Ship Pipe System Aerodynamic Noise Simulation And Optimization Design

There are numerous pipe systems in modern ships that ensure routine work. With the operation of these pipe systems, it brings noise problem to the people on board which can not be ignored. Among all different kinds of noises, the aerodynamic noise generating from ventilation pipe which is directly connecting to the ship’s life cabin is primary. Since the forms of pipe system diverse greatly, including round/square pipe in shape of section, straight/bend pipe in the form of trend, elbow/round bend in the form of corner shape and various kinds of tapered section pipes. With the characteristics of long distance, widespread and complex of ship’s pipe system, the forecast of the pipe aerodynamic noise has always been a problem for whom is concerned.The paper firstly establishes several common pipe models according to the characteristics of complex piping systems on board. According to the method of computational fluid dynamics, adopting large fluid simulation software Fluent to carry out the transient calculations of the internal flow field within the tube wall of the vent piping, getting the fluctuating pressure distribution of within the tube wall in time domain. Then inputting the time domain results into acoustic calculation software LMS Virtual.Lab Acoustics acoustic to carry out acoustic finite element calculation, and obtaining the sound pressure contours and the aerodynamic noise level curve at the monitoring point in the exit position of the pipe. Finally, after comparing the analyses in different sets of pipe models, the regulation of aerodynamic noise of pipe system and the optimized form of pipe system are obtained, the data and regulation collected can apply to the forecast of ship cabin noise level.The results show that, the aerodynamic noise level of round section pipe is lower than that of the square section pipe in terms of the section shape, so the round section pipeline aerodynamic noise characteristic is better than the square section pipe’s; the aerodynamic noise level of rounded bend pipe is lower than that of the elbow bend pipe, as a result, it should make the stream flow more smooth and steady so it should be avoiding sharp corners when designing the pipe system and use as much rounded bend than the elbow as possible. To reduce the aerodynamic noise of the ship pipe system, the most important measure is to limit the wind speed inside the tubes, according to the calculations of this paper, doubling the wind speed in the pipeline results in an increase of 14dB to 15dB aerodynamic noise level at the exit monitoring point. According to relevant regulations, the wind speed inside the ship pipe tube should normally be no more than 10m/s, when the noise level requires more strict, wind speed in the main pipe line could be controlled within about 5m/s.