| Transmission lines are developed in a large number for the need of power supply,thus making a greater chance to cross the population gathering area.With enhancement of the awareness of environment protection,there will be more complaints against the Aeolian noise of transmission lines,which seriously influences people's daily life nearby and brings negative effect on the society.The consideration of Aeolian noise in transmission lines design in our country now is inadequate and the research on preventing Aeolian noise by institutes is currently not widely carrying on.So it is very necessary to do the systematical research on Aeolian noise of transmission lines and the research on relevant noise generated by circular cylinders is of great value for reference.Firstly,in this paper the mechanisms of Aeolian noise of circular cylinders and transmission lines was demostrated,and a review on current development of the research was made.It also summarized main approaches to the Aeolian noise research,including acoustic wind tunnel experiments,numerical simulation and field measurement.Besides,main methods of noise reduction currently used was summarized.Secondly,the monitoring facility for Aeolian noise of transmission lines was set in-situ and the noise data of a long period was analyzed.Results show that the frequency spectrum in high wind speed is different from the back ground noise in low wind speed and peak noise occurs in two different frequency ranges,which shows the property of Aeolian noise of transmission lines.It means the Aeolian noise of transmission lines exists in high wind speed.Then the acoustic wind tunnel tests of Aeolian noise generated from circular cylinders and transmission lines were conducted.ZD-2 Acoustic Wind Tunnel was built and its characteristics of flow field and acoustic field satisfied the requirments of the Aeolian noise experiments after testing.The similarities and differences of different cases between circular cylinders and transmission lines were analyzed.Results show that the peak sound pressure level and peak frequency of Aeolian noise from circular cylinders and transmission lines increase with rising wind speed and increase with larger diameters to some degree before it shows a decreasing trend.A-weighted sound pressure level of transmission lines shows a falling trend with larger diameters.The smooth circular cylinders gain louder Aeolian noise than the transmission lines with same diameters.Then the results of numerical simulation of two dimensional Aeolian noise of smooth circular cylinders and LGJ300/25 current line were discussed.It reveals that the Aeolian noise of circular cylinders gains an increasing trend before decreasing with larger diameters and the St number corresponding to the noise's peak frequency is 0.2,which both agree with experiments.The sound pressure distribution of circular cylinders and transmission lines is 8-shaped and both the overall sound pressure level and peak sound pressure level of noise of circular cylinders with similar diameters to transmission lines are louder.The noise of two circular cylinders 40cm away from each other shows smaller Aeolian noise when arranged up and down,which the overall sound pressure level and peak sound pressure level are the combination of those of two single circular cylinders.Finally,the experiments of transmission lines with spiral rods and several measures of noise reduction on circular cylinders were conducted in the acoustic wind tunnel.Results show that the reduction method of spiral rods is significantly effective and the Aeolian noise of transmission lines is largely reduced.This method also shows the best and most stable effect in all the reduction methods for circular cylinders.Some of the other methods even enlarge the Aeolian noise. |
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