温度示踪法量化地表水-地下水交换中的自由对流效应评估  

Necessity of analysis of free convection effects in quantification of surface water-groundwater exchange by temperature tracer

作　　者：于攀文 高增文[1] YU Panwen;GAO Zengwen(Qingdao University,Qingdao 266071,China)

机构地区：[1]青岛大学,山东青岛266071

出　　处：《环境工程》2025年第2期31-38,共8页Environmental Engineering

基　　金：国家自然科学基金“海湾水库底边界层对水体突然泛咸的双重影响机制与效应”(51279075)。

摘　　要：温度示踪法是一种基于热运移扩散方程,通过反演确定沉积物孔隙水流速的常用方法。但实际应用中通常忽略自由对流及其效应,并且相关研究也没有探讨过这种忽略处理的合理性。设计了砂箱装置模拟沉积物-上覆水系统的自由对流现象,通过R语言程序建立一维热传输模型,探讨温度示踪法应用中考虑自由对流效应的必要性;研究中以额外的热扩散系数表达自由对流效应,并主要通过参数敏感性分析评估忽略自由对流对反演结果(流速)的影响程度。结果表明,额外热扩散系数可以达到饱和水填充物固有热扩散系数的1~6倍;参数的敏感性分析表明,55%的热扩散系数偏差可以导致约13%流速估值误差;实验条件下忽略自由对流会引起反演流速结果出现最大0.012 cm/min的偏差,这种程度的偏差将严重影响沉积物-上覆水之间热量与污染物交换通量的计算。在应用温度示踪法时宜先评估自由对流对反演结果的影响程度,并据此决定是否将其效应考虑在热传输机制内。Temperature tracing is a widely used method for determining pore water velocity in sediments,based on the thermal diffusion equation.This technique is valuable for understanding fluid dynamics in subsurface environments.However,in practice,the phenomenon of free convection and its associated effects are often overlooked.The assumption that free convection can be ignored is not always justified,and the implications of this assumption have not been thoroughly discussed in the literature.This oversight can lead to inaccuracies in the results obtained from temperature tracing methods.In this paper,a sandbox device was designed to simulate free convection in the sediment-water system to address this issue.This experimental setup provided a controlled environment where the effects of free convection can be systematically observed and quantified.A one-dimensional heat transfer model was developed using the R Language Program to explore the necessity of incorporating free convection effects in application of temperature tracing.This model offered a robust framework for simulating and analyzing heat transfer processes.In the study,the impact of free convection was quantified by introducing an additional thermal diffusion coefficient.This coefficient accounted for the enhanced heat transfer due to the buoyancy-driven movement of fluids.The primary focus was to assess how neglecting free convection affects the inversion results,particularly the velocity estimates.This was done through a detailed parameter sensitivity analysis,which helps understand how variations in model parameters influence the output.The findings revealed that the additional thermal diffusion coefficient can be 1 to 6 times greater than the inherent thermal diffusion coefficient of the saturated water filling material.This indicated a significant potential impact of free convection on temperature tracing results.The sensitivity analysis showed that a 55%deviation in the thermal diffusion coefficient could lead to a 13%error in velocity estimation.Disrega

关 键 词：地表水-地下水交换 温度示踪法 沉积物孔隙水运动 热运移扩散方程 自由对流 砂箱实验 

分 类 号：P641.2[天文地球—地质矿产勘探]