Sediment characterization of bottom propagating reversing buoyancy particle-bearing

M. Kapil, B.R. Sutherland and S. Balasubramanian

We develop theory and perform laboratory experiments on reversing buoyancy particle-bearing wall jets in a uniform ambient fluid, examining the lofting characteristics of the jet and particle sedimentation. Theoretical considerations involving several parameters predict the lofting location and the deposition pattern. The suction forces present at the bottom wall dominantly influence the lofting location of the jet. The sediment dynamics are influenced by the drag at the bottom wall, entrainment of ambient fluid into the jet, and several scale factors involving the settling of the particles. Our theory shows that the ratio of deposit width to length depends on the jet's drag coefficient and entrainment dynamics. Experimentally we find that this ratio is higher when the particle concentration is large, suggesting that sedimenting particles exert a non-negligible additional drag on the jet. The results clearly show the change in the jet dynamics brought about by the presence of particles in reversing buoyancy jets.