Simulation numérique adaptative de l'aérodynamique d'insectes avec ailles flexibles / Aerodynamics of insects with flexible wings using adaptive numerical simulations

Résumé Francais : cf. resumé anglais.

Résumé Anglais : Insects have evolved solutions for flight which astonish us with their elegance, efficiency as well as fast and robust control. Only in the past decade our understanding of flapping flight has advanced such that we can build machines as small as insects, which are able to lift their body weight with flapping wings [1]. Experimental and computational studies have revealed important unsteady aerodynamic effects such as leading edge vortices due to delayed stall [2], clap-and-fling or the passive wing tip reversal [3] insects use to fly efficiently. While experimental studies in principle are restricted to the animal’s natural kinematics and morphology, in computational studies all parameters can be controlled allowing detailed studies about the influence of special morphological features or certain details of the kinematics. For better biomimetic designs, it is necessary to better understand the function of animals' organs used for flight. Flapping flight research is therefore an intrinsically multidisciplinary activity, equally important for biologists and for engineers. The objective of this project is to develop efficient numerical tools for the fluid-structure interaction (FSI) in flapping flight. Earlier studies have demonstrated the usefulness of numerical modelling. Further progress requires constant improvement of computational techniques. One on the major recent areas of research is free flight manoeuvring stability and control, and it is believed that the wings deformation plays a significant role in these processes. It presents new challenges to the numerical modelling in terms of efficiency and accuracy. Therefore, the proposed work focuses on the development of an adaptive method for numerical simulation of animal free flight with flexible wings. The new development will be based on our previous work on a Navier-Stokes solver with volume penalization [4,5,6]. While the fluid structure interaction can be simulated using the FSI extended volume penalization method [4], adaptive grid refinement has yet to be developed in this context. Our approach to space-time adaptivity will be based on multiresolution techniques [7]. Validation and application of the solver will be carried out in collaboration with specialists in experimental biomechanics, i.e. the group of Professor Fritz-Olaf Lehmann at the Institute of Biological Sciences at the University of Rostock, Germany. The thesis is planned to be jointly supervised by the French and German team (thèse cotutelle franco-allemande). [1] D. Lentink, S. R. Jongerius, N. L. Bradshaw (2010): The scalable design of flapping micro-air vehicles inspired by insect flight. In Flying insects and robots (pp 185-205). Springer, Berlin. [2] C. P. Ellington, C. van den Berg (1996): Leading-edge vortices in insect flight. Nature 384, 626-630. [3] A.J. Bergou, S. Xu, Z.J. Wang (2007). Passive wing pitch reversal in insect flight. Journal of Fluid Mechanics 591, 321-337. [4] T. Engels, D. Kolomenskiy, K. Schneider, J. Sesterhenn (2015). Numerical simulation of fluid-structure interaction with the volume penalization method. Journal of Computational Physics 281, 96-115. [5] D. Kolomenskiy, H. K. Moffatt, M. Farge and K. Schneider (2011). Two- and three-dimensional numerical simulations of the clap-fling-sweep of hovering insects. Journal of Fluids and Structures 27(5-6), 784-791. [6] G. Bimbard, D. Kolomenskiy, J. Casas, R. Godoy-Diana (2013). Large kinematic variability during take-off in butterflies due to varying relative timing of legs and aerodynamic forces. Journal of Experimental Biology 216, 3551-3563. [7] M.O. Domingues, S.M. Gomes, O. Roussel, K. Schneider (2008). An adaptive multiresolution scheme with local time stepping for evolutionary PDEs. Journal of Computational Physics, 227, 3758-3780.

Débouchés : Enseignement supérieur, recherche académique, industrie aéronautique.