Aerodynamic ground effect in flapping-wing insect flight is of importance to comparative morphologies and of interest to the micro-air-vehicle (MAV) community. Recent studies, however, show apparently contradictory results of either some significant extra lift or power savings, or zero ground effect. Here we present a numerical study of fruitfly sized insect takeoff with a specific focus on the significance of leg thrust and wing kinematics. Flapping-wing takeoff is studied using numerical modelling and high performance computing. The aerodynamic forces are calculated using a three-dimensional Navier--Stokes solver based on a pseudo-spectral method with volume penalization. It is coupled with a flight dynamics solver that accounts for the body weight, inertia and the leg thrust, while only having two degrees of freedom: the vertical and the longitudinal horizontal displacement. The natural voluntary takeoff of a fruitfly is considered as reference. The parameters of the model are then varied to explore possible effects of interaction between the flapping-wing model and the ground plane. These modified takeoffs include cases with decreased leg thrust parameter, and/or with periodic wing kinematics, constant body pitch angle. The results show that the ground effect during natural voluntary takeoff is negligible. In the modified takeoffs, when the rate of climb is slow, the difference in the aerodynamic forces due to the interaction with the ground is up to 6%. Surprisingly, depending on the kinematics, the difference is either positive or negative, in contrast to the intuition based on the helicopter theory, which suggests positive excess lift. This effect is attributed to unsteady wing-wake interactions. A similar effect is found during hovering.
Dmitry Kolomenskiy, Masateru Maeda, Thomas Engels, Hao Liu, Kai Schneider, et al.. Aerodynamic Ground Effect in Fruitfly Sized Insect Takeoff. PLoS ONE, 2016, 11 (3), pp.e0152072. ⟨10.1371/journal.pone.0152072⟩. ⟨hal-01299261⟩
T. Engels, D. Kolomenskiy, Kai Schneider, F.-O. Lehmann, J. Sesterhenn. Bumblebee Flight in Heavy Turbulence. Physical Review Letters, 2016, 116 (2), pp.028103. ⟨10.1103/PhysRevLett.116.028103⟩. ⟨hal-01299332⟩ Plus de détails...
High-resolution numerical simulations of a tethered model bumblebee in forward flight are performed superimposing homogeneous isotropic turbulent fluctuations to the uniform inflow. Despite tremendous variation in turbulence intensity, between 17% and 99% with respect to the mean flow, we do not find significant changes in cycle-averaged aerodynamic forces, moments or flight power when averaged over realizations, compared to laminar inflow conditions. The variance of aerodynamic measures, however, significantly increases with increasing turbulence intensity, which may explain flight instabilities observed in freely flying bees.
T. Engels, D. Kolomenskiy, Kai Schneider, F.-O. Lehmann, J. Sesterhenn. Bumblebee Flight in Heavy Turbulence. Physical Review Letters, 2016, 116 (2), pp.028103. ⟨10.1103/PhysRevLett.116.028103⟩. ⟨hal-01299332⟩
Thomas Engels, Dmitry Kolomenskiy, Kai Schneider, Jörn Sesterhenn. Numerical simulation of fluid–structure interaction with the volume penalization method. Journal of Computational Physics, 2015, 281, pp.96-115. ⟨10.1016/j.jcp.2014.10.005⟩. ⟨hal-01299253⟩ Plus de détails...
We present a novel scheme for the numerical simulation of fluid–structure interaction problems. It extends the volume penalization method, a member of the family of immersed boundary methods, to take into account flexible obstacles. We show how the introduction of a smoothing layer, physically interpreted as surface roughness, allows for arbitrary motion of the deformable obstacle. The approach is carefully validated and good agreement with various results in the literature is found. A simple one-dimensional solid model is derived, capable of modeling arbitrarily large deformations and imposed motion at the leading edge, as it is required for the simulation of simplified models for insect flight. The model error is shown to be small, while the one-dimensional character of the model features a reasonably easy implementation. The coupled fluid–solid interaction solver is shown not to introduce artificial energy in the numerical coupling, and validated using a widely used benchmark. We conclude with the application of our method to models for insect flight and study the propulsive efficiency of one and two wing sections.
Thomas Engels, Dmitry Kolomenskiy, Kai Schneider, Jörn Sesterhenn. Numerical simulation of fluid–structure interaction with the volume penalization method. Journal of Computational Physics, 2015, 281, pp.96-115. ⟨10.1016/j.jcp.2014.10.005⟩. ⟨hal-01299253⟩
Thomas Engels, Dmitry Kolomenskiy, Kai Schneider, Jörn Sesterhenn. Two-dimensional simulation of the fluttering instability using a pseudospectral method with volume penalization. Computers & Structures, 2013, 122, pp. 101-112 ⟨10.1016/j.compstruc.2012.12.007⟩. ⟨hal-01299992⟩ Plus de détails...
We present a new numerical scheme for the simulation of deformable objects immersed in a viscous incompressible fluid. The two-dimensional Navier-Stokes equations are discretized with an efficient Fourier pseudo-spectral scheme. Using the volume penalization method arbitrary inflow conditions can be enforced, together with the no-slip conditions at the boundary of the immersed flexible object. With respect to Kolomenskiy and Schneider (2009) [1], where rigid moving obstacles have been considered, the present work extends the volume penalization method to account for moving deformable objects while avoiding numerical oscillations in the hydrodynamic forces. For the solid part, a simple and accurate one-dimensional model, the non-linear beam equation, is employed. The coupling between the fluid and solid parts is realized with a fast explicit staggered scheme. The method is applied to the fluttering instability of a slender structure immersed in a free stream. This coupled non-linear system can enter three distinct states: stability of the initial condition or maintenance of an either periodic or chaotic fluttering motion. We present a detailed parameter study for different Reynolds numbers and reduced free-stream velocities. The dynamics of the transition from a periodic to a chaotic state is investigated. The results are compared with those obtained by an inviscid vortex shedding method [2] and by a viscous linear stability analysis [3], yielding for both satisfactory agreement. New results concerning the transition to chaos are presented.
Thomas Engels, Dmitry Kolomenskiy, Kai Schneider, Jörn Sesterhenn. Two-dimensional simulation of the fluttering instability using a pseudospectral method with volume penalization. Computers & Structures, 2013, 122, pp. 101-112 ⟨10.1016/j.compstruc.2012.12.007⟩. ⟨hal-01299992⟩
Dmitry Kolomenskiy, Thomas Engels, Kai Schneider. Numerical Modelling of Flexible Heaving Foils. Journal of Aero Aqua Bio-mechanisms, 2013, 3 (1), pp. 22-28 ⟨10.5226/jabmech.3.22⟩. ⟨hal-01299235⟩ Plus de détails...
We consider the effects of chordwise flexibility on the aerodynamic performance of flapping wings using numerical simulation. The two-dimensional Navier-Stokes equations are solved using a Fourier pseudo-spectral method with no-slip boundary conditions imposed by the volume penalization method. The flexible wing is modelled with a non-linear beam equation. Our numerical simulations of heaving plates show that the maximum thrust is achieved at a stroke frequency lower than resonant, which is in agreement with experiments. The oscillatory part of the force only increases in amplitude when the frequency increases. We also consider aerodynamic interactions between two heaving foils.
Dmitry Kolomenskiy, Thomas Engels, Kai Schneider. Numerical Modelling of Flexible Heaving Foils. Journal of Aero Aqua Bio-mechanisms, 2013, 3 (1), pp. 22-28 ⟨10.5226/jabmech.3.22⟩. ⟨hal-01299235⟩
Eric Serre, Sandrine Hugues, Emilia Crespo del Arco, Anthony Randriamampianina, Patrick Bontoux. Axisymmetric and three-dimensional instabilities in an Ekman boundary layer flow. International Journal of Heat and Fluid Flow, 2001, 22 (1), pp.82-93. ⟨hal-01023080⟩ Plus de détails...
Eric Serre, Sandrine Hugues, Emilia Crespo del Arco, Anthony Randriamampianina, Patrick Bontoux. Axisymmetric and three-dimensional instabilities in an Ekman boundary layer flow. International Journal of Heat and Fluid Flow, 2001, 22 (1), pp.82-93. ⟨hal-01023080⟩
Journal: International Journal of Heat and Fluid Flow
