Physical model study for mitigating local scour downstream of clear over-fall

Abstract

Local scouring action downstream of clear over-fall weirs associated with three-dimensional turbulent flow field is a common morphological problem in mobile channel bed. The objective of this study was to assess and quantify the impact of hydraulic structural measures (double lines water jets) on minimizing the scour-hole dimensions downstream of a Fayoum type weir. Ninety runs were conducted considering flow Froude number, different jet discharges and locations. The experimental program was performed under the clear-water scour conditions for a quasi-equilibrium scour hole. A reference case of flat floor without water jets was included in order to evaluate the influence of using the proposed measure. The experiments’ results confirm the acceptability and the effectiveness of the proposed measure (floor water jets) in enhancing the flow hydraulic conditions and the local scour dimensions downstream of hydraulic structures.

Keywords

• Scouring
• Weir
• Floor water jets
• Scour equations
• Physical model