Large-eddy simulations (LES) of supercritical flow in a straight-wall, open-channel contraction of 6° and contraction ratio of 2:1 are performed. The LES code solves the filtered Navier-Stokes equations for two-phase flows (water-air) and employs the level-set method. The simulation was validated by replicating a previously reported experiment. Contours of the time-averaged velocities indicate that the flow loses energy and momentum in the contracting channel. Further, secondary currents in the contraction are redistributing momentum and are responsible for local up-and down-flows. The turbulent kinetic energy reaches very high values at the entrance of the contraction, mainly contributed by the streamwise normal stress. The flow contains coherent turbulence structures which are responsible for carrying low-momentum from the bed and the water surface towards the channel centre. Flow deceleration results in significant turbulence anisotropy in the contracted section. It is shown that mainly pressure drag contributes to the energy loss in the contraction.

对直壁、明渠收缩 6° 和收缩比 2:1 中的超临界流动进行大涡模拟 (LES)。LES 代码求解两相流（水-空气）的过滤 Navier-Stokes 方程，并采用水平集方法。通过复制先前报告的实验来验证模拟。时间平均速度的等高线表明流动在收缩通道中失去能量和动量。此外，收缩中的次级电流正在重新分配动量，并负责局部向上和向下流动。湍流动能在收缩开始时达到非常高的值，主要由流向法向应力贡献。流动包含连贯的湍流结构，这些结构负责将低动量从河床和水面带向通道中心。流动减速导致收缩部分的湍流各向异性显着。结果表明，主要是压力阻力导致收缩中的能量损失。