Dune formation in dilute phase pneumatic transport system: PIV & PTV based analysis

Department of Energy Science and Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, India – 400076

^* Corresponding author: manaswita.bose@iitb.ac.in

Published online: 30 June 2017

Abstract

Flow of gas-solid mixture through horizontal conveying section show a large variety of phenomena and is broadly classified into dilute and dense unstable regimes. Different types of instabilities are observed in the dense phase flow and are widely studied in literature; however, clustering instabilities are observed in the very dilute regime of flow with volume fraction ~0.001. A recent study has shown that regular, stable dune shaped clusters are formed in a small regime of the dilute phase of conveying. The dunes become unstable as the superficial gas velocity is decreased before it finally leads to the dense mode of conveying. The motivation of the current work is to investigate the velocity distribution on the surface of the stable and unstable dunes and thereby understand the cause behind the formation of the dunes in the conveying section. To that end, particle image and tracking velocimetry techniques are employed with the specific objective to determine the volume fraction and the velocity profile of the solid phase on the stable dune surface. A drastic change in the solid fraction within a few particle diameters from the dune surface suggests that PTV is more appropriate in the bulk whereas PIV is suitable for near surface investigation.