Turbulent flow of shear thinning slurries in a flume

The transport of fine particle slurries in open channels has broad application in tailings disposal. There are situations in which the slurry's yield stress or plastic viscosity is sufficiently small that the flow is transitional or turbulent. The turbulent transport characteristics of non-Newtonian fluids in open channels is one that has received scant attention. For design and operational reasons, it is important to understand the relationships between forcing (determined by channel inclination), rheological parameters and flow rates. An understanding of the magnitude of the unsteady vortical structure is also important for understanding the flow's potential to suspend larger particles. Here we simulate open channel flows of power-law fluids via Direct Numerical Simulation (DNS) in the weakly turbulent regime and shed some light on these relationships. The key finding is that similar to a Newtonian fluid, for the power-law fluid also the bulk velocity is almost independent of aspect ratio if the hydraulic radius is fixed, which suggests that the hydraulic radius is an appropriate length scale for the turbulent flow of a power law fluid. The general characteristics of the flow of both fluids are affected similarly with increasing aspect ratio. The effect of shear thinning observed here is similar to that seen in a pipe flow in earlier studies.