Analysis and prediction of thin-airfoil stall phenomena with hybrid turbulence methodology
Analysis and prediction of thin-airfoil stall phenomena with hybrid turbulence methodology
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DOI：
10.2514/1.11672
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发表时间：
2005-05-01
期刊：
影响因子：
2.5
通讯作者：
Fujii, K
中科院分区：
文献类型：
--
作者：
Kawai, S;Fujii, K
采用大涡模拟(LES)/雷诺平均N-S(RANS)混合方法和高阶紧致差分格式，对NACA 64A006翼型的薄翼型失速现象进行了数值分析和预报。在高雷诺数Re=5.8×10(6)的情况下，考虑了M-无穷大=0.17的亚音速流动，迎角从4.0°变化到11.0°。结果表明，与单纯的大涡模拟方法相比，本文提出的LES/RANS混合方法对具有层流分离和湍流再附着的大分离高雷诺数流动的预测具有更实际的计算代价。使用LES/RANS混合方法和比纯LES方法成本更低的高阶紧致差分格式，成功地预测了薄翼型失速气动特性。对于薄翼型失速现象的预报，必须妥善解决相对较小攻角的前缘附近的层流小气泡和吸力峰值随迎角增大而坍塌的气泡的生长问题。从瞬时流动和时间平均流动来看，前缘附近的层流小气泡是前缘脱落的非定常小涡平均一定时间后出现的现象。高阶紧凑差分格式即使在合理的网格点数目下，也能为NACA 64A006翼型失速附近的复杂和分离的流场提供极高的保真度结果。用原Baldwin和Lomax湍流模型中的数值过渡方法对薄翼型失速特性进行了较好的预测，该方法根据计算结果自动确定转折点。LES/RANS混合方法和简单过渡方法被认为是一种有效的流动预测工具，其中RANS可以很好地预测过渡。
Analysis and prediction of thin-airfoil stall phenomena of a NACA 64A006 airfoil are numerically investigated using large-eddy simulation (LES)/Reynolds-averaged Navier-Stokes (RANS) hybrid methodology with a high-order compact differencing scheme. Subsonic flow of M-infinity = 0.17 with the high Reynolds number of Re = 5.8 x 10(6) is considered, and the angle of attack is varied from 4.0 to 11.0 deg. The results illustrate the possibility of the present LES/RANS hybrid methodology for the prediction of the massively separated high Reynolds number flows with laminar separation and turbulent reattachment within more practical computational cost than that of a pure LES approach. Thin-airfoil stalling aerodynamic characteristics are successfully predicted using the LES/RANS hybrid methodology with a high-order compact difference scheme that is less costly than pure LES approaches. For the prediction of thin-airfoil stall phenomena, it is necessary to resolve properly the laminar small bubble near the leading edge at relatively low angles of attack and the growth of the bubble where suction pressure peak collapses with increasing angles of attack. From the instantaneous and time-averaged flows, it is confirmed that the laminar small bubble near the leading edge is a phenomenon that appears when the unsteady small vortices shedding from the leading edge are averaged for a certain length of time. High-order compact differencing scheme provides extremely high-fidelity results for the complicated and separated flowfields associated with a NACA 64A006 airfoil near stall, even under the reasonable number of grid points. Thin-airfoil stall characteristics are well predicted with the numerical transition method implemented in the original Baldwin and Lomax turbulence model that detects the transition point automatically from the computation. The LES/RANS hybrid methodology with the simple transition method is considered to be an effective prediction tool for flows where the RANS can predict the transition reasonably well.