TRANSIENT CFD ANALYSIS OF FLOW OVER A CIRCULAR CYLINDER

Resumo

The flow of air over a circular cylinder can be observed in many civil engineering problems.
Tall buildings, towers and silos can be subject to strong winds that can impact the structure local or
global stability. The flow over a cylindrical structure is a dynamic problem with transient response
characterized by vortex shedding. If the Reynolds number is sufficiently high, an alternate vortex
shedding pattern is formed, known as von Karman vortex street. In this scenario, the flow applies
dynamic drag and lift forces on the structure. This paper presents a methodology to simulate the fluid
flow over a circular cylinder and compute the drag and lift coefficients using Computational Fluid
Dynamics (CFD). A two-dimensional cross-section of a structure is modelled in ANSYS Fluent
applying the proper boundary conditions. The pressure fields are computed from the simulations and
numerical integration is used to obtain the drag and lift coefficients. From the simulations, the
streamlines, and pressure fields can also be obtained and plotted. Geometry, mesh and time step size
independence studies are conducted to ensure convergence. The results are compared to numerical data
found in the literature.