Investigation of a drag reduction on a circular cylinder in rotary oscillation (Q2710581)

The authors study the influence of oscillatory rotation of a cylinder on the drag exerted by a viscous flow on this cylinder. It is known from the literature that at \(\text{Re}= 15000\) the drag reduces till 80 percents when the cylinder oscillates compared to the fix cylinder. Here the authors confirm this result through a theoretical analysis of the motion, considering the influence of Reynolds number, boundary layer on the cylinder surface, and the vortex dynamics in the wake. They use the vortex method, representing the vorticity as a collection of Gaussian distributions. Two different approaches are employed. The first approach considers Laplacian as an integral operator, and treats the particle core sizes as uniform in time and space. The second approach considers the core expansion. The results are presented in many plots, diagrams, tables and photos, some of them in colours.