Analysis Of The Wave Blocking Characteristics And Vibration Reduction Performance Of Acoustic Black Holes In Ship Base Structure

Vibration and noise quality is an important technical indicator to measure modern ship equipment,and the main cause of noise is the vibration of mechanical equipment.Therefore,controlling vibration can not only protect personnel and equipment from vibration,but also effectively control noise pollution.In recent years,various ships have increasingly higher requirements for vibration and noise reduction.Traditional vibration reduction methods are likely to cause shafting alignment problems or greatly increase the overall mass of the ship.Therefore,this paper proposes a new type of "acoustic black hole".The base,while reducing vibration and noise,greatly reduces the side effects caused by vibration reduction measures.In this paper,the finite element numerical simulation method is used to study the wave blocking effect and vibration characteristics of acoustic black hole structure in thin plate and base.In this paper,the theory of acoustic black holes is firstly explained.The basic idea of acoustic black hole effects is introduced using geo metric acoustic approximation.The related applications of one-dimensional and two-dimensional acoustic black holes and ideal,non-ideal acoustic black holes and acoustic black hole structures are introduced respectively.Then,the multi-physics software COMSOL was used to establish the finite element model of the thin plate containing the acoustic black hole,the simulation calculation was carried out to explore the wave blocking effect and energy concentration effect of the acoustic black hole structure.By comparing the velocity level and average velocity level of each point of the acoustic black hole thin plate with the ordinary thin plate,the vibration damping effect of the acoustic black hole thin plate is explored.The calculation results show that the acoustic black hole structure can effectively reduce the vibration peak of the thin plate and has a good vibration reduction effect in a wide frequency range.Several common acoustic black hole structures are introduced and finite element simulations are carried out.The simulation results show that these structures can effectively reduce the vibration peak to varying degrees.Subsequently,a thin plate of acoustic black holes was introduced into the base structure.The feasibility of applying the acoustic black hole structure in the base is analyzed.The simulation results show that the vibration energy of each plate in the base is mainly concentrated in its normal direction,which matches exactly with the application of the acoustic black hole structure.Several bases with different acoustic black hole structures were subjected to finite element simulation,and the results were compared with ordinary bases.The results show that in addition to the natural frequency of the acoustic black hole base structure at 400 Hz,acoustic black holes are in a wide frequency range.The vibration speed of the base structure is lower than that of the ordinary base,and even exceeds 15 d B at some peaks.Therefore,the acoustic black hole structure still has obvious damping effect in the complex structure of the base.Optimized the design of the acoustic black hole base structure,introducing vibration damping into the acoustic black hole base structure,achieving vibration reduction in the entire frequency range except for individual natural frequencies,greatly improving the acoustic black hole base structure at low frequencies The vibration damping performance at the same time also makes the vibration damping effect better at high frequencies,and the vibration damping effect can reach 10 dB-15 dB in a wide frequency range.