翼梢小翼若干几何参数对翼尖涡流场的影响研究

CFD-based study of several geometrical parameters of winglet

为解决使用CFD方法研究翼尖涡流场时存在的传统湍流模式难以准确计算翼尖涡的强旋流场的问题，本文使用添加旋转修正的SST-RC模式计算了光滑机翼的翼尖涡流场，并通过与实验结果进行对比，验证了该模式对于翼尖涡流场的有效性。然后使用该模式计算了翼梢小翼后的翼尖涡流场，发现翼梢小翼作为一种涡扩散器能够将原来强度集中的翼尖涡破碎分解成两个旋涡，这两个旋涡互相作用，加速了翼尖涡的粘性耗散。通过改变小翼的三个几何参数：根弦长Cr、倾斜角θ、外撇角φ，计算了不同外形翼梢小翼后的翼尖涡流场，同时引入一个翼尖涡的强度尺度s，考察s在尾缘下游的分布，发现添加小翼后S普遍下降了10％～20％。改变小翼根弦长对s的衰减影响不太明显，不同根弦长对应的s值相差2％-4％，Cr=0．7c时效果最佳；改变小翼倾斜角汐对S的影响在初始时差别较大，不同倾斜角对应的S相差约9％，在下游后期S差别较小，相差约3％，0=20°时效果最佳；与倾斜角θ类似，改变小翼外撇角φ对s的影响在初始时差别较大，不同外撇角对应的S相差约10％，在下游后期S差别较小，相差约1％，φ=5°时效果最佳。

Using the rotating corrected SST-RC model,numerical simulation of the flow field of wing tip vortex of a smooth straight wing is carried out,and corresponding comparison with the experimental results is given to verify the effectiveness of the proposed model.Then the model is used to compute the wing tip vortex flow field for both straight wing and wings with winglet.It is found that the winglets as a vortex diffuser could broke a strong intensive wing tip vortex down into two vortices and the two vortices interact and accelerate the viscous dissipation of wing tip vortex.By changing three geometry parameters of the winglet,that is to say,the root chord length,the cant degree and the toe out degree,the flow fields of different shapes of winglet are calculated.Meanwhile,a wingtip vortex strength scale S is introduced to investigate the distribution of S downstream of the trailing edge.It is found that after adding winglets,S generally decreased by about 10%.Different shapes of winglets have obvious different impact on the wingtip vortex strength scale S in the near-filed,but no different impact on the far-field can be observed.