开孔平板水下振动及声辐射特性

The Characteristics of Vibration and Sound Radiation of Underwater Perforated Plates

采用有限元与间接边界元相结合的方法,以开有圆孔、四边简支、无障板的钢制平板为对象,开展开孔板水下振动及声辐射特性研究。首先,计算开孔板在空气中和水中的固有频率。在空气中,开孔板的固有频率较无孔板低,随着开孔面积增大,大部分固有频率降低;在水中,由于开孔可明显降低平板水下振动的附连水质量,开孔板的固有频率升高,且随开孔面积的增大,固有频率升高。然后,开展单位力激励下开孔板的水下振动声辐射研究,相同激励下,开孔板大部分频段的辐射噪声和辐射效率明显降低,且随着开孔面积的增大,降低量增大,辐射声功率和辐射效率的峰值向高频移动。研究结果表明,开孔可显著改变平板水下振动与声辐射特性。

In this paper, the underwater vibration and sound radiation of perforated plates are discussed employing the finite element method and the indirect boundary element method. Firstly, the inherent fre- quency of perforated plates is calculated both in air and water. It is seen that the frequency of perforated plates in air is lower than that for non-perforated ones ： as the opening area increases, most of the inherent frequencies decrease. However, in water, the inherent frequency of perforated plates is higher than that of non-perforated ones, since the added fluid mass is reduced by perforation. In this case, the frequencies in- crease as the opening area rises. Secondly, the sound radiation of perforated plates in water excited by a normal unit force is analyzed. Compared with the features of non-perforated plates, both the radiated pow- er and radiation efficiency are significantly reduced for perforated one in most frequencies. It might be not- ed that the increasing area of perforation leads to the drop in radiated power and radiation efficiency, whose peaks gradually move to higher frequencies. To sum up, the plates＇ vibration and sound radiation characteristics are dramatically changed in water by perforation.