Vibration Response Characteristics of Tandem Circular Cylinders Subjected to Two-Phase Cross Flows. (4th Report. Comprehensive Study on Effects of Bubble Size and P/D).

Abstract

Based on the experimental data of vibrational response of two tandem circular cylinders, in two-phase cross flows, at the pitch-to-diameter ratios of 1.5 and 3.0 and for average bubble sizes from 3 to 4.0mm and 6 to 7.0mm, comprehensive investigations to the effects of pitch-to-diameter ratio and bubble size on the vibrational response characteristic cylinders were carried out. The following major results are found: (1) for both P/D=1.5 and 3.0, air bubbles caused the cylinder system to excite vibrationally when the flow velocity was smaller than that generating the lock-in state in the two-cylinder system: (2) in higher reduced velocity, air bubbles had suppression and excitation effects on the cylinder system which were dependent on the bubble size and P/D: and (3) in the lift direction of downstream cylinder's vibrathon, the large bubble size and P/D were more effective on the vibration response with respect to the reduction and excitation of vibration, but for thec upstream cylinder's vibration, the small bubble size and P/D were more influential.