Abstract
We present laboratory measurements of simultaneous velocity and concentration fields for the transfer of CO2 across a free surface. The interface is subject to the effects of free shear turbulence generated far beneath the surface, exhibiting low mean flow and excellent homogeneity. From measurements of the spatio-temporal mass flux we examine coherent structures below the free surface, as well as one-point statistics to better understand the fundamental physics of turbulent transport at a free surface in the absence of mean shear. We observe surface penetration events caused by bulk fluid impacting the interface from below, as well as downwelling events in which the near-surface fluid is injected into the bulk in narrow filaments. Both types of events contribute to the turbulent mass flux, and we measure that downwelling events are responsible for at least as much mass transfer as the upwellings on which existing models are based. Our measurements indicate that the dominant length and time scales are different for upwellings and downwellings; the quantification of these will be important to modeling efforts.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Asher W.J., Pankow J. (1986) The interaction of mechanically generated turbulence and interfacial films with a liquid phase controlled gas/liquid transport process. Tellus 38B: 305–318
Asher W.J. (1987) An examination of the hydrodynamics governing a liquid-phase rate controlled gas/liquid mass transport process at clean and film-covered liquid surfaces. PhD Thesis, Environmental Science and Engineering, Oregon Graduate Center, Oregon
Asher W.J., Jessup A.T., Atmane M.A. (2004) Oceanic application of the active controlled flux technique for measuring air-sea transfer velocities of heat and gases J. Geophys. Res. 109
Banerjee S. (1990). Turbulence Structure and Transport Mechanisms at Interfaces. 9th Int. Heat Transfer Conference, Hemisphere Press, NY
Banner, M.L., Peirson W.L. (1998) Tangential stress beneath wind-driven air-water interfaces. J. Fluid Mech. 364: 115–145
Brumley B., Jirka G. (1987). Near-Surface Turbulence in a Grid-Stirred Tank. J. Fluid Mech. 183: 235–263
Cowen E.A., Monismith S. (1997). A hybrid digital particle tracking velocimetry technique. Exp. Fluids 22: 199–211
Danckwerts P.V. (1951) Significance of liquid-film coefficients in gas adsorption Industrial and Engineering Chemistry 43(6): 1460–1467
DeSilva I., Fernando H.J.S. (1994). Oscillating grids as a source of nearly isotropic turbulence. Phys Fluids 6(7): 2455–2464
Falkenroth A., Degreif K., Jähne B. (2007) Visualisation of Oxygen Concentration Fields in the Mass Boundary Layer by Fluorescence Quenching. In: Garbe C.S., Handler R.A. and Jähne B. (eds) Transport at the Air Sea Interface-Measurements, Models and Parameterizations. Chapter 4, pages 59–72, Springer Verlag. This volume.
Fortescue G.E., Pearson J.R.A. (1967) On Gas absorption into a turbulent liquid. Chemical Engineering Science 22: 1163–1176
Hanratty T.J. (1990). Effect of Gas Flow on Physical Absorption. In: Air-Water Mass Transfer: Selected Papers from the Second International Symposium on Gas Transfer at Water Surfaces, American Society of Civil Engineers, NY
Herlina, Jirka G.H. (2004) Application of LIF to investigate gas transfer near the air-water interface in a grid-stirred tank Exp. Fluids 37: 341–349
Lamont J.C., Scott D.S. (1970) An eddy cell model of mass transfer into the surface of a turbulent liquid AIChE J 16:513–519
Magnaudet J., Calmet I. (2006). Turbulent mass transfer through a flat shear-free surface. J. Fluid Mech. 553: 155–185
McKenna S.P., McGillis W.R. (2004). The role of free-surface turbulence and surfactants in air-water gas transfer. International Journal of Heat and Mass Transfer. 47(3):539–553
Nagaosa R. (1999). Direct numerical simulation of vortex structures and turbulent scalar transfer across a free surface in a fully developed turbulence. Phys. Fluids 11(6): 1581–1595
Schladow S.G., et al. (2002) Oxygen transfer across the air-water interface by natural convection in lakes. Limnology and Oceanography 47(5): 1394–1404
Takehara K., Etoh G. (2002) A Direct Visualization Method of CO2 Gas Transfer at Water Surface Driven by Wind Waves. In: Donelan et al. (eds) Gas Transfer at Water Surfaces. Geophysical Monograph 127, 2002, American Geophysical Union
Variano E.A., Bodenschatz E., Cowen E.A. (2004). A random synthetic jet array driven turbulence tank. Exp. Fluids. 37(4):613–615
Variano E.A. (2005) Quantitative Visualization of Carbon Dioxide gas transfer at a turbulent free surface. MS Thesis, Cornell University, New York
Variano E.A., Cowen E.A. (2006). A turbulent stirred tank using randomized jets. J. Fluid Mech. (submitted)
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2007 Springer-Verlag Berlin, Heidelberg
About this chapter
Cite this chapter
Variano, E.A., Cowen, E.A. (2007). Quantitative Imaging of CO2 Transfer at an Unsheared Free Surface. In: Garbe, C.S., Handler, R.A., Jähne, B. (eds) Transport at the Air-Sea Interface. Environmental Science and Engineering. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-36906-6_3
Download citation
DOI: https://doi.org/10.1007/978-3-540-36906-6_3
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-540-36904-2
Online ISBN: 978-3-540-36906-6
eBook Packages: Earth and Environmental ScienceEarth and Environmental Science (R0)