Large Eddy Simulation of a Finite Swept Wing undergoing Plunging Manoeuvre
Large Eddy Simulation of a Finite Swept Wing undergoing Plunging Manoeuvre
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发表时间：
2018
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通讯作者：
C. Badoe;Z. Xie;N. Sandham
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作者：
C. Badoe;Z. Xie;N. Sandham
通过数值模拟NACA 0012有限长机翼的垂荡绕流，研究了后掠角对吸力面分离流动的影响。采用一种经过广泛验证的高保真大涡模拟（LES）方法，研究了雷诺数Rec = 20，000时基于弦线的非定常气动载荷和流动结构。模拟是在折合频率k=0.94、弦标准化峰-峰振幅A/c=0.5、后掠角θ = 0和θ = 40、攻角15（代表过失速状态）的情况下进行的。与实验的比较表明，在时间平均升力的良好协议，为= 0。扫掠的影响被发现，导致在时间平均升力，最大升力值的减少，以及在动态失速过程中的延迟。一系列瞬时展向涡量图表明，在下冲程开始期间，吸力面上方形成的反向流动区域中存在显著的展向变化，从而导致分离剪切层中的不稳定性。当λ = 0时，LEV在尖端区域附近是高度三维的，而当λ = 40时，LEV看起来更二维。对φ = 0后掠机翼与展向周期（2D）计算的比较表明，中展区域周围的动态失速涡结构具有很强的相似性。
Simulations of the flow over a heaving NACA0012 finite wing are conducted to study the effect of sweep on the separated flow phenomena on the suction surface. An extensively-validated high-fidelity largeeddy simulation (LES) approach is used to examine the unsteady aerodynamic loads and flow structures at Reynolds number Rec = 20,000 based on the chord. The simulations are carried out for reduced frequency k=0.94, a chord-normalized peak-to-peak amplitude of A/c=0.5, sweep angles ⇤ = 0 and ⇤ = 40 and angle of attack of 15 , representing post-stall conditions. Comparisons to experiment show good agreement in the time-averaged lift for ⇤ = 0 . The effect of sweep was found to result in a decrease in the time-averaged lift, maximum lift value as well as a delay in the dynamic stall process. A series of instantaneous spanwise vorticity plots show significant spanwise variations in the reverse flow region that develops over the suction surface during the start of the downstroke, giving rise to instabilities in the detached shear layer. For ⇤ = 0 the LEV is highly three-dimensional near the tip region whereas it appears to be more two-dimensional for ⇤ = 40 . A comparison of the ⇤ = 0 swept-wing with span-periodic (2D) computations show strong similarities of the dynamic stall vortex structure around the mid span region.