Author(s): Kadota Akihiro; Aragao Ricardo De; Suzuki Koichi
Linked Author(s):
Keywords: Two-in-tandem cylinders; Particle Tracking Velocimetry (PTV); Proper Orthogonal Decomposition (POD); Conditional Sampling Analysis
Abstract: Two-in-tandem circular cylinders are an important combination, which is widely encountered in several areas such as flow around bridge piers and vegetated open channel flow. One of typical Japan-river characteristics is the sudden change of discharge due to big amount of rainfalls so that the bridge piers are affected by surrounding instantaneous flows such as separated and wake flows which lead to the serious scouring problem. In order to reveal such kind of flow effects, flow visualization around two-in-tandem cylinders is conducted under non-submerged condition in the present study by means of particle tracking velocimetry (PTV), which is developed especially to estimate more accurate velocity under conditions of large-velocity difference. In addition to this technique, 2 set of digital cameras and lens are implemented in order to record the wide-range area to cover both areas between and downstream of cylinders, because small scale vortex and large scale wake are generated and developed, respectively. This technique enables to reveal the detail flow structure for the both areas simultaneously. In order to discuss flow pattern around the two-in-tandem cylinders, flow pattern around single cylinder is also measured to compare the structure of wake flow generated downstream cylinder. Then the statistical analysis is applied to estimate the mean properties such as Reynolds stress and so on. Also, the POD analysis of typical fluctuating pattern, spectral analysis and conditional sampling analysis are applied to reveal the coherent structures. The result shows the high turbulence area near the surface of cylinders and the strong wake downstream cylinders. The differences with flow around single cylinder are distributions of large turbulence area at downstream side of cylinders.
Year: 2007