A GENERALIZED CONSERVATION OF CIRCULATION MODEL IN VORTICITY DYNAMICS AND ITS APPLICATION TO VORTEX CALCULATION METHOD

In nature, vortices and vortex motions are the principal phenomena during fluid flow. Except for inviscid potential flow where vorticity is zero, the viscous effects of fluid on solid can be completely represented by vorticity and vortex motions in the fluid. In the present thesis, the generation and decay of vorticity in fluid are analyzed in details under the condition that the fluid is incompressible and homogeneous. A Generalized Conservation of Circulation (GCC) concept in viscous fluid flow is then established. It can fully represent the generation, evolution and decay of vorticity as well as vortex motions in viscous fluid. Based on the GCC concept, a new numerical method (GCCM) was proposed and developed to solve the Navier-Stokes equations for two-dimensional, incompressible, homogeneous and viscous fluid flow. The GCCM has the advantages of being simple and highly computational efficient. As a verification of GCCM, an impulsively started flow around a circular cylinder is simulated. The numerical results obtained showed that the pressure distribution on the cylinder and wake structures compared well with experimental results and numerical solutions by other investigators. The GCCM is then extended to study the added mass of an accelerating circular cylinder in fluid, which is of practical importance. However at present, there is no satisfactory mathematical description of the added mass due to the lack of an exact physical definition. In this thesis, the definitions of added mass force and corresponding added mass coefficient are proposed and presented. The GCCM is then used to simulate two types of accelerating fluid motions. One is due to the uniformly accelerated motion of a circular cylinder. The other is due to a mean plus oscillatory flow around a cylinder. Detailed wake structures and dynamic features were obtained. By application of the present definition of the added mass, the added mass force and instantaneous added mass coefficient were obtained.

Author dc:creator

• PAN LUN SHENG

• Generalized Conservation Of Circulation
• Diffusion Velocity
• Vortex Method and Added Mass