Utilisation rhéométrique d'écoulements gravitaires à surface libre : le cas des fluides viscoplastiques

International audience; We present experimental results concerning the behaviour of two viscoplastic fluids (Carbopol gel and kaolin slurry) in a free surface flow configuration. Our experiments are conducted in a 3 meter long and 0.4 meter wide inclined channel whose bottom consists of a conveyor belt moving upstream with a controlled velocity. At channel upper boundary, fluid recirculation is forced by a rigid wall perpendicular to the bottom. These specificities allow us to generate gravitary surges that are stationary in the laboratory frame. We compare the properties of these surges (height and non dimensional characteristic numbers) to predictions based on independent measurements of the fluid rheological parameters. Lastly, the perspectives offered by the conveyor belt channel to characterize the rheological behaviour of complex natural fluids, such as muddy debris flow matrix, are discussed.