness, being one of the most important parameters to evaluate underwater vehicles＇ operational performance, has received widespread attention. However, the hydrodynamic noise of underwater vehicles has seldom been studied. In this paper, hydrodynamic noise is classified into four categories： the flow-induced noise of the shell, the noise of flow excited-vibration of the shell, the flow induced-noise of the propeller, and the noise of flow excited-vibration of the propeller, all of which are predicted by using the Large Eddy Simulation （LES） and the Lighthill＇s acoustic analogy method. Firstly, the effectiveness of these hybrid acoustic simulation methods is verified with present research results. Then, the simulation of four noise types is conducted, where the analysis is made respectively by sound power level, sound pressure level contours, and total sound pressure levels. It is seen that the relations between the four types and the relevant speed are all non-linear. Specifically, the major noise in the upstream is that from the flow-induced vibration of propellers, while the major noise in the downstream is the flow-induced noise of shells. Furthermore, the hydrodynamic noise induced by the shell is the major noise at low speed, and the hydrodynamic noise induced by the propellers gradually increases with the increase of speed.