Francesco Viola

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Related publications (19)

Hub vortex instability within wind turbine wakes: Effects of wind turbulence, loading conditions, and blade aerodynamics

François Gallaire, Giacomo Valerio Iungo, Francesco Viola

The near wake of wind turbines is characterized by the presence of the hub vortex, which is a coherent vorticity structure generated from the interaction between the root vortices and the boundary layer evolving over the turbine nacelle. Bymoving downstrea ...

Amer Physical Soc2016

Mode selection in trailing vortices: harmonic response of the non-parallel Batchelor vortex

François Gallaire, Francesco Viola, Cristobal Manuel Arratia Martinez

In the present study, the response of model trailing vortices subjected to a harmonic forcing is studied. To this purpose, a globally stable non-parallel Batchelor vortex is considered as the baseflow. Direct numerical simulations (DNS) show that a large v ...

Cambridge University Press2016

Foam on troubled water: Capillary induced finite-time arrest of sloshing waves

François Gallaire, Francesco Viola, Pierre-Thomas Paul Brun, Benjamin Jérémy Dollet

Interfacial forces exceed gravitational forces on a scale small relative to the capillary length-two millimeters in the case of an air-water interface-and therefore dominate the physics of sub-millimetric systems. They are of paramount importance for vario ...

Amer Inst Physics2016

Resonance in swirling wakes and sloshing waves : non-normal and sublinear effects

Francesco Viola

Similarly to mechanical structures, stable flows can exhibit resonance when perturbed by an impulsive or harmonic forcing. Swirling wakes and sloshing waves belong to this kind of flows and manifest large energy response when excited close to their natural ...

EPFL2016

Effects of incoming wind condition and wind turbine aerodynamics on the hub vortex instability

François Gallaire, Giacomo Valerio Iungo, Francesco Viola

Dynamics and instabilities occurring in the near-wake of wind turbines have a crucial role for the wake downstream evolution, and for the onset of far-wake instabilities. Furthermore, wake dynamics significantly affect the intra-wind farm wake flow, wake i ...

Iop Publishing Ltd2015

Data-driven RANS for simulations of large wind farms

Giacomo Valerio Iungo, Francesco Viola

In the wind energy industry there is a growing need for real-time predictions of wind turbine wake flows in order to optimize power plant control and inhibit detrimental wake interactions. To this aim, a data-driven RANS approach is proposed in order to ac ...

Iop Publishing Ltd2015

Instability of wind turbine wakes immersed in the atmospheric boundary layer

Fernando Porté Agel, François Gallaire, Giacomo Valerio Iungo, Francesco Viola

In this work a technique capable to investigate the near-wake stability properties of a wind turbine immersed in the atmospheric boundary layer is presented. Specifically, a 2D local spatial stability analysis is developed in order to take into account typ ...

Iop Publishing Ltd2015

Prediction of the hub vortex instability in a wind turbine wake: stability analysis with eddy-viscosity models calibrated on wind tunnel data

Fernando Porté Agel, François Gallaire, Giacomo Valerio Iungo, Francesco Viola

The instability of the hub vortex observed in wind turbine wakes has recently been studied by Iungo et al. (J. Fluid Mech., vol. 737, 2013, pp. 499–526) via local stability analysis of the mean velocity field measured through wind tunnel experiments. This ...

Cambridge University Press2014

Linear stability analysis of wind turbine wakes performed on wind tunnel measurements

Fernando Porté Agel, François Gallaire, Giacomo Valerio Iungo, Francesco Viola

Wind tunnel measurements were performed for the wake produced by a three-bladed wind turbine immersed in uniform flow. These tests show the presence of a vorticity structure in the near-wake region mainly oriented along the streamwise direction, which is d ...

Cambridge University Press2013

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Prediction of the hub vortex instability in a wind turbine wake: stability analysis with eddy-viscosity models calibrated on wind tunnel data

Fernando Porté Agel, François Gallaire, Giacomo Valerio Iungo, Francesco Viola

Cambridge University Press2014