含沙量变化对U型渠道垂线流速分布的影响

Effects of change of sediment concentration on vertical velocity distribution in U-Channel

【目的】探索含沙量变化对U型渠道挟沙水流垂线流速分布的影响,进而从理论上完善挟沙水流流速分布规律。【方法】通过U型渠道水槽试验,测定水流中含沙量为1.12～500kg/m3时,最大流速所在位置的变化,同时引入卡门常数κ,来反映含沙量对垂线流速分布的影响。【结果】当水流含沙量s<300kg/m3时,随着含沙量的增加,最大流速点的位置逐渐下降,在主流区、底流区和表面区,挟沙水流均遵循对数流速分布规律,但κ的变化规律不同;当含沙量s≥300kg/m3时,水流的流型发生了变化,表面区、主流区水流不再遵循对数流速分布规律,底流区虽仍遵循对数流速分布规律,但κ的变化规律与s<300kg/m3时不同,κ的变化趋势总体随着含沙量的增大而减小。【结论】U型渠道挟沙水流遵循对数流速分布规律,κ的变化规律与普通明渠不同,应该分别对待。

【Objective】 The experiment was done to search for effects of change of sediment concentration on vertical velocity distribution in U-Channel,thus theoretically to perfect velocity distribution of sediment-laden flow.【Method】 We surveyed change of the location of maximum velocity when the sediment concentration was 1.12-500 kg/m3 in flow by the flume experiments in U-Channel.At the same time,introducing Karman constant κ was to reflect effects of change of sediment concentration on vertical velocity distribution.【Result】 With sediment concentration s〈300 kg/m3,as sediment concentration increased,the location of maximum velocity point decreased.Sediment-laden flow followed logarithmic law of velocity distribution at main-flow area,bottom-flow area and surface area,but variation of κ was different.With sediment concentration s≥300 kg/m3,flow pattern changed,except that sediment-laden flow followed logarithmic law of velocity distribution at bottom-flow area,sediment-laden flow didn＇t follow logarithmic law of velocity distribution at surface area and main-flow area,and variation of κ was different from sediment concentration s〈300 kg/m3 at bottom-flow area.The general trend of κ reduced with the increase of sediment concentration at bottom-flow area.【Conclusion】 Sediment-laden flow follows logarithmic law of velocity distribution in U-Channel,compared with common channel,variation of κ is different and should be treated separately.