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P. Léard, P. Le Gal and M. Le Bars
Photography of the experimental set-up
Sketch of the setup
We investigate experimentally the dynamics of a convective layer of water situated underneath a stable stratified layer of water. The water is cooled from below at 0°C and heated from above at 35°C. Since water has its maximum density around 4°C, the two-layers configuration described above spontaneoulsy appears. The main advantage of this setup is that the system is self generated. We are interested in the spectral characteristics of the convection, of the internal gravity waves (IGWs) propagating in the stratified layer and in the property of a large scale flow generated by the wave-wave's non-linear interactions.
Time-resolved velocity measurements are performed using PIV. The tank dimensions are 32x32x20 cm. A cylinderof diameter d = 29 cm is placed inside the cubic tank and the measurements are performed in this cylinder.
We have shown that a wide spectrum of waves is generated from the convection. The propagative behaviour of the IGWs depends on their frequency. The waves non-linear interactions drive a large-scale flow with reversals within the cylinder.
This experimental work is completed with an analytical model. This model is based on the Plumb theory (1977) and extended to compute a spectrum of waves as the driving mechanism for the lage-scale flow generation (the Pumb model originally took into account only 2 waves).
Time evolution of the large-scale flow (top view PIV, from an horizontal laser sheet in the stratified layer)
We are currently writing an article presenting these results in detail.
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