Experimental study on the interactions between a turbulent flow and a bed of visco-elasto-plastic synthetic mud.

An experimental method to study the response of a synthetic mud bed under turbulent flow is presented. In this study, this problem is considered as the interaction between a turbulent flow and a visco-elasto-plastic bed in a similar way to the studies on compliant walls. The synthetic material is presented and has rheological properties similar to those of natural mud. The interaction between a bed of this synthetic mud and a turbulent flow is studied in a channel using particle image velocimetry and adapted planar laser induced fluorescence. The paper focuses on the analysis of the onset of the bed motion for which oscillations of the interface are observed. Tests are performed at different flow velocities and for different bed stiffnesses. The results show surface deformations that depend both on the shear modulus of the material and on the flow properties. Two deformation patterns are highlighted and linked to the material properties. Correlations between this interface deformation and the flow fluctuations are highlighted and discussed.