Vortex induced vibrations of a cylinder in a narrow channel.*

The two-dimensional flow around cylinder tightly confined in a channel was numerically studied. Attached to a linear spring and subject to hydrodynamic forces and torques, the circular cylinder is free to move in both the cross-flow and in-line directions as well as to rotate about its axis. Low mass ratios and moderate Reynolds numbers were considered. The system behavior shares some features with the well studied unconfined case. Despite the similarities, the close presence of the channel walls has an impact in the cylinder's behavior, specially within the lock-in region. We managed to find a modified Strouhal parameter that collapses the range of excitation. Results offer a portrait of the motion, forces, and flow around the cylinder under such constrains.