Abstract
Abstract This paper presents detailed numerical analysis for two-dimensional pollutant dispersion within, and over permeable bed. The analysis is by using a Computational Fluid Dynamics (CFD) technique. The aim of this study is to improve the general knowledge about tracer dispersion in water within and over a permeable bed. It is held in fully developed turbulent flow zone within and over the porous zone. The main aim of this test is to recognize the effect of bed porosity on tracer dispersion. The studied cases were two different porosity mediums with the same flow depth. Different injection scenarios were incorporated within the study for the tracer movement located far from the source zone. The tracer tests were for the whole flow stream either within the porous zone or over it. Two tracer injection scenarios were held. One for a short time (pulse), and continuous within the tested time (continuous). For both scenarios, three different injection locations were tested for each case. The numerical simulation was using Fluent Software within Ansys 12. The simulated cases were verified with previously published experimental data for tracer free flow. A good consistency with experimental data was established. This paper incorporates detailed results for tracer concentration at different locations and different time intervals. One of the results is that the pulse injection across the whole flow of the free stream thickness shows that the exchange with the porous zone occurs faster for the sparse case compared with the dense case. Further, the location of the injection surface at the porous layer has some effect on the tracer migration. The injection surface in the middle of the vertical gap between the obstacles showed faster tracer penetration into the free stream than the injection across the narrow throats of the horizontal pores