翼型附加气动弹片流动控制研究

STUDY ON FLOW CONTROL OF AIRFOIL BASED ON AERODYNAMIC FLAP

通过数值模拟计算不同攻角(2°~30°)下弹片抬起角度的气动性能和噪声特性,确定某攻角下的最佳弹片抬起角度。计算结果表明:与原始翼型相比,附加气动弹片翼型在失速攻角之后升阻力系数明显减小,失速攻角也延迟了约2°;气动弹片的存在一定程度上延缓分离点向前缘方向发展,且上表面较大分离涡被分割成尺度较小的涡,相应分离区域也有所减小。小攻角下,气动弹片的存在破坏了附着流动,导致升力下降而阻力增大,攻角增大,弹片开始产生积极效果;弹片最优角度很大程度上跟攻角有关,弹片角度变化对气动性能的影响并非线性的,而是在某角度存在最优。攻角越大,弹片最优角度越大;小攻角下弹片抬起亦会增大翼型噪声声压级,且抬起角度越大,产生的负面影响越严重;弹片产生效果之前,噪声指向性声压级随弹片角度增大而增加,产生效果后,指向性分布声压级呈先增后减趋势,约在最佳弹片角度下效果最好;翼型噪声指向性分布呈现明显偶极子特性。研究结果为提高风力机翼型的气动性能和降低噪声水平提供理论指导和实现途径。

The aerodynamic performance and noise characteristics of a series of flap angles under different angles of attack(2°-30°)were calculated by numerical simulation,and the optimal flap angle at certain attack angle was found.The calculation results show that the lift and drag coefficient of the flap airfoil is better than the original airfoil after the stall angle of attack,and the stall angle of attack is also delayed by about 2 degrees.The flap postpones the development of the separation point to the leading edge to a certain extent,and the larger separation vortices on the upper surface are divided into smaller vortices and the separation regions has also been reduced corresponding.The existence of flap damage the attachment flow,resulting in the lift decrease and the drag increases under the small angle of attack(AOA),but the flap began to produce positive effect with the increase of angle of attack;the optimal flap angle is largely related to the AOA,the influence of the change of the flap angle on the aerodynamic performance is nonlinear,but are the optimum at a certain angle.The bigger of the AOA,the greater of the flap optimal angle;at small AOA,the flap could also increase the noise sound pressure level,the greater the flap angle,the negative impact of the flap is more serious;before the flap do the need,the noise directivity of sound pressure level increases with flap angle increases,and after the flap do the need,the directional distribution of sound pressure level is first increased and then decreased at about the optimum angle is best;the noise directivity distribution showed obvious airfoil characteristics of dipole.The research results provide a theoretical guidance and approach to improve the aerodynamic performance of the wind turbine and reduce the noise level.