Growth of boundary layer thickness and length of fully developed flow in open channel

Abstract

The aim of the present work was to study the growth of boundary layer thickness and length of fully developed flow in an open channel flow which has a great applications in fields like, hydrodynamics (ships, torpedoes, submarines), wind engineering (buildings, water towers, bridges), aerodynamics (airplanes, rockets, projectiles), ocean engineering (buoys, breakwaters, cables) and transportation (trucks, automobiles, cycles). Boundary layer thickness and length of fully developed flow is crucial for solving many engineering problems such as management of rivers and floodplains, it is important to understand the behavior of flows within compound channels for designing of flood control, hydraulic structure, sedimentation, water management and excavation. In pipe flow, where boundary layer thickness is equal to radius of pipe which can be obtained easily whereas one finds difficulty in obtaining boundary layer thickness in open channels due to the presence of free surface. This challenge motivated us to study the growth of boundary layer thickness and length of fully developed flow in open channel flow. Experiments were performed to measure the characteristics of a boundary layer and fully developed flow by making use of velocity profiles developing on a rough concrete surface placed in an open channel flow from bottom to close proximity to the free surface. Section wise velocity measurements were made with a pitot tube-manometer combination and Acoustic Doppler velocimeter system along the flow depth ranging from 0, 0.2h, 0.4h, 0.6h, 0.8h.