| Research Abstract |
The following conditions for vibration experiments have been decided taking account for the first year's results which the upstream circular cylinder was stationary and was set off from the axial line ; Reynolds number Re=5X10^4 (const.), diameter ratios d_1/d_2=5/30 (const.), non-dimensional amplitude of upstream cylinder A/d_2=0-0.25 and forced oscillating frequencies fc=0.125-11.08 Hz which is smaller than the natural frequency of a single circular cylinder. Under these experimental conditions, mass transfer characteristics have been examined by naphthalene sublimation methods, and several fluid flow behaviors have been clarified using the phase-averaged methods, such as, pressure distributions around a downstream cylinder, time-averaged and fluctuating lift and drag forces and velocity flow field between two cylinders. The instant flow pattern have also been photographed by smoke-wire methods and so no. The main results are as follows :
(1) Stationary offsetting the upstream cylinde
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r produced the marked effect on time-averaged drag and lift coefficients and Strouhal number under the offset ratio Y^*/d_2=0.5, especially, the drag force had the minimum and lift force had the maximum in the case of Y^*/d_2=0.25.
(2) Under the offset conditions, the fluctuating drag coefficients remained constant(C_Drms=0.1) in spite of the variations of Y^*/d_2 and the fluctuating lift coefficients had the maximum value and had the magnitude of time-averaged drag coefficient at Y^*/d_2=0.65.
(3) When upstream cylinder had a simple harmonic oscillation normal to the main flow, so called "dynamic characteri stics", the oscillation frequency in this experimental range had not an influence on the mass (heat) transfer characteristics around a downstream cylinder in both cases of two gaps between cylinders, X^*/d_1=5.0 and 7.9. Local and peripherally averaged mass (heat) transfer coefficients could be estimated by the linear-superposed technique using the stationary offset data.
(4) Phase-averaged fluid forces and pressure distribution were given as a period variation of upstream cylinder's vibration and phase shift phenomena for lift and drag forces was discovered. Less
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