نوع مقاله : پژوهشی
نویسندگان
1 دانشجوی دکتری، دانشکدۀ مهندسی آب و خاک، دانشگاه علوم کشاورزی و منابع طبیعی گرگان
2 دانشیار، دانشکدۀ مهندسی آب و خاک، دانشگاه علوم کشاورزی و منابع طبیعی گرگان
3 پژوهشگر، دانشکدۀ هیدروژئولوژی، مرکز تحقیقات محیط زیست هلمهولتز، لایپزیک، آلمان
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Hyporheic zone is related to the saturated zone beneath the river which has an important role in ecology. In this zone, part of surface water, transfer oxygen and nutrients to the organism and then returns to the surface water after certain amount of time. Hyporheic exchanges between surface flow and flow in porous media can be created due to the different bed forms of river. Riffle-pools are topographical features found in straight, meander and braided rivers. Variation of pressure along these bed forms lead hyporheic exchanges. The precise estimation of hyporheic exchanges and residence time can be useful for rivers restoration projects. So, in this paper, in addition to laboratory investigation of hyporheic exchanges along riffle-pool bed forms, the variation of pressure along bed surface has been simulated numerically by Large Eddy Simulation (LES) model and then a groundwater model and particle tracking method have been applied to simulate the flow within the hyporheic zone. The results show that the interFoam solver with LES model is able to model laboratory conditions accurately. The mean percentage error of water surface profile was 1.8% for present laboratory study, which leads to an accurate estimation of pressure along the bed form and as a result an accurate prediction of hyporheic exchanges. The results of hyporheic characteristics show that as Reynolds number increases, the hyporheic exchanges increase and the residence time decreases. The results also show that the residence time distribution follows generalized extreme value distribution. In this study, on average, 20 percent of surface flow exchange with sub-surface flow.
کلیدواژهها [English]