We developed two original measures based on ultrasonic echography in suspensions. We add tracers in small quantities in Newtonian fluids to image them. These tracers will backscatter ultrasonic pulses emitted at regular time intervals. The recorded pressure signal called speckle is then recorded for further use.
Our ultrasonic transducer images in the vertical plane crossing the center of the Couette cell. The speckle phase and its intensity provide information on the local particle concentration and velocity. Our technique can be used both at constant shear rate and in oscillatory experiments, in which case it is synchronised to standard rheological measurements (a technique called LORE).