Vortex Shedding from Tube Banks with Serrated Fin.

Abstract

We measured a vortex shedding frequency, gap velocity and the intensity of velocity fluctuation in the fin-tube banks set in a wind tunnel. Two discrete peaks were formed in the spectrum of the velocity fluctuation at the frequencies of 115 Hz and 74 Hz. The vortex shedding phenomena with those frequencies were independent with each other. The peak of 115 Hz mainly formed within the fin-tube banks and the other peak of 74 Hz was in the wake of the fin-tube banks. The applicability of the equivalent diameter obtained by a single circular cylinder with serrated fin to the fin-tube banks was examined. Strouhal numbers were calculated by using the measured values of vortex frequency, gap velocity and the equivalent diameter. Strouhal number in case of 115 Hz agreed well with Strouhal number 0.3 obtained from Fitz-Hugh map for tube banks without fin, and the other Strouhal number in case of 74 Hz was about 0.18 which is similar to vortex shedding from a circular cylinder.