| Numbers of precision scientific instruments are required to work together when a research ship conducts its research.Moreover,the vibration and noise control levels of the ship directly affect the accuracy and effectiveness of such scientific research equipment.At the same time,the vibration and noise of the power equipment have a significant impact on the physical,mental,and emotional well-being of scientists and researchers.In this study,the research object is a new manned submersible supporting mothership.and uses a combination of simulation and experiment research methods to study and analyze the vibration and noise of the entire ship of the new scientific investigation ship.The main research content of this article is as follows:Firstly,a refined finite element model of a new type of manned submersible supporting the mother ship was established.After analyzing the ship simulation conditions,boundaries,and excitation forces of the main operating equipment of the ship,modal evaluation calculations were conducted on the ship’s vibration.The study found that the second order vertical bending modal frequency of the ship(f=5.7Hz)was within the fundamental frequency excitation range of the bow thruster,and there was a risk of resonance in the bow thruster opening condition.We analyzed and evaluated the vibration response of key points in the aft area of the ship’s main deck and the submarine storage area under the DESIDEP working condition,as well as the vibration response of typical decks such as the ship’s compass deck,driving deck,captain’s deck,forecastle deck,and main deck under the main excitation forces such as the fully rotating pod and generator set.The study found that: under the excitation of the fully rotating pod and generator set,The vibration response of each deck layer meets the requirements of the preliminary design specifications.Secondly,the statistical energy analysis method was used to establish a statistical energy(SEA)model for the entire ship.A comprehensive analysis was conducted on the structural and aerodynamic noise of the main noise sources of the manned submersible supporting the mother ship,including generator sets,pod thrusters,telescopic thrusters,air conditioning units,pump sets,and various types of fans.The predicted cabin noise levels for the entire ship were calculated.The study found that the evaluated noise values of the 117 cabins on the ship were all less than the design limits,The maximum noise value evaluated for the ship’s cabin is 98.92 d B,located in the engine room and also meets the design limit requirements.Analyze the frequency spectrum characteristics of low-frequency underwater radiation noise from ships using the combination of finite element and boundary element methods;Comprehensively analyze the sources of underwater radiation noise,use vibration energy as the basic parameter to describe vibration,use statistical energy method to calculate the high-frequency underwater radiation noise of ships,and obtain the full frequency range of underwater radiation noise of scientific research ships.Point out the locations where there is a risk of exceeding the standard.Research has found that in most frequency bands,the underwater radiation noise of ships meets the design requirements,but in the 1000-3150 Hz frequency band,the evaluation results are slightly higher than the reference curve,Noise reduction measures should be taken.Analyzed the contribution of various main noise sources of ships’ underwater radiation noise,founds that the nacelle is the most significant contributor to underwater radiation noise,followed by propeller noise from the propeller.The air noise of the generator set stimulates the vibration of the ship shell and radiates sound energy outward,which is the third largest noise source.In comparison,the contribution of the pump set to underwater radiation noise is relatively limited;Similarly,the statistical energy model of the entire ship was used to evaluate the self-noise of multiple beams,and the predicted self-noise values of multiple beam positions under different speed conditions were obtained.The study found that under the 12 kn speed condition,the self-noise of multiple beams met the indicator requirements.Under the 8kn speed condition,the self-noise of multiple beams exceeded the standard in the 1-2 k Hz frequency band,and under the 2-4kn speed condition,the self-noise met the limit requirements.By conducting noise assessment on newly built scientific research ship cabins,underwater radiation noise,multi beam self-noise,etc.,the existing risks of exceeding the standard are pointed out,and feasible and targeted vibration and noise reduction plans are proposed.Finally,according to the national standards and the requirements of China Classification Society,the vibration and noise tests of the whole cabin and deck and the underwater radiation noise tests were carried out on the completed scientific research ship.A total of 87 functional cabins and 102 measuring points were tested on the driving deck,captain’s deck,lifeboat deck,forecastle deck,main deck and lower deck of ship,and measured the underwater radiated noise of ships at speeds of 11 kn,10kn,8kn,6kn,and 4kn.Not only did it verify the accuracy of establishing the ship finite element model and calculating the excitation force in the early design stage,but it also verified the accuracy of simulating the ship vibration and noise level using finite element software,and the vibration and noise control measures taken during the ship construction process have good practical application effects.By comparing the measured and evaluated values of underwater radiation noise from the mother ship supported by a manned submersible,it was found that the measured and evaluated values of underwater radiation noise from the scientific research ship were basically consistent.The average sound pressure levels were 141.795 d B and 143.674 d B,respectively.The error between the evaluated and measured values was about 1.31%,which met the technical requirements.The combination of finite element and boundary element methods was verified to evaluate the low-frequency underwater sound radiation of ships and statistical energy method evaluates the accuracy of underwater acoustic radiation in the high-frequency range of ships,as well as the calculation of ship finite element models and excitation forces.Through the actual measurement of the underwater radiated noise of the ship vibration noise,data support is provided for the successful acquisition of the China Classification Society vibration noise certificate of the manned submersible support mother ship,as well as the scheme reference for the underwater radiated noise control of the follow-up new scientific research ships in China. |
