Experimental investigation on particle deposition patterns from turbulent pipe flow

This paper reports an experimental study on sand particles deposition pattern in a horizontal circular pipe for several air flow rates and particle - air volumetric loading ratios. The experiments are conducted in a horizontal circular pipe with air - sand particles flow to simulate the solid particles movement in turbulent flow. A 50 mm diameter pipe was used in the current study while the averaged sand particles size used is around 100 ìm. The particles are injected into the fully developed turbulent air flow. Digital cameras are used to capture the images of scaled test sections. The time dependent deposition layer properties including the geometry of deposition layers and the agglomeration pitch are studied. Hence, the average velocity of dune movement could also be calculated. The experimental results show that, in general, the deposition layer is continuous near the injection point, while small agglomerates are observed at the remote end. For the low air flow rate, striped-like dunes were found near injection point. For relatively higher air flow rates, the dunes became longer in size. Similarly, the length of agglomerates increased and the area fraction occupied by the agglomerates increased. Small aggregates are re-entrained from the frontal dunes of the deposition layer, and new agglomerates were gradually formed behind the next dune. The free flight length of solid particles for a range of air flow rates with different solid loading ratios was studied. It is found that for a given solid loading ratio, decreasing air velocity decreased the free-flight length of particles.