On the aerodynamic forces on heaving and pitching airfoils at low Reynolds number

Moriche, Manuel; Flores, Oscar; García-Villalba, Manuel

doi:10.1017/jfm.2017.508

Cited by 81 publications

(59 citation statements)

References 39 publications

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“…The balance between circulatory and non-circulatory forces is in qualitative agreement with that obtained for comparable configurations (e.g. , Moriche et al 2017.…”

Section: Dynamics Of Perching Manoeuvressupporting

confidence: 88%

Influence of pitch rate on freely translating perching airfoils

Jardin

Doué

2019

J. Fluid Mech.

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We numerically investigated the unsteady dynamics of a two-dimensional airfoil undergoing a continuous, prescribed pitch-up motion and freely translating as a response to aerodynamic forces and the gravity field. The pitch-up motion was applied about an axis located $1/6$ chord away from the leading edge and was parameterized using the shape change number, with a Reynolds number set to 2000. It was shown that the minimum kinetic energy reached by the airfoil depends stochastically and asymptotically on shape change numbers for values below and above 1, respectively. Very low kinetic energy levels (close to zero) can be reached in both stochastic and asymptotic regions but high shape change numbers are accompanied by significant gain in altitude which may be undesirable from a practical perspective. Rather, shape change numbers in the range [0.1–0.3] allow us to reach relatively low levels of kinetic energy for close perching locations. We showed that highly nonlinear fluid–structure interactions induced by massive flow separations and strong vortices are conducive to low kinetic energy, but responsible for the stochastic dependence of kinetic energy to shape change number, which can make perching manoeuvres hardly controllable for flying vehicles.

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“…The balance between circulatory and non-circulatory forces is in qualitative agreement with that obtained for comparable configurations (e.g. , Moriche et al 2017.…”

Section: Dynamics Of Perching Manoeuvressupporting

confidence: 88%

Influence of pitch rate on freely translating perching airfoils

Jardin

Doué

2019

J. Fluid Mech.

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“…The time is discretized with a fractional-step method, in which the time advancement is performed with a low-storage Runge-Kutta scheme of three stages. The interested reader can find more details about TUCAN in [31,32,33].…”

Section: Methodsmentioning

confidence: 99%

From flapping to heaving: A numerical study of wings in forward flight

Gonzalo

Arranz

Moriche

et al. 2018

Journal of Fluids and Structures

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Direct Numerical Simulations of the flow around a pair of flapping wings are presented. The wings are flying in forward flight at a Reynolds number Re = 500, flapping at a reduced frequency k = 1. Several values of the radius of flapping motion are considered, resulting in a database that shows a smooth transition from the wing rotating with respect to its inboard wingtip (flapping), to a vertical oscillation of the wing (heaving). In this transition from flapping to heaving, the spanwise-averaged effective angle of attack of the wing increases while the effect of the Coriolis and centripetal accelerations becomes weaker. The present database is analyzed in terms of the value and surface distribution of the aerodynamic forces, and in terms of 2D and 3D flow visualizations. While the former allows a decomposition of the force in pressure (i.e., the component of the force normal to the surface of the wing) and skin friction (i.e., tangential to the surface of the wing), the latter allows the identification of specific flow structures with the corresponding forces on the wing. It is found that the aerodynamic forces in the vertical direction (lift) tend to increase for wings moving with larger radius of flapping motion, becoming maximum for the heaving configuration. This is mostly due to the increase of the spanwise-averaged effective angle of attack of the wing with the radius of the flapping motion. Also, the local changes in the effective angle of attack have a strong effect on the structure of the leading edge vortex, resulting in changes in the distribution of suction along the span near the leading edge of the wing. The effect of the apparent accelerations is mostly felt on the spanwise position where the separation of the LEV occurs. On the other hand, the differences in the force in the streamwise direction (thrust/drag) between the configurations with different radius of flapping motion seems to be linked to the position of the stagnation point dividing the suction and pressure side boundary layers, which seems to be controlled by the local effective angle of attack. Finally, the results of the DNS are used to evaluate the performance of an unsteady panel method, and to explain its deficiencies.

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“…Flapping-wing-based propulsion is ubiquitous in Nature, such as the swimming of fish, and the flying of birds and insects. Researching the dynamics of such biological flapping-wing systems is not only scientific, but also technological, since it can be applied to designing efficient micro aerial/underwater robots (Platzer et al 2008;Moriche, Flores & García-Villalba 2017). Consequently, the biological flapping-wing system has received considerable attention for several decades (Anderson et al 1998;Platzer et al 2008).…”

Section: Introductionmentioning

confidence: 99%