Flow-induced sound of wall-mounted finite square cylinder with the change of angles of attack

The flow-induced noise of wall-mounted finite square cylinder at different angles of attack was investigated in an aeroacoustics tunnel. The experiments were conducted at a Reynold number of Re=1.21×10⁵ based on the width of cylinder and the thickness of the boundary layer δ is 0.67 times the width D. Flow noise generated by finite cylinder with aspect ratios of 0 ≤ AR ≤ 30 at angle of attack of 0 was measured and the results showed that the aspect ratios can be divided into four regimes according to the number of tonal noise. For 0<AR ≤ 2, no tonal noise was found, and one single tonal noise appeared in the range of 2<AR ≤ 9. Two and three tonal noises were detected in the range of 9<AR ≤ 17 and 17<AR ≤ 30, respectively. Then aspect ratios of AR=4, 7, 11, 15, 22 and 30 were chosen to investigate the flow-induced noise of finite cylinder in different regimes at the angles of attack of 0 ≤ α ≤ 45, surface microphone and free field microphone were used to acquire the near-field and far-field sound signals. Within the same regime, the frequency of tonal noise changed with angles of attack in the same trend, and the frequencies and magnitudes of tonal noise experienced dramatic change near the angle of attack. However, clear distinction was found between the aeroacoustics of finite square cylinders with aspect ratios in different regimes. Moreover, the characteristics of flow-induced noise become more two-dimensional with the increase of aspect ratio.