Thermal Sensor of Groundwater Flow Velocity and Direction Measurement According to In Situ Monitoring of Thermal Conductivity and Dynamic Viscosity

Landslide mechanisms research relies significantly on groundwater flow velocity and direction, and typical thermal flow velocity and direction sensors can scarcely achieve the measurement precision needed. Through numerical simulation analysis, the researchers uncover the mechanism underlying the flow velocity solution error caused by the variation of groundwater physical parameters in the existing thermal sensors. Additionally, the thermal conductivity and dynamic viscosity as the critical parameters are pinpointed from the groundwater physical parameters that contribute to the solution error. To improve the accuracy of the flow velocity solution, the existing simplified model is optimized by employing the current values of thermal conductivity and dynamic viscosity of groundwater, which are obtained in real time by integrating the in situ measurement functions of thermal conductivity and dynamic viscosity. A sensor prototype and an experimental system based on the improved model are constructed for experimental validation. The experimental results demonstrate a significant improvement in the accuracy of the flow velocity solution complying with correction applying this method as compared to the accuracy of the flow velocity solution when thermal conductivity and dynamic viscosity are taken into account as standard constant values. The sensor’s benefits of compactness, cheap production costs, straightforward hardware implementation, and ease of utilization make it preferred for deployment in deep-hole and small-bore groundwater monitoring applications. The sensor, featuring a wide range of potential applications in the field of in situ precision monitoring of microfluidic flow velocity and flow direction in landslide groundwater, rivers, and lakes, is portable.