Transport of Particulates in a Rotating Internal Cooling Ribbed Duct

Abstract

A ribbed square duct (P/e = 10, e/Dh = 0.10, and rotating with an angular velocity ωz) subjected to sand ingestion is studied using an Eulerian-Lagrangian framework. Particle sizes of 10μm and 50μm with response times (normalized by friction velocity and hydraulic diameter) of 0.06875 and 1.71875 respectively are considered. The calculations are performed for a nominal bulk Reynolds number of 20,000 and a Rotation number of 0.35 (based on hydraulic diameter and mean velocity) under fully-developed conditions. It is found that at any given instant in time about 67% of the total number of 10 micron particles are concentrated in the vicinity (within 0.05 Dh) of the duct surfaces, compared to 99% of the 50 micron particles. Both the particle sizes show preferential concentration near the smooth walls. The 10 micron particles, which are more sensitive to changes in flow, exhibit selective concentration on the trailing wall as compared to negligible concentration of the 50 micron particles. Both the particle sizes show negligible accumulation on the leading wall due to the action of Coriolis forces which push the particles towards the trailing wall. At the side walls of the duct, the 10 micron particles exhibit a high potential to erode the region in the vicinity of the rib due to secondary flow impingement. At the ribbed walls, while the 10 micron particles exhibit a fairly uniform but low propensity for erosion, the 50 micron particles show a much higher tendency to erode the surface. The trailing wall rib face facing the flow is by far the most susceptible to erosion and deposition for all particle sizes. In comparison to the front surface, the top and back surfaces of the rib do not exhibit a large propensity to be eroded. The potential for erosion in the rotating duct at the trailing wall and rib is at least an order of magnitude larger than in a stationary duct, whereas the leading wall has little or no erosion.