Measurements of Transitional and Turbulent Flow in a Randomly Packed Bed of Spheres with Particle Image Velocimetry

Particle image velocimetry (PIV) has been used to investigate transitional and turbulent flow in a randomly packed bed of mono-sized transparent spheres at particle Reynolds number, 20< Reₚ< 3220 . The refractive index of the liquid is matched with the spheres to provide optical access to the flow within the bed without distortions. Integrated pressure drop data yield that Darcy law is valid at Reₚ ≈ 80 . The PIV measurements show that the velocity fluctuations increase and that the time-averaged velocity distribution start to change at lower Reₚ . The probability for relatively low and high velocities decreases with Reₚ and recirculation zones that appear in inertia dominated flows are suppressed by the turbulent flow at higher Reₚ . Hence there is a maximum of recirculation at about Reₚ ≈ 400 . Finally, statistical analysis of the spatial distribution of time-averaged velocities shows that the velocity distribution is clearly and weakly self-similar with respect to Reₚ for turbulent and laminar flow, respectively.