Application of Background-Oriented Schlieren to Counterflow Diffusion Flames for Refractive Index Gradient Identification

Daeyoung Jun; Jungmu Hur; Seo Hee Cho; Bok Jik Lee

doi:10.6108/JPNE.2026.6.1.087

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2026 Vol.6, Issue 1 Preview Page

Research Article

Application of Background-Oriented Schlieren to Counterflow Diffusion Flames for Refractive Index Gradient Identification

31 May 2026. pp. 87-97

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Abstract

BOS (Background-Oriented Schlieren) is an optical diagnostic technique for measuring refractive index gradients associated with density variations. In this study, BOS was applied to a counterflow diffusion flame to quantify refractive index gradients. The displacement field was extracted using a Fourier transform-based demodulation method and converted into refractive index gradients, followed by an inverse Abel transformation. The reconstructed refractive index gradient profiles agree well with one-dimensional numerical solutions in both shape and peak location. The results reveal a distinct double-peak structure in the refractive index gradient, arising from density variations induced by mixing and heating. The peak-to-peak distance obtained from BOS agrees well with one-dimensional solutions across varying strain rates controlled by the nozzle spacing, demonstrating its capability to capture the thermal expansion zone and its thickness.

Keywords

Background-Oriented Schlieren

Counterflow Flame

Non-Premixed Flame

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Information

Publisher :The Korean Society of Propulsion Engineers
Publisher(Ko) :한국추진공학회
Journal Title :Journal of Propulsion and Energy
Journal Title(Ko) :Free Open Access International Journal on Propulsion and Energy Science and Technology
Volume : 6
No :1
Pages :87-97
Received Date : 2026-04-05
Revised Date : 2026-05-15
Accepted Date : 2026-05-25
DOI :https://doi.org/10.6108/JPNE.2026.6.1.087

Journal of Propulsion and Energy ISSN:2734-1887(Print) 2765-0049(Online) Free Open Access International Journal on Propulsion and Energy Science and Technology

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