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Flow measurements with a cross-type Automatic Pulse Tracer Velocimeter (APTV) in heterogeneous environments

Understanding the surface water velocities of a surface water system is important for studying the fate and transport of nutrients and contaminants in heterogeneous aquatic environments. This paper presents a new sensor for measuring low range water velocities and this innovative new device is named the Automatic Pulse Tracer Velocimeter (APTV). The APTV operates by measuring the time for a pulse of saline solution to travel a fixed distance from an injection port to a set of copper wire detectors. The detectors consistently measure the change in conductivity and establish a tracer curve of the passing pulse. Using an empirical method velocity components are derived from the tracer curves. A calibration curve is then developed by comparison of the APTV with a Sontek Flow Tracker Acoustic Doppler Velocimeter in a hydraulic flume. The calibrated APTV velocities are then verified by comparison with a Nortek ADV in both a hydraulic flume and field environment. Both lab and field measurements indicate that APTV technology is capable of measuring flow velocities as low as 0.2 cm/sec and as high as 6.0 cm/sec. The sensor network may host a few sensors to collect velocity profile horizontally and vertically.