Experimental Study of Flow-Induced Noise from Two Side-by-Side Cylinders

Flow around two closely spaced cylinders in a side-by-side configuration is a canonical aeroacoustic problem in aerospace systems such as landing gear struts. The aerodynamic interaction between the cylinders strongly affects surface pressure fluctuations and aerodynamic noise generation, motivating detailed studies. In this work, the near-field surface pressure and far-field noise of two identical circular cylinders were experimentally investigated at [Formula: see text] for center-to-center spacings [Formula: see text] ranging from 1.2 to 3 times the cylinder diameter [Formula: see text]. Surface pressure fluctuations were measured in both the spanwise and azimuthal directions using miniature transducers, while far-field noise was captured with a set of microphones. Except for spacing ratios close to [Formula: see text], which behaved similarly to a single cylinder, the side-by-side arrangements exhibited reduced tonal noise, with the most pronounced attenuation at [Formula: see text]. This reduction was attributed to suppression of surface pressure fluctuations and their spanwise correlation over shorter lengths. At [Formula: see text], multiple tones also appeared, with frequencies both lower and higher than the dominant tone of the single cylinder. Additionally, the stagnation and other critical points around the cylinders shifted by approximately 20° (clockwise for the lower and counterclockwise for the upper cylinder) resulting in an elliptical surface pressure distribution, pronounced gap-flow deflection, and a highly unsteady, asymmetric wake.