Moving Surface Boundary-Layer Control on the Wake of Flow around a Square Cylinder

Te Song,Xin Liu,Feng Xu

doi:10.3390/app12031632

Abstract

In this paper, the entire process of the flow around a fixed square cylinder and the moving surface boundary-layer control (MSBC) at a low Reynolds number was numerically simulated. Two small rotating circular cylinders were located in each of the two rear corners of the square cylinder, respectively, to transfer momentum into the near wake behind the square cylinder. The rotations of the two circular cylinders were realized via dynamic mesh technology, when the two-dimensional incompressible Navier–Stokes equations for the flow around the square cylinder were solved. We analyzed the effects of different rotation directions, wind angles θ, and velocity ratios k (the ratio of the tangential velocity of the rotating cylinder to the incoming flow velocity) on the wake of flow around a square cylinder to evaluate the control effectiveness of the MSBC method. In the present work, the aerodynamic forces, the pressure distributions, and the wake patterns of the square cylinder are discussed in detail. The results show that the high suction areas near the surfaces of the rotating cylinders can delay or prevent the separation of the shear layer, reduce the wake width, achieve drag reduction, and eliminate the alternating vortex shedding. For a wind angle of 0°, the inward rotation of the small circular cylinders is the optimal arrangement to manipulate the wake vortex street behind the square cylinder, and k=2 is the optimal velocity ratio between the control effectiveness and external energy consumption.

Highlights

The development of complex structures has led to the construction of structures with reduced stiffness, such as large-span bridges and high-rise buildings, and wind-induced forces have become the main controlling factors in the design of these types of structures
From the perspective of vortex dynamics, Gao et al [7] presented a selective review of recent progress on the mechanism of vortex-induced vibrations (VIV) occurred in long-span bridges and proposed several passive and active flow control methods to manipulate the surrounding flow patterns around the girder
The results revealed the significant effect of the moving surface boundary-layer control (MSBC), which changes the height of the boundary-layer separation and reattachment, affecting the fluid dynamical parameters

Summary

Introduction

The development of complex structures has led to the construction of structures with reduced stiffness, such as large-span bridges and high-rise buildings, and wind-induced forces have become the main controlling factors in the design of these types of structures. On the basis of the existing research methods, Munshi et al [31] conducted numerical simulations and analyzed the drag of two-dimensional flat plates and rectangular prisms with MSBC Both the numerical and the flow visualization results showed narrowing of the wake as the momentum injection increased, leading to eventual suppression of the vortex shedding. Kubo et al [33] conducted extensive wind tunnel experiments to study the role of the MSBC in the suppression of torsional flutter of a shallow rectangular prism, which was one of the typical fundamental configurations of bridge deck sections The results that they obtained from measurements of surface pressure distributions and aeroelastic vibration responses showed that the proposed boundary-layer control method through momentum injection was effective in suppressing the torsional flutter of a shallow rectangular prism. Where ui is the velocity components in the i direction, ρ is the fluid density, μ is the kinematic viscosity coefficient, and p is the pressure in the flow field

Numerical Model and Solution Setting

Results and Discussion

Aerodynamic Statistics and Frequency Characteristics

Aerodynamic Time History Analysis

Conclusions