TY - JOUR
T1 - Two-degree-of-freedom flow-induced vibration of two rigidly coupled tandem cylinders of unequal diameters
AU - Zhu, Hongjun
AU - Tan, Xiaonian
AU - Gao, Yun
AU - Zhou, Tongming
AU - Liu, Wenli
PY - 2020/11/15
Y1 - 2020/11/15
N2 - This paper reports the results of a numerical investigation in to the two-degree-of-freedom (2-DOF) flow-induced vibration (FIV) of two rigidly coupled tandem cylinders of unequal diameters at a low Reynolds number of 150. Three typical center-to-center spacing ratios of L/D = 1.5, 3.75 and 6.0 are examined in the reduced velocity range of Ur = 3–12. For the rigidly coupled tandem cylinders, three typical flow regimes are observed including extended-body regime, reattachment regime and co-shedding regime. The occurrence of flow regime transition is associated with the spacing ratio (L/D) and the reduced velocity (Ur). Accordingly, the flow regime is illustrated in the L/D–Ur diagram. The hydrodynamic forces of both cylinders are significantly reduced in the extended-body regime, resulting in an excellent suppression of FIV. In contrast, both the hydrodynamic forces and response amplitudes are augmented at L/D = 3.75 and L/D = 6.0 as compared with those at L/D = 1.5. Furthermore, the cross-flow amplitude is even larger than that of an isolated cylinder at Ur ≥ 8 with the associated response frequency deviating from the Strouhal curve. The transition of flow regime affects the phase angle of the upstream cylinder. As a greater lift force exerted on the downstream cylinder and the corresponding phase difference with the vibration displacement is either close to 0° or about 180°, the downstream cylinder dominates the movement of the rigidly coupled cylinders in the majority of an oscillating cycle.
AB - This paper reports the results of a numerical investigation in to the two-degree-of-freedom (2-DOF) flow-induced vibration (FIV) of two rigidly coupled tandem cylinders of unequal diameters at a low Reynolds number of 150. Three typical center-to-center spacing ratios of L/D = 1.5, 3.75 and 6.0 are examined in the reduced velocity range of Ur = 3–12. For the rigidly coupled tandem cylinders, three typical flow regimes are observed including extended-body regime, reattachment regime and co-shedding regime. The occurrence of flow regime transition is associated with the spacing ratio (L/D) and the reduced velocity (Ur). Accordingly, the flow regime is illustrated in the L/D–Ur diagram. The hydrodynamic forces of both cylinders are significantly reduced in the extended-body regime, resulting in an excellent suppression of FIV. In contrast, both the hydrodynamic forces and response amplitudes are augmented at L/D = 3.75 and L/D = 6.0 as compared with those at L/D = 1.5. Furthermore, the cross-flow amplitude is even larger than that of an isolated cylinder at Ur ≥ 8 with the associated response frequency deviating from the Strouhal curve. The transition of flow regime affects the phase angle of the upstream cylinder. As a greater lift force exerted on the downstream cylinder and the corresponding phase difference with the vibration displacement is either close to 0° or about 180°, the downstream cylinder dominates the movement of the rigidly coupled cylinders in the majority of an oscillating cycle.
KW - Flow regime
KW - Flow-induced vibration
KW - Gap ratio
KW - Rigidly coupling vibration
KW - Tandem cylinders
UR - http://www.scopus.com/inward/record.url?scp=85092004939&partnerID=8YFLogxK
U2 - 10.1016/j.oceaneng.2020.108142
DO - 10.1016/j.oceaneng.2020.108142
M3 - Article
AN - SCOPUS:85092004939
VL - 216
JO - Ocean Engineering
JF - Ocean Engineering
SN - 0029-8018
M1 - 108142
ER -