Three-dimensional instability of an oscillating viscous flow past a circular cylinder

A systematically numerical study of the sinusoidally oscillating viscous flow around a circular cylinder was performed to investigate vortical instability by solving the three_dimensional incompressible Navier_Stokes equations. The transition from two_ to three_dimensional flow structures along the axial direction due to the vortical instability appears,and the three_dimensional structures lie alternatively on the two sides of the cylinder. Numerical study has been taken for the Keulegan_Carpenter(KC) numbers from 1 to 3.2 and frequency parameters from 100 to 600. The force behaviors are also studied by solving the Morison equation. Calculated results agree well with experimental data and theoretical prediction.