舱壁对圆柱壳振动声辐射影响研究

Effects of bulkhead on vibration and sound radiation of finite cylindrical shell

文章研究了加舱壁构成的多舱段圆柱壳的振动声辐射特性。壳体振动基于薄壳控制方程,舱壁振动分别考虑相互独立的面内伸缩与面外弯曲振动,建立用阻抗矩阵表示的壳体振动和辐射声功率解。通过数值计算研究舱壁对共振声辐射的影响,讨论舱壁个数、厚度及激励力位置对辐射声功率的作用,并分析舱壁作用机理。针对舱段长度与壳体直径之比在1.5到2.0之间的情况,计算结果表明,舱壁附加机械阻抗的作用导致壳体模态频率向低频移动,但基本不改变低频共振辐射的状态。多道舱壁在高频段降低壳体的均方振速,增加辐射效率,但对辐射声功率影响较小。激励力位置对低频共振辐射产生较大影响,特别是谷值变化可能高达10dB。舱壁的作用主要由其伸缩振动引起,因为伸缩振动产生的径向力的声激励效率最高。

The vibration and sound radiation of multiple-cabin finite cylindrical shell is studied. The cylin- drical shell is modeled by thin shell theory and the bulkheads are modeled as circular plates with decou- pied in-plane extensional motion and out-plane bending motion. The expressions of the shell vibration and radiated sound power are established in the form of impedance matrix. The effects of bulkheads on res- onance radiation are analyzed by numerical calculations. The influences of the bulkhead numbers, the thick- ness and the location of exciting force on the radiated sound power are discussed and the effect mechanism is also analyzed. With the ratio of length to diameter for cabin being between 1.5 to 2, the numerical re- sults show that： at low frequencies, the modal frequencies shift toward lower frequencies due to the addi- tional mechanical impedance of the bulkheads, but the status of resonance radiation essentially unchanged; at high frequencies, multiple bulkheads could bring down the quadratic velocity and raise the radiation ef- ficiency, and have minor impact on the radiated sound power. The location of exciting force has a signifi- cant effect at low frequencies, especially the fluctuation of the valley of radiated sound power may up to 10dB. The effects of bulkheads are caused mainly by the in-plane extensional motion, since the radial forces generated by the extensional motion may lead to the most effective sound radiation.