Lock-in mechanism of flow over a low-Reynolds-number airfoil with morphing surface

Kang, Wei; Xu, Min; Yao, Weigang; Zhang, Jiazhong

doi:10.1016/j.ast.2019.105647

Cited by 19 publications

(5 citation statements)

References 40 publications

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“…This can be identified from the clear resonance peaks in the power spectrum and periodic orbit in the phase portrait. A similar lock-in phenomenon has been reported in several recent studies of airfoils with morphing surfaces [52][53][54].…”

Section: Flow-induced Response Of a Foil With An Active Flapsupporting

confidence: 85%

Mode Competition in a Plunging Foil with an Active Flap: A Multi-Scale Modal Analysis Approach

Wang¹,

Shoele²

2022

Preprint

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The flow-induced flutter has a significant role in aircraft stability, renewable energy extraction, animal locomotion, among many other applications. While being a ubiquitous phenomenon, the control of the flutter response has been primarily limited to simplified systems and, often, with the help of linear inviscid flow theories. In this paper, we numerically investigate how the plunging response of a foil can be regulated using an active flap to improve structural safety or enhance the energy extraction efficiency of the foil with a tightly coupled fluid-structure interaction algorithm. A broad range of foil and flap settings was tested and their flow dynamics have been investigated. A novel multi-scale modal analysis technique suitable for fluid-structure interaction system successfully isolates the active flap-induced and the flow-induced modes. It is observed that the competition between these two modes dictates the plunging response of the foil. The active flap can modulate the leading edge vortex shedding with larger flapping amplitude and regulate the foil heaving motion. The ratio of the competing modal energy is proposed to evaluate the control efficacy of the morphing surface, and the onset of the lock-in is associated with the ratio approaching unity. It is shown that the morphing flap is a good candidate for active flow control.

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Section: Flow-induced Response Of a Foil With An Active Flapsupporting

confidence: 85%

Mode Competition in a Plunging Foil with an Active Flap: A Multi-Scale Modal Analysis Approach

Wang¹,

Shoele²

2022

Preprint

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“…Therefore, structural optimization of the energy harvester device is often necessary to achieve high-efficiency energy conversion. In recent years, flow-induced vibration piezoelectric energy harvesting (FIVPEH) [ 4 , 5 , 6 , 7 ] has emerged as an environmentally friendly, sustainable, and efficient energy harvesting technology that is gaining popularity among researchers. In light of the successful application of hyperstructures in various fields, integrating hyperstructures into flow-induced vibrations may be a possible method to improve the performance of harvesters.…”

Section: Introductionmentioning

confidence: 99%

Exploring the Potential of Flow-Induced Vibration Energy Harvesting Using a Corrugated Hyperstructure Bluff Body

et al. 2023

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Fluid-induced vibration is a common phenomenon in fluid–structure interaction. A flow-induced vibrational energy harvester based on a corrugated hyperstructure bluff body which can improve energy collection efficiency under low wind speeds is proposed in this paper. CFD simulation of the proposed energy harvester was carried out with COMSOL Multiphysics. The flow field around the harvester and the output voltage in different flow velocities is discussed and validated with experiments. Simulation results show that the proposed harvester has an improved harvesting efficiency and higher output voltage. Experimental results show that the output voltage amplitude of the harvester increased by 189% under 2 m/s wind speed.

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“…The first issue is the lock-on mechanism, which is also called the lock-in mechanism. 13 The lock-on mechanism is important, and it may be an intermediate process that leads to effective control. This mechanism is also significant for engineering applications.…”

Section: Introductionmentioning

confidence: 99%

“…Meanwhile, unsteady flow control techniques have been proven to be more efficient than steady flow control techniques because they require less momentum to achieve the same control effect. 2,3 Typical unsteady flow control methods include acoustic excitation, 4,5,6 synthetic jet, 7,8 pulsed jet, 9,10 pulsed suction, 11 periodic morphing surface, 12,13 and plasma actuation, 14,15 In the last decade, researchers have been focusing on the applications and comparisons of unsteady flow control methods. 16,17 However, an essential understanding of the mechanism of unsteady flow control has yet to be gained.…”

Section: Introductionmentioning

confidence: 99%

Duffing–van der Pol nonlinear reduced-order model for explaining the phenomena and mechanism in pulsed jet flow separation control

Huang

Yang

2022

Proceedings of the Institution of Mechanical Engineers, Part G:

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A two-equation nonlinear reduced-order model is established to describe the interaction between external periodic excitation from a pulsed jet and unsteady flow separation. This model, which is based on a 2D Navier–Stokes equation, the Stuart vortex row model, and the Stuart–Landau model, can approximately describe the typical phenomena occurring in pulsed jet flow separation control. These phenomena include the frequency-dependent, threshold, and lock-on effects, which are related to the frequency, intensity, and phase of excitation. Two indices, namely, the maximum Lyapunov exponent and the entrainment degree, are introduced to identify the mechanism of flow control via external periodic excitation. These indices are used to reflect the order degree and momentum transfer of the flow field. A comparison of the results of the model and those of a numerical simulation in a curved diffuser shows that the nonlinear reduced-order model is effective for qualitatively featuring the behavior of pulsed jet flow separation control. Moreover, the mechanism of pulsed jet flow separation control is explained via the model. Three aspects (i.e., flow instability, flow field ordering, and momentum transfer) are assumed to function together, resulting in an efficient flow control performance.

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Lock-in mechanism of flow over a low-Reynolds-number airfoil with morphing surface

Cited by 19 publications

References 40 publications

Mode Competition in a Plunging Foil with an Active Flap: A Multi-Scale Modal Analysis Approach

Mode Competition in a Plunging Foil with an Active Flap: A Multi-Scale Modal Analysis Approach

Exploring the Potential of Flow-Induced Vibration Energy Harvesting Using a Corrugated Hyperstructure Bluff Body

Duffing–van der Pol nonlinear reduced-order model for explaining the phenomena and mechanism in pulsed jet flow separation control

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