Abstract: A new type of desilting channel with swirling flows is developed to optimize the gradation of sediment for water diversion from a heavy sediment-laden river and to improve its sediment sorting effect. Based on the orthogonal experimental design, its key parameters are optimized by combining numerical simulations and model tests, using objective functions of the flow diverting ratio and average flow velocity in the sediment transport pipe; its hydraulic characteristics and desilting characteristics before and after shape optimization are compared and analyzed. The results show that the approach of orthogonal experimental design and numerical simulation effectively improves the optimization efficiency of the channel structure and achieves a good performance of the swirling flows. When the shape-optimized channel has an inflow of 30 L?s-1, the sediment pipe has an outflow reduced by 21.5% relative to the original shape and a diverting ratio reduced by 4.6%. Its maximum outflow velocity is increased by 10.8%, enhancing its sediment carrying capacity, and a rotating flow condition more conducive to its sediment movement is formed. For the desilting channel with swirling flows carrying sediment with the particle size of 0.075 - 3.0 mm, its overall sediment interception rate is as high as 90% and 88% before and after the shape optimization respectively, indicating it has good sediment desilting characteristics; sediment deposition in the optimized transport pipe is 61.8% lower than that of the original shape. The results help optimize the shape of desilting channels and make use of swirling flows for water diversion projects.

Key words: desilting channel with swirling flow, orthogonal numerical experiment method, shape optimization, diverting ratio, water-sediment characteristics