In this study, a numerical simulation using the vortex method was performed to understand the characteristics of vortex shedding from a cylindrical object with an asymmetric cross-sectional shape. The main flow velocity U was set to 0.0654 m/s. The cylindrical object used was a square cylinder with a side length of 12 mm. Numerical experiments were performed by changing the installation angle and vibration conditions of this square cylinder. The installation angle of the square cylinder ranged from 0 to 45 degrees in 7.5 degrees increments (α = 0°, 7.5°, 15°, 22.5°, 30°, 37.5°, 45°). The oscillation amplitude ratios 2a/d were 0.0, 0.33, and 0.67 for three types. The frequency ratios f/fK were 1.5 and 4.0 when the oscillation amplitude ratio 2a/d = 0.33, and 2.0 and 3.5 when the oscillation amplitude ratio 2a/d = 0.67. All calculations were performed up to the non-dimensional time T = 150 (1500 iterations). Numerical calculations showed that lock-in occurred even with cylindrical objects with asymmetric cross-sectional shapes, and flow patterns similar to those observed in experiments were obtained. By drawing Lissajous figures based on the drag and lift coefficients, the scale of the influence of oscillation could be understood. The larger the difference between the maximum and minimum drag coefficients, the more it can be seen that the influence of the distance between the separation points due to the installation position of the square cylinders.
Yoshifumi YOKOI (Wed,) studied this question.