Control of Velocity Profiles by using Baffle Blocks in Open Canals

Abstract

Roughness elements is one of the solutions use to protect open channels from erosion and sedimentation. It can be large stone or concrete blocks placed at bed of the channel to impose more resistance in the bed. The geometry of these roughness elements, and their configuration are parameters that play an important role in changing the hydraulic characteristics of the flow. This change can create desirable effects helps to develop better flow management. Velocity distributions along the flume was investigated by conducting a series of tests to find the best height and configuration of roughness elements. Computational Fluid Dynamics, CFD, was applied to simulate the flow in open canal with roughness elements. Standard baffle block was used with heights equal to 3, 4.5, and 6cm placed in three different configurations, two lines, four lines and fully rough configurations. The results showed that the velocity values are affected by increasing baffle blocks height and increasing number of lines of roughness elements. The four lines configuration was more effective by decreasing the velocity near the bed compared with two lines and fully rough configurations by about 50% and 10%, respectively. The velocity values increased near the free surface in cases with baffle blocks height 6cm or fully rough configuration much more than other cases by about 10 to 50%. Furthermore, in all cases the roughness height 6cm is more effective in decreasing the velocity near the bed than other roughness heights by about 10% to 30%.