Shear Layer Instability of Flow Around a Circular Cylinder Based on Large Eddy Simulation

Abstract

The flow around a cylinder is a common research object of fluid mechanics. As the Reynolds number (Re) increases, the Kelvin-Helmholtz instability of the shear layer will occur in the wake behind the cylinder. Using the large eddy simulation method to investigate the problem numerically in a medium range of Re (Re=2000, 3900, 5000), the refined flow field behind the cylinder can be obtained, and an in-depth study of the instability of the shear layer can be conducted. To get the characteristic frequency of the shear layer instability, two methods, i.e., the traditional analysis of monitoring points and the dynamic mode decomposition method on the local flow field, are used. The results show that the frequencies obtained by the two methods are basically the same. However, compared with the traditional method, the dynamic mode decomposition method can overcome the random error caused by the artificial selection of monitoring points, and can give the characteristic frequency of shear layer instability more conveniently. In addition, it can further analyze the influence of different Re values on the instability characteristics of the shear layer based on different flow field modes.

Keywords

• flow around circular cylinder
• kelvin-helmholtz instability
• large eddy simulation
• dynamic mode decomposition