Holtappels, Moritz; Noss, Christian; Hancke, Kasper; Cathalot, Cecile; McGinnis, Daniel F; Lorke, Andreas; Glud, Ronnie N (2014): (Exp. 14op) Artificial oxygen fluxes measured by the eddy correlation method using oxygen optodes in a flume experiment. PANGAEA, https://doi.org/10.1594/PANGAEA.838415, In supplement to: Holtappels, M et al. (2015): Aquatic Eddy Correlation: Quantifying the Artificial Flux Caused by Stirring-Sensitive O2 Sensors. PLoS ONE, 10(1), e0116564, https://doi.org/10.1371/journal.pone.0116564
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Flume experiments were conducted in February 2013 at the Institute for Environmental Sciences, University of Koblenz-Landau Landau. Experiments were performed in a closed oval-shaped acrylic glass flume with cross-sectional width of 4 cm and height of 10 cm and total length of 54 cm. The fluid flow was induced by a propeller driven by a motor and mean flow velocities of up to 20 cm s-1 were generated by applying voltages between 0 V and 4 V DC. The flume was completely sealed with an acrylic glass cover. Oxygen sensors were inserted through rubber seal fittings and allowed positioning the sensors with inclinations to the main flow direction of ~60°, ~95° and ~135°. A Clark type electrochemical O2 microsensor with a low stirring sensitivity (0.7%) was tested and a fast-responding needle-type O2 optode (PyroScience GmbH, Germany) was used as reference as optodes should not be stirring sensitive.
Instantaneous three-dimensional flow velocities were measured at 7.4 Hz using stereoscopic particle image velocimetry (PIV). The velocity at the sensor tip was extracted. The correlation of the fluctuating O2 sensor signals and the fluctuating velocities was quantified with a cross-correlation analysis. A significant cross-correlation is equivalent to a significant artificial flux.
For a total of 18 experiments the flow velocity was adjusted between 1.7 and 19.2 cm s-1, and 3 different orientations of the electrochemical sensor were tested with inclination angles of ~60°, ~95° and ~135° with respect to the main flow direction. In experiments 16-18, wavelike flow was induced, whereas in all other experiments the motor was driven by constant voltages. In 7 experiments, O2 was additionally measured by optodes. Although performed simultaneously with the electrochemical sensor, optode measurements are listed as separate experiments (denoted by the attached 'op' in the filename), because the velocity time series was extracted at the optode tip, located at a different position in the flume.
|#||Name||Short Name||Unit||Principal Investigator||Method/Device||Comment|
|1||Flow velocity, water||Vel water||m/s||Holtappels, Moritz||Particle image velocimetry (PIV)||longitudinal velocity|
|2||Flow velocity, water||Vel water||m/s||Holtappels, Moritz||Particle image velocimetry (PIV)||vertical velocity|
|3||Flow velocity, water||Vel water||m/s||Holtappels, Moritz||Particle image velocimetry (PIV)||transversal velocity|
|4||Oxygen||O2||µmol/l||Holtappels, Moritz||Oxygen optode (PyroScience GmbH, Germany)|
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