Unsteady separation of flow around airfoil with local elastic structure
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摘要: 对在低雷诺数下局部弹性翼型绕流中, 局部弹性导致的自激振动所产生的复杂非定常流动分离现象和描述方法进行了分析. 采用ALE-CBS方法数值模拟了具有可动边界的绕流流场问题, 同时采用Galerkin方法求解局部弹性结构的控制方程. 着重研究了翼型的局部弹性对流动分离和翼型性能的影响, 并分别从Eulerian和Lagrangian的角度分析了局部弹性结构导致的不同非定常分离现象, 其中Lagrangian角度可以方便地揭示出局部弹性翼型大幅度提高升力的机理和流动中的能量迁移. 结果表明翼型的局部弹性对非定常分离和分离泡的演化过程有着明显的影响, 可以使得流体质点由主流获取动量实现再附, 并且在一定的攻角下可以将固定分离转变为移动分离, 从而明显地提高了翼型的升力.
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关键词:
- 增升
Abstract: For flow around airfoil with local elastic structure at low Reynolds number, the unsteady flow separation excited by the self-induced oscillation of local elastic structure has been analyzed in detail. The arbitrary Lagrangian Eulerian-characteristic-based split (ALE-CBS) scheme is developed to simulate the flow field with moving boundary. Moreover, Galerkin method is used to approximate the governing equations of the local elastic structure. The analysis is focus on the influences of the local elastic structure on the flow separation and airfoil performance. Further, different unsteady separation phenomena are studied from both Eulerian and Lagrangian viewpoints. The results show that local elastic structure of airfoil has significant effect on the unsteady separation and streamline structure, and can enhance the lift performance by the moving separation on airfoil surface, resulting in reattachment. Compared with Eulerian description, the Lagrangian description of separation can reveal the nature of lift enhancement and momentum transfer from main flow to boundary.-
Key words:
- lift enhancement
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