Large eddy simulation of flow past an inclined finite cylinder. (15th August 2022)

• Record Type: Journal Article
• Authors: Zhou, Bo; Wang, Jie; Jin, Guangqiu; Zhou, Ying; Wang, Xikun; Gho, Wie Min
• Is Part Of: Ocean engineering. Volume 258(2022)
• Publication Date: 2022-08-15
• Subjects: Inclined cylinder -- Finite cylinder -- Large eddy simulation -- Independent principle -- Corrugated shear layer -- Wake mode; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2022.111504
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: This paper presents the numerical analysis of the hydrodynamic characteristics and wake structures of an inclined finite cylinder with large eddy simulation (LES). The Reynolds number (Re) is fixed at 3, 900 and the inclination angle θ is varied over the range 0 ° ≤ θ ≤ 45 ° with an increment Δ θ = 7 . 5 ° . The numerical method applied in the present study is first validated for the case of an upright finite cylinder ( θ = 0 ° ), which shows reasonably good agreement with the literature. According to the results, the hydrodynamic force coefficients and Strouhal number of the inclined cylinder do not comply with the independent principle (IP), despite they remain constant in the range 15 ° ≤ θ ≤ 30 ° . In this range, the magnitude of these parameters is considerably smaller than that of the upright case, which is favorable to the structural stability. The wake structures in the lee of the cylinder are visualized quantitatively, which are shown to be dependent of the inclination angle. Intermittent switching in vortex mode from parallel to the cylinder axis (Mode I) to re-orientation towards downstream (Mode II) at small inclination angle, and from the vortex diminished zone (Mode VD) to that with vortex tubes (VDT) at large inclination angle, are captured. Moreover, the breakup mechanism of the corrugated shear layer (CSL) can be elaborated in two forms, one associated with strong downward flow and the other with helical upward flow in the wake of the inclined finite cylinder. Highlights: A sharp reduction in force coefficients and Strouhal number is achieved with inclined angle in the range 15 ° ≤ θ ≤ 30 ° . The independent principle is invalid under the specified aspect ratio and boundary condition. Mode switch is observed at a small ( θ = 7 . 5 ° ) and a large ( θ = 37 . 5 ° ) cylinder inclination angle. Break mechanism of the corrugated shear layer is summarized.