Effect of semi-circular baffle blocks on local scour downstream clear-overfall weirs

Local scour downstream hydraulic structures may result in damage or complete structural failure and loss of life and property. In this paper, an experimental study was conducted to predict the scour geometry downstream a Fayoum type weir and to minimize the scour using a row of semi-circular baffle blocks. The considered shape in this research is easy to be used as an extra element to existing water structures in order to minimize local scour downstream these structures. A hundred 53 runs were carried out considering various heights and positions of baffle blocks with different flow conditions. A case of flat floor without baffles was included in the test program to estimate the influence of using the baffle piers. Results were analyzed and graphically presented, and simple formulae were provided to evaluate the scour parameters

Environmental and hydraulic design of thermal power plants outfalls “Case study: Banha Thermal Power Plant, Egypt”

A physical model study was conducted for designing the intake/outfall combination to comply with the Egyptian environmental laws. Based on the dominant flow patterns, and temperature measurements, two alternatives were examined. The first alternative of outfall structure consists of surface open channel. The output of this design did not comply with the environmental laws and has negative impacts on the water quality and ecological life. It was proposed to widen the outfall with 24 nozzles (multi port diffuser) arranged in two rows and separate the outfall into many jets. This new alternative for the outfall hydraulic design succeeded to improve the mixing process and complies with the Egyptian environmental laws

Updated regime equations for alluvial Egyptian canals

Real accuracy of several regime relationships for designing stable alluvial channels in Egypt was determined. Extensive field measurements had been carried out on 26 Egyptian stable canals, which cover various categories of irrigation canals starting from distributary, branch to carrier canals in Egypt. Analysis of 1484 velocity profiles for 371 cross sections was employed in order to formulate new regime equations characterizing Egyptian canals. The functional formulations to include the flow depth, cross section area, hydraulic radius and mean velocity were achieved. This research compared the deduced formulas from the measured data with the equations derived by other researchers for stable channel design. It was found that the derived formulas are reliable and could help in the design of Egyptian canals to convey a discharge ranging from 0.11 to 287.5 m3/s (0.0095–24.84 millions m3/day)

Pressure-Flow Scour under a Bridge Deck in Clear Water Conditions

The issues of scouring around a bridge have become prominent in recent research mainly due to recurrent extreme weather events. Thus, designing a bridge with the appropriate protection measures is essential to safeguard it against failure, which may take place due to scouring from high flows resulting from extreme weather events. Bridges may become partially or entirely submerged during extreme weather events such as large floods and are subject to pressure-flow scour, a condition where the flow is directed downward and under the bridge deck, creating an increase in flow velocity and a corresponding increase in bed scour. This study aims to explore the pressure-flow scour depth under a bridge deck without piers in the presence of two vertical wall abutments under clear water experiments. Sixty-six tests were conducted involving the approach flow depth, bed material size, contraction length, contraction width, and bridge opening for both pressure and free surface flow conditions. An empirical equation was deduced to determine the maximum scour depth, which could be applied as a preliminary design for bridges under pressure-flow conditions. The experimental data were used to determine the performance of the earlier models of pressure-flow scour. The results revealed that for pressure-flow conditions, the maximum scour depth increased by a factor between 2.15 and 9.81 times the maximum scour depth under free surface flow conditions. With same flow depth, when the relative bridge length was increased from 5 to 7.5 and 7.5 to 10, the maximum scour depth decreased by up to about 7.4% and 2.3%, respectively. When the relative bridge width was decreased from 5.5 to 5.2 and 5.2 to 4.4, the maximum scour depth increased by up to about 45.6% and 81.2%, respectively

Minimizing downstream scour due to submerged hydraulic jump using corrugated

Local scour downstream of hydraulic structures due to hydraulic jump is considered one of the tedious and complicated problems facing their stability. Throughout this paper, an experimental study was conducted to study the effect of using different spaced corrugated aprons on the downstream local scour due to submerged jump. Sixty runs were carried out in a horizontal rectangular flume to determine the optimal corrugation wavelength which minimizing the scour. A case of flat apron included to estimate the influence of corrugated aprons on scour holes dimensions. Two types of non-cohesive soil were used. Experiments were performed for a range of Froude numbers between 1.68 and 9.29. The results showed that using spaced triangular corrugated aprons minimize the scour depth and length of fine sand by average percentage of 63.4% and 30.2%, respectively and for coarse sand by 44.2% and 20.6% in comparing with classical jump