ANALYSIS OF AEROACOUSTIC GENERATED FROM A ROTATING TIRE WITH A LONGITUDINAL GROOVE USING LARGE-EDDY SIMULATION

Flow fields obtained by large-eddy simulations around a rotating tire with the longitudinal groove are investigated to clarify the relationships between the shape parameters of the grooves and the directivity of aeroacoustic noise and to clarify noise sources. To obtain acoustic field around the rotating tire, the large-eddy simulations using the sixth-order compact finite difference scheme and the tridiagonal filter are performed. The four computational cases including the case without groove are considered in the present study. The proper orthogonal decomposition (POD) analysis revealed the distribution of bipolar modes that spread from the tire to the left and right. This result indicates two symmetrical sound sources near the front of the tire side surface regardless of the presence or absence of the groove shape. It is also found that the presence of grooves in the tire weakens the amplitude of the POD mode that spreads to the left and right. This fact is consistent with the fact that the sound pressure level on the lateral side of the tire weakens as the groove width widens. Based on the observation of the instantaneous field and these analyzes, the following is found. The noise-induced by the flow around the tire considered in the present study is emitted when the turbulent flow generated in front of the tire collides with the tire and flows along the tire's side surface. Besides, when the tire has a groove, a part of the flow that collides with the tire flows into the groove so that the flow rate flowing on the side surface of the tire decreases and the noise itself also decreases. Therefore, the wider the tire's groove width, the less noise is emitted from the tire's lateral side.