Kinematics of Lagrangian Flow Separation in External Aerodynamics
Kinematics of Lagrangian Flow Separation in External Aerodynamics
复制标题
外部空气动力学中拉格朗日流动分离的运动学
作者：
B. Klose;M. Serra;G. Jacobs
本文在拉格朗日坐标系下研究了外部空气动力学中流动分离的运动学问题。具体而言，从壁面上涌的流体材料的初始运动与流场中的长期吸引歧管有关。虽然短时间的运动学是由形成的材料尖峰上游的零表面摩擦点和喷射的粒子在渐近分离线的方向，流体示踪剂的轨迹被引导吸引脊的有限时间的李雅普诺夫指数，一旦他们离开附近的壁。这种最初的流体上涌事件的壁签名，即所谓的 extit{尖峰点} [Serra，M.，Vetel，J.，Haller，G.，“流动分离中材料尖峰形成的精确理论”， extit{J. Fluid Mech.}，第845卷，2018年]，是根据平流物质线的曲率计算的，第一次，根据圆柱体和弯曲NACA 65（1）-412翼型的直接数值模拟获得的壁面法向速度的高阶数值导数计算。由于翼型轮廓的基于样条的边界参数化引起振荡，因此可以通过适当的滤波鲁棒地恢复主尖峰点。短期的运动学密切相关的边界层中的标度长度。
Kinematic aspects of flow separation in external aerodynamics are investigated in the Lagrangian frame. Specifically, the initial motion of upwelling fluid material from the wall is related to the long-term attracting manifolds in the flow field. While the short-time kinematics are governed by the formation of a material spike upstream of the zero-skin-friction point and ejection of particles in direction of the asymptotic separation line, the trajectories of the fluid tracers are guided by attracting ridges in the finite-time Lyapunov exponents once they leave the vicinity of the wall. The wall signature of this initial fluid upwelling event, the so-called extit{spiking point} [Serra, M., Vetel, J., Haller, G., "Exact theory of material spike formation in flow separation", extit{J. Fluid Mech.}, Vol. 845, 2018], is computed from the curvature of advected material lines and, for the first time, from high-order numerical derivatives of the wall-normal velocity obtained from direct numerical simulations of a circular cylinder and a cambered NACA 65(1)-412 airfoil. As the spline-based boundary parametrization of the airfoil profile induces oscillations, the principle spiking point can be recovered robustly through appropriate filtering. The short-term kinematics correlate strongly with the scaling lengths in the boundary layer.
影响因子：
3.7
作者：
Jones, L. E.;Sandberg, R. D.;Sandham, N. D.
通讯作者：
Sandham, N. D.