基于气弹耦合的旋翼桨涡干扰噪声预测方法

Blade vortex interaction acoustic prediction method for rotor based on aerodynamic/elastic coupling

建立了基于气动/弹性耦合的旋翼桨涡干扰(BVI)气动和噪声分析方法。气动模型包括修正Beddoes尾迹模型和CFD模型,噪声计算采用基于声学类比法推导出的FW-H(Ffowcs-Williams Hawkings)方程,弹性桨叶动力学建模采用有限元方法。应用所建立的方法,对刚性的OLS(operational load survey)旋翼桨涡干扰状态的气动和噪声特性进行了计算,对比了两种气动模型在研究桨涡干扰问题的有效性;以弹性的HARTⅡ旋翼为研究对象,分析了桨叶弹性、时间步长对桨涡干扰气动载荷和噪声的影响。结果表明:进行桨涡干扰计算时所采用的时间步长不宜超过2°。CFD方法由于固有的数值耗散,计算出的OLS旋翼噪声声压峰值仅为试验值的60%,而修正Beddoes尾迹模型能够避免数值耗散,且具有高效率的优势。考虑桨叶气动弹性能够提高旋翼桨涡干扰噪声的预测精度。

An engineering method suitable for blade vortex interaction （BVI） airload and acoustic analysis was established based on aerodynamic/elastic coupling. The aerody- namic model includes modified Beddoes wake method and CFD method. Acoustic prediction was based on Ffowcs-Williams Hawkings （FW-H） equation derived by acoustic analogy, and the elastic blade model was based on finite element method. By applying the established models, the airload and acoustic characteristics of rigid operational load survey （OLS） rotor were calculated under BVI flight state firstly, and the validity of the two aerodynamic models was compared, then the influences of elasticity and time step on HART II rotor BVI airload and acoustic were analyzed. The results indicate that the time step adopted in BVI calculation should be no more than 2 degree. Peak acoustic pressure of OLS rotor predicted by CFD is only 60 % of experimental data because of inherent numerical dissipation, while the modified Beddoes wake method can address this problem with high computation efficiency. Taking blade elasticity into consideration is beneficial for BVI acoustic prediction accuracy.