Effects of Degrees of Motion Freedom on Free-Fall of A Sphere in Fluid

• Published in: China ocean engineering Vol. 32; no. 5; pp. 605 - 613
• Main Authors: Liu, Lei, Yang, Jian-min, Lyu, Hai-ning, Tian, Xin-liang, Peng, Tao
• Format: Journal Article
• Language: English
• Published: Nanjing Chinese Ocean Engineering Society 01.10.2018; Springer Nature B.V; Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration (CISSE), Shanghai 200240, China; State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
• Subjects: Coastal Sciences; Computational fluid dynamics; Computer simulation; Engineering; Fluid- and Aerodynamics; Marine & Freshwater Sciences; Movement; Numerical and Computational Physics; Oceanography; Offshore Engineering; Oscillations; Rotating spheres; Rotation; Simulation; Strouhal number; Vertical oscillations; Vortex shedding; degree of motion freedom; direct numerical simulation; free-fall
• ISSN: 0890-5487; 2191-8945
• DOI: 10.1007/s13344-018-0062-5

Free-fall of a sphere in fluid is investigated at a Galileo number of 204 by direct numerical simulations (DNS). We mainly focus on the effects of different degrees-of-freedom (DOFs) of the sphere motion during free-fall. The characteristics of free-fall are compared with those of flow past a fixed sphere. Additional numerical tests are conducted with constraints placed on the translational or rotational DOFs of the sphere motion to analyze different DOFs of sphere motion. The transverse motion contributes significantly to the characteristics of free-fall; it results in the retardation of the vortex shedding, leading to the decrease of the Strouhal number. In addition, the transversal sphere motion exhibits the tendency to promote the sphere rotation. On the contrary, the effects of the sphere rotation and vertical oscillations during free-fall are negligible.