报告时间：2019年6月4日（星期二） 15:00-16:00
报告地点：天津大学地科院（第16教学楼）221报告厅
报告嘉宾：Tian-Chyi Jim Yeh, 美国亚利桑那大学水文与大气系终身教授
报告简介：
Environmental fluids migrate at velocities of many scales, influenced by many factors at a multiplicity of scales. Due to difficulties in predicting exact motions of water molecules, and consideration of the scale of our interests (bulk behaviors of many molecules), Fick’s law (diffusion concept) has been developed for predicting solute diffusion process in space and time. Further, G.I. Taylor (1921) demonstrated that the random motion of the molecules reach the Fickian regime in less a second and will reach the ergodic condition if our sampling scale is large enough. Fick’s law is widely accepted for describing molecular diffusion as such. This fits the definition of the parsimony principle at the scale of our concern.
Similarly, advection-dispersion or convection-dispersion equation (ADE or CDE) generally has been found suitable for predicting solute concentration breakthroughs in uniformly packed soil columns. This is due to the fact that the solute is released over the entire cross-section of the column, and it thus has encountered many pore-scale heterogeneities and met the ergodicity assumption. Further, the uniformly packed column contains a large number of stationary pore-size heterogeneity. The solute thus can reach the Fickian regime after traveling a short distance along the column. Besides, observed breakthrough curves are the concentrations integrated over the column cross-section (the scale of our interest), and they meet the ergodicity assumption embedded in the ADE and CDE.
To the contrary, scales of heterogeneity in most groundwater pollution problems evolve as contaminants travel. They are much larger than the scale of our observations and our interests. The ergodic and the Fickian conditions are thus difficult to be met. Upscaling and modifying Fick’s law for solute dispersion, and deriving universal scaling rules of the dispersion for the field- or basin-scale pollutant migrations are merely misuse of the parsimony principle. They create red herrings and fake sciences ( i.e., the development of theories for predicting processes that can not be observed.) The appropriate principle of parsimony for these situations is to map large-scale heterogeneities as detailed as possible (or to the scale of our observations and interests) and to adapt Fick’s law for effects of small-scale heterogeneity resulting from our inability to characterize them at high resolutions.
嘉宾简介：
叶天齐（Tian-Chyi Jim Yeh）教授是亚利桑那大学水文与大气系终身教授、亚利桑那大学土壤-水-环境系以及滑铁卢大学地球环境科学系客座教授。曾入选中国教育部海外名师(2009-2014)计划，受聘每年在吉林大学做短期讲座。他是分析介质非均质性对水流以及溶质运移影响的国际领军人物。叶教授提出的连续线性估计随机反演算法SLE为含水层参数获取方法“水力层析法”（Hydraulic Tomography）的发展做出了重要贡献。目前已发表160余篇学术论文，被引用7061次，H指数高达46（2019年5月数据），出版专著1部。曾担任国际期刊Water Resources Research等的副主编以及美国能源部、环保局、国防部以及美国国家自然科学基金的项目评审专家。作为主要项目负责人，主持过美国能源部、环保局、国防部、美国地质调查局、美国国家自然科学基金以及其他工业组织的项目，负责科研经费达2100万美元。
