Flow past a Square Cylinder at Small Incidence Angles: Characteristics of Leading Three-Dimensional Instabilities

Abstract – A detailed linear stability analysis is conducted on the flow past a square cylinder inclined at an angle to an oncoming flow. At shallow incidence angles two distinct three-dimensional instabilities present as the first-occurring modes in the wakes with increasing Reynolds number. At incidence angles below 10.5 degrees, the flow becomes three-dimensional via the classical Mode A instability seen behind circular cylinders. However, at higher incidence angles the wake experiences a period-doubling bifurcation as a subharmonic instability develops in place of the Mode A wake. Index Terms – Square cylinder, three-dimensional, wake instabilities. I