Due to the complexity on the response of highly flexible cylinder in water flow it is still required a large number of data from different
point of view to establish a better basic understanding on its highmirlti mode response behavior. This paper presents experimental
results of a long flexible horizontal cylinder in a sense of small model. The cylinder was towed in still water and it wds free to respond in
two degree of freedoms in-line and transverse directions. The length-to-diameter ratio of the test model was around 269 with a low mass
ratio of 1.7. Reynolds number varied from 900 up to 4500. The model has initial position in two angles of 0o and 50 on horizontal plane
which respect to the fluid flow. Pretension was applied to the test cylinder for towing speed of 0.1 up to 0.5 ms in each case of the test.
The motion data were recorded as digital image data using CCD cameras and were analyzed using image processing technique. The experiment
successfully simulates a multi-mode vibration behavior even though only with a small-scale model by using the image processing
technique. The dominant frequencies of the CF VIV response increased by following a linear function for both cylinder position g
0o and d 5 o and the response frequency in IL direction was approximately twice the corresponding CF response frequency for the related
flow velocity. The effects of the cylinder inclination on the magnitude increasing of the CF VIV dominant response frequency was
little but significantly changing the onset of flow velocity where the response changing from narrow-banded into broad-banded frequency.
ln addition for the case of inclined cylinder higher modes vibrations have been participated in the cylinder response in both CF and IL
direction even at low flow velocities which is for IL response low mode vibration also participated in the cylinder response.
Long flexible horizontal cylinder; In-line and cross-flow motion; Multi-mode Vortex-induced Vibration (VIV) response;
Image processing technique; Low and high mode vibration
: 629.831 2 Pra o
Source Article of Proceedings
Coverage ITS Community
Rights Proceedings of lnternational Conference on Violent Flows (VF-2007) Organized by RIAM, Kyushu [Jniversity, Fukaoka, Japan