Investigation of Episodic Flow Events From Unsaturated Sand Media Into Macropores (Preprint).

Podgorney, R. K. ; Fairley, J. P.

Technical Information Center Oak Ridge Tennessee

关键词: Episodic flow;    Sand;    Geologic fractures;    Permeability;    Porous materials;   

RP-ID  :  DE2008911649

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

Episodic or intermittent flow, under constant influx conditions, has been observed under a number of scenarios in unsaturated flow systems. Flow systems characterized by a porous media underlain by a macropore, as well as discrete fracture networks, have been cited in recent literature as examples of systems that can exhibit episodic outflow behavior. Episodic outflow events are significant because relatively large volumes of water can move rapidly through an unsaturated system, carrying water and possibly contaminants to depth greatly ahead of a diffusive wetting front. In this study, we examine the modeled behavior of water flow through a sand column underlain by a vertical capillary tube in order to assess to potential for rapid vertical water movement, and compare the results to conventional modeling approaches and with experimental data from the literature. Capillary pressure relationships were developed for the macropore domain that capture the complex interrelationships between the porous materials above and control the flow out of the system. Modeling results using the new relative permeability and capillary pressure functions capture the behavior observed in laboratory experiments remarkably well, while simulations using conventional relative permeability and capillary pressure functions fail to capture some of the observed flow dynamics.