Laser Detection of Thermal Flows: An Analytical Model and Experimental Investigation
Keywords:
laser detection of thermal flows, temperature inhomogeneities, refractive index of air, coherent radiation, phase fluctuations, photocurrent spectrum, anisotropy, spatial correlation, two-pass optical arrangementAbstract
This paper presents an analytical model for laser detection of thermal flows based on recording temporal fluctuations in the total power of coherent radiation after it interacts with temperature inhomogeneities in air. The model links the spatiotemporal correlation of refractive-index fluctuations to the measured photocurrent spectrum. It accounts for the two-pass optical geometry, the lateral offset of the photodetector, the finite receiving aperture, anisotropy in the spatial structure of the inhomogeneities, and possible changes in their intensity with distance from the heat source.
Experiments were conducted using a hair dryer as the thermal-flow source. Horizontal and vertical geometries were investigated, together with several positions of the interaction region along the optical path and fan-to-beam distances ranging from 2 to 40 cm. Photocurrent spectra were obtained by averaging spectral estimates over selected informative intervals of the recordings.
The study establishes an analytical relationship between the statistical properties of thermal inhomogeneities, the optical-system geometry, and the recorded photocurrent spectrum. The experimental results are used for a preliminary qualitative comparison with the model. The attenuation parameters and spatial correlation scales have not been determined from the available measurements.
References
1. Drain, L. E. The Laser Doppler Technique. Chichester: John Wiley & Sons, 1980. ISBN 0-471-27627-8.
2. Tropea, C. Laser Doppler anemometry: recent developments and future challenges. Measurement Science and Technology, 6, 605–619 (1995). DOI: 10.1088/0957-0233/6/6/001.
3. Li Jiwei, Luo Kai, Shang Jiahao, Wang Yejun, Wang Qiu, Zhao Wei. Research progress of laser diagnostics for velocimetry in hypersonic flows. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(4): 890-914.DOI: 10.6052/0459-1879-23-242
4. Evans MJ and Medwell PR (2019) Understanding and Interpreting Laser Diagnostics in Flames: A Review of Experimental Measurement Techniques. Front. Mech. Eng. 5:65. DOI: 10.3389/fmech.2019.00065
5. Andrews L. C., Phillips R. L. Laser Beam Propagation through Random Media. 2nd ed. Bellingham, WA: SPIE Press, 2005.
6. Pérez D. G., Farfán-Bachiloglu H., Sepúlveda M. Spatiotemporal statistics of optical turbulence beyond Taylor’s frozen turbulence hypothesis. Journal of the Optical Society of America A. 2024. Vol. 41, No. 6. P. B135–B143. DOI: 10.1364/JOSAA.520550.
7. Schock M., Spillar E. J. Method for a quantitative investigation of the frozen flow hypothesis. Journal of the Optical Society of America A. 2000. Vol. 17, No. 9. P. 1650–1658. DOI: 10.1364/JOSAA.17.001650.
8. G.N. Dolya, E.S. Litvinova. Retroreflective laser detector of acoustic oscillations// Proceedings of 12th International Conference on Laser & Fiber-Optical Networks Modeling (LFNM’2016), Sept.15-18, Odessa, Ukraine. P.108-111 DOI: 10.1109/LFNM.2016.7851212
9. Dolya G.N., Katunin A.N, Sadovy K.V., Chudovskaja E.S. Laser radiation parameters at detection of decay and fire sources. / Proceedings of 4-th International Conference on Advanced Optoelectronics and Lasers. Alushta, Crimea, 2008, p.351-353
Downloads
Published
Issue
Section
License
Copyright (c) 2026 Author(s)
This work is licensed under a Creative Commons Attribution 4.0 International License.
Articles published in the Journal of Advanced Multidisciplinary Studies (JAMS) are licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0), unless otherwise stated. Authors retain copyright of their work and grant JAMS the right of first publication.
