Title: Flow visualisation of natural convection around a heated vertical plate using background oriented schlieren

Authors: Su-Min Jeong; Dae-Hyun Kim; Dong-Wook Oh

Addresses: Department of Mechanical Engineering, Chosun University, 10 Chosundae 1 Beon-gil, Dong-Gu, Gwangju 61452, South Korea ' Department of Mechanical Engineering, Chosun University, 10 Chosundae 1 Beon-gil, Dong-Gu, Gwangju 61452, South Korea ' Department of Mechanical Engineering, Chosun University, 10 Chosundae 1 Beon-gil, Dong-Gu, Gwangju 61452, South Korea

Abstract: This study employed the background oriented schlieren (BOS) technique to visualise and quantify natural convection flow around a heated vertical plate. The BOS system comprised a camera, a heated plate, and a background image. The surface temperature of the vertical plate was set to 75, 100, 125, and 150°C, and natural convection was observed under ambient conditions. The recorded images were processed using a probabilistic optical flow algorithm to calculate pixel displacements and derive the velocity field, which was then calibrated by comparison with two-dimensional computational fluid dynamics (CFD) simulations of the same geometry and conditions. BOS successfully reproduced the velocity distribution in the high-temperature, high-speed core region, agreeing with CFD results within approximately 10% for peak velocity. However, in low-velocity and stagnant flow regions near the plate edges, minimal refractive index changes limited accurate velocity detection. These findings demonstrate the potential for extending BOS applications to thermal-fluid system monitoring and leak detection.

Keywords: flow visualisation; BOS; background oriented schlieren; natural convection; heated vertical plate; velocity profile.

DOI: 10.1504/IJNT.2025.152234

International Journal of Nanotechnology, 2025 Vol.22 No.1, pp.78 - 86

Published online: 11 Mar 2026 *

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