Enhancement of heat transfer by a self-oscillating inverted flag in a Poiseuille channel flow

Saleel, C. Ahamed; Kim, Boyoung; Chang, Cheong Bong; Ryu, Jaeha; Sung, Hyung Jin

doi:10.1016/j.ijheatmasstransfer.2016.01.043

Cited by 72 publications

(19 citation statements)

References 18 publications

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“…The dynamics of cantilevered plates in incompressible reverse axial flows, otherwise known as inverted flags, is of considerable interest, not only as an abstract problem with rich dynamics, but also for engineering applications such as small scale energy harvesting systems [19,28] and heat transfer enhancement in heat exchangers [35,20]. Generally speaking, an inverted flag may lose stability at a sufficiently high flow velocity and exhibit a flapping motion.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear dynamics of slender inverted flags in uniform steady flows

Tavallaeinejad

Legrand

Paı̈doussis

2020

Journal of Sound and Vibration

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A nonlinear fluid-elastic continuum model for the dynamics of a slender cantilevered plate subjected to axial flow directed from the free end to the clamped end, also known as the inverted flag problem, is proposed. The extension of elongated body theory to large-amplitude rotations of the plate mid-plane along with Bollay's nonlinear wing theory is employed in order to express the fluid-related forces acting on the plate, while retaining all time-dependent terms in both modelling and numerical simulations; the unsteady fluid forces due to vortex shedding are not included. Euler-Bernoulli beam theory with exact kinematics and inextensibility is employed to derive the nonlinear partial integro-differential equation governing the dynamics of the plate. Discretization in space is carried out via a conventional Galerkin scheme using the linear mode-shapes of a cantilevered beam in vacuum. The pseudo-arclength continuation technique is adapted to construct bifurcation diagrams in terms of the flow velocity, in order to gain insight into the stability and post-critical behaviour of the system. Integration in time is conducted using Gear's backward differentiation formula. The sensitivity of the nonlinear response of the system to different parameters such as the aspect ratio, mass ratio, initial inclination of the flag, and viscous drag coefficient is investigated through extensive numerical simulations. It is shown that for flags of small aspect ratio the undeflected static equilibrium is stable prior to a subcritical pitchfork bifurcation. For flags of sufficiently large aspect ratio, however, the first instability encountered is a supercritical Hopf bifurcation giving rise to flapping motion around the undeflected static equilibrium; increasing the flow velocity further, the flag then displays flapping motions around deflected static equilibria, which later lead to fully-deflected static states at even higher flow velocities. The results exposed in this study help understand the dynamics of the inverted-flag problem in the limit of inviscid flow theory.

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Section: Introductionmentioning

confidence: 99%

Nonlinear dynamics of slender inverted flags in uniform steady flows

Tavallaeinejad

Legrand

Paı̈doussis

2020

Journal of Sound and Vibration

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“…Additionally, the vortex shedding produced by the large amplitudes of motion can be exploited in applications that involve mixing and heat transfer enhancement (Park et al. 2016). Kim et al.…”

Section: Introductionmentioning

confidence: 99%

“…The larger strains exhibited by the inverted flag make this configuration particularly useful for energy harvesting (Kim et al 2013;Orrego et al 2017). Additionally, the vortex shedding produced by the large amplitudes of motion can be exploited in applications that involve mixing and heat transfer enhancement (Park et al 2016). Kim et al (2013) showed that the inverted flag presents three main regimes of motion depending on the magnitude of the dimensionless flow speed κ = ρU 2 L 3 /D, where ρ is the fluid density, U is the free-stream flow speed, L the length of the flag and D the flexural rigidity of the flag.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of an inverted cantilever plate at moderate angle of attack

et al. 2020

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“…Compared with a conventional flag, an inverted flag enters the unstable state at a lower critical velocity and with a larger amplitude (Kim et al 2013). Therefore, an inverted flag is more valuable than a conventional flag in energy harvesting (Kim et al 2013;Ryu et al 2015;Tang, Liu & Lu 2015a;Tang, Gibbs & Dowell 2015b;Shoele & Mittal 2016;Orrego et al 2017) and wall heat transfer (Park et al 2016;Yu, Liu & Chen 2017Chen et al 2018). Kim et al (2013) first studied the dynamic behaviours of an inverted flag.…”

Section: Introductionmentioning

confidence: 99%

“…The numerical results of Ryu et al (2015) and Tang et al (2015a) showed that the energy conversion ratio from the fluid kinetic energy to the strain energy of an inverted flag was as high as 0.4-0.6, indicating that the energy harvesting ability of an inverted flag was higher than that of a conventional flag, which was usually approximately 10 −3 . Park et al (2016) and Yu et al (2017) recently applied an inverted flag to wall heat transfer and found that its periodical influence on the fluid near the wall enhanced the heat transfer effect. For two parallel inverted flags, five coupled flapping modes were observed by Huertas-Cerdeira, Fan & Gharib (2018), namely in-phase, anti-phase, staggered, alternating and decoupled flapping modes.…”

Section: Introductionmentioning

confidence: 99%