The changes of flow profile due to the construction of cylindrical structure as a hydraulic control structure in open channel

Construction of hydraulic control structures is generally aimed to control the velocity of water flow in open channels. Controlled velocity water flow in open channels very important to reduce the hydrodynamic forces in the flow to be able to erode the banks of the canal and structure. This study focuses on changes of the flow profile and the specific energy that occurs in an open channel structure as a result of the construction of cylindrical hydraulic control structures and to obtain the effectiveness of cylindrical structure. A cylindrical structure with a diameter of 0.3 meters constructed in the middle of an open channel structure measuring 10 meters long and 0.3 meters wide. The effectiveness of the cylindrical structure derived from the results of two different conditions studied. case 1, the opening in the surface of the cylindrical structure at a distance of 50 mm from the base of the structure at the upstream of the channel, while in the case 2 openings are positioned at a distance of 50 mm from the surface of the cylindrical structure at upstream of the open channel. As the consequence, the higher the opening on cylindrical structure at upstream channel which in case 2 more effective in controlling the flow in open channel. This is because the structure able to withstand greater upstream flow of up to 0.004m3/s compared to case 1 were only able to withstand until 0.002m3/s. In addition, case 2 is able to reduce the specific energy flow in the downstream channel by 21% and sub critical transition flow occurred at downstream. This structure also able to withstand water without causing flooding the upstream channel until 14.42s. Based on the overall results of the laboratory testing, the structure capable to control the flow in open channels and also can reduce the flow of energy that occurs in the downstream.