Scour from flow downstream of a sluice gate after a horizontal apron.
1994
Mohamed A.
The present experimental study investigated the local scour of loose sand after a horizontal apron caused by flow from a sluice gate. The experiments concerned with this study were conducted in the hydraulic laboratory of the Mediterranean Agronomic Institute of Bari, in a flume 7.72 m long having a rectangular section of 0.30 m width by 0.40 m depth. The following conclusions are formulated: the maximum scour depth, for all the experimental test runs, was found to increase with time until it reaches an equilibrium state where its rate of increase becomes relatively slow. This great scour in a short time is due to the formation of the jump on the sand bed and this short time is needed for the tailwater depth to increase and for the flow to develop from the initial attached jet. This phenomenon is very important in the initial of flow in channels downstream of irrigation and other hydraulic control structures. To study the type of the formed jump, the obtained experimental results were plotted on the regime chart obtained by Mohamed et al. (J. of Hydr. Res., IAHR, v.30, no. 5, 1992) which relates the flow regime to the relative tailwater depth and the initial Froude number. It was found that the jump tended to repeat itself in a periodic form starting from wave jump and this wave jump dig the sand particles towards the upstream of the flume until the level of the sand bed directly after the apron became approximately equal to the apron level. Muller and Valentin formulae which enable the calculation of the maximum scour depth were used for the comparison between the calculated and measured maximum scour depths for the test runs of the second part.
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