Original title: Dopad kapky na porézní oxid železa: VOF simulace
Translated title: Droplet Impingement on the Porous Iron Oxide Layer: VOF Simulation
Authors: Cheng, Xin ; Hvožďa, Jiří (referee) ; Boháček, Jan (advisor)
Document type: Master’s theses
Year: 2026
Language: eng
Publisher: Vysoké učení technické v Brně. Fakulta strojního inženýrství
Abstract: Droplet impact on the porous iron oxide layer is a multiphase flow problem of practical significance in spray cooling, in which the cooling spray interacts with the oxide skin formed on the surface of high-temperature metal. This paper adopts the Volume of Fluid (VOF) method realized in the open source CFD software OpenFOAM, combined with the MULES algorithm for interface capture and continuous surface force model for surface tension calculation, and conducts a numerical study of this phenomenon. All solid surfaces have a static contact angle of 20°, which is consistent with the hydrophilicity of iron oxide. The porous oxide layer is represented by a pore-resolved computational mesh instead of a volume-averaged continuum model. The grid is reconstructed from the micrograph stack of the actual oxide sample: the micrograph image is loaded into ParaView, resampled to the uniform OpenFOAM grid through the ResampleWithDataset function, denoising with a median filter, and the solid and pore regions are separated by applying an intensity threshold. The generated oxide geometry is embedded in the refined background grid through the mergeMeshes and stitchMesh functions, thus forming a single composite domain. A reference case of droplet diameter D0 = 0.1 mm and impact speed U0 = 1 m/s was established and extended it through two parameters: one is the speed parameter, U0 is 1, 2, 5 and 10 m/s respectively; the other is the droplet size parameter D0, with values of 0.1, 0.3 and 1 mm, the latter of which is obtained by rescaling the geometry using the transformPoints function. Pore penetration is quantified by two indicators extracted along the internal reference path of the oxide: the maximum penetration depth d(t) and the interface position through specific path dint (t) that changes with time. These two indicators together reveal that the early inertial dominant stage is followed by a slower capillary-driven phase. The grid of the reference case was refined to verify the sensitivity of the grid, the current non-convergence is due to several factors, which are discussed below.
Keywords: Droplet impingement; OpenFOAM; Porous iron-oxide layer; Volume of Fluid (VOF); Droplet impingement; OpenFOAM; Porous iron-oxide layer; Volume of Fluid (VOF)

Institution: Brno University of Technology (web)
Document availability information: Fulltext is available in the Brno University of Technology Digital Library.
Original record: http://hdl.handle.net/11012/259960

Permalink: http://www.nusl.cz/ntk/nusl-776927


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Universities and colleges > Public universities > Brno University of Technology
Academic theses (ETDs) > Master’s theses