绕振荡水翼流动及其转捩特性的数值计算研究简

通过对比标准k-ω SST 湍流模型和基于标准k-ω SST 湍流模型修正的γ-Re_θ 转捩湍流模型对绕振荡NACA66 水翼流动的数值计算结果与实验结果，对水翼振荡过程的水动力特性和流场结构变化进行了分析研究. 结果表明：与标准k-ω SST 湍流模型的数值计算结果相比，基于标准k-ω SST 湍流模型修正的γ-Re_θ 转捩湍流模型能有效预测绕振荡翼型流场结构和水动力特性，捕捉流场边界层发生的流动分离和转捩现象；绕振荡水翼的流动过程可分为5 个特征阶段，当来流攻角较小时，在水翼前缘发生层流向湍流的转捩现象，水翼动力特征曲线出现变化拐点；随着来流攻角的增大，顺时针尾缘涡逐渐形成并向水翼前缘发展；当攻角较大时，前缘涡分离导致动力失速，水翼的动力特征曲线出现大幅波动；水翼处于顺时针向下旋转阶段，绕水翼的流动状态逐渐由湍流过渡为层流.

NUMERICAL METHODS AND TRANSITION INVESTIGATION OF TRANSIENT FLOWS AROUND A PITCHING HYDROFOIL

In order to investigate the numerical method for transient flows around a pitching hydrofoil, the numerical simulations for a NACA66 hydrofoil are performed by using the standard k-ω SST turbulence model and revised γ-Re_θ transition model respectively. The simulation results are compared with the experimental results, and the hydrodynamic property and the fluid structure during the pitching process are studied. It is revealed that, compared with the standard k-ω SST turbulence model, the revised -Re transition model is able to present the hydrodynamic property and the fluid structure of the transient flow around a pitching hydrofoil more accurately, and better predict the separation and transition process in the boundary layer. The transient flow process around a pitching hydrofoil can be divided into 5 parts. At small angle of attack, transition is observed at the leading edge of the foil, resulting in the inflection of dynamic property curves. As the angle of attack increases, a clockwise trailing edge vortex expands toward the leading edge of the foil. At high angles of attack, large-scale load fluctuations are observed due to the stall caused by separation of the leading edge vortex. The transition from turbulent flow to laminar flow occurs during the downward pitching process.