Three-Dimensional Flow Analysis around a Circular Cylinder. 2nd Report. In the Case of a Forced Oscillating Cylinder.

Abstract

In uniform flow, periodic Karman vortex shedding is observed in the wake of a stationary circular cylinder. When the cylinder oscillates transversely at a frequency close to the Karman vortex frequency, the vortex shedding is synchronized with the vibration of the cylinder. This is well known as the lock-in phenomenon in wind engineering. In this study, incompressible flow past a forced oscillating circular cylinder at Reynolds number 1100 is computed by finite-difference method using the moving grid technique, and the lock-in phenomenon is simulated by two- and three-dimensional calculation. In the results of the three-dimensional calculation, the lock-in region and drastic change of the phase angle between lift force and cylinder displacement show good agreement with experimental values. Furthermore, it is qualitatively shown that the correlation length of vortex shedding increases in the lock-in region, However, in the case of the two-dimensional calculation, lock-in phenomenon cannot be simulated with sufficient accuracy.