Towards an innovative mechanistic model to predict the detachment process of a deposited layer

Abstract

Solid contaminants dispersed in the air can heavily influence the performance and reliability of several engineering apparatuses. Particles that impact the surfaces of these devices can generate deposits that, under certain conditions, can be partially removed and transported away by the airflow, leaving unpredictable step-wise deposit shapes. As a consequence, performance losses due to the modification in the geometry and in the roughness of the contaminated surface arise. A combined experimental and computational study was conducted to provide a new mechanistic model for deposit layer removal from substrates exposed to fluid flows. A specific test bench was built to analyze the detachment of solid nano-sized particle deposits from a flat target, whereas numerical simulations for the flow field were employed to determine its characteristics at the target wall. Deposit influence on the flow has been considered by using roughness and thickness variations. It is found that the shear stress guides the particle removal until a certain adhered thickness, beyond which the dominant factor becomes the weight of the build-up deposit. By the mechanistic model proposed in this study, it is possible to predict either the area interested in deposit detachment and the critical thickness at which it occurs without using expensive particle-laden-flow simulations.