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Accueil > Actualités > Séminaires > Séminaires 2018

Mardi 5 juin 2018 à 11h00 en amphi K118

K. Arul Prakash, Associate Professor, Department of Applied Mechanics, Indian Institute of Technology, Madras, Chennai, India.

Titre/Title : Fluid flow and heat transfer characteristics over textured superhydrophobic surfaces

Contact : Olivier Métais (Equipe MoST)

Résumé/Abstract : The unique interaction that exists between liquids and superhydrophobic surfaces has been a topic of recent interest. Structured superhydrophobic surfaces (SHS) allow liquids to slip over the air film trapped inside textured grooves, providing immense skin friction gains compared to that of a smooth wall. SHS with streamwise aligned grooves are known to exhibit secondary flow structures owing to anisotropies in Reynolds stresses, while such flow patterns are observed to be weaker over isotropic structures such as posts. In this work, a series of Direct numerical simulations (DNS) is employed to investigate the influence of secondary flows on turbulence statistics and scalar transport over different structured surfaces (posts and ridges) at a friction Reynolds number, Reτ = 180 and a Prandtl number, Pr = 7.0. We compare the hydrodynamic and thermal statistics over two-dimensional (ridges) and three-dimensional (posts) structured surfaces, analyzingthe effect of structural spacing and the pattern geometry. Even though there is a considerable drag reduction, the average Nusselt number is remarkably decreased as the plastrons act as an impediment to heat transfer and the net thermal resistance across a superhydrophobic surface is increased. Also, a novel sinusoidal texture is proposed to enhance drag reduction and heat transfer where these textures induce asymmetric lateral secondary motions, emulating the effect of known drag reduction mechanism by lateral wall oscillations.