Quantification of turbulent flow anisotropy in an alluvial channel mining pit

Abstract

In this paper, turbulence anisotropy over a mining pit is studied. Laboratory experiment is performed in a flume with non-cohesive sand under steady flow condition. Two different geometric shaped mining pits, namely trapezoidal pit and irregular pit were excavated and instantaneous velocity data along the flow depth are taken at upstream, downstream and inside the mining pit. Turbulent anisotropy at various locations of the pit are compared. Stream-wise turbulence anisotropy is more in the upstream flow and nearly constant over the flow depth as compared to the other sections. For near bed flow in the pit, span-wise and vertical anisotropic contribution is more prominent as compared to the other components. Anisotropic invariant map (AIM) explains presence of two dimensional anisotropy near the bed for all the sections. It further illustrates the occurrence of two dimensional anisotropy in the outer flow zone in the pit. Mostly cigar shaped turbulence is observed in the upstream of the pit that changes to pancake shaped for near bed flow in the pit. At downstream of the pit, two dimensional anisotropy occurs near the bed and further it inclines to the three dimensional isotropy in the upper flow region.