الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Local scour downstream hydraulic structures may cause damage or complete failure to the control structure. The cost of protection layer downstream stilling basin can be
reduced by using some appurtenances that used to dissipate energy such as end step or baffle blocks which are installed on stilling basin downstream the control structures to
improve the stilling basin behavior and dissipate energy.
This study involved studying the effect of using multiple lines of water jets for enhancing
the flow characteristics and dissipate the energy downstream the control structures in order to reduce or eliminate completely the scour downstream it (Fayoum type weir).
Different variables will be used during this study (5 variables) such as; different flow
discharges, jet discharges, locations, tail water depths and bed material.
The proposed designs of stilling basins were classified according to the arrangement of used rows of floor jets into 5 designs. Design (A) refers to the case without using jets that
was the reference case. Design (B) refers to the case with using all rows of floor jets that divided into three scenarios. Design (B1) that use all rows with discharge 2.0L/s from
each row, at which design (B2) use all rows with jet discharge 3.0L/s per row and design
(B3) use all rows with jet discharge 4.0 L/s/ row.
After the comparison between three scenarios (1, 2 and 3) of design (B) the jet discharge of scenario (B3) was selected to apply at other location.
Design (C) refers to the design of using rows (1, 2 and 3) of floor jets with jet discharge 4.0L/s/row. Design (D) refers to the design of using rows (3, 4 and 5) with jet discharge
4.0 L/s/row. Design (E) is the last design that refers to stilling basin with using floor jet
rows (1, 3 and 5) with jet discharge 4.0L/s/row. The first row was located at 0.40m from the weir toe and the distance between each rows
was 0.40m. Each row of floor jet contained five jets with diameter 0.9cm.
The experimental work was performed at Hydraulics Research Institute (HRI), National Water Research Center (NWRC), Delta Barrage, Egypt. The flume is 26.0 m long, 1.0 m wide and 1.20m deep. The side walls along the entire length of the flume are made of
glass with steel-frames to allow visual observation of the flow patterns and the movement
of bed material. The total number of designs were seven. For each design several runs
were performed using nine different flow conditions. Three different discharges with three tailwater depths. All test runs were operated for two bed materials medium sand and
fine grvael. Medium sand with d50= 0.423mm and fine gravel with d50= 1.397mm The study indicated that the stilling basin design with using floor jet rows number (3, 4 and 5) had the lowest velocity distribution and high energy dissipation. Consequently,
design (D) is the safest design regarding to movement of the bed material.