A NEW GENERAL 3DOF QUASI-STEADY AERODYNAMIC INSTABILITY MODEL

Abstract This paper proposes a three degrees of freedom (3DOF) quasi-steady aerodynamic model and instability criterion for a bluff body which is uniform along the length axis. The model and criterion has been developed in the frame of investigating aerodynamic instability of cables due to ice accretions but can generally be applied for aerodynamic instability prediction for prismatic bluff bodies. The 3DOF, which make up the movement of the model, are the displacements in the XY-plane and the rotation around the bluff body’s rotational axis. The proposed model incorporates inertia coupling between the three degrees of freedom and is capable of estimating the onset of aerodynamic instability for changes in drag, lift and moment, which is a function of wind angle of attack in relation to the x-axis of the bluff body, Reynolds number and wind angle in relation to the length axis of the bluff body. Further more the model is capable of predicting an estimate for the structural damping needed for avoiding instability of the bluff body. = displacement direction. = displacement direction. = rotation direction. = angle offset for mass centre. = mass centre offset. = structural stiffness in x direction. = structural stiffness in y direction. = structural damping in θ direction. = structural damping in x direction. = structural damping in y direction. = structural stiffness in θ direction. (XG,YG) = mass centre.