任意拉格朗日-欧拉描述的薄平板大幅扭转振动气动特性研究

Investigation on aerodynamics of thin plate undergoing large-amplitude torsional oscillation with Arbitrary-Lagrangian-Eulerian descriptions

采用任意拉格朗日-欧拉(Arbitrary La grangian-Eulerian,ALE)描述法,推导了二维流变区域不可压流体流动的控制方程。基于刚性断面边界特点,简化得到了薄平板强迫振动绕流场控制方程,采用有限差分法开展了薄平板大幅强迫扭转振动的CFD模拟。研究发现,薄平板小幅扭转振动气动力呈线性特性,但大幅扭转振动气动力非线性显著,且气动力非线性随来流折算风速的增大而变得显著。从一个周期内气流做功来看,虽然大幅扭转振动时薄平板转动轴到后缘是耗散气流能量的气动稳定区,但当折算风速较高后,上游侧的半个薄平板表面变为气动不稳定区,此时气流对整个薄平板所作总功由负变为正,薄平板将从气流中吸收能量。研究认为,当折算风速较高时,大幅扭转振动的薄平板将进入气动不稳定状态。

Based on the Arbitrary Lagrangian-Eulerian descriptions,the governing equations of incompressible fluid flow in two-dimensional deformed region are derived.Due to the boundary features of a rigid section,the governing equations of forced vibration flow around thin plate are simplified.The finite difference method is used to carry out the CFD simulations of the large-amplitude forced torsional vibration of a thin plate.The research shows that the aerodynamics of the thin plate with small-amplitude torsional vibration are linear.However,when the thin plate is forced to oscillate with large amplitude,aerodynamically significant non-linearity will present.Considering the total work acting on the moving thin plate by the airflow in one cycle,the downstream half plate is defined as stabilizing zone characterized by energy dissipation when large-amplitude torsional oscillation occurs.It is noted that when the reduced wind speed is high,the upstream half plate becomes the aerodynamic instability zone,with the total work being positive,which means the thin plate absorbs the energy from the flow.It is concluded that when the reduced wind speed is high,the aerodynamic instability occurs if the thin plate is forced to perform large-amplitude oscillations.