保水堰是一种新型溢流堰结构形式，为提升保水堰在大型调水工程中的输水能力，利用实测数据进行模型 验证，在确保模拟保水堰堰内水流流态规律准确性的前提下，探究工程中保水堰体型参数对输水系统过流能力的 影响。研究揭示了堰井段环状旋涡区的产生与发展机理，并对 11 种降低堰高方案进行数值计算，分析堰井段流 速矢量分布和环状旋涡区范围及能量耗散的变化，发现使输水系统过流能力增加的最佳堰高区间为 [1.0?P1≥P≥ 0.7P1]（P 为保水堰堰高；P1为堰前堰高）。当堰高在此区间内，通过降低 P 使堰前流速矢量仰角和堰后环状旋涡 区变小，能量耗散显著降低，降低 0.1P1，流量平均增加 2.1%。考虑到工程改造成本和过流能力提升效果，故在本 研究提出最佳堰高区间内修改保水堰的结构，为输水系统过流能力提升提供参考。

Water?keeping?weir?is?a?new?type?of?overflow?weir,?characterized?by?small?pressure?in?two?sections?of?the transmission?line,?and?simple?hydraulic?control.?In?order?to?enhance?the?water?conveyance?capacity?of?water?keeping weir?in?large?water?diversion?projects.?First?of?all,?based?on?the?actual?operation?of?the?project,?the?RNG?k-ε?turbulent flow?model?is?used?to?close?the?control?equations?and?establish?a?three-dimensional?isometric?numerical?simulation model?of?the?water?keeping?weir,?and?the?simulated?head?and?flow?velocity?of?the?pressure?measuring?tube?are?in good?agreement?with?the?measured?data,?and?on?the?premise?of?ensuring?the?accuracy?of?the?flow?pattern?in?the simulated?water?keeping?weir,?the?influence?of?the?water?keeping?weir?body?parameters?on?the?over-flow?capacity?of the?box?culvert?-?water?keeping?weir?water?conveyance?system?is?investigated.?It?revealed?the?mechanism?of?the generation?and?development?of?annular?vortex?zones?in?the?weir?section,?and?determined?that?the?dispersion?of?high velocity?water?flow?zone?caused?by?the?height?of?the?water?keeping?weir?and?the?presence?of?annular?vortex?zones are?the?main?bottlenecks?affecting?the?improvement?of?flow?capacity.?Thus,?the?proposed?solution?of?reducing?the height?of?the?water?keeping?weir?concentrate?the?high?velocity?water?flow?zone?and?reduce?the?scope?of?the?annular vortex?zone?to?reduce?the?energy?dissipation?in?the?weir?section,?so?as?to?achieve?the?purpose?of?improving?the overflow?capacity?of?the?water?conveyance?system. ??????Numerical?calculations?were?carried?out?for?11?options?of?reducing?the?weir?height?of?water?keeping?weirs,?and the?flow?velocity?vector?distribution?and?the?extent?of?the?annular?vortex?zone?in?the?weir?section?as?well?as?the variation ?of ?turbulent ?kinetic ?energy ?dissipation ?and ?overflow ?flow ?were ?analyzed. ?The ?results ?show ?that ?the overflow?of?the?water?conveyance?system?can?be?enhanced?by?the?weir?reduction?scheme,?and?by?compared?between different?weir?height?schemes,?the?optimal?weir?height?interval?that?increases?its?overflow?capacity?is?finally?found?to be?[1.0?P1≥P≥0.7P1]?(where?P is?water?keeping?weir?height).?When?the?weir?height?is?within?this?range,?the compression?effect?on?the?high?velocity?flow?area?is?weakened?by?lowering?P,?resulting?in?smaller?flow?vector elevation?angle?in?front?of?the?weir?and?the?annular?vortex?zone?behind?the?weir,?and?significantly?lower?energy dissipation,?lowering?0.1P1?flow?rate?increases?by?2.1%?on?average,?where?the?weir?height?P?is?lowered?to?0.7P1 when?the?flow?rate?is?increased?up?to?6.3%,?which?can?basically?meet?the?water?demand?requirements?of?the?project; Outside?this?interval,?although?lowering?P?reduces?the?annular?vortex?zone?after?the?weir?and?the?flow?velocity?vector angle?becomes?smaller,?the?energy?dissipation?is?reduced,?but?the?rapid?expansion?of?the?annular?vortex?zone?before the?weir?consumes?part?of?the?water?flow?energy,?resulting?in?the?flow?lift?decay,?at?this?time,?lowering?0.1P1?flow rate?only?increases?by?0.5%?on?average.?In?consideration?of?the?project?modification?cost?and?the?effect?of?overflow capacity ?enhancement, ?the ?structure ?of ?the ?water ?keeping ?weir ?is ?modified ?in ?the ?optimal ?weir ?height ?interval proposed??to?provide?reference?for?the?overflow?capacity?enhancement?of?the?water?transmission?system.