Numerical Study of a Rotationally Oscillating Cylinder at Low Reynolds Numbers

A numerical study on the rotary oscillating cylinder subjected to a free stream has been conducted. Two-dimensional direct numerical simulations have been performed using the spectral/hp element method implemented in the Nektar++ source code. The numerical simulations have been conducted at low values of the Reynolds number of 200. This paper focuses on three characteristics of flow: the hydrodynamic forces exerted on the cylinder, the wake patterns behind the cylinder, and the lock on phenomenon. The numerical simulations on the rotary oscillating cylinder have been performed over the extensive range of non-dimensional forcing frequency, from 0.2 to 5 and two different values of the cylinder oscillation amplitude equal to 2π/3 and 5π/3. It was observed that increase in the oscillation amplitude greatly influences the wake pattern and the lock on phenomenon. It was found that a more than double increase in the cylinder oscillation amplitude produces a significant increase in the maximum mean drag and the fluctuating lift. The influence of the forcing frequency and oscillation amplitude on the drag and lift has been quantified. Furthermore, the effect of the forcing frequency and oscillation amplitude on the cylinder wake has been thoroughly analyzed.