Laboratory Methods

An off-the-shelf 30-cm TDR probe from Campbell Scientific was tested under laboratory conditions using a range of controlled air:water ratios, both in calm and turbulent conditions.

Calm versus Turbulent Single Phase Test

Because rivers are highly turbulent, two tests were carried out to determine if turbulence affects the performance of the TDR probe. In the first, the probe was sequentially immersed in calm and turbulent air. In the second, it was sequentially immersed in calm and turbulent water.

Calm Air:Water Mixture Calibration

To obtain a regression between signal frequency and air content, the TDR probe was incrementally immersed into a calm water reservoir. This was done for both 30-cm and 10-cm wave guide configurations.

Turbulent Air:Water Calibration

A turbulent air:water mixture calibration was created for the 30-cm probe by incrementally immersing the rate of air injected through a porous plate into the bottom of a cylindrical acrylic bubble chamber for water contents of 65 - 100 %.

Lab Setup

Background - Objectives - Air Content Measurements - Conclusions - Lab Methods - Single Phase Test Results - Air-Water Mixture Calibrations - Turbulent Air-Water Mixture Time Series
Field Methods - Field Site - Field Results

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