Séminaire de Mécanique d'Orsay

Le Jeudi 17 janvier 2019 à 14h00 - Salle de conférences du LIMSI

Influence of superhydrophobic surfaces on the laminar-to-turbulent transition in a channel flow

Francesco Picella
Dynfluid, Arts et Métiers ParisTech

Many passive control strategies have been recently proposed by researchers for reducing drag in wall bounded shear flows. Among them, Underwater SuperHydrophobic Surfaces (U-SHS) have proven to be capable of dramatically reduce the skin friction of a liquid flowing on top of them, due to the presence of gas bubbles trapped within the surface nano-sculptures. In specific geometrical and thermodynamical conditions for which wetting transition is avoided (in particular, when the roughness elements characterizing the U-SHS are several orders of magnitude smaller than the overlying flow), the so-called ’Lotus effect’ is achieved, for which the flow appears to slip on the surface with a non zero slip length. In this framework we propose to study, by means of numerical simulations, the influence of U-SHS on laminar-turbulent transition in a channel flow. The complete evolution from laminar, to transitional and fully developed turbulent flow is studied numerically using different numerical approaches. At first, homogeneous slip conditions are used. Then, the dynamics of each microscopic liquid-gas free-surface has been taken into account by means of a fully coupled fluid-structure solver. Using this approach we show that U-SHS can triple the transition time to turbulence.

Accès Salle de conférences du LIMSI