带襟翼的机翼尾涡合并数值计算

Numerical simulation of trailing vortex merge in a flapped wing wake

为获得带有襟翼的机翼尾涡的合并动力学过程,在验证数值方法的基础上,数值模拟带有襟翼的机翼绕流尾流场,根据涡合并特征将合并过程划分为诱导共转阶段、合并阶段和轴对称化阶段.采用涡间距量纲—化尾流区域描述二涡诱导合并.变换弦长雷诺数、襟翼翼梢与机翼翼梢的间距、襟翼角度,改变襟翼翼梢涡与机翼翼梢涡的强度比,得到尾涡合并差异的特征.计算结果表明:随着雷诺数的增加涡的强度增加,涡量的扩散程度减低,涡合并过程被推迟,空间诱导运动过程得到延长,涡系空间诱导运动增强,涡合并的雷诺数效应随着雷诺数增加而减弱,缩短涡间距,加速涡合并过程,但合并后的远场涡尺寸和形态没有显著改变;襟翼涡随着襟翼角的减小而减弱,强度逐渐减弱的襟翼涡逐步被翼梢涡拉伸卷吸,微弱的襟翼涡系在近场中的合并过程完全改变,翼梢涡的运动轨迹并未受到诱导运动.翼梢涡合并的雷诺数效应表现为诱导运动过程的增强,尾流中强度小的涡系起不到明显的诱导作用.

A validated numerical simulation modeling of flapped wing wake is carried out by using RANS discretion.The flapped wing wake region is divided into three regions with significant different dynamic features. Three regions including co-rotation field,merging field and axial symmetry far field are induced. A non dimensional parameter of vortex interval is used to describe above regions. The Reynolds number,vortex interval,flap angle are used as control variables to change ratio of circulation of flap vortex and tip vortex. Reynolds effect is found as prolonged corotation field and enhanced rotation motion in wake. Decreased vortices interval leads an accelerated merging in near field but a limited dimension of resulted vortex. Small flap angle leads a weak flap vortex. The dominated tip vortex stretches and filament flap vortex in free share layer. The merging process is totally changed. The tip vortex trajectory does not expand. Reynolds number effect is the enhancement of induction in tip vortices merge. Induction of vortices with low intensity is not obvious in the wake.