缝翼尖端延伸对流场及噪声特性的影响

Effects of Slat Cusp Extension on Characteristics of Flow Field and Noise

尖端延伸可改变自由剪切层的形成和发展,并对缝翼噪声辐射产生影响。首先,基于30P30N多段翼型及DDES瞬态流场仿真方法,分析该翼型在两种尖端延伸方式下的压力、湍动能及瞬态涡量等参数的分布趋势;其次,利用FW-H积分法分析缝翼的远场噪声声压级与指向性分布特征;最后,基于∇2ρ瞬态流场结构分析方法,研究缝翼尖端延伸对剪切层涡结构的动态演变规律,及其对气动噪声特性的影响。结果表明:尖端延伸可有效改变缝翼流场参数分布,其中沿剪切层方向延伸,可减弱缝翼凹腔的湍动能强度,减小气流分离涡的特征尺度,在一定程度上抑制缝翼噪声的辐射(低频段窄带峰值降低约3 dB)。

Combining the existing slat cusp extension with the noise reduction technique proposed in this paper,based on the 30P30N multi-segment aerofoil,unsteady flow of three-dimensional airfoil structure is simulate by DDES algorithm.Firstly,the pressure and vorticity transient parameters of the model are obtained.And then,the sound pressure level and directivity are studied by FW-H integration method to study the effects of slat cusp geometric extensions on the surrounding flow field and noise characteristics.Finally,based on the instantaneous vortex structure analysis method of ∇^(2)ρ,the generation and evolvement of flow structures in slat cove and corresponding noise distributions are investigated for various extensions.The investigation shows,cusp extension can effectively change the distribution of parameters of slat flow.Among which,extensions along the sheer layer can reduce the strength of turbulence kinetic energy in slat cove and decrease the characteristic dimension of vortices of separating flow,as a result,suppressing the radiation of slat noise(narrow band noise can be reduced by 3 dB in low frequencies).