밀도비가 낮은 자유 상승 실린더의 궤적 및 유동장 특성에 관한 실험적 연구

Abstract

The motion and wake structure of a freely rising two-dimensional cylinder with a density ratio (the ratio of the cylinder density to the fluid density) of 0.195 were investigated experimentally in a quiescent fluid. The cylinder exhibited a periodic zigzag trajectory characterized by repeated cusp-like points where the instantaneous velocity reached a local minimum. Flow field measurements revealed that, during deceleration, the shear layer developed along the rear surface and remained attached to the cylinder, resulting in an increase in the vortex force. After passing each cusp, the shear layer underwent stretching, splitting, and shedding, which caused the formation and detachment of roll-up vortices and led to a decrease in the vortex force. The alternation between acceleration and deceleration phases was closely associated with changes in the wake structure and unsteady hydrodynamic forces acting on the cylinder.