• experimental study on viv dynamics of a flexible cylinder in uniform cross-flow

    نویسندگان :
    جزئیات بیشتر مقاله
    • تاریخ ارائه: 1392/07/24
    • تاریخ انتشار در تی پی بین: 1392/07/24
    • تعداد بازدید: 664
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    • شماره تماس دبیرخانه رویداد: -
     in this paper we present the experimental results of a study on the effects of pre-tension and axial stiffness on vortex-induced vibration (viv) of a horizontally mounted flexible cylinder. the parameters examined included vibration amplitude and its suppression, mean and fluctuating tensions, frequency increase rate, drag and lift coefficients, and in-line (il) and cross-flow (cf) harmonics. the test model was selected with a low bending-stiffness, low mass ratio (cylinder’s mass/mass of replaced water), and high aspect ratio (length/diameter=162). the tests were conducted in the subcritical reynolds number regime (re=2000-20000). the effects of pre-tension and axial stiffness were studied for five different cases in which these parameters were varied. our results showed that high pre-tension, which reduces vibration amplitude, can significantly raise the lift coefficient. specifically, a four-fold increase in pre-tension from 73.5 n through 294 n was found to correspond to an increase of approximately 57% in lift coefficient and a decrease of approximately 30% in vibration amplitude. we also observed that the lock-in bandwidth of amplitude response narrowed with increase in pre-tension, whereas, it broadened with axial stiffness. in contrast to the vibration amplitude bandwidth, the lift bandwidth increased with increase in pre-tension. the ratio of dominant il-to-cf frequency was almost 2.0 except for the il lock-in and upper branch regions. in the il lock-in region the ratio was found to be 1, and in the upper branch the ratio reached 4.0 for the highest pre-tension (294 n), accompanied by broadening of the region in which this ratio is over 2.0.

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