Concentration measurement in the wake of a free rising bubble using planar laser-induced fluorescence (PLIF) with a cali
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RESEARCH ARTICLE
Concentration measurement in the wake of a free rising bubble using planar laser-induced fluorescence (PLIF) with a calibration taking into account fluorescence extinction variations Pierre Valiorgue • Nicolas Souzy • Mahmoud El Hajem Hamda Ben Hadid • Serge Simoe¨ns
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Received: 20 July 2012 / Revised: 18 March 2013 / Accepted: 20 March 2013 / Published online: 11 April 2013 Ó Springer-Verlag Berlin Heidelberg 2013
Abstract A planar laser-induced fluorescence (PLIF) data treatment taking into account variations of the fluorescence extinction due to pH is presented. It is shown that the proposed method needs to be implemented when the product of extinction coefficient variations, path length travelled by the laser and fluorescence concentration become large as in large tank experiments. The influence of extinction coefficient variations has been evaluated on CO2 concentration measurement for a test case in the wake of a free rising bubble. List of symbols Greek symbols d Diffusive length scale (m) e Molar extinction coefficient L mol m / Quantum yield of the fluorescence Latin symbols A Fraction of the available light collected Asc Area of a spherical cap bubble (m2) a Semi-width of a bubble, (m) C Carbon dioxide molar concentration mol m3 c Fluorescein molar concentration mol m3 e FCO2
Thickness of the laser beam (mm) Molecular gas flux mol FCO2 ¼ KLCO2 ðCsat CCO2 ðaqÞ Þ sm 2
P. Valiorgue (&) N. Souzy M. E. Hajem H. B. Hadid S. Simoe¨ns LMFA, UMR CNRS 5509, Ecole Centrale de Lyon, Universite´ de Lyon, Universite´ Lyon 1, INSA de Lyon, ECL, 20, Avenue Albert Einstein, 69621 Villeurbanne Cedex, France e-mail: [email protected]
h I0 Ie If kdehyd khyd kl Ld Lfluo
Ls Lw r Vb
Length of the vertical sides of the region of interest (ROI) (m) Initial light intensity (U.A.) Laser excitation intensity (U.A.) Fluoresced intensity (U.A.) Dehydration rate of H2CO3 (1s ) Hydration rate of CO2 (aq) (1s ) Mass transfer coefficient (ms ) Distance between the diverging lens and the camera field of view (m) Distance traversed by the laser beam in the fluorescent fluid to reach the considered element of the ROI (m) Length of the sampling volume along the incident beams (m) Width of the camera field of view (m) Coordinate in the downstream direction along a beam of light (m) Bubble rising velocity (ms )
Subscripts k Pixel column position along the laser beam l Pixel column position along the laser beam pH Value of the parameter for a given pH ref Value of the parameter for a reference pH before measurements
1 Introduction This study is concerned with quantitative experimental concentration field measurements of dissolved CO2 in water using planar laser-induced fluorescence (PLIF). CO2 concentration measurements in the wake of a free rising bubble have been carried out. Such measurements could be
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useful as a validation for numerical simulations of interfacial gas/liquid mass transfer. Those simulations are often applied to free rising bubble test cases.
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