Flow and Scour Characteristics Around Fully Submerged Tandem And Skewed Cylinders

Abstract

Hydraulics of group of fully submerged structures are frequently encountered in newlinevarious engineering applications such as in restoration of the river ecosystem, newlinesupports of submerged pipelines, tidal beams in shallow coastal water, submerged newlinelogs and vanes, fish habitat structures etc. In the present study, the flow and scour newlinecharacteristics around fully submerged tandem and skewed cylinders is carried out. newlineFirstly, the scour characteristics around fully submerged tandem and skewed cylinders newlinewere observed in a laboratory recirculating flume. The scour depths around both newlinecylinders increase with increase of Froude number and decrease with increase in the newlinesubmergence ratio and sediment size. The scour depth around the downstream newlinecylinder increases with increase of skew angle. Using the experimental parameters, newlineregression equations are developed to determine the scour depth around the cylinders newlineseparately for the upstream and downstream and for the circular and square cylinders. newlineFurther, the time variations of scour modeling around the tandem and skewed newlinecylinders are developed with uniform and non-uniform sediment beds. Video analysis newlinetechnique was used to formulate the equations for determining the diameter of the newlinehorseshoe vortex around the submerged cylinders. The diameter of the horseshoe newlinevortex is found to depend on the diameter of respective cylinder, submergence ratio, newlinespacing, and skew angle. This formulation along with the dislodgement and newlinetransportation of a single sediment particle is further incorporated in the proposed newlinemodel for determining the time variation of scour around the submerged cylinders. newlineFinally, the flow field characteristics around submerged tandem and skewed cylinders newlineover plane and scoured beds were measured using acoustic Doppler velocimeter along newlinevarious radial directions from the cylinders. The measured flow characteristics are newlinesubsequently used for studying the velocity distributions; bed shear stress, power newlinespectral analysis and quadrant analysis around the submerged cylinders.