%0 Generic
%A Krah, Nils
%D 2014
%F heidok:16895
%K gas exchange, air-sea interaction, visualization
%R 10.11588/heidok.00016895
%T Visualization of air and water-sided concentration profiles in laboratory gas exchange experiments
%U https://archiv.ub.uni-heidelberg.de/volltextserver/16895/
%X In this work, the transport of a tracer gas from air into water is studied experimentally under turbulent, wavy conditions imposed by a unidirectional wind field in a laboratory flume. To this end, a technique based on laser induced fluorescence recorded with cameras is developed to visualize the spatial tracer distribution in both phases simultaneously. Dedicated image processing procedures are developed to determine statistically averaged vertical profiles of absolute concentration in coordinates relative to the wavy water surface. A thorough characterization of the technique in terms of systematic errors is presented and a simple method to estimate the vertical probability distribution of turbulent eddies in water is proposed.   Invasion experiments are performed in which supersaturation of acetone in the flume's air compartment is imposed giving rise to a vertical flux into the water.   The equivalence of momentum and mass transport in air, presumed by many theoretical descriptions, is confirmed experimentally by comparing characteristic scaling properties of wind and concentration profiles.   Results also suggest that surfactants suppress gas exchange by modifying the water-sided boundary conditions and altering the turbulent water flow close to the surface regardless of the wind regime. Furthermore, observed discontinuity of complete air-water concentration profiles leads to the hypothesis that kinetic processes on molecular scale at the interface must be considered additionally to fluid mechanical descriptions.