Study on velocity field of the flow asymmetrically constrained by through spurs

Abstract

Erosion of river banks, as a type of water erosion, is widespread worldwide. To combat the harmful effects of water flow, various types of channel regulation and bank protection structures are widely used. Piled-through structures are common on flat rivers. Compared to solid structures, the advantage of these structures is lesser flow disturbance, resulting in shallower erosion depths at the head of the structure. Previous studies have addressed many issues such as one-sided and symmetrical two-sided constriction, erosion depths at the head and between piles, etc. This article examines the asymmetric constriction of flow by through spurs, which typically occurs when the flow is directed towards a water intake point. Experimental studies were conducted in a flume with dimensions of 40x75x800, with a longitudinal slope of 0.00012 and a Froude number less than 0.25, typical for flat rivers. The degree of flow constriction ranged from zero to one, and the angle of spur installation varied from 60° to 90°. The concept of asymmetry coefficient was introduced as the ratio of the length of the shorter spur to the longer one, ranging from zero to one. Affinity of the velocity field in the intensive mixing zone was experimentally established, following the theoretical dependence of Schlichting-Abramovich. The angle of jet expansion on the main section was found to be 0.15. Using momentum and continuity equations, dependencies were derived to determine flow velocity on the jet axis, side flows, and lengths of expansion zones, facilitating the determination of subsequent spur installation locations.