PRESSURE FLUCTUATIONS OVER THE SPILLWAY BOTTOM UNDER UNSTEADY FLOW

Pressure fluctuations over the bed are important for the stability of water structures bottoms, such as spillways, stilling basing, and pressurized bottom outlets. Pressure fluctuations highly depend on turbulence characteristics over the bed. There are many structural failures observed at the hydraulic structures during their operations. Pressure fluctuations were mostly determined with direct measurements on the model studies or by using numerical models. In these studies, flow conditions are taken as steady during experiments, but in real-time operations, unsteady flows often occur during gate operations or flood conditions. Pressure fluctuations are highly affected by these unsteady flow conditions, and different unsteady flow situations like rising, falling, or peak stages show different situations. In the presented work, pressure fluctuations on the spillway bottom were investigated under the unsteady flow conditions. Gate opening procedure took consideration for generating unsteady flow conditions, and rising limb fluctuations always take higher RMS (root mean square) values regarding the other stages and steady flow conditions.