Numerical study of flow over periodically deforming circular cylinder

Two-dimensional incompressible fluid flows over a periodically deforming circular cylinder are simulated with lattice Boltzmann method for Reynolds number 200. The periodic deformation is controlled by the ratios of deforming amplitude relative to the cylindrical radius and deforming frequency relative to natural vortex shedding frequency. The flow features are mainly decided by the periodic deformation. So three deforming amplitude ratios (0.05, 0.075, 0.1) are considered and deforming frequency ratios range from 0.75 to 2.0. The vortex structures are divided into three categories and two type transitional structures are observed. The correlation between vortex shedding patterns and periodic deformation is analyzed. In addition, the impact of periodic deformation to drag coefficient is studied. Numerical results show that special deformation can reduce the drag.