Analytical model for measuring flow velocity of groundwater by heating distributed optical fibers through pulses

Abstract

The invention discloses an analytical model for measuring the flow velocity of underground water by heating distributed optical fibers through pulses, which is characterized in that the distributed optical fibers are buried in a water-containing medium, the magnitude and the direction of the seepage flow velocity are quantitatively determined through the difference of the optical fiber cooling process, and a convective heat transfer analysis model of the seepage field is deduced under the action of a continuous linear heat source, wherein the model is more suitable for the heat transfer problem of the optical fibers buried in the porous medium. Model calculation results show that if the optical fibers are continuously heated, long heating time is needed when the temperature of the opticalfibers reaches the maximum temperature rise, so that more energy is consumed, a theoretical model for quantitatively calculating the flow velocity of underground water by adopting a thermal pulse-timedomain reflection technology is constructed, and a double-optical-fiber thermal pulse method and a four-optical-fiber thermal pulse method are provided. That is to say, after thermal pulses are injected into a heating element, the flow velocity of underground water can be conveniently calculated and the flow direction of the underground water can be determined by utilizing difference values or ratios of optical fiber temperature measurement data at different positions.

Description

technical field [0001] The invention relates to the technical fields of water conservancy and hydropower engineering and hydrogeological detection, in particular to an analytical model for measuring groundwater flow velocity by using pulse heating distributed optical fibers. Background technique [0002] The dam temperature field and the seepage field interact and influence each other. By monitoring the dam temperature field, the seepage status can be reflected indirectly. In recent years, water conservancy and hydropower projects have begun to use Distributed Optical Fiber Temperature Sensor System (DTS) to monitor seepage heat. Optical fiber for finding leaks in peripheral seams. Distributed optical fibers are also buried in the reservoir bottom of the Xilongchi Pumped Storage Power Station and the dam body of the Shiniu Reservoir to monitor reservoir water seepage. In the 1990s, the Swedish HydroResearch Institute carried out applied research on temperature seepage moni...

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Problems solved by technology

These studies provide theoretical support for distributed optical fiber seepage heat monitoring technology, but the above models have simplified the heat transfer process to a certain extent, and have not fully considered the influence of porous media. to further improve

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