基于热示踪的饱和层状介质水热参数反演

发布时间：2018-05-21 13:37

本文选题：热示踪 + 层状介质　；参考：《水利学报》2017年11期

【摘要】：多孔介质的水热运移参数是影响介质中水热运动过程的主要因素。本文基于热示踪方法,开展了稳定流场条件下饱和层状石英砂的热示踪实验,分别采用热电偶与热成像两种方法测定了砂箱内部和表面的温度,同时结合HYDRUS模型的反问题算法对层状石英砂的水热运移参数进行了反演。研究结果表明:当介质中存在细粒夹层时,热成像图像能反映非均匀流场中热流峰面在分层界面处出现的"收束"现象;层状介质中的细颗粒夹层可导致热流锋面沿水流方向迁移速率下降、热量沿垂直于水流方向运移范围加大、温度分布更均匀。同时对于热源持续输入的系统,热成像温度在前期能较好的反映层状介质对水流运动的影响。将热示踪与HYDRUS模型相结合可较好地用于反演介质水热运移参数,反演所得的饱和导水率估值随粒径的减小显著降低,纵向热弥散度随粒径的减小而增大,而横向热弥散度变化趋势与之相反;纵横弥散比变化范围在10~120之间,且纵横弥散比随粒径减小而逐渐增大。对细砂饱和导水率的估计不足及热量损失是造成水流通量估计误差的主要原因,在模拟模型中增加细砂层测点数量可显著降低水流通量的估计误差。本研究可为非均质介质中水热迁移过程模拟与参数反演提供相应的方法。
[Abstract]:The hydrothermal transport parameters of porous media are the main factors affecting the hydrothermal movement. Based on the thermal tracer method, the thermal tracer experiments of saturated layered quartz sand under steady flow field are carried out. The internal and surface temperatures of the sand box are measured by thermocouple and thermal imaging, respectively. At the same time, the hydrothermal migration parameters of layered quartz sand are inversed with the inverse problem algorithm of HYDRUS model. The results show that the thermal imaging images can reflect the "bunching" phenomenon of the thermal flow peak at the stratified interface when there is a fine interlayer in the medium. The fine grain intercalation in layered media can lead to the decrease of heat flux front along the direction of water flow, the increase of heat migration range perpendicular to the direction of water flow, and the more uniform distribution of temperature. At the same time, the thermal imaging temperature can reflect the influence of stratified media on the water flow in the early stage for the system with continuous heat source input. The combination of thermal tracer and HYDRUS model can be used to invert the hydrothermal transport parameters of the medium. The estimated saturated water conductivity decreases significantly with the decrease of the particle size, and the longitudinal thermal dispersion increases with the decrease of the particle size. The variation trend of transverse thermal dispersion is opposite, and the range of longitudinal and transverse dispersion ratio is between 10 and 120, and the ratio increases gradually with the decrease of particle size. The insufficient estimation of saturated water conductivity of fine sand and the loss of heat are the main reasons for the error of water flux estimation. Increasing the number of measuring points in fine sand layer can significantly reduce the estimation error of water flux in the simulation model. This study can provide a method for simulation and parameter inversion of hydrothermal migration in heterogeneous media.
【作者单位】：中国农业大学水利与土木工程学院;中国-以色列国际农业研究培训中心;
【基金】：国家自然科学基金项目(51379209,51639009)
【分类号】：P641

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