Journal ID : TRKU-09-03-2020-10489
[This article belongs to Volume - 62, Issue - 02]
Total View : 174

Title : PREDICTING THE FLOW VELOCITY AT THE TOE OF A LABYRINTH STEPPED SPILLWAY

Abstract :

The velocity at the toe of a spillway is a major variable when designing a stilling basin. Reducing this velocity leads to reduce the size of the basin as well as the required appurtenances which needs for dissipating the surplus kinetic energy of the flow. If the spillway chute is able to dissipate more kinetic energy, then the resulting flow velocity at the toe of spillway will be reduced. Typically, stepped spillway is able to dissipate more kinetic energy than that of a smooth surface. In the present study, the typical uniform shape of the steps has been modified to a labyrinth shape. It is logical to expect that the labyrinth shape will lead to dissipate more kinetic energy. This impression comes through creating the more regions of circulation and turbulence along the lateral sides of each step in addition of those occurs towards the streamwise. This action is also can reduce the jet velocities near the surfaces, thus minimizing cavitation. At the same time the increasing in circulation regions will maximize the opportunity for air entrainment which also helps to dissipate more kinetic energy. The undertaken physical models were consisted of three labyrinth stepped spillways with magnification ratios (width of labyrinth to width of conventional step) WL/W are 1.1, 1.2, and 1.3 as well as testing a conventional stepped spillway (WL/W=1). Two empirical forms of coefficient are proposed, one for labyrinth shape stepped spillway denoted KL and another for conventional stepped spillway denoted KS. Once the value of the coefficient is known the actual flow velocity at the toe of a stepped spillway can easily computed without having to resort to measurements in site. It is concluded that the spillway chute coefficient is directly proportional to the labyrinth ratio and its value decreases as this ratio increases

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