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Comparative Analysis Of Brightness-Based Laser-Induced Fluorescence (BBLIF) And Structured Planar Laser-Induced Fluorescence (S-PLIF) For Film Thickness Measurement In Two-Phase Flow

Ahmed Abou Sherif, Kathy Johnson, David Hann

The University of Nottingham, Nottingham, United Kingdom


Improved understanding of the interactions between gas and liquid phases in gas sheared film flow is crucial for n improved capability to employ computational modelling in the future to optimize systems, thereby reducing environmental impact, increasing efficiency, and enhancing productivity. This abstract compares two techniques for measuring the thickness of the film in different regimes visible in a rectangular cross-section gas-sheared liquid film rig, namely previously published Brightness Based Laser Induced Fluorescence (BBLIF) data and Structured Planar Laser Induced Fluorescence (S-PLIF) from the current investigation. The study presents and compares examples at a specific liquid flow rate (8 litres per minute) for superficial gas velocities in the range 1 m/s to 10 m/s, noted as being in different flow regimes. The investigation reveals that the S-PLIF technique produces results that are within the uncertainty bands of the BBLIF data for most scenarios. However, in the transition regime, statistical variations emerge. The frequency content of the two film heights is analyzed using a Hilbert-Huang Technique. This shows clearer results for the S-PLIF than for BBLIF which is attributed to the erratic values that can occur in BBLIF when total internal reflection occurs. It is concluded that the S-PLIF technique demonstrates promise as a reliable method for determining film thickness which is highly advantageous as it can be applied to images obtained with seeded flow intended for PIV analysis. The S-PLIF film thickness data can be used for generating automated masks for PIV analysis concurrently conducted in both the gas and liquid phases. This advancement facilitates the enhanced capability to advance understanding of complex fluid dynamics and optimize system performance.

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