Infrastructure uniqueness

The Marseille-Luminy wind wave facility is known by the scientific community working in the fields of air-sea interactions and marine technologies as a unique installation owing to its large dimensions and the exceptional quality of the air and water flows generated respectively in the wind tunnel and the water tank. The facility is intensively used for measuring air-water surface fluxes in realistic sea conditions (momentum, energy, mass and gas exchanges), investigating small-scale wind wave roughness and the associated acoustic and electromagnetic wave backscatterring at the water surface and more recently, characterizing the aerodynamic and hydrodynamic responses of marine structures as floating wind turbines.

The recirculating wind tunnel and the fan was specially designed to generate a low-noise and constant-velocity air flow at the entrance of the water tank. The smooth transition between the air and water flows insures the development of a typical high-Reynolds turbulent boundary layer just above the very first meters of the water surface. The slightly-increasing height of the air flume allows to maintain a constant-flux turbulent boundary layer above surface waves whatever the measuring section. Owing to the exceptionally long water tank length, gravity wave fields in quasi-equilibrium with wind can be observed over the whole surface area downwind fetches higher than 10 to 20 m, depending on wind speed. These characteristics make the facility particularly suitable for studies on the turbulent structure of the marine air boundary layer and small-scale wind-wave-current interactions.

The wavemaker generating regular or irregular wave trains is immersed under the upstream air-water junction device. This arrangement allows to study interactions between mechanically generated waves and the turbulent air flow above over the whole length of the water tank without any development of wake-type disturbances. An absorbing beach is located at the end of the water tank to damp wave reflection.

The large width of the water tank allows to study three-dimensional properties of wind or mechanically-generated wave fields. The very good simulation of the three-dimensional features of wind wave fields allows to investigate interactions between waves and marine structures and to test small-scale prototype models in realistic wind sea conditions.

Due to these outstanding specifications, the installation enables to perform model experiments in which one particular process can be discriminated among others to be investigated, then providing high quality data sets for direct comparison with numerical simulations and theoretical models. Some of the main characteristics of the wave field and the air turbulent boundary layer observed are illustrated by the figures given below (Figures 7 to 10).

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Figure 07

Typical wind wave fields observed in LASIF at 26 m fetch, the wind blowing from right to left

Crédit : G. Caulliez
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Figure 08

Three-dimensional wind wave field development observed in LASIF from initial waves to breaking waves with a wind blowing from right to left, the fetch and wind conditions being respectively : a) X = 2 m – U = 6 m/s, b) X = 6 m – U = 4 m/s, c) X = 6 m – U = 5 m/s, d) X = 9 m – U = 6 m/s, e) X = 18 m – U = 5 m/s, f) X = 26 m – U = 12 m/s.

Crédit : G. Caulliez
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Figure 10

Wind and fetch dependencies of characteristic wind and wave parameters

Crédit : G. Caulliez
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Figure 11b

Pictures of typical experimental arrangements - PIV and PTV measurements of the air flow velocity field above wind waves.

Crédit : G. Caulliez