Complex Flow Phenomena of Horizontally Placed Underwater Cylinder Above Water Bed

This research is a presentation of complex flow phenomena in between the flow past a horizontally placed cylinder 8 cm above water channel bed and vertically placed plate placed at its downstream. Original experimental setup consists of a cylinder of 5 cm diameter placed about 5.5 cm horizontally away from a vertical plate having 5 cm width, where both causing hindrance to flow. Strict maintenance of 52 lps water flow and 20 cm flow depth for water recirculation in flume were followed. In such water flow, turbulence condition is obvious and the vortex formation is also in expectation as depicted in earlier researches. Acoustic Doppler Velocimeter (ADV) helped to determine the velocity and its direction while vortices were being created around the cylinder and in its wake, and also to record the velocity and observe its characteristics in the boundary layer.

With the determination of flow fields of the underwater composite hydrodynamic structures various other environmental issues come into play. These types of under-laying structures not only helps in dispersion of sediment decomposition in the river bed but also in this juncture help to get a free passage and movement area for aquatic fauna for a shallow type of water channel. Seeing so many advantages of this type of study could really boost to maintain aquatic ecological balance in addition to the territorial environment and socio-economic development. Vector plots of the flow fields at vertical plane reveal the complex characteristics of the horseshoe vortex flow and alternate vortex shedding by the cylinder. The circulation of the horseshoe vortex as created by the plate is determined by using Stokes theorem and forward difference technique.