  In this study, we investigated the flow dynamics in a fixed bed of hydrogel
beads using Particle Tracking Velocimetry to compute the velocity field in the
middle of the bed for moderate Reynolds numbers. We discovered that despite the
overall stationarity of the flow and relatively low Reynolds number, it
exhibits complex multiscale spatial dynamics reminiscent of those observed in
classical turbulence. We found evidence of the presence of an inertial range
and a direct energy cascade, and were able to obtain a value for a "porous"
Kolmogorov constant of $C_2 = 3.1\pm 0.3$. This analogy with turbulence opens
up new possibilities for understanding mixing and global transport properties
in porous media.
