Active thermography to investigate small-scale air-water transport processes in the laboratory and the field.

Nagel, Leila (2014) Active thermography to investigate small-scale air-water transport processes in the laboratory and the field. (PhD/ Doctoral thesis), Universität Heidelberg, Heidelberg, Germany, 119 pp.

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The active controlled flux technique is a tool to measure heat transfer velocities with a high temporal and spatial resolution. As heat, momentum and gas transport underlie the same physical processes, heat can be used as a proxy tracer for gases. Nevertheless the scaling of the measured heat transfer rates to the ones for gases is under discussion since the last decade due to the large differences in the diffusion constants of heat and gas. In this thesis simultaneous heat and gas transfer measurements have been conducted in the laboratory. Using an amplitude damping method, where the system response to different large-scale laser stimulations is investigated, a good agreement between scaled heat and gas transfer rates is found. The results show that, knowing the actual Schmidt number exponent, a scaling of heat to gas transfer rates is possible. During three campaigns in the Baltic Sea reliable transfer rates were determined. The obtained values are in the range of the expectations obtained from the laboratory measurements in the Aeolotron. They show, that the wind speed alone is not able to parametrise the gas transfer. Due to the different laser forcings required for this analysis, the integration time is in the order of 30 minutes. For an investigation of the underlying transport processes two fast analysis methods have been evaluated during laboratory measurements. The used methods are based on the surface renewal model. The results show, that these assumptions are too restrictive. To obtain reliable transfer velocities with a high temporal resolution, the development of a model independent analysis method is necessary.

Document Type: Thesis (PhD/ Doctoral thesis)
Thesis Advisor: Schöler, Heinz Friedrich
Open Access Journal?: Yes
Projects: SOPRAN
Date Deposited: 04 Dec 2014 13:24
Last Modified: 04 Dec 2014 13:27

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