ASYMMETRIC DISTURBANCE EFFECT ON BLUFF BODY FLOW USING LARGE EDDY SIMULATION*

The present study performed the large eddy simulation for the flow around the asymmetric wavy (ASW) cylinders with different wavelengths at the Reynolds number of 3000. The ASW disturbance is introduced to achieve the drag reduction and the lift fluctuation as the passive control flow. Moreover, the flows around the smooth cylinder and the symmetric wavy (SW) cylinder are also considered for the purpose of the comparison. The ASW cylinders revealed about the same variations of the drag and the lift fluctuation according to the wavelength with the SW cylinder, regardless of the asymmetric degree. In the long wavelength regime, the drag and the lift fluctuation become small with increasing the asymmetric degree. Therefore, the asymmetric disturbance provided the addition reduction of the drag and the suppression of the lift fluctuation in comparison with the SW cylinder with the optimal wavelength in the long wavelength range. When the asymmetric degree increases, the flow near the wake in the short wavelength part is more inclined to the long wavelength part, which contributes the vortex dislocation. However, this effect gives different roles to the drag and lift fluctuation.