Flow visualization observation of the interference vortex flow from a pair of square cylinders

Abstract

In order to investigate the aspect of the mutual interference flow from two square cylinders, the visual water-flow observation experiment was performed. In the experiment, the pitch ratio L/d and the arrangement angle α were made into the parameter, and investigation of vortex shedding frequency or the flow pattern was performed. The pitch ratio L/d is 3 kinds, 1.13, 1.89 and 4.15, and an arrangement angle α is 7 kinds per 15 degree from 0 degrees to 90 degrees. The water flow velocity U was 0.04 m/s which correspond to the Reynolds number about 850. As the result of experiment, the complicated flow becomes clear by classification by color of tracer ink, and the aspect of the mutual interference vortex flow can understand better. Even if the pitch ratio was the same, the vortex shedding characteristics changed with arrangement angles. If an arrangement angle is smaller than a geometric duplication angle, the vortex shedding frequency from each square cylinder is the same. On the other hand, when an arrangement angle is larger than the geometric projection angle, the vortex shedding frequency from each square cylinder differs. In the smallest pitch ratio as L/d= 1.13, it is not dependent on the arrangement angle, and produce mutual interference.