The effect of the helical groove start angle on the flow drag and noise of a cylinder

The helical groove structure has emerged as a promising passive control technology for drag and noise reduction, with the potential to optimize the operational efficiency of underwater equipment and reduce energy consumption. This paper employs a hybrid numerical simulation method that combines the large eddy simulation method and Lighthill's acoustic analogy to investigate the effects of different helical groove starting angles on the drag and noise of a cylindrical flow at Reynolds numbers of 15 000, 45 000, 75 000, and 105 000. The results indicate that increasing the start angle of a helical groove promotes vortex expansion and accelerates the fluid transition to the turbulent state, achieving a maximum drag reduction of ∼30% and noise reduction of about 6 dB.