2009 Volume 31 Issue 4 Pages 193-202
A new probe for groundwater flow measurement using a single borehole has been developed, which provides a simple and economical way to estimate the flowing velocity and its direction simultaneously. The principle of the measurement is based on mixed convection temperature field around a vertical heated cylinder subject to a uniform lateral flow. It is found by numerical analysis that the magnitude of temperature deviation from the concentric field has a proportionality to the strength of lateral velocity. A simple probe consisting of an electric heater and thermistors has been built and its performance is examined by a calibration system, consisting of a two-meter long water tank filled with sand. According to the calibration, a good correlation has been obtained between the temperature deviation and the lateral water velocity. In order to simulate a more practical situation, we have also examined a case, where the flow meter is placed in a casing pipe. The space between the flow meter and the perforated casing pipe is filled with rectification material, and an equally good correlation has been confirmed.
