Numerical Investigation of Vortex-Induced Vibration of a Circular Cylinder with Control Rods and Its Multi-Objective Optimization

The flow past a 2D circular cylinder with control rods is numerically simulated in the present paper. The suppression effects of the control rods on the vortex-induced vibration (VIV) characteristics of the cylinder are investigated using the overlapping grid method and user defined function. By setting the cylinder’s vibration amplitude and drag force coefficient as the expected objective function, a multi-objective optimization is carried out to enhance the suppression performance at different reduced velocities, for which the rod-to-cylinder diameter ratio, gap ratio, incidence angle and reduced velocity are used as design variables. The regression expressions, which are obtained by Box–Behnken design (BBD), are employed in nondominated sorting genetic algorithm II (NSGA-II) to minimize the objectives. It is found that both the optimized vibration amplitude and drag force coefficient exhibit a monotonically decreasing linear trend with the reduced velocity, and as the reduced velocity decreases, the range of the optimized points gradually decreases. Subsequently, the optimized cases are verified by CFD simulations and compared with the original cases. For the samples at the reduced velocity of 4, 5, and 6, the vibration amplitude after optimization decreases by 15.1%, 24.8%, and 21.6%, respectively.