Vibration And Sound Radiation Analysis Of Plate-shell Structures Interacting With Water

Cylinderical shells with strengthen ribs are widely used in the designing of submarines.The vibration response and the sound radiation caused by certain excitations of such structure would play an important part in its safety and stealth characterstics.A set of efficient and accurate calculation method of such structure’s sound radiation from 0Hz to 10000 Hz would provide great help to the engineers and researchers in this area.This paper focuses on a ribbed cylindrical shell cabin with two circle plates on both ends and a plate-formed structures inside it.The theoretical model and simulation methods of vibration response and sound radiation of cylindrical shell structures interacting with water raised by former researchers are examined in the first Chapter,while the engineering applications of neural networks are investigated as well.The simulations of rectangular and circle plates with different boundry conditions are performed in Chapter.2 by methods of MSM,FEM and SEA.The applicability and suitable frequency band of each method is analysed by the comparision of the results of root-meansquare velocity,modal radiation efficiency and sound pressure level(SPL).In conclusion,the sound radiation will be calculated by FEM in low frequencies and by SEA in high frequencies in the next chapter,to satisify the requirement of accuracy and efficiency.The simulation model of cylinderical shells with stiffener,circle seal plates and inside structures are established in Chapter.3.The relationship between aspect ratio (?),thickness ratio (?) and half wave number n of the first mode of cylinderical shell is analyzed in this chapter.The results show that the natural frequency would be reduced due to the added mass of the fluids.The natural frequency and the first mode’s half wave number n would be influenced by the ring stiffener,both in air and water environment.The full-band vibration response and sound radiation of the full structure is obtained as well with FEM and SEA methods.Two different types of neural networks,BP Network and RBF Network are used in Chapter.4 to train the data set gained by the previous chapter.The results of the neural networks’ fitting program show that BP network may not be an effective method to deal with such problem of a quick SPL forecast,while the Exact RBF Network and Approximate RBF Network perform well with appropriate spread value.In conclusion,a full-frequency-band numerical simulation research of ribbed cylindrical shells’ vibration and sound radiation is finished in this paper.The usage of BP Network and RBF Network to carry out a quick SPL forecast of underwater structures is explored,which might provide a reference to the designing processes and experimental research of underwater shell structures like submarines.