Abstract
In the present paper the attention is focused on the vortex shedding in normal triangular tube arrays with closely mounted twist serrated fin. We measured the spectrum of velocity fluctuation, the phase delay and the gap velocity in the simulated tube arrays. We found two types of vortex shedding with different Strouhal number of 0.40 and 0.20 in the case of Reynolds number R_e, based on the equivalent diameter and the measured gap velocity, between 6.2×10^4 and 9.6×10^4. The vortex shedding of S_t=0.40 mainly formed within the fin-tube arrays and the other vortex of S_t=0.20 was in the wake of the fin-tube arrays. Strouhal number of vortex shedding within the fin-tube arrays changed from 0.40 to 0.32 between R_e=6.2×10^4 and 7.7×10^4. Strouhal number 0.32 agreed well with Strouhal number 0.30 obtained from Fitz-hugh's map for bare tube arrays and other Strouhal number of 0.20 is similar to the vortex shedding from a circular cylinder.
