Piccardo, G., Carassale, L. & Freda, A. (2011). J. Wind Engrg. Ind. Aerodyn., 99, 748-756.

Abstract
This paper concerns the study of galloping critical conditions on square cylinders with an arbitrary
attitude in the wind flow. It is based on a consistent theoretical model of wind actions, which permits
the analysis of a generic-shaped cross-section. A generalized definition of the aerodynamic damping
matrix as function of both the angle of incidence and the angle of skew is proposed. The availability of
specific experimental data allows a sound definition of aerodynamic actions. The analysis of critical
conditions can be performed in closed form in the plane of the aerodynamic damping matrix invariants.
Preliminary results obtained in smooth-flow conditions point out that yaw effects might influence
critical conditions from a quantitative point of view, but do not destroy the instability domain obtained
in the classical cross-flow conditions.

http://www.sciencedirect.com/science/article/pii/S0167610511000547