Groundwater flow depends on the heterogeneity of hydraulic properties whose field characterization is challenging. Recently developed active‐Distributed Temperature Sensing (DTS) experiments offer the possibility to directly measure groundwater fluxes resulting from heterogeneous flow fields. Here, based on fundamental principles and numerical simulations, two interpretation methods of active‐DTS experiments are proposed to estimate both the porous media thermal conductivities and the groundwater fluxes in sediments. These methods rely on the interpretation of the temperature increase measured along a single heated fiber‐optic (FO) cable and consider heat transfer processes occurring both through the FO cable itself and through the porous media. The first method relies on the Moving Instantaneous Line Source model that reproduces the temperature increase and provides estimates of thermal conductivity and groundwater flux as well as an evaluation of the temperature rise due to the FO cable. The second method, based on the graphical identification of three characteristic times, provides complementary estimates of flux, fully independent of the effect of the FO cable. Sandbox experiments provide an experimental validation of the interpretation methods, demonstrate the excellent accuracy of groundwater flux estimates (<5%), and highlight the complementarity of both methods. Active‐DTS experiments allow investigating groundwater fluxes over a large range spanning 1 × 10⁻⁶−5 × 10⁻² m/s, depending on the duration of the experiment. Considering the applicability of active‐DTS experiments in different contexts, we propose a general experimental framework for the application of both interpretation methods in the field, making active‐DTS field experiments especially promising for many subsurface applications.

中文翻译：

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Active-DTS实验用于估算多孔介质中导热系数和地下水通量的适用性的数值和实验验证

地下水流量取决于水力特性的非均质性，而水力特性的现场表征具有挑战性。最近开发的主动分布温度感测（DTS）实验提供了直接测量非均质流场产生的地下水通量的可能性。在此，基于基本原理和数值模拟，提出了主动DTS实验的两种解释方法，以估算多孔介质的热导率和沉积物中的地下水通量。这些方法依赖于沿单根加热的光纤（FO）电缆测得的温度升高的解释，并考虑通过FO电缆本身和多孔介质发生的传热过程。第一种方法依赖于移动瞬时线源模型，该模型可再现温度升高并提供热导率和地下水通量的估计值，以及由于FO电缆引起的温度升高的评估。第二种方法基于三个特征时间的图形识别，提供了磁通量的补充估计，完全独立于FO电缆的影响。沙箱实验提供了解释方法的实验验证，证明了地下水通量估算的出色准确性（<5％），并突出了这两种方法的互补性。Active-DTS实验允许调查大范围内的地下水通量，范围为1×10 提供完全独立于FO电缆影响的通量补充估计。沙箱实验提供了解释方法的实验验证，证明了地下水通量估算的出色准确性（<5％），并突出了这两种方法的互补性。Active-DTS实验允许调查大范围内的地下水通量，范围为1×10 提供完全独立于FO电缆影响的通量补充估计。沙箱实验提供了解释方法的实验验证，证明了地下水通量估算的出色准确性（<5％），并突出了这两种方法的互补性。Active-DTS实验允许调查大范围内的地下水通量，范围为1×10^-6 -5×10 ^-2  m / s，取决于实验的持续时间。考虑到主动DTS实验在不同环境下的适用性，我们为两种解释方法在野外的应用提出了一个通用的实验框架，这使得主动DTS野外实验对许多地下应用尤为有希望。