Abstract:A numerical simulation study is conducted to investigate the effect of the mass ratio (m* = 3, 10, and 20) on vortex-induced vibration (VIV) of two tandem square cylinders at Re = 150. In this study, we mainly focus on the mass ratio effect on the vibration response, force characteristics, wake mode pattern, and fluid–structure-interaction (FSI) mechanism. The results show that mass ratio plays an important role in the VIV response of the two cylinders. With increasing reduced velocity, both the upstream cylin… Show more
“…It is worth highlighting that Gu et al. (2023) also studied the effect of on 2-DOF vibrations of tandem square cylinders at and observed qualitatively similar and variation. In their study, the peaks of and are also close to the peaks and of the present study, even though the cross-sections are significantly different.…”
Section: Characteristics Of Cylinder Vibrationsmentioning
We numerically study the transverse flow-induced vibration (FIV) of elastically coupled tandem cylinders at Reynolds number
$100$
, using an in-house immersed boundary method-based solver in two-dimensional coordinates. While several previous studies considered tandem cylinders coupled through flow between them, a hitherto unexplored elastic coupling with fluid flow between them significantly influences FIV. We consider a wide range of gap ratio, reduced velocity, an equal mass ratio of both cylinders and zero damping. A systematic comparison between the classic elastically mounted tandem cylinders and elastically coupled cylinders is presented. The latter configuration exhibits two vibration modes, in-phase and out-of-phase, with corresponding natural frequencies approaching the Strouhal frequency of the system. We quantify variation of the following output variables with reduced velocity and gap ratios: cylinders’ displacement; fluid forces; amplitude spectral density of displacement and force signals; phase characteristics; energy harvesting potential; and discuss the wake characteristics using flow separation, pressure distribution, gap flow quantification, and dynamic mode decomposition characterization. The FIV response is classified into several regimes: initial desynchronization with and without gap vortices; final desynchronization; mixed mode; initial branch; lock-in; upper and lower branch; wake-induced vibration; galloping. We draw upon similarities of computed FIV characteristics with those of an isolated cylinder, in which the lower branch exhibits larger a amplitude than the upper branch. The elastically coupled cylinders show a galloping response similar to an isolated D-section cylinder. By invoking the elastic coupling, we demonstrate FIV suppression and augmentation for in-phase and out-of-phase systems. Our calculations show larger energy harvesting potential at reduced cost for elastically coupled cylinders.
“…It is worth highlighting that Gu et al. (2023) also studied the effect of on 2-DOF vibrations of tandem square cylinders at and observed qualitatively similar and variation. In their study, the peaks of and are also close to the peaks and of the present study, even though the cross-sections are significantly different.…”
Section: Characteristics Of Cylinder Vibrationsmentioning
We numerically study the transverse flow-induced vibration (FIV) of elastically coupled tandem cylinders at Reynolds number
$100$
, using an in-house immersed boundary method-based solver in two-dimensional coordinates. While several previous studies considered tandem cylinders coupled through flow between them, a hitherto unexplored elastic coupling with fluid flow between them significantly influences FIV. We consider a wide range of gap ratio, reduced velocity, an equal mass ratio of both cylinders and zero damping. A systematic comparison between the classic elastically mounted tandem cylinders and elastically coupled cylinders is presented. The latter configuration exhibits two vibration modes, in-phase and out-of-phase, with corresponding natural frequencies approaching the Strouhal frequency of the system. We quantify variation of the following output variables with reduced velocity and gap ratios: cylinders’ displacement; fluid forces; amplitude spectral density of displacement and force signals; phase characteristics; energy harvesting potential; and discuss the wake characteristics using flow separation, pressure distribution, gap flow quantification, and dynamic mode decomposition characterization. The FIV response is classified into several regimes: initial desynchronization with and without gap vortices; final desynchronization; mixed mode; initial branch; lock-in; upper and lower branch; wake-induced vibration; galloping. We draw upon similarities of computed FIV characteristics with those of an isolated cylinder, in which the lower branch exhibits larger a amplitude than the upper branch. The elastically coupled cylinders show a galloping response similar to an isolated D-section cylinder. By invoking the elastic coupling, we demonstrate FIV suppression and augmentation for in-phase and out-of-phase systems. Our calculations show larger energy harvesting potential at reduced cost for elastically coupled cylinders.
“…(2016) and Qiu et al . (2021 b ), as shown in figure 3. Figure 3.Comparison of the VIV results of a square cylinder with m * = 3 and ξ = 0 at Re = 100.…”
Section: Numerical Methods For Cfd Simulationmentioning
confidence: 96%
“…The present DNS model is benchmarked first against available results reported in the literature for a single square cylinder undergoing two-degree-of-freedom VIV with m* = 3 and ξ = 0 at Re = 100 and U r = 3-16. The calculated results versus U r , involving the cross-flow amplitude and frequency, are compared with those from Zhao, Cheng & Zhou (2013), Jaiman et al (2016) and Qiu et al (2021b), as shown in figure 3.…”
Section: Numerical Validationmentioning
confidence: 99%
“…Qiu et al (2021a) 150 2.0-6.0 3.0-12.0 10.0 Num. Qiu et al (2021b) 150 4.0 1.0-12.0 3.0, 10.0, 20.0 Num.…”
The flow-induced vibrations (FIVs) of two identical tandem square cylinders with mass ratio m* = 3.5 at Reynolds number Re = 150 are investigated through two-dimensional direct numerical simulation (DNS) and linear stability analysis over a parameter range of spacing ratio 1.5 ≤ L* ≤ 5 and reduced velocity 3 ≤ Ur ≤ 34. Three kinds of FIV responses, namely vortex-induced vibration (VIV), biased oscillation (BO) and galloping (GA), are identified. The FIVs are then further classified into the branches of initial VIV (IV), resonant VIV (RV and RV′), flutter-induced VIV (FV), desynchronized VIV (DV), VIV developing from GA (GV), transitional state between VIV and GA (TR), BO and GA based on the characteristics of the vibration responses. The transitions among different FIV branches are examined by combining the DNS with linear stability analysis, where the transition boundaries among the VIV, BO and GA branches over the concerned parameters are identified on the branch maps. The transition from IV to RV or RV′ is found to be related to the unstable wake mode, while the FV, transiting from RV or RV′, is induced by the unstable structural factor in the wake-structure mode. The structural instability is considered as the physical origin of GA, whereas the mode competition between unstable wake and structure leads to DV, GV and TR, and thus delays the appearance of GA. The transition from DV to BO with biased equilibrium position, accompanied by the even-order harmonic frequencies, is essentially induced by the symmetry breaking bifurcation.
“…Flow-induced vibration (FIV) and vortex-induced vibration (VIV) are crucial research subjects for the flow characteristics of two tandem square cylinders. Qiu et al [14] used numerical simulations to study the influence of variables on the VIV of two tandem square cylinders under the condition of Re = 150 and mass ratios (m*) of 3, 10, and 20, respectively. They reported that the mass ratio has an important influence on the vortex-induced vibration response of the double cylinders, and the mass ratio has a great influence on the distance between the two cylinders.…”
The drag and lift force of a twin-cylinder structure are often greater than those of a single cylinder, causing serious structural safety problems. However, there are few studies on the passive control of twin cylinders. The study aimed to investigate the performance of passive drag reduction measures using small cylinders on twin cylinders at a Reynolds number of 100. The effects of small cylinder height (HD/D = 0~1.0, D is the side length of the twin cylinder) and cross-sectional shape on fluid force and flow structures were studied by direct numerical simulations. The control mechanism was analyzed using high-order dynamic mode decomposition (HODMD). The results showed that significant drag reduction occurred in the co-shedding state, particularly when the gap length of the twin cylinders L/D = 6.0. The small control cylinders with HD = 0.6, by contrast, showed the best performance in reducing the mean drag and fluctuating lift of the twin cylinders. It reduced the mean drag of the upstream cylinder (UC) by 2.58% and the downstream cylinder (DC) by more than 62.97%. The fluctuating lift coefficient for UC (DC) was also decreased by more than 70.41% (59.74%). The flow structures showed that when the flow hit UC under the action of small control cylinders, a virtual missile-like aerodynamic shape was formed at the leading edge of UC. In this way, the gap vortex consisted of two asymmetric steady vortices and the vortex length significantly increased. This was also confirmed by HODMD. The coherence modes in the gap were suppressed and thus the interaction between gap flow and wake flow was mitigated, which resulted in the fluid force reduction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
