Séminaires DAEP 2014

Large Eddy Simulation of an Asymmetric Jet in Crossflow

Vendredi 5 décembre 2014 10h30 salle Cazalbou par Mikko Folkersma

Wall-Modeling for Large Eddy Simulations of Rotating Flows

Vendredi 5 décembre 2014 10h30 salle Cazalbou par Niki Loppi

Stabilité 2D d’un dipôle tourbillonnaire visqueux

Vendredi 28 novembre 2014 10h45 salle Cazalbou par Rémi Jugier (Présentation)

Interaction Fluide-Structure : Algorithmes de couplage et application

Jeudi 23 octobre 2014 10h45 salle Cazalbou par Emerry Rajaomazava (Présentation)

Méthodes hybrides en aéroacoustique numérique (CAA) pour les écoulements anisothermes

Vendredi 3 octobre 2014 10h45 salle Cazalbou par Cyril Nana (Présentation)

Développement et validation de la technique Doppler Global Velocimetry

Vendredi 23 mai 2014 14h00 Salle des thèses par Philippe Barricau (Présentation)

Méthodes Lattice-Boltzmann

Vendredi 18 avril 2014 10h45 DAEP Jolimont par Nicolas Gourdain (Présentation)

Wall modeled LES of high-lift devices at realistic Reynolds numbers

Vendredi 28 mars 2014 10h45 Salle des thèses par Julien Bodart (Présentation)

Accurate predictions of the flow field over complex aerodynamic configurations, such as high lift devices is of particular interest for airframe noise predictions as well as wing design with or without active flow control. In particular, computing the flow at high angle of attack and in particular predicting the maximum lift coefficient remains a challenge using RANS solvers. We discuss how large eddy simulation can be used in this context, together with wall-modeling to reduce the grid requirements. I will specifically address two challenges wall-modeling has to face when dealing with complex geometries : i) its implementation in massively parallel, unstructured solvers and ii) its ability to predict transitional flows. The wall-model methodology implemented in the solver CharLES^X relies on flow sensors, to activate the wall model only in turbulent regions of the boundary layers. I will first discuss results obtained for a canonical (H-type) transitional boundary layer, and for the flow around McDonnell-Douglas 30P/30N airfoil, at the realistic Reynolds number (based on the stowed chord) of Re_c=9.10⁶.

Aerodynamics of America’s Cup yatchs

Jeudi 9 janvier 2014 14h00 DAEP Jolimont par Ignazio Maria Viola

Yacht sails are very efficient aerodynamic fins, which operate at similar conditions to several emerging industrial applications. Increasing the knowledge in sail aerodynamics may lead to new ideas for improving the fluid dynamic efficiency of these applications. For instance, sails operate at Reynolds numbers of the order of 106-107 such as wind and tidal energy converters, unmanned aerial vehicles and autonomous underwater vehicles. The onset velocity profiles experienced by a sail has similarities with the one experienced by a propeller blade, and the high level of background turbulence during a fleet race have similarities with the one of arrays of wind and tidal energy converters.

The talk will present recent wind tunnel tests and numerical simulations of America’s Cup yachts, including Reynolds-averaged Navier Stokes simulations (RANS) and the first Detached Eddy Simulations (DES) on sails. The computed forces and sail pressure distributions were also used to demonstrate a novel verification and validation procedure for yacht sail aerodynamics. In particular, the talk will focus on an AC33-class yacht in upwind and downwind conditions. The two configurations were tested in the Twisted Flow Wind Tunnel of the University of Auckland with a 1:15th model-scale boat using both flexible and rigid sails. Forces and surface pressure distributions were measured. These configurations were modelled numerically with RANS and DES using high performance computing facilities in Edinburgh, Newcastle and Milan. The numerical uncertainty of the results was computed with a novel verification procedure, which overcome the limitation of knowing a priori the theoretical order of convergence and allows dealing with formally non-converging results. The validation of the pressure distributions allowed the estimate of the modelling error and to highlight the sensitivity of the results to the thickness of the sails. DES allowed drawing a map of the turbulent structures in the sails’ wake and the identification of flow features, which were not known on sails. For instance, it allowed new insights on the characteristics of the leading edge vortex and the discovery of a mid-span vortex with a streamwise core due to the spinnaker’s twist.