Analysis of vortical gust impact on airfoils at low Reynolds number

Martínez-Muriel, C.; Flores, Oscar

doi:10.1016/j.jfluidstructs.2020.103138

Cited by 13 publications

(7 citation statements)

References 31 publications

(74 reference statements)

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“…TUCAN has already been employed successfully, for both two-dimensional (Moriche, Flores & Garcia-Villalba 2017; Martínez-Muriel & Flores 2020) and three-dimensional (Moriche, Flores & García-Villalba 2016; Arranz et al. 2018; Arranz, Flores & Garcia-Villalba 2020; Moriche et al.…”

Section: Methodsmentioning

confidence: 99%

Fluid–structure resonance in spanwise-flexible flapping wings

et al. 2023

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We report direct numerical simulations of the flow around a spanwise-flexible wing in forward flight. The simulations were performed at $Re=1000$ for wings of aspect ratio 2 and 4 undergoing a heaving and pitching motion at Strouhal number $St_c\approx 0.5$ . We have varied the effective stiffness of the wing $\varPi _1$ while keeping the effective inertia constant, $\varPi _0=0.1$ . It has been found that there is an optimal aerodynamic performance of the wing linked to a damped resonance phenomenon, that occurs when the imposed frequency of oscillation approaches the first natural frequency of the structure in the fluid, $\omega _{n,f}/\omega \approx 1$ . In that situation, the time-averaged thrust is maximum, increasing by factor 2 with respect to the rigid case with an increase in propulsive efficiency of approximately 15 %. This enhanced aerodynamic performance results from the combination of larger effective angles of attack of the outboard wing sections and a delayed development of the leading edge vortex. With increasing flexibility beyond the resonant frequency, the aerodynamic performance drops significantly, in terms of both thrust production and propulsive efficiency. The cause of this drop lies in the increasing phase lag between the deflection of the wing and the heaving/pitching motion, which results in weaker leading edge vortices, negative effective angles of attack in the outboard sections of the wing, and drag generation in the first half of the stroke. Our results also show that flexible wings with the same $\omega _{n,f}/\omega$ but different aspect ratio have the same aerodynamic performance, emphasizing the importance of the structural properties of the wing for its aerodynamic performance.

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Section: Methodsmentioning

confidence: 99%

Fluid–structure resonance in spanwise-flexible flapping wings

et al. 2023

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“…In this work we employ the direct forcing formulation proposed by Uhlmann [45]. TUCAN has been successfully used for the simulation of aerodynamic flows, both in two- [46,47] and three-dimensions [48,49,50,51,52,53,54].…”

Section: Computational Set-upmentioning

confidence: 99%

Numerical simulation of flow over flapping wings in tandem: wingspan effects

Jurado,

Arranz,

Flores

et al. 2022

Preprint

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We report direct numerical simulations of a pair of wings in horizontal tandem configuration, to analyze the effect of their aspect ratio on the flow and the aerodynamic performance of the system. The wings are immersed in a uniform free-stream at Reynolds number Re = 1000, and they undergo heaving and pitching oscillation with Strouhal number St = 0.7. The aspect ratios of forewing and hindwing vary between 2 and 4. The aerodynamic performance of the system is dictated by the interaction between the trailing edge vortex (TEV) shed by the forewing and the induced leading edge vortex formed on the hindwing. The aerodynamic performance of the forewing is similar to that of an isolated wing irrespective of the aspect ratio of the hindwing, with a small modulating effect produced by the forewing-hindwing interactions. On the other hand, the aerodynamic performance of the hindwing is clearly affected by the interaction with the forewing's TEV. Tandem configurations with a larger aspect ratio on the forewing than on the hindwing result in a quasi-two-dimensional flow structure on the latter. This yields an 8% increase in the time-averaged thrust coefficient of the hindwing, with no change in its propulsive efficiency.

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“…From a more global perspective, understanding how flow structures influence the force can help interpret experimental or computational results. As an example, Martinez-Muriel & Flores [23] found that the peak force experienced by a wing, as externally created vortices of various sizes and strengths pass by at different distances, scales with the average velocity induced on the wing by the vortex. In situations like this, knowledge of how a particular flow structure affects the force can be useful to provide a more holistic understanding of why certain patterns exist and importantly, what their limitations may be.…”

Section: Introductionmentioning

confidence: 99%

“…The derivation discussed above uses a cylinder as the body of interest but there is of course no conceptual difference between for example, a lift-generating spinning cylinder or any other lifting body. This therefore allows us to revisit the work by Martinez-Muriel & Flores [23] who studied a wing encountering a vortical gust. The authors observed that the peak force experienced by the wing was dependent on the average velocity induced onto the wing by the passing vortex.…”

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confidence: 99%

Vortex Force Decomposition - Forces Associated with Individual Elements of a Vorticity Field

Gehlert

Andreu-Angulo

Babinsky

2023

Preprint

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The impulse theory used to calculate the force from a vorticity distribution in two-dimensional, incompressible flow, is re-cast with the aim of approximating, to a first order, the forces generated by a specific flow feature, such as a free vortex passing by an object. To achieve this, the force acting on the body is split up into several core contributions. The first component arises from the time variation of the body's boundary layer. The second is generated by the advection of any free vorticity located in the flowfield by the object's boundary layer vorticity. The final force contribution is due to new vorticity being shed. To test the theory, it is applied to two multi-body flowfields consisting of a circular cylinder and a flat plate wing at incidence in close proximity. Force balance measurements and planar particle image velocimetry data are simultaneously obtained at Reynolds numbers of 10 000 and 20 000. The forces acting on the cylinder are successfully recovered from the vorticity data using the derived formulation, verifying its accuracy. Subsequently, the proposed force formulation is used to create force heat maps that demonstrate how the location of a leading edge vortex affects its force contribution around a pitching NACA-0021 wing translating at a Reynolds number of 10 000.

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Analysis of vortical gust impact on airfoils at low Reynolds number

Cited by 13 publications

References 31 publications

Fluid–structure resonance in spanwise-flexible flapping wings

Fluid–structure resonance in spanwise-flexible flapping wings

Numerical simulation of flow over flapping wings in tandem: wingspan effects

Vortex Force Decomposition - Forces Associated with Individual Elements of a Vorticity Field

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