Velocity fluctuations in fluidized suspensions probed by ultrasonic correlation spectroscopy

Velocity fluctuations in a fluidized suspension of particles are investigat ed using two new ultrasonic correlation spectroscopies: diffusing acoustic wave spectroscopy and dynamic sound scattering. These techniques probe both the local strain rate and rms velocity of the particles, providing importa nt information about the spatial extent of velocity correlations. Our resul ts demonstrate the power of these techniques to probe particle dynamics of fluidized suspensions, and suggest that the velocity correlations are essen tially independent of Reynolds numbers for Re-p < 1.