Flow-structure interactions of multiple inverted flags in different arrangements

Feng, Li-Hao; Hu, Yao-Wei; Wang, Jinjun

doi:10.1007/s00348-021-03345-x

Cited by 2 publications

(1 citation statement)

References 34 publications

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“…They found that when the gap between boundaries was small, the bending energies generated by inverted flags were much lower than isolated flags. Feng et al [ 56 ] experimentally investigated the dynamic behavior of three inverted flags by extending the tandem configuration to either triangular or inverted triangular configurations. They reported that the dynamic response of the inverted flags with the triangular configuration was the same as that of the staggered configuration due to the weak coupling interaction between the two downstream inverted flags.…”

Section: Introductionmentioning

confidence: 99%

Wind Energy Harvesting with Vertically Aligned Piezoelectric Inverted Flags

Yang,

Cioncolini,

Revell

et al. 2023

Sensors

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Wind-energy-harvesting generators based on inverted flag architecture are an attractive option to replace batteries in low-power wireless electronic devices and deploy-and-forget distributed sensors. This study examines two important aspects that have been overlooked in previous research: the interaction between an inverted flag and a neighboring solid boundary and the interaction among multiple contiguous inverted flags arranged in a vertical row. Systematic tests have been carried out with metal-only ‘baseline’ flags as well as a ‘harvester’ variant, i.e., the baseline metal flag covered with PVDF (polyvinylidene difluoride) piezoelectric polymer elements. In each case, dynamic response and power generation were measured and assessed. For baseline metal flags, the same qualitative trend is observed when the flag approaches an obstacle, whether this is a wall or another flag. As the gap distance reduces, the wind speed range at which flapping occurs gradually shrinks and shifts towards lower velocities. The increased damping introduced by attaching PVDF elements to the baseline metal flags led to a considerable narrowing of the flapping wind speed range, and the wall-to-flag or flag-to-flag interaction led to a power reduction of up to one order of magnitude compared to single flags. The present findings highlight the strong dependence of the power output on the flapping frequency, which decreases when the flag approaches a wall or other flags mounted onto the same pole. Minimum flag-to-flag and flag-to-wall spacing values are suggested for practical applications to avoid power reduction in multi-flag arrangements (2-3H and 1-2H respectively, where H is flag height).

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Section: Introductionmentioning

confidence: 99%

Wind Energy Harvesting with Vertically Aligned Piezoelectric Inverted Flags

Yang,

Cioncolini,

Revell

et al. 2023

Sensors

View full text Add to dashboard Cite

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Hydrodynamic Coupling of Inverted Flags in Side-by-Side, Left Triangular and Right Triangular Configurations in a Uniform Flow

et al. 2022

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The hydrodynamic coupling of inverted flexible flags in side-by-side, left triangular and right triangular configurations in a uniform flow is investigated numerically. Various arrangements can be characterized by the lateral and longitudinal gaps, i.e., H and G, respectively. For the side-by-side configurations, three typical modes are identified in flapping region, i.e., in-phase quasi out-of-phase (QOP) and out-of-phase (OP) modes, corresponding to 2P, irregular and 4(P + S) wake patterns, respectively. Further analysis on the mean drag coefficient (Cd̄) and bending energy (Eb̄) indicates that the side-by-side flags can not harvest more bending energy from surrounding flows than the isolated one, except for a narrow range of H ∈ (1.8, 2.5). Moreover, an additional inverted flag is placed in front or rear of the side-by-side flags to explore possible favorable arrangements for bending energy enhancement. Three typical modes have been identified in the H − G planes for both left and right triangular configurations, i.e., the regular-coupled (RC), irregular-coupled (IC) and decoupled (DC) modes, respectively. For left triangular configurations, the overall system may experience significant performance enhancement in some favorable configurations, corresponding to harvest enhancement region (HER) in the G − H plane; For the case in HER, especially, the Eb̄ of the rear flag may increase by up to 30% than isolated flag. While for right triangular configurations, no HER is observed. The unsteady flow characteristics are further explored to reveal the mechanism of hydrodynamic coupling in system. The present study may shed some light on understanding the dynamics of this multi-flag system.

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Flow-structure interactions of multiple inverted flags in different arrangements

Cited by 2 publications

References 34 publications

Wind Energy Harvesting with Vertically Aligned Piezoelectric Inverted Flags

Wind Energy Harvesting with Vertically Aligned Piezoelectric Inverted Flags

Hydrodynamic Coupling of Inverted Flags in Side-by-Side, Left Triangular and Right Triangular Configurations in a Uniform Flow

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