Mathematical Modeling of the Vortex Shedding Structure and Sound Pressure Level of a Large Wind Turbine Tower

Abstract

The level of noise emission of a circular cylinder, especially a tower of a wind turbine, is remarkably dependent on vortex shedding behind the body of the tower. For these configurations, the key element to reduce noise emission is the upstream flow control of the body. In this paper, the sound pressure level of a wind turbine tower was investigated numerically. In this regard, an in-house OpenFoam solver with Curle’s acoustic analogy was used, and the results were compared with available experimental data, showing proper consistency among them. Then, three passive control methods such as longitudinal slot, splitter plate, and helical strake were applied to control the Kármán vortex shedding behind the tower, followed by the reduction in the level of sound pressure. The results showed that all the above control methods play an essential role in diminishing the fluctuation forces and affect the frequency of vortex shedding. However, the helical strake can lead to the significant suppression of Kármán vortex shedding due to the delay of boundary layer flow separation. Based on the observations, the tower with helical strake reduced the overall level of sound pressure as well as the Aeolian tones in a specific Strouhal number range.