考虑温度效应的多孔介质中悬浮颗粒反复渗透迁移过程研究

The hydrodynamic processes of repeated transport and deposition of suspended particles in permeable saturated porous media considering temperature effect are studied by laboratory tests. For this purpose, a temperature-controlled apparatus suited for permeability tests of suspended particles is developed. The patterns of the breakthrough curve between two suspended particles with different sizes and fluorescein (i.e. uranine; as a dissolved tracer) by pulse injection are compared by the test results of laboratory columns, which are used to analyze the existence of the so-called "critical flow velocity" and the impacts of temperature. Following these results, the models of the transport and deposition of suspended particles are then proposed. The processes of the transport and deposition of suspended particles for different sizes and different concentration during repeated heating-cooling processes are discussed, and furthermore the mechanism of the migration, deposition and release of suspended particles due to temperature variation are analyzed. Based on a convection-dispersion-deposition equation, a theory considering the coupled effects of the flow velocity, particle size and concentration of suspended particles is established by introducing a temperature factor. For one-dimensional problem, an analytical solution for the coupled migration and deposition of suspended particles in permeable porous media with varying initial concentration of suspended particles with time is obtained using the Laplace transformation and numerical inversion schemes. These studies can be widely used in various engineering fields such as the pollutant purification, extraction of geothermal energy, exploration of groundwater, storage of hot fluids, and chemical industry, etc.

研制一个可控制温度的悬浮颗粒渗透迁移试验装置，研究水力渗流作用下饱和多孔介质中悬浮颗粒的反复渗透迁移和沉积动力学过程。通过脉冲注入条件下两种不同尺度的悬浮颗粒与溶液中荧光素钠（示踪剂）穿透过程差异性的比较试验，探索"临界渗透速度"是否存在以及温度效应对它的影响，然后建立悬浮颗粒的迁移和沉积模式。研究热-冷交替变化过程中，不同尺度的悬浮颗粒和不同浓度的悬浮颗粒的迁移和沉积过程，揭示温度的反复变化对悬浮颗粒迁移、沉积和释放相互转化过程的物理机制。基于对流-扩散-沉积动力学过程，引入温度效应影响因子，建立一个考虑渗透速度、悬浮颗粒大小和浓度变化等耦合影响的理论模型。以一维问题为例，利用Laplace变换及其数值逆变换，示范性地发展一个悬浮颗粒浓度随时间变化的悬浮颗粒迁移和沉积过程的理论求解方法。这些研究在诸如污染物治理、地热资源开发、地下水开采、热能贮存和化学工业等工程领域有重要的应用价值。

研制了一个可控制温度的悬浮颗粒渗透迁移试验装置。在此基础上，研究水力渗流作用下饱和多孔介质中悬浮颗 粒的反复渗透迁移和沉积动力学过程。通过脉冲注入条件下悬浮颗粒与溶液中荧光素钠（示踪剂）穿透过程差异性的比较试验，探索了"临界渗透速度"是否存在以及温度效应对它的影响，然后建立悬浮颗粒的迁移和沉积模式，揭示温度的反复变化对悬浮颗粒迁移、沉积和释放相互转化过程的物理机制。基于对流-扩散-沉积动力学过程，引入温度效应影响因子，建立了一个考虑渗透速度、悬浮颗粒大小和浓度变化等耦合影响的理论模型。利用 Laplace 变换及其数值逆变换，发展悬浮颗粒浓度随时间变化的悬浮颗粒迁移和沉积过程的理论求解方法。.作为重点，本研究通过室内土柱试验系统分析了多孔介质中温度对悬浮颗粒渗透迁移特性的影响，包括粒径范围为10–47微米的粒径、不同的渗透速度等。研究结果表明，温度的升高加速了悬浮颗粒不规则的运动，进而减小了它们的迁移速度，结果使得悬浮颗粒穿透曲线的峰值孔隙体积相应滞后而它们的峰值则相应减小。悬浮颗粒的迁移速度随粒径的增大而减小，而与渗透速度和温度无关。对悬浮颗粒的渗透迁移参数进行的拟合表明，悬浮颗粒的弥散系数随温度的升高而略有减小，然后几乎保持一个稳定值。对于粒径较大的悬浮颗粒而言，由于受多孔介质孔隙尺寸的限制和阻塞，其不规则运动更为明显，因此导致了更大的弥散系数。沉积系数随温度的升高而增大，特别是当渗透速度较大时，然后逐渐趋于稳定值。对于大的悬浮颗粒而言，其沉积系数远高于小的悬浮颗粒的沉积系数，原因可归结为大的悬浮颗粒在多孔介质孔隙中的约束效应。悬浮颗粒的回复率随温度的升高而略有减小并存在一个临界值，之后保持不变。总体而言，温度是一个影响诸如颗粒迁移速度、弥散系数和沉积系数等重要迁移参数的物理量。.这些研究在诸如污染物治理、地热资源开发、地下水开采、热能贮存和化学工业等工程领域有重要的应用价值。