Three-dimensional instability in the wake of the square cylinders in side-by-side arrangements

초록

Three-dimensional linear instability in the flow past two square cylinders in side-by-side arrangements are numerically studied by using a Floquet stability analysis. The distance between the neighboring faces of the two cylinders (G) is the key parameter which affects the secondary instability under consideration. In this paper, we propose a stability diagram which shows the critical Reynolds number for the three-dimensional instability for each G considered, and illustrates the spanwise wave numbers of the most unstable (or least stable) wave for some selected Reynolds numbers. Vortical structures of the Floquet mode are also discussed.