مطالعه آزمايشگاهي اثر تراز آب مخزن و مشخصات هيدروليكي و رسوبي دهانه ورودي مخزن بر سرعت پيشروي دلتا

Experimental study of the reservoir water level, hydraulic and sediment properties of reservoir entrance on the rate of delta progression

In this research, an experimental investigation of the process involved in delta formation and its progression in reservoirs has been undertaken. The process depends on hydraulic, sediment, and physical parameters of the reservoirs and their associated river. In this research, a number of the influencing parameters, such as water and sediment discharges in the river, the reservoir flow depth, and the entrance diverging angle of reservoir, have been studied. For each run, the rate of bed changes and progression of bottom set and crest of a delta in specific stations have been observed and recorded, The results showed that the rate of crest progression can be predicted using an exponential function (with exponent of 0.624). Submerged angle of sediment with dso= Imm has been obtained between the range of 30 -40 degrees. Using dimensional analysis and SPSS software for the independent variables (progression of bottom set and crest of delta) and the dependent variables (dimensionless time, water and sediment discharges, reservoir flow depth), a multiple linear regression model to experimental data is fitted. Due to weak prediction of the linear model in the first stage of progression, an exponential model has been carried out for this stage. Using a combination of these two models, a combined model is developed. Analysis of this model showed that the average and standard deviation of discrepancy ratio (A) for the bottom set of delta are 0.99 and 0.139, and those for the crest are 1.005 and 0.211 which show a good prediction when the new model is applied. Sensitivity analysis of the new model showed that the discrepancy ratio, (A), for the bottom set and the crest of delta are not sensitive to water discharge and flow depth in the reservoir. However, the parameter is sensitive to the bottom set and the crest of delta in high and low sediment rates, respectively.