跨音速颤振计算方法研究

A Study of Calculation Method for Transonic Flutter

采用快捷的动态弹性变形技术生成三维块结构动态贴体网格。结构运动方程采用二级精度的龙格—库塔时间推进。气动力求解则用非定常欧拉方程的双时间有限体积推进,外时间为物理时间,与结构运动方程同步;对每个真实物理时间步采用五步Runge Kutta时间推进进行虚拟定常迭代。针对可压流颤振计算中存在的质量不相似问题,采用变质量、变刚度的方法计算出质量匹配点处的颤振速压值,并根据颤振速压随质量或刚度倍数的变化趋势,得出可用的飞机跨音速颤振速压。对一飞机简化外形的跨音速颤振特性计算得到了合理的计算结果。

A rapid deforming technique is developed to generate three-dimensional multi-block dynamic attached meshes. A second-order accuracy Runge-Kutta time stepping is used to solve structural equations of motion and a dual-time method is applied to the finite-volume element method for unsteady Euler equations to calculate the aerodynamic forces, in which the physical time step is synchronous with the structural equations of motion. In a real-time step, a five-stage Runge-Kutta time stepping is applied to the fictitious steady iterations. Because of mass dissimilarity exiting in flutter calculations for a compressible flow, a method of variable mass and variable stiffness is developed to calculate the fluttering dynamic pressure at the point of mass similarity, and the flutter characteristics are then obtained in accordance with similarity rule. For completeness, the transonic flutter characteristic results, calculated using the method, are presented for a simplified fighter model.