Modelling of an actuated elastic swimmer
M. Piñeirua, B. Thiria & R. Godoy-Diana
Journal of Fluid Mechanics 829 731-750 (2017)
We studied the force production dynamics of undulating elastic plates as a model for fish-like inertial swimmers. Using a beam model coupled with Lighthill’s large-amplitude elongated-body theory, we explore different localised actuations at one extremity of the plate (heaving, pitching and a combination of both) in order to quantify the reactive and resistive contributions to the thrust. The latter has the Continue reading “Flapping elastic plates as a model of fish-like swimmers”
Four-winged flapping flyer in forward flight
R. Godoy-Diana, P. Jain, M. Centeno, A. Weinreb & B. Thiria
In Klapp et al. (eds.), Selected Topics of Computational and Experimental Fluid Mechanics, Environmental Science and Engineering, pp. 147-158. Springer (2015).
We study experimentally a four-winged flapping flyer with chord-wise flexible wings in a self-propelled setup. For a given physical configuration of the flyer (i.e. fixed distance between the forewing and hindwing pairs and fixed wing flexibility), we explore the kinematic parameter space constituted by the flapping frequency and the forewing-hindwing phase lag. Continue reading “Four-winged flapping flyer in forward flight”
Large-amplitude undulatory swimming near a wall
R. Fernández-Prast, V. Raspa, B. Thiria, F. Huera-Huarte & R. Godoy-Diana. Bioinspiration and Biomimetics 10 016003 (2015).
We study experimentally the propulsive dynamics of flexible undulating foils in a self-propelled swimming configuration near a wall. Measurements of swimming speed and propulsive force are performed, together with full recordings of the elastic wave kinematics and particle image velocimetry. Continue reading “Undulatory swimming near a wall”
Bio-inspired swimming and flying – Vortex dynamics and fluid/structure interaction
Habilitation à diriger des recherches, Université Pierre et Marie Curie, 2014.
PDF file here (19.4 MB)
The present document, prepared in view of obtaining the Habilitation à diriger des recherches, reviews my main research subject at PMMH since 2006, which concerns the study of swimming and flying inspired by nature. Canonical examples of flapping flight and undulatory swimming are explored using simplified experimental models as a starting point. This allows for the discussion of some fundamental questions related to the physics of bio-inspired locomotion at “intermediate” Reynolds numbers. In particular, we address the strong fluid-structure interactions that arise in these problems, where we have focused on: simplified models of flapping foils in hydrodynamic tunnel experiments, especially in the dynamics of vorticity in the wake of an oscillating foil ; mechanical models of flapping flyers with flexible wings in a self-propelled configuration (in the spirit of the pioneer experiments of Etienne-Jules Marey), as well as novel experimental models of undulatory swimming.
Continue reading “Habilitation à diriger des recherches (HDR)”
Vortex-induced drag and the role of aspect ratio in undulatory swimmers
V. Raspa, S. Ramananarivo, B. Thiria & R. Godoy-Diana. Physics of Fluids, 26 : 041701 (2014).
During cruising, the thrust produced by a self-propelled swimmer is balanced by a global drag force. For a given object shape, this drag can involve skin friction or form drag, both being well-documented mechanisms. However, for swimmers whose shape is changing in time, the question of drag is not yet clearly established. Continue reading “Drag in undulatory swimmers”
Topology-induced effect in biomimetic propulsive wakes
V. Raspa; R. Godoy-Diana & B. Thiria.
Journal of Fluid Mechanics, 729: 377-387 (2013).
Abstract: It is known that the wake pattern observed in a cross-section behind swimming or flying animals is typically characterized by the presence of periodical vortex shedding. However, depending on species, propulsive wakes can differ according to the spatial ordering of the main vortex structures. We conducted a very precise experiment to analyse the role of the topology of the wake in the generation of propulsion by comparing two prototypical cases in a quasi-two-dimensional view. Continue reading “Topology-induced effect in biomimetic propulsive wakes”
Force balance in the take-off of a pierid butterfly: relative importance and timing of leg impulsion and aerodynamic forces
G. Bimbard, D. Kolomenskiy, O. Bouteleux, J. Casas & R. Godoy-Diana.
Journal of Experimental Biology, 216 : 3551-3563 (2013).
Abstract: Up to now, the take-off stage remains an elusive phase of insect flight relatively poorly explored compared to other maneuvers. An overall assessment of the different mechanisms involved in the force production during take-off has never been explored. Focusing on the first downstroke, we have addressed this problem from a force balance perspective in butterflies taking-off from the ground. Continue reading “Force balance in the take-off of a pierid butterfly”
Stabilizing effect of flexibility in the wake of a flapping foil
C. Marais; B Thiria; Wesfreid, J. E. & R. Godoy-Diana.
Journal of Fluid Mechanics, 710 : 659-669 (2012).
Abstract: The wake of a flexible foil undergoing pitching oscillations in a low-speed hydrodynamic tunnel is used to examine the effect of chordwise foil flexibility in the dynamical features of flapping-based propulsion. Continue reading “Stabilizing effect of flexibility in the wake of a flapping foil”
Rather than resonance, flapping wing flyers may play on aerodynamics to improve performance
S. Ramananarivo; R. Godoy-Diana & B. Thiria.
Proceedings of the National Academy of Sciences (USA), 108 (15): 5964-5969 (2011).
Abstract: Saving energy and enhancing performance are secular preoccupations shared by both nature and human beings. In animal locomotion, flapping flyers or swimmers rely on the flexibility of their wings or body to passively increase their efficiency using an appropriate cycle of storing and releasing elastic energy. Despite the convergence of many observations pointing out this feature, the underlying mechanisms explaining how the elastic nature of the wings is related to propulsive efficiency remain unclear. Here we use an experiment with a self-propelled simplified insect model allowing to show how wing compliance governs the performance of flapping flyers. Continue reading “Behind the performance of flapping wing flyers”
How wing compliance drives the efficiency of self-propelled flapping flyers
B. Thiria & R. Godoy-Diana.
Physical Review E, 82 : 015303(R) (2010).
*arXiv preprint blogged in MIT Technology Review (March 2, 2010)
*Also referenced in Vir. J. Bio. Phys. Res. / Volume 20 / Issue 3 / (August 1, 2010)
Abstract: Wing flexibility governs the flying performance of flapping-wing flyers. Here, we use a self-propelled flapping-wing model mounted on a ”merry go roun” to investigate the effect of wing compliance on the propulsive efficiency of the system. Continue reading “Bending to fly”
A model for the symmetry breaking of the reverse Bénard-von Kármán vortex street produced by a flapping foil
R. Godoy-Diana; C. Marais; J. L. Aider & J. E. Wesfreid.
Journal of Fluid Mechanics, 622 : 23-32 (2009).
Abstract: The vortex streets produced by a flapping foil of span-to-chord aspect ratio of 4:1 are studied in a hydrodynamic tunnel experiment. In particular, the mechanisms giving rise to the symmetry breaking of the reverse Bénard-von Kármán vortex street that characterizes fish-like swimming and forward flapping flight are examined. Two-dimensional particle image velocimetry measurements in the mid-plane perpendicular to the span axis of the foil are used to characterize the different flow regimes. Continue reading “Symmetry breaking of the reverse Bénard-von Kármán vortex street”
Transitions in the wake of a flapping foil
R. Godoy-Diana; J. L. Aider & J. E. Wesfreid.
Physical Review E, 77 : 016308 (2008).
Abstract: We study experimentally the vortex streets produced by a flapping foil in a hydrodynamic tunnel, using two-dimensional particle image velocimetry. An analysis in terms of a flapping frequency-amplitude phase space allows the identification of (i) the transition from the well-known Bénard-von Kármán (BvK) wake to the reverse BvK vortex street that characterizes propulsive wakes, and (ii) the symmetry breaking of this reverse BvK pattern giving rise to an asymmetric wake. Continue reading “Transitions in the wake of a flapping foil”