基于RANS-LES混合方法的翼型大迎角非定常分离流动研究

使用雷诺平均Navier-Stokes方程-大涡模拟（RANS-LES）混合方法中的延迟分离涡模拟（DDES）方法，模拟了NACA 0015翼型在大迎角下的静态绕流和强迫振荡运动并与实验值进行了比较。在大迎角静态翼型大分离流动模拟中，DDES方法捕获了非定常RANS计算未能获得的机翼背风面的涡脱落现象。在所采用的RANS和DDES模型中，基于剪切应力输运（SST）湍流模型的SST-DDES混合方法给出的时均压力系数分布与实验吻合得最好。在大迎角强迫振荡翼型绕流模拟中，DDES方法得到的非定常气动载荷与实验值吻合得很好，正确地反映了最大迎角处阻力和俯仰力矩的阶跃性突变，而非定常RANS计算则给出了完全错误的趋势。

Study of Unsteady Separation Flow Around Airfoil at High Angle of Attack Using Hybrid RANS-LES Method

A delayed detached eddy simulation (DDES) method, which is a hybrid Reynolds average Navier-Stokes-large eddy simulation (RANS-LES) method, is proposed for static and oscillating NACA 0015 airfoil flow simulations and the computational results are compared with experiment data. The vortex shedding phenomenon of the massive separation flow on the leeward of the airfoil at high angles of attack is captured by the DDES method in static simulations, while it is ignored in unsteady RANS computations. The time averaged pressure coefficients given by the SST-DDES method which is based on the original shear stress transport (SST) turbulence model agree very well with experiment data in all proposed RANS and DDES models. The unsteady aerodynamic loads hysteresis curves obtained by the DDES method in forced oscillation airfoil flow computation at high angles of attack agree with the experiment data better than the traditional unsteady RANS simulation results do, and the step jump of the drag and pitch moment coefficients at the maximum angle of attack is described accurately, while the RANS method gives the absolutely wrong trend.