Groundwater flow velocity and direction measurement sensor based on an equivalent pendulum model and visual measurement

Abstract Groundwater plays a pivotal role in the formation and evolution of landslide disasters. To efficiently and environmentally acquire information about groundwater flow velocity and direction, a novel method is proposed that integrates the equivalent pendulum model with visual measurement technology. This method is based on the principle that a tethered buoyant sphere will experience drag and deviate from its initial position until a state of equilibrium is reached when the viscous fluid flows around the sphere. To measure the offset and the angular deviation of the buoyant sphere, a visual technique is employed. Research findings demonstrate a positive correlation between the buoyant sphere’s offset and groundwater flow velocity. Measuring the angular deviation of the buoyant sphere determines the current heading. This approach exhibited significant accuracy during experimentation, with the sensor displaying a precision of 5.6% in measuring flow velocity within the range of 0–0.2 mm s −1 , and ±4.31° in measuring flow direction. Compared to conventional methods, this technique allows for the convenient acquisition of groundwater flow velocity and direction data without the need for auxiliary tracing agents. Furthermore, its measurements remain unaffected by factors such as water quality, temperature, pressure, and salinity within hydrogeological boreholes, or environmental conditions, fulfilling the requirement for real-time monitoring of minimal flow rates and directions in landslide groundwater, rivers, and lakes.