Non-across-wind galloping of a square-section cylinder

This paper presents new insights on the galloping instability phenomenon of square-section prisms. The role of the orientation of the structural axes on the galloping response is studied through wind tunnel tests and quasi-steady theory. A new series of dynamic wind tunnel tests on a square section model were conducted to evaluate non-across-wind galloping vibrations, as well as conventional across-wind galloping. The results are then compared with theoretical predictions to evaluate the reliability of quasi-steady theory in assessing the galloping phenomenon. It is found that for a given angle of attack, the structure has different aeroelastic behaviour for different orientations of the principal axis. At an angle of attack close to the critical angle of attack of square prisms, the quasi-steady theory well predicts the critical wind velocity for the onset of non-across-wind galloping but it is not successful for the case of across-wind galloping.