Motion of Vortices of an Abruptly-Stopped Falling Circular Cylinder ─ Reynolds Number 500 to 600

• Main Authors: Yu-hsuan Lin, 林昱瑄
• Other Authors: Shian-wei Jeng
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/73n9u3

碩士 === 逢甲大學 === 水利工程與資源保育學系 === 104 === Flow Passed a cylindrical structure is a classical problem of Fluid Mechanics. This study investigated the vortex shedding behind a circular cylinder. A numerical model was used to solve Navier-Stokes equations for the flow field of a free-falling circular cylinder abruptly-stopped at five different times and at three different Reynolds numbers, higher then laminar flow. According to the transverse amplitude of the cylinder, the historical motion of the cylinder could be divided into three stage, i.e. the initial, the transitional, and the mature stages. The five abruptly-stopped times were all in the transitional stage. This study found that the vortices moved forward and produced a huge force on the cylinder right after the abrupt stop. An induced vortex was generated attached to the cylinder when a vortex was passing by the cylinder. The vortices moved faster and might circle back to the downstream side as the Reynolds number increased. More types of vortex were observed at higher Reynolds number, such as vortex split into two when struck the cylinder, a pair of vortices were induced near the cylinder, the center of a vortex was moving along the surface of the cylinder, and a new vortex was generated in the flow field due to the interaction of surrounding zones of high and low pressures.