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Accueil > Actualités > Séminaires > Séminaires 2021

Mardi 19 Octobre 11h00 - LEGI Salle K118

Kostas Steiros, Imperial College London

Title : Towards uncovering the physics of the turbulent wake

Contact : Martin Obligado

Abstract : There has been a renewal of interest in the physics of the turbulent wake, as they determine the efficiency of wind and tidal turbines, a topic which enjoys increasing popularity. In this talk, I discuss two recent contributions of my colleagues and myself. First, I introduce and validate a simple model for the evolution of the wake pressure of bluff bodies, with application to wind turbine modelling. Up to now, all engineering flow models for wind turbines completely neglect the effect of pressure, a fact which limits their accuracy and applicability. Here, I show that inclusion of a wake pressure term can significantly improve three types of turbine models : (i) Blade Element Momentum theory models for the power output of wind turbines ; (ii) wake velocity models for wind farm optimization ; and (iii) blockage correction models for turbine measurements in wind tunnels.

Second, I discuss the turbulence properties of wakes. Much of our understanding there stems from Kolmogorov K41 framework of the turbulence cascade, based on the assumption of equilibrium. However, turbulent wakes are ever-evolving with their larger scales significantly out-of-equilibrium. To model those, I propose an extension of K41 for out-of-equilibrium phenomena. The main result is a correction to the -5/3 law for large, out-of-equilibrium eddies, supported by laboratory and numerical experiments. Notable corrections to the -5/3 law (K62, Pao’s spectrum) are briefly discussed.