Flow past an inclined Square Cylinder

초록

Numerical investigation has been carried out for laminar flow (Re<150) past an inclined square cylinder in cross freestream. The motivation stems from characterization of flow-induced forces on a sharpedged cylindrical object immersed in cross flow with an angle of attack. From the viewpoint of wind hazards, this study would be the first step towards understanding flow-induced forces on cylindrical structures under a strong gust of wind. In this flow configuration, there exist two kinds of critical Reynolds numbers in laminar regime; flow separation occurs at a lower critical Reynolds number (Rec1) and flow becomes unsteady at an upper critical Reynolds number (Rec2). It is seen that the values of Rec1 and Rec2 change depending on the inclination angle (theta) of the cylinder. In particular, Rec2 decreases as theta increases, being consistent with the instability theory based on Stuart-Landau equation in literature. Furthermore, the cylinder vertices at which flow separation takes place are determined by theta. Consequently, key flow characteristics such as drag/lift forces on the cylinder and vortex-shedding frequency could drastically alter depending on theta. We propose contour diagrams of mean drag/lift coefficients, Strouhal number (St) of vortex shedding, and rms of lift coefficient fluctuationon Re&#8211;theta plane.