Time evolution of scour hole and flow characteristics upstream of a flushing orifice

ABSTRACT

Reservoir sedimentation is significant for the efficiency and life of a dam. Flushing orifices have been used in many small dams and other hydraulic structures to remove deposited sediments. Temporal variations of scour hole dimensions, velocity distribution, and secondary flows in the scour hole upstream of an orifice are investigated here. The experiments were conducted under clear water conditions with three sediment sizes, and three different pressure heads upstream of the orifice. The maximum depth, length, and volume of the scour hole were measured with time. Three flow zones were observed in the scour hole, including inward, outward, and semi-spiral flow zone. Based on regression analysis, some simple equations are presented for the determination of the dimensions of the scour hole. Also, results showed that the maximum scour depth was 10% larger for smaller sizes of the sediments.

KEYWORDS:

• Flushing
• orifices
• reservoir
• sedimentation
• scour

Disclosure Statement

No potential conflict of interest was reported by the authors.