低雷诺数分布式螺旋桨滑流气动影响

Distributed electric propulsion slipstream aerodynamic effects at low Reynolds number

以高空长航时(HALE)太阳能无人机(UAVs)研究为背景,采用基于混合网格技术及k-kL-ω转捩模型求解雷诺平均Navier-Stokes(RANS)方程的多重参考系(MRF)方法,对3种螺旋桨-机翼构型的低雷诺数气动特性进行了高精度准定常数值模拟,在等拉力前提条件下,通过对比机翼气动力系数及表面流场结构特征分析了分布式螺旋桨(DEP)滑流对FX63-137机翼的气动影响。研究表明:螺旋桨滑流影响使得桨后总压及流速显著增大,这是机翼升力增大的主要原因,但同时机翼阻力特性急剧恶化,升阻比反而降低;螺旋桨滑流向机翼边界层内注入丰富湍动能从而抑制流动分离,扩大机翼表面湍流范围及附着流动区域;分布式螺旋桨滑流与低雷诺数机翼表面复杂流动相互作用显著,主要表现为滑流区域边界展向涡结构的产生。

Based on the research of the high altitude long endurance（HALE）solar-powered unmanned aerial vehicles（UAVs）,the low Reynolds aerodynamic properties of three different propeller-wing configurations are numerically simulated by quasi-steadily solving the Reynolds averaged Navier-Stokes（RANS）equations of multiple reference frames（MRF）based on the hybrid grid technology and k-kL-ωtransition model.Under the request of equal thrust,the distributed electric propulsion（DEP）slipstream effects on the FX 63-137 wing are analyzed by the comparison of the aerodynamic forces and flow characteristics between different configurations.It shows that the application of DEP is supposed to improve the lift property but to worsen the drag property heavily,which is mainly due to the increase of the flow speed and total pressure;the propeller slipstream helps expand the area of turbulent adherent flow by bringing turbulent energy into the boundary layer to sustain strong adverse pressure gradient;the appearance of vortex structures at the boundaries of slipstream regions indicates that multiple propellers＇ slipstream regions strongly interact with the flow field on the wing at low Reynolds numbers.