密なセレイティッドフィン付き千鳥配列円管群からの渦放出(流体工学,流体機械)

概要

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In the present paper the attention is focused on the vortex shedding from the tube banks with closely mounted twist serrated fin. The tube banks were installed rigidly in the test section of the wind tunnel. We measured the mean velocity, the spectrum of velocity fluctuation and the gap velocity in the simulated tube banks which has same pitch ratio as that of a boiler heat exchanger, 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 gap velocity, between 2.8×10^4 and 6.2×10^4. Strouhal numbers S_t were calculated by using the measured values of vortex shedding frequency, gap velocity and the equivalent diameter. The vortex shedding of S_t=0.40 mainly formed within the fin-tube banks and the other vortex of S_t=0.20 was in the wake of the fin-tube banks. Strouhal number of vortex shedding inside the fin-tube banks changed from 0.40 to 0.32 over R_e=6.2×10^4. The applicability of the equivalent diameter obtained by a single circular cylinder with serrated fin to the fin-tube banks was examined. Strouhal number 0.32 agreed with Strouhal number 0.30 obtained from Fitz-hugh's map for bare tube banks and other Strouhal number of 0.20 is similar to the vortex shedding from a circular cylinder.
2009-07-25