Prediction of stall-induced vibrations using two-dimensional computational fluid dynamics

摘要

Aeroelastic stability of an airfoil is investigated using a coupling of a simple 3-DOF structural dynamics model to a 2D CFD code. ^The airfoil under consideration is a wind turbine airfoil, which during certain operational conditions exhibits stall-induced edge-wise vibrations. ^Results are presented as time series and damping characteristics for different wind speeds and for different direction of the principal bending axis. ^Results indicate that for a certain wind speed range, corresponding to a range of angle of attack, negative aerodynamic damping, causing unstable vibrations, occurs as a function of the direction of vibration. ^Results using CFD are compared with similar aeroelastic analysis using simple quasi-steady aerodynamics. ^When the flow is attached and the dynamic effects are small, good agreement is obtained. ^Damped oscillations are predicted at most directions of vibration. ^But when the airfoil vibrates in the edge-wise direction, negative aerodynamic damping is present, and oscillations will grow causing unstable motion. ^At higher angles of attack, where unsteady separation is taking place, dynamic effects are present. ^These dynamic effects influence the aeroelastic stability to a great extent, and the stability characteristics are different using the two aerodynamic models. ^(Author)