Abstract
The variation between flow depth generated in front of gabion barrier and flow rate has been studied in open laboratory flume. Flow profiles have been observed for each of "Transition Flow" and "Overflow" regimes. Effects of gabion height and material coarseness on the upstream flow depth are studied by testing four different gabion heights and four different medium aggregate sizes. The analysis of experimental results showed that the relative decrease in flow depth varies between 38% and 17% for "Through Flow" type when material coarseness and discharge increase. In "Transition Flow" regime, increasing material coarseness and discharge causes an average decreases in relative flow depth of 7.6% and 4.4% for gabion heights 15cm and 30cm, respectively. Gabion begins to operate as an overflow weir when the average water depth to the gabion height (H/P) is 1.19. While the overall average increase in discharge relative to solid weir is 15%. Prediction relationships for flow depth upstream the gabion for each of the three flow regimes is suggested. Also, dimensionless relation to predict discharge coefficient are proposed with good accuracy.
Highlights
Rock and gravel have been used as obstacle in streams for lifting water surface level and reducing flow velocity, these practices motivate creativity and inspiration which had leaded to the creation of the weirs
Free surface flow condition and submerged flow condition on gabion weir has been studied by Mohamed [15], the study included three mean sizes of gravel and has shown that two types of flow occur over the gabion weir and through its body, showed that the generated water depth upstream gabion weir is less than that caused by solid weir for the same discharge
Salmasi and Sattari [16] have found the value of discharge coefficient by M5 tree model using experimental data, the results showed that the value of this coefficient is less 20% for the submerged flow compared with free flow, show that model technique created linear relationship for discharge coefficient and four independent parameters
Summary
Rock and gravel have been used as obstacle in streams for lifting water surface level and reducing flow velocity, these practices motivate creativity and inspiration which had leaded to the creation of the weirs. Free surface flow condition and submerged flow condition on gabion weir has been studied by Mohamed [15], the study included three mean sizes of gravel and has shown that two types of flow occur over the gabion weir and through its body, showed that the generated water depth upstream gabion weir is less than that caused by solid weir for the same discharge. In the present experimental investigation, the effect of height and aggregate size of gabion in waterways on the accumulated upstream water during seasonal incoming discharge is studied for free flow conditions.
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