Flopping behavior of side-by-side cylinders in shallow flow

In this study, flopping regime behind two and three side-by-side circular cylinders in shallow water flow was investigated by Particle Image Velocimetry Technique. During the experiments, the cylinders used was made of plexiglas material and their diameter was 40mm. Experiments were carried out at three different water heights (10mm, 20mm and 40mm) and three different spacing (10mm, 20 mm, 30 mm) between cylinders were used. The value of Reynolds number based on the cylinder diameter was Re=5000. Time-averaged flow characteristics were obtained from averaging 3000 images which were acquired at 2 Hz frequency. Flopping regime looks completely random process of flow. However, flopping occurs in between 10 and 60 seconds time period. Moreover, this time period decreases with decreasing water height. Finally, for the flows where flopping regime occurs, instantaneous flow characteristics are more informative than the time-averaged flow characteristics.Key Words: Flopping regime, Side-by-side circular cylinders, Shallow water, PIV.