Flapping wing energy harvesting: aerodynamic aspects

Geißler, W.

doi:10.1007/s13272-019-00394-1

Cited by 6 publications

(7 citation statements)

References 9 publications

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“…In these two last equations, C t is the mean thrust coefficient, C d is the drag coefficient, C l is the lift coefficient, and C P is the mean power coefficient, which are parameters vastly used by researchers to evaluate the aerodynamic performance [24].…”

Section: Methodsmentioning

confidence: 99%

“…Natural flyers use these forces effectively where thrust and lift production means that energy is transferred from the wings to the fluid. However, the study of oscillating airfoils has undergone a drastic shift when researchers identified the potential of flapping airfoils to extract energy from the flow field [24]. Studies on energy harvesting efficiency over oscillating airfoils revealed that a harvester could achieve maximum efficiency of about 30% on sinusoidal motion for Re = 1000 and 40% to 50% on nonsinusoidal motion; other efficiency-enhancing mechanisms might include corrugations at the foil surface, its structural flexibility, and multiple foil configuration [25] such as the parallel foil configuration numerically investigated in [26].…”

Section: Introductionmentioning

confidence: 99%

“…This concept was studied by Bouzaher et al [29], who added a Gurney flap at the trailing-edge that when synchronized with the flapping motion at a Re = 1100 created this virtual camber that improved the output power. The lift production can be further improved by controlling the development of the leading-edge vortex than, when attached to the airfoil surface, contributed to the improvement in lift generation which brings once again an increase in the energy harvesting magnitude [24]. The same concept may be applied for thrust enhancement where camber morphing also reveals the potential to maximize the ratio of thrust to lift of flapping airfoils in several flight conditions [30].…”

Section: Introductionmentioning

confidence: 99%

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Numerical Investigation of Frequency and Amplitude Influence on a Plunging NACA0012

et al. 2020

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Natural flight has always been the source of imagination for Mankind, but reproducing the propulsive systems used by animals that can improve the versatility and response at low Reynolds number is indeed quite complex. The main objective of the present work is the computational study of the influence of the Reynolds number, frequency, and amplitude of the oscillatory movement of a NACA0012 airfoil in the aerodynamic performance. The thrust and power coefficients are obtained which together are used to calculate the propulsive efficiency. The simulations were performed using ANSYS Fluent with a RANS approach for Reynolds numbers between 8500 and 34,000, reduced frequencies between 1 and 5, and Strouhal numbers from 0.1 to 0.4. The aerodynamic parameters were thoroughly explored as well as their interaction, concluding that when the Reynolds number is increased, the optimal propulsive efficiency occurs for higher nondimensional amplitudes and lower reduced frequencies, agreeing in some ways with the phenomena observed in the animal kingdom.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Numerical Investigation of Frequency and Amplitude Influence on a Plunging NACA0012

et al. 2020

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“…In the present application a combination of pitching and plunging motion has been realized as well as a special instantaneous airfoil shape modification which has already been investigated in [17].…”

Section: Gridmentioning

confidence: 99%

“…c) Dynamic deformation of the airfoil during sinusoidal or modified time variation. The latter problem has already been studied in Geissler, [17] for the NACA0012 airfoil. Similar investigations are included in Maqusud et.…”

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confidence: 99%

Flapping Wing Energy Harvesting, Experiences with Modified Time Variations at high Re-Number

Geißler

2024

Preprint

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Wind energy converters with rotating blades are most common for energy harvesting. In special cases a system of flapping wings may be of interest where the wings are oscillating in combined flapping (plunging) and pitching modes respectively. Then the ratio of plunging and pitching amplitudes is of main concern: for animal flight the thrust production and its optimization as well as the sufficient lift force are important, for energy harvesting the maximum energy extraction from the oncoming flow and a minimized energy input into the system are of main importance. If one looks into the details of energy flows it is obvious that for animal flight the energy input via muscles is dominating whereas for energy harvesting main energy flow is transferred from the fluid into the oscillating system i.e., the direction of energy flow is reversed in both cases. With these fundamental aspects in mind, it is of interest to increase and optimize the energy input from the fluid. One important measure may be the modification of the time variation: usually the time varies harmonically within one period of oscillation. In the present paper modified time variations are investigated in detail. Phase variation between modes as well as dynamic deformation of the airfoil are of further concern and will be discussed in the present paper.

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The single flapping rotor: detailed physical explanations

Geißler

2023

CEAS Aeronaut J

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A motor-driven helicopter rotor generates a reaction torque. This torque would accelerate the airframe of the helicopter about the yaw axis opposite to the rotor rotation if no measures are taken to compensate it. In the early days of helicopter development, a diversity of measures was considered: Henrich Focke has discussed these different measures. Not well known is a torque compensation measure which is restricted to only one main rotor, thus skipping the tail rotor or any additional rotor as well. This principle is worth looking into the details of the physical mechanism involved. The German scientist Prof. Hans-Georg Küssner of the AVA-Göttingen, Germany (Aerodynamic Research Institute with heads at this time: L. Prandtl and A. Betz) was the first to study the method successfully. He constructed a wind tunnel model and showed that the reaction torque could indeed be completely compensated. The present author has reviewed Küssner’s experimental data and could show that numerical calculations are in good correspondence with the measured results. In the present paper, the details of the method to compensate the reaction torque will be discussed. Corresponding numerical data will be presented taking into account Navier–Stokes calculations on rotor blade sections. Blade element theory will then be applied and combined with the Navier–Stokes data. Calculated forces and moments of a complete four-bladed helicopter rotor will be presented.

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Flapping wing energy harvesting: aerodynamic aspects

Cited by 6 publications

References 9 publications

Numerical Investigation of Frequency and Amplitude Influence on a Plunging NACA0012

Numerical Investigation of Frequency and Amplitude Influence on a Plunging NACA0012

Flapping Wing Energy Harvesting, Experiences with Modified Time Variations at high Re-Number

The single flapping rotor: detailed physical explanations

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