Study On The Cabin’s Vibration Prediction And Control Method Of Three-hulled High-speed Passenger And Freight Transport Ship

The cabin’s structural vibration level is an important technical indicator of thehigh-performance ships. The vibration prediction of cabins is necessary work for the ship’sstructural vibration control and acoustic design. In order to meet the requirements for theship’s structural vibration indicators, it’s necessary to investigate the vibration control methodsand their effects on the vibration reduction. In view of the facts that the structure of thethree-hulled high-speed passenger and freight transport ship is huge, complex and thin, aswell as the modal density is high, the statistical energy analysis method is employed to predictthe cabin’s structure vibration in the present thesis. The characteristics of vibration attenuationby using different types of vibration control methods are examined, and their effects on thevibration reduction are evaluated. The main works are described as bellow:According to the CAD drawings of the three-hulled high-speed ship, the model ismodified by making appropriate simplifications. Due to the different characteristics of theupper deck and the lower structure, the ship’s model is separated into two parts. For the upperdeck, the software VA One is used to build the statistical energy model, while the softwareAnsys is employed to build the structure model which is then introduced to the softwareHyper Mesh to generate the finite element mesh, and then the finite element mesh is input intothe software VA One to form the statistical energy model for the lower structure. Finally, thecomplete statistical energy model is built by merging the two parts on VA One’s platformwhen the subsystems’ properties were defined as well.Choosing the frequency range from16-630Hz, and using the1/3octave band analysis,the vibration responses of each subsystems are examined, especially the vibration levels ofthe upper deck are predicted, for a given excitation of the main engines. The resultsdemonstrated that, the mass of the main engines may affect the upper cabin’s structures,and the vibration levels of cabin’s structures are decreased gradually as the increase ofdistance from the vibration source.Based on the predicted results of vibration, the effects of normal vibration controlmethods such as using the damped plates, dense rib-plates, thick plates on the vibrations ofthe shop’s front and rear walls, driving deck, passenger cabin windows, and their effects areinvestigated by using the statistical energy theory. The results indicated that different methods may have individual effective control area. Then, taking the cabin’s walls, driver’s cabin floorand passenger cabin deck as the objects, the effects of combined measures on the vibration arestudied. The results showed that the combined method using damping, dense rib-plates, andthick plates may avoid the blind control areas of the individual method, and achieve an idealcontrol of vibration. Finally, taking the resting room’s floor as the object, the floating floor’scontrol quality is examined, and the results showed that floating floor can reduce the vibrationefficiently and supposed to be used in the cabins where need high comfortable levels.