Wing performance and 3-D vortical structure formation in flapping flight

Bos, Frank M.; Oudheusden, B.W. van; Bijl, H.

doi:10.1016/j.jfluidstructs.2013.04.002

Cited by 30 publications

(14 citation statements)

References 32 publications

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“…The information concerning flapping wings in the forward flight regime is more scarce, apart from the particular case of heaving wings, reviewed by Gursul and Cleaver [16]. In recent years, flapping wings in forward flight have been studied by several authors, simulating both idealized configurations [17,18,19] as well as realistic configurations corresponding to insects [20,21,22,23] birds [24], bats [25] and even micro air vehicles [26,27]. While the emphasis in most of these studies lies in the characterization of the aerodynamic forces for the particular geometry or kinematics selected, few works analyze systematically the effect on the forces of varying kinematics or geometries.…”

Section: Introductionmentioning

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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Section: Introductionmentioning

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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“…Widmann and Tropea [75] have recently used experiments to investigate mechanisms responsible for the formation and detachment of LEVs. Other recent contributions characterizing 3D vortical structures on unsteady plates using high-fidelity simulations and experiments include those by Visbal et al [72], Devoria and Ringuette [15], Carr et al [9], Jones and Babinsky [32,33], Panah et al [53], and Bos et al [5].…”

Section: Introductionmentioning

confidence: 99%

Leading-edge flow criticality as a governing factor in leading-edge vortex initiation in unsteady airfoil flows

Ramesh

Granlund

et al. 2017

Theor. Comput. Fluid Dyn.

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A leading-edge suction parameter (LESP) that is derived from potential flow theory as a measure of suction at the airfoil leading edge is used to study initiation of leading-edge vortex (LEV) formation in this article. The LESP hypothesis is presented, which states that LEV formation in unsteady flows for specified airfoil shape and Reynolds number occurs at a critical constant value of LESP, regardless of motion kinematics. This hypothesis is tested and validated against a large set of data from CFD and experimental studies of flows with LEV formation. The hypothesis is seen to hold except in cases with slow-rate kinematics which evince significant trailing-edge separation (which refers here to separation leading to reversed flow on the aft portion of the upper surface), thereby establishing the envelope of validity. The implication is that the critical LESP value for an airfoil-Reynolds number combination may be calibrated using CFD or experiment for just one motion and then employed to predict LEV initiation for any other (fast-rate) motion. It is also shown that the LESP concept may be used in an inverse mode to generate motion kinematics that would either prevent LEV formation or trigger the same as per aerodynamic requirements.

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“…The flow around a plunging airfoil needs to be computed in a time varying computational domain. For solving such moving boundary problems there exists both mesh based methods [16][17][18] as well as mesh free methods. 19 The main mesh based approaches are the immersed boundary method, overset grids and arbitrary Lagrangian Eulerian (ALE) method.…”

Section: Iia Governing Equationsmentioning

confidence: 99%

“…RBF interpolation provides superior mesh quality near the moving body even for large displacements and rotations compared to other mesh motion solvers. 26 The implementation of the RBF interpolation used here is similar to the one used by Bos et al 18 The simulations are performed in OpenFOAM R , 27 an open source finite-volume based CFD solver. The spatial and temporal discretization are done using second order accurate schemes.…”

Section: Iib Solver Detailsmentioning

confidence: 99%

Intermittency Behaviour in the Flow Past an Oscillating Airfoil

Badrinath

Sarkar

2015

45th AIAA Fluid Dynamics Conference

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The flow over a plunging airfoil is investigated by means of a Navier-Stokes solver at a Reynolds number of 1,000. A parametric analysis by varying the plunge amplitude (h) at a fixed frequency (k = 2) revealed the presence of a new flow dynamics for a flapping airfoil. For h > 0.91, the dynamics is characterized by long intervals of periodicity with abrupt chaotic intervals for short durations. The occurrence of such chaotic intervals increases as the amplitude is increased and finally, the flow field becomes chaotic for the entire time history. This type of dynamical behaviour where irregular chaotic intervals appear in between periodic intervals is known as intermittency. We use time series analysis techniques such as phase space reconstruction and recurrence plots to establish the presence of intermittency. Recurrence plot is an excellent tool for analysing phase space trajectories since it provides good insights into the system dynamics even with a short time series.

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Wing performance and 3-D vortical structure formation in flapping flight

Cited by 30 publications

References 32 publications

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

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

Leading-edge flow criticality as a governing factor in leading-edge vortex initiation in unsteady airfoil flows

Intermittency Behaviour in the Flow Past an Oscillating Airfoil

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