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| Abstract No.: |
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Scheduled at:
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Thursday, May 05, 2022, Hall G1 2:20 PM
Modeling & Simulation III
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| Title: |
The role of adsorbates on splat fragmentation during the impact of plasma spray particles: a numerical investigation
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| Authors: |
Mohammad Mahdi Nasiri / Concordia University, Canada
Ali Dolatabadi / University of Toronto, Canada
Christian Moreau*/ Concordia University, Canada
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| Abstract: |
The impact and flattening of droplets on a surface play a fundamental role in thermal spray processes. A droplet usually takes the shape of a disk after impact on a surface. However, the shape of the final splat may change from a "disk splat" to a "fragmented splat" depending on the substrate temperature. In air plasma spray (APS), fragmented splats are typically observed at low substrate temperatures while disk splats are dominant at temperatures above the so-called transition temperature. The formation of fragmented splats has been attributed to the desorption of adsorbates from the substrate surface during droplet impact. Even though the desorption hypothesis is well accepted, its dynamics has not been adequately addressed and requires further investigation.
In this study, a numerical model is developed to investigate the role of the adsorbates on the formation of fragmented splats at room temperature. To do so, compressible Navier—Stokes equations are solved and the volume of fluid (VOF) method is used to capture the liquid and gas interface. It is assumed that gas desorption occurs at the rim of the droplet as it spreads on the surface. The numerical results show that the desorption of less than 0.1 ?g/cm2 of adsorbed gas is sufficient to induce splat fragmentation. The gas desorption contributes to the formation of a high-pressure zone at the droplet rim that induces its detachment from the surface and the formation of a liquid sheet spreading above the substrate surface followed by its fragmentation. As a result, only a portion of the initial droplet remains at the location of the impact, which forms a small solidified splat.
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