Large-Eddy Simulation is adopted to reproduce the wake of an axial-flow hydrokinetic turbine. The process of momentum recovery is correlated with the destabilization of the wake system, starting wake contraction and radial flows from the free-stream towards the wake core. All terms of the momentum balance equation are analyzed. The radial advection dominates the momentum recovery at the outer radii (in the vicinity of the radial boundary of the wake), just downstream of the instability of the system of tip vortices. Further downstream the reduction of the mean radial gradients makes advection less significant and the radial turbulent transport becomes the main source of momentum replenishment at inner radii, near the wake axis. The details of the process of momentum recovery and its correlation with the instability of the wake system, revealed by the present high-fidelity eddy-resolving computations, provide new insight on the development of the wake of axial-flow hydrokinetic turbines.

采用大涡模拟来再现轴流式流体动力涡轮的尾流。动量恢复的过程与尾流系统的不稳定，尾流开始收缩以及从自由流向尾流芯的径向流有关。分析了动量平衡方程的所有项。径向对流控制着外半径处（尾流径向边界附近）的动量恢复，正好位于尖端涡旋系统不稳定性的下游。在更下游，平均径向梯度的减小使对流的重要性降低，并且径向湍流传输成为靠近尾轴的内半径处动量补充的主要来源。动量恢复过程的细节及其与尾流系统不稳定性的关系，