风洞端壁对翼型气动特性的影响

Effects of Wind Tunnel Sidewalls on the Aerodynamic Performance of Airfoils

采用风洞实验和数值模拟相结合的方法,研究风洞端壁对翼型气动特性的影响。实验在IET低速回流风洞中实施,采用表面测压法。试验对象为三个不同尾缘厚度的翼型,分别为DU91-W2-250,DU91-W2-250_6和DU91-W2-250_10。实验雷诺数为2.62×10^(5),数值模拟采用RANS方法。结果表明:DU91-W2-250翼型在流动发生失速之前,随攻角增加,风洞端壁与翼型连接处产生的角区分离涡不断增大。流动进入失速区后,翼型自身产生的三维失速胞与风洞端壁诱导的角区分离涡共同作用,随着三维失速胞的增大,角区分离涡变小;随尾缘厚度增大,风洞端壁对翼型绕流影响减小;风洞端壁诱导产生的角区分离涡对翼型绕流产生下洗作用,使得有效攻角和升力系数减小、阻力系数增加。同时风洞端壁延迟了翼型段中间截面的流动分离。

The effects of wind tunnel sidewalls on the airfoils were studied in this paper by experimental method and numerical simulation. The experiment was carried out in IET low-speed wind tunnel and the surface pressure was measured. Blunt airfoils is DU91-W2-250_6, DU91-W2-250_6and DU91-W2-250_10. The Reynolds number is 2.62×10^(5)based on the tunnel size and wind speed available. Simulation was done with RANS method and SST-transition model for turbulence. The domain and boundary condition for calculation were set basically to model the experiment. For the baseline airfoil before stall, it shows that the corner vortices increase with the angle of attack, as well as the effect of sidewalls on the airfoil flow. After stall, the corner vortices decrease due to production of the three-dimensional separation cell. As for blunt airfoils, the results show that the enlarge of trailing edge weakens the influence of sidewalls on airfoil flow. The simulation results show that long vortex lines appear at both ends of the airfoil model due to corner vortices. Therefore, the effective angle of attack and the lift coefficient decrease but the drag coefficient increase due to the downwash of tip vortices. When the flow separates at large angles of attack, the sidewalls tend to suppress the separation under the specific model setup in this study.