Near Wakes behind Two Circular Cylinders Forming a Cross.

Abstract

Flow structures of wakes near two circular cylinders forming a cross shape in contact each other in a uniform flow are studied from the mean velocity and turbulent intensity profiles, and flow visualizations by tuft-stick and smoke-wire methods. In the wake behind the cross part of the two cylinders, there is a characteristic region in which the mean velocity is high and the turbulence intensity is low. According to the flow visualization results, the high velocity and low turbulence region is due to jet bleeding from the neighborhood of a contact point of two cylinders. In addition, the bleeding jet produces secondary flows which go from the the uniform flow region toward the bleeding jet region, and go away from the jet region along each cylinder axis. Then, those secondary flows form eight large scale longitudinal vortices around the wake center. Therefore, the mean velocity becomes high and the turbulent intensity becomes low in the wake center region, down-stream of about x/d=10, as compared with those in the quasi two-dimensional region out of the center region.