THE PROCESS OF GENERATION OF APPROACH VELOCITY THAT AFFECTS THE ESTIMATION OF OUTFLOW CAUSED BY A FLOOD INTO A SMALL CAPACITY DAM RESERVOIR

Abstract

 Past studies indicated that the outflow from a small capacity dam in a large flood period was greatly underestimated. This is because the approach velocity head was not taken into consideration in the calculation of outflow from the dam. However, the process by which approach velocity is generated has not been investigated in past studies. In this study, the process by which approach velocity is generated was investigated by 3D simulation targeting a small capacity dam reservoir in which the occurrence of approach velocity was confirmed in a past study. Furthermore, in this study, the condition in which approach velocity is generated and the influence of approach velocity on outflow estimation were investigated by an experiment on flow on a weir. When the overflow depth is larger than the height of the weir, it was shown that approach velocity becomes so large that it cannot be ignored when calculating outflow.