Characteristic of Fluid Forces on Stepped Ground Sill with 2 Steps

Abstract

There are some cases in which the downstream apron is made to be stairs shape whenthe river bed downstream of headworks degrades. The apron with such shape, called stepped ground sill, is demanded to dissipate the energy of flow securely and to prevent the local scour downstream of itself. In this research, characteristic of fluid forces on stepped ground sill with 2 steps is investigated by hydraulic model testand numerical model test. And then, it is clarified that the peak of the fluid forces on the horizontal plane in each steps relatively becomes small with shape which negative pressure is not caused on the horizontal plane in each steps if when the total height of the stepped ground sill is constant. Additionally, it is clarified that the index of the condition that negative pressure is not caused on the horizontal plane in each steps are the ratio of total head to critical depth of flow before falling, and the inclination of central step.