Very Large-Eddy Simulations of the Flow Past an Oscillating Cylinder at a Subcritical Reynolds Number

Xiaomin Liu,Zhongying Xiong

doi:10.3390/app10051870

Abstract

This work focuses on flow past a circular cylinder at a subcritical Reynolds number. Although this classical study has been a concern for many years, it is still a challenging task due to the complexity of flow characteristics. In this paper, a high-efficiency very large-eddy simulation method is adopted and verified in order to handle the oscillating boundary. A series of numerical simulations are conducted to investigate the transient flow around the oscillating cylinder. The results show that the vortex shedding mode varies with an increase in the excitation amplitude and the excitation frequency. Vortex shedding is a lasting process under the condition of a low excitation amplitude that leads to irregular fluctuations of the lift and drag coefficients. For a vortex shedding mode that exhibits a strong vortex pair and a weak vortex pair or a weak single vortex, the temporal evolution of the lift coefficient of the oscillating cylinder shows irregular ”jumping” at a specific time per cycle corresponding to the shedding of the strong vortex pair. The vortex shedding mode and the frequency and time of the vortex shedding co-determine the temporal evolutions of the lift and drag coefficient.

Highlights

As the exploitation of offshore oil and gas expands into deep water and regions with strong ocean currents, the significance of vortex-induced vibration (VIV) has attracted the attention of engineers.some grave engineering problems are due mainly to VIV, similar to fatigue failure on submarine pipelines
The results showed that the velocity fluctuations and the Reynolds stress from the particle image velocimetry (PIV) results at Reynolds numbers (Re) = 4000 agreed well with the simulation studies at Re = 3900 using the direct numerical simulations (DNSs) method, illustrating that the fluid mechanics between and Dong et al found that the Strouhal number (St) number at Re = 3900 was within the range 0.2–0.22 [16,23]
The temporal evolutions of the lift and drag coefficients, and the frequency and mode of the vortex shedding is discussed in detail, respectively

Summary

Introduction

As the exploitation of offshore oil and gas expands into deep water and regions with strong ocean currents, the significance of vortex-induced vibration (VIV) has attracted the attention of engineers.some grave engineering problems are due mainly to VIV, similar to fatigue failure on submarine pipelines. The prediction of the hydrodynamic forces on an oscillating cylinder is still paramount to the design of the structures. Numerical and experimental studies on the flow around a cylinder oscillating in the fluid have always been the focus of related studies for many years. It is still a significant primary task because of the complexity of flow characteristics. One of the common methods to determine the VIV phenomenon is a circular cylinder that is forced to oscillate with a preset motion including an excitation amplitude (A) and a frequency (fe ) approximating VIV. Given the richness of the research on VIV, only a forced oscillating cylinder problem is included in the following discussion

Methods

Results

Conclusion