الفهرس 
CHAPTER (1): INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Abstract Scour is a natural phenomenon that caused due to the erosive action of flowing stream on alluvial beds, which removes the sediment around or near structures located in flowing water. Many of studies were conducted trying to understand the local scour phenomena for the safety and economical design of any hydraulic structures. Most of the existing heading-up hydraulic structures as regulators consist of multi-vents and most of the problems downstream such structures are due to wrong operations of the multi-vents, which leads to unexpected scour patterns. Most of studies considered that all gates are operated with equal openings, which are not happened in reality. The flow downstream sudden expanding channels is asymmetric, and hence the scouring patterns resulting from sudden expanding stilling basin are asymmetric. Severe and excessive scour may be largely due to unsymmetric operation of gates especially when a multi-vents barrages or regulator is being considered. Regulators are considered one of the main irrigation structures that are used for many purposes. One of the main purposes of regulators is to measure and control the discharge of rivers, also, they used to control the water levels and to generate power. They may be operated under free or submerged flow depending on the tailwater depth. Hundred and thirty-five experimental tests were conducted in the irrigation and hydraulics laboratory, Faculty of Engineering, Menoufia University. The experimental program was carried under free flow conditions. Experimental model with 5 gates was used. Five operating cases of gates were considered according to the number of the opened gates with different arrangements. The considered parameters were Froude number, upstream water head, gates opening, and tailwater depth. The experimental results showed that, the number of operating gates and their arrangements had a significant effect on the scour hole dimensions. The best operating case was opening the five gates approximately, while the worst operating case was opening one gate, the side gate only. The maximum relative scour depth, length, and position of maximum scour depth increased with increasing Froude number, the relative upstream water head, and relative gate opening. While it decreased with increasing sequent depth ratio.