Experimental Study on Tandem-Cylinder Interference Noise Suppression with Spanwise Square-Wave Structures

A periodic square-wave structure was designed on the cylinder surface to control the interaction noise of the tandem double cylinders. Experiments were carried out to measure the interaction noise and flow field with the particle image velocimetry technique in a 0.55 × 0.4 m acoustic wind tunnel. The influences of the square-wave structure with different parameters on the interaction noise and the noise reduction mechanism were investigated. The incoming flow velocity is in the range of 20–80 m/s. The experimental results show that a cylindrical surface with a periodic square-wave structure can significantly reduce the interaction noise of double cylinders, and the reduction in the sound pressure level is mainly in the middle- and low-frequency ranges. The amplitude parameter of the square-wave structure with the best noise reduction is within the range of 5%–7.5% of the cylinder diameter. The maximum reduction in tonal noise and the overall sound pressure level can reach 28 and 18 dB, respectively. When the airflow velocity was 40–60 m/s, the noise reduction effect of the square-wave structure was the best, and the frequency range of noise reduction was wide. Compared with the baseline cylinder, the periodic square-wave structure changes the shedding vortex characteristics of the wake of the bluff body, making the large-scale discrete alternating vortex change to a small-scale continuous banded vortex. The structure also prolongs the low-velocity region of the mean velocity field in the wake of the cylinder. It effectively reduces the turbulent fluctuation intensity, intensity of the power spectral density of the velocity field, and incoming flow disturbance intensity in the interference region, which is beneficial for the reduction of interaction noise