The Development of Broad-Crested Weir by Using Physical Modelling

This study aimed to improve irrigation efficiency by simplify discharge distribution mechanism on, tertiary, sub tertiary, quarter and secondary level where all this time its operation was unreliable. Physical model that being tested was in the form of broad crested weir (channel 2), pipe in diameter 3” (channel 1) and pipe in diameter 4” (channel 3) they will going to distribute discharge to the left, frontal and to the right. Stream flow phenomenon that occurred was used to plan the determining design of new irrigation construction. Measure instrument of discharge in this experiment was calibrated before the experiment took place, in order to decrease the experiment relative error smaller than 5%. Physical model of distribution box has ratio 1 : 1 in prototype and it has used verification in order to get result carefulness that fulfils the prerequisite. There are three conditions in this testing, that is one channel operations, three channels operation and three channels operation with discharge plan on two channels (right and left) and one gate operation to frontal side. This study used six variations discharge testing to stream flow type respectively on distribution box in order to get discharge distribution pattern. One channel has gotten the same headwaters discharge and downstream discharge. Three channels has gotten discharge coefficient (Cd) 0.56 and friction coefficient (f) 0.046, whereas discharge distribution has gotten ratio 11.44%, 71.24% and 18.35% (no gate). Three channels that using gate has gotten discharge distribution in ratio 12.68%, 65.89%, and 21.05% (a = 4 cm, frontal) and 11.77%, 68.90% and 19.33% (a = 8 cm, frontal) on discharge plan has gotten equation on pipe one y = 0.1097 (h) 1.4901 and on pipe three y = 0.101