The laminar flow on a curved surface transits to turbulent induced by streamline curvature which generates pressure gradient field and separated shear layer flow. We performed a direct numerical simulation investigation on transitional flow through a linear cascade consist of S-shaped S3525 hydrofoil which has different curvature variations on the two surfaces, i.e., concave-to-convex and convex- to-concave in the streamwise direction. The objectives are to quantitatively assess the effects of streamline curvature of the hydrofoil surface on the three-dimensionality of the separated and transitional flow, including the patterns of separation and reattachment, formation and development of three-dimensional boundary layer flow, and statistics on non-homogeneous turbulent near-wall flow. Comparisons between the near-wall flows of the two surfaces demonstrate the effect of streamline curvature and its associated influential mechanisms such as pressure gradient field. Numerical data reveal that transition and occurrence of three-dimensional flow are observed earlier for the concave-to-convex surface; intermittent flow is generated in the concave section near the leading edge and convex section near the trailing edge where three-dimensionality of flow and turbulent fluctuations are the most pronounced. However, the boundary layer and near-wall flow for the convex-to-concave surface is quite stable until the concave section, thus three-dimensionality of separation and reattachment, boundary layer flow and turbulent behaviors are only notable near the trailing edge.

曲面上的层流过渡到由流线曲率引起的湍流，产生压力梯度场和分离的剪切层流。我们对通过由 S 形 S3525 水翼组成的线性叶栅的过渡流进行了直接数值模拟研究，该水翼在两个表面上具有不同的曲率变化，即沿流向的凹凸和凸凹。目的是定量评估水翼表面流线曲率对分离和过渡流三维度的影响，包括分离和重新附着的模式，三维边界层流的形成和发展，以及非- 均匀湍流近壁流。两个表面的近壁流动之间的比较证明了流线曲率的影响及其相关的影响机制，例如压力梯度场。数值数据表明，凹凸表面较早地观察到三维流动的转变和发生；在前缘附近的凹部和后缘附近的凸部产生间歇流，其中流动的三维度和湍流波动最为明显。然而，凸凹面的边界层和近壁面流动在凹面部分之前是相当稳定的，因此分离和重新附着的三维度、边界层流动和湍流行为仅在后缘附近显着。