Study On Vibro-Acoustic Characteristics Of Ship Floating Cabin

The fact that vibration affects the comfort of the personnel, reliability of equipment and the safety of the structure sparks the marine industry's growing concern towards the prediction on Vibro-acoustic environment and ship's vibration and noise reduction. With the constantly updated "Guide for Overall Evaluation of Vibration in Merchant Ships" made by International Standardization Organization(ISO) and "Code on Noise Levels on Board Ships" with more strict standards issued by International Maritime Organization(IMO), the performance design of noise and vibration(NV)on board is facing new challenges. To effectively perform related conventions and regulations, China Classification Society gives the corresponding guidance in documents. This thesis combines technology research and standard research by connecting ship structure vibration and noise calculation based on numerical calculation method to develop a study on the common problem of low frequency structure vibration and noise on modern vessels. Four aspects were included:The study focuses on the dynamic characteristics and the influence law of parameters of the marine combined floating floor. The model of the floating floor structural dynamics was established based on the theory of elastic laminated composite material; floating floor surface layer dynamics model was established based on Kirchhoff-Love theory; floating floor sandwich layer dynamics model was established based on Mindlin-Reissner theory; and the dynamic response and its influence law were described by ship cabin floating floor finite element equation. Based on the experimental platform of the second deck floor of the auxiliary engine room, the combined floating floor structure was put forward to carry out the real ship test, Analysis of the effect of different structure form combined floating floor on vibration reduction performance, analyzes the effect of different types of combined floating floor on vibration reduction performance, and finds out the potential characteristic parameters that can reduce the peak response of problematic frequency and the structure that needs to be improved. The result shows that the partial vibration onboard caused by the incentives such as imbalanced element of force of power generated diesel engine could be effectively contained.Research on numerical calculation and experimental verification of vibro-acoustic performance of ship floating floor model. It targeted the typical ship floating floor, studied output characteristics of lab simulated load and the dynamic response characteristics of structure. Based on the physical model to carry out the research of the vibro-acoustic characteristics of the ship floating floor model, A simplified model of vibro-acoustic measurement system for floating floor is established, Test the acceleration frequency response and sound pressure level, It set up floating floor model and vibro-acoustic characteristics testing system and tested acceleration frequency response and radiated sound pressure level respectively, Analysis of the relationship between Floating floor rock wool core thickness and vibro-acoustic characteristics, The reliability of the experiment result can be shown by analyzing experiment errors and thus the effectiveness of numerical simulated method can be verified. It provides an effective method for floating cabin structure dynamics performance and sound radiation computation.Influence of tank fluid-structure interaction vibration on ship vibration sound dynamics environment was conducted. The fresh water-generated tank was simplified into steel tank; and fluid-structure interaction numerical calculation was carried out; LMS structural mode analysis system was adopted to carry out the experiment. On the basis of analyzing and studying the vibration features of ship tank structure, this structural-acoustical coupling system was simplified into boxed multi-tanks structure. Structure vibration and sound radiation experiment was executed by establishing multi-cavity structure and the finite element model of its individual cavity. By analyzing the transitive relations between the source of incentives, structural response and radioactive sound field, the thesis mainly studied the features of structural vibration and sound radiation of simplified models of tank arrangement and filling and laying damping coating, and further evaluated vibration and sound radiation features of ship cabin structures under the incentives.Numerical calculation regarding ship cabin structural-acoustical coupling system was carried out and method of internal noise analysis of the cabin onboard was put forward. ANSYS Parametric Design Language(APDL)was applied to develop parameterized computation procedure to complete the three-dimensional modeling of the ship floating cabin. Then the analysis of parameterized design and finite element method(FEM)was combined to realize structural parameter modeling of complex models as well as finite element analysis. Boundary Element Method(BEM)was adopted to predict sound pressure level of engine room work shop and comparison analysis of the response result sound pressure level frequency domain before and after the modification was conducted. The influence of laying floating floor structure on engine room vibration environment was verified. As to engine control room, which requires the highest level of vibro-acoustic environment, the effect of control platform and switch panel thin-shell structure was considered, and internal noise value of the engine control room was predicted. Between the sitting posture before the control platform and standing posture before switch panel of the engineers on watch, the most obvious frequency peak value was selected and focused. The intensity of sound radiation from the surface of the structure is related to the structural vibration mode. Damping was adopted to inhibit structural Dominant mode of engine control room plates. Controlling vibration energy of engine control room plates at the focused frequency was effective in reducing noise within the ship cabin. The general method and procedure of numerical computation of cabin model vibration serves as a valuable reference in guiding ship vibration and noise reduction.