基于多孔介质内加热小球的混合对流同时测量地下水渗流速度与温度的方法研究

A novel method for simultenously measuring the velocity and temperature of ground water will be proposed based on the mixed convection characteristics of a Joule heated sphere buried in porous media. To this end, a complicated mixed convection model around a heated sphere will be established accounting for variable geometrical structure, permeable features of porous media, and thermophysical properties of surrounding matrix and fluids, which includes the coupled effect of bouyancy force due to gravity, inertial and viscous diffusion forces. The powerful Lattice Boltzmann method (LBM) will be adopted to deal with the coupled heat and fluild flow direct problem of heated sphere in porous media. After that the Adjoint Problem for the simultaneous identification of two boundary conditions (inlet veclocity and temperature) in mixed convection inverse problems will be solved by using the Conjugate Gradient Method of function estimation in such a porous media. An emphasis will be given on the corresponding relationship between the features of mixed convection with those of geometry parameter and intesnsities of various forces, which include the information of inlet velocity and temperature. A series of experiemnts will be carried out for the mixed convection around a heated sphere buried in porous media that checking the effectiveness, reliability, and correctness of the proposed measuring method both in a laboratory scale and in situ field test. It is believed that a demo of alternative and cheapter testing rig for simultenouly measuring ground water velocity and temperature is possible by the careful and detailed investigation on the mixed convection behaviour of a Joule heated sphere in porous media. This is of importance in oil exploitation, geothermal energy ultilization, and ground pollution monitoring, enviroment recovery and management.

基于埋入多孔介质内加热小球外的混合对流换热特性研究提出一种新的地下水测温测速方法，建立加热小球在不同几何结构、渗透特性及热物性等参数条件下，以及包括浮力、重力等各种力耦合作用下的混合对流换热机理模型，采用格子-Boltzmann (LBM) 数值方法对有复杂边界和耦合力项作用下的混合对流正问题求解。在此基础上研究伴随问题、共轭梯度寻优等方法对该复杂结构下的混合对流反问题的数值求解方法，重点研究加热小球外多孔介质内的混合对流与结构参数、耦合力项的作用关系，及表现出的物理现象。探讨通过加热小球同时获取多孔介质渗流速度与温度反问题解的快速、可靠数学方法，以及影响计算结果的主要因素，在实验室进行实验验证和现场试验研究。通过对多孔介质内加热小球外复杂对流换热机理研究，探讨测量低渗流速度及温度新方法，对石油开采、地热能开发利用、以及地下污染治理有重要的理论指导意义和应用价值。

实现地下水（地热水）的局部速度大小与方向的快速且经济测量对地下水资源评价、地下污染源防治、地热资源评价等有重要的应用价值。国外现有几种形式的测试探头都比较昂贵，不适合普及应用。本课题拟采用多孔介质内运动流体的非稳态传热传质原理，研发可以测量地下含水层水流速的测试装置。围绕该研究目标，从物理模型建立、数学求解方法的选择与完善、实验探头的3D打印加工与测量精度提高等方面进行了大量研究工作。搭建了可以测定~10-7m/s低渗流速度的实验系统，对加热小球、加热圆柱、加热条带等多种形式的测试探头进行了不同速度、不同加热功率工况情况下的实验研究，分析了加热功率、自然对流、以及周边热电偶布置等对测试精度的影响规律。在基础理论研究方面，着重研究了有不同热物性、不同水文参数等复杂构造下的复合材料含水层内流动与传热计算方法，提出了求解溶质迁移-扩散方程，热对流扩散方程的改进格子-Boltzmann（LBM）方法，以及直接求解Boltzmann的宏观有限体积法，所提出的方法不仅兼顾常规LBM方法的并行计算、稳定性好特点，同时提高的计算精度，减少内存需求。目前在实验室所提出的测量方法可以较精确的对大于10-5m/s的地下水速度与方向测量。以上成果都是实验室内完成的，实现可以实地应用的最终研究目标该课题还有一些研究工作要做。