We study experimentally the hydrodynamic-interaction-controlled random walk (RW) of noncolloidal spheres in a quasi-2D fluidized suspension. This macroscopic ``molecular'' system is anisotropic. Particle trajectories are Brownian-like and, from time to time, fast upward correlated. The vertical RW is hyperdiffusive, but the horizontal one is Gaussian. Velocity fluctuation distributions vary from Gaussian to exponential as particle concentration C increases. The dynamics varies from liquidlike to gaslike as C decreases. These features are attributed to the formation of ``transient channels'' at higher C.
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Rouyer et al. (1999) studied this question.