Applicability of Non-Uniformly Varying the Fin Density of Tandem Finned Cylinders As a Viable Vortex and Noise Suppression Technique

This article explores the applicability of using non-uniform finned tubes in tandem arrangement at L/D_eq(avg) = 2.5 to suppress flow-induced acoustic resonance. Particle Image Velocimetry (PIV) measurements are performed to visualize the vortex development in the wake before and during flow-induced acoustic resonance. Acoustic pressure measurements are performed to characterize the aeroacoustic response of the tandem finned tubes. It was found that non-uniform finned tubes weaken the vortex shedding process and reduce the sound pressure level (SPL) during flow-induced acoustic resonance associated with the vortex shedding process by 50%. However, non-uniform finned tubes do not hinder the instability of the shear layers within its gap. This makes non-uniform finned tubes susceptible to flow-induced acoustic resonance associated with the instability of the gap shear layers. During this type of acoustic resonance excitation, highly discrete and well-organized vortex cores are formed in the gap and wake of both uniform and nonuniform finned tubes with SPL similar to that generated by the uniform finned tubes. A summary of the results are presented in the paper.