EXPERIMENTAL STUDY OF FLOW PATTERN IN U-SHAPE BEND CHANNEL

摘要

Prediction of flow pattern and velocity distribution in a curved channel can provide the basis for rational planning and design, or maintenance, of structures to control the flow and sediment movement, as well as bank erosion, in a meandering river. Other structures whose design depends on the knowledge about flow and bed topography are bridges and water intakes. It is well understood that curvature results in centrifugal force acting away from the center of curvature. The resulting tilt of the free surface produces a counteracting transverse (cross-channel) pressure gradient force. The centrifugal force and the pressure gradient force will nearly balance out in the vertically averaged flow. Therefore, the surface flow is turned outwards and the slow near-bed flow inwards. The net effect is a spiral motion of the flow, sometimes described as a secondary current. However, experiments were carried out in a rectangular rigid bed U shape bend flume with 0.6 m wide, 0.6 m high and 2.6 m radius of curvature. Experiments are designed to understand variation of hydraulic parameters on two-dimensional velocity distribution along the channel for the length equivalent to the radius of curvature. The results obtained from this have shown that Froude Number was the most effective parameter on flow pattern in U shape channel.