مقایسه تبادلات هایپریک در خیزاب-چالاب دو بعدی و سه بعدی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجو دکتری/ گروه مهندسی آب، دانشکده آب و خاک، دانشگاه علوم کشاورزی و منابع طبیعی گرگان

2 گروه مهندسی آب، دانشکده مهندسی آب و خاک، دانشگاه علوم کشاورزی و منابع طبیعی گرگان

3 پژوهشگر،‌ دانشکده هیدروژئولوژی،‌ مرکز تحقیقات محیط زیست هلمهولتز، لایپزیک، آلمان

4 دانشیار/ گروه مهندسی آب، دانشکده آب و خاک، دانشگاه علوم کشاورزی و منابع طبیعی گرگان

چکیده

تبادل آب و مواد محلول بین جریان سطحی و جریان داخل محیط متخلخل بستر رودخانه بعنوان تبادلات هایپریک شناخته می‌شود. تبادلات هایپریک آب و مواد مغذی را به ارگانیسمهائی که در ناحیه هایپریک زندگی می‌کنند، رسانیده و شرایط اکولوژیکی و چرخه مواد غذائی را در این ناحیه تحت تأثیر قرار می‌دهد. یکی از عوامل مؤثر بر این تبادلات، گرادیان‌های فشار در اطراف فرم بستر رودخانه می‌باشد. خیزاب‌ها و چالاب‌ها از اشکال ژئومورفیک رودخانه‌ها ً در پروژه‌های احیاء رودخانه‌ها تلقی می‌شوند که گرادیان فشار در امتداد آنها منجر به تبادلات هایپریک شده و اخیرا مورد توجه قرار گرفته‌اند. هدف از تحقیق حاضر مقایسه میزان دبی تبادلات هایپریک و زمان ماندگاری جریان داخل بستر رسوبی در خیزاب-چالاب دو بعدی و سه بعدی می‌باشد. برای این منظور ابتدا به شبیه‌سازی جریان سطحی با استفاده از مدل OpenFOAM پرداخته شده و سپس فشار حاصله بر روی فرم بستر بعنوان شرط مرزی به مدل آب زیرزمینی ً 50 درصدی دامنه فرم بستر، دبی MODFLOW معرفی می‌گردد. نتایج این تحقیق نشان می‌دهد با افزایش تقریبا تبادلات هایپریک هم در حالت دو بعدی و هم در حالت سه بعدی 26 درصد افزایش و زمان ماندگاری در مدل دو بعدی 36 درصد و در مدل سه بعدی 41 درصد کاهش می‌یابد. همچنین، مقایسه نتایج خیزاب-چالاب سه بعدی با مدل دو بعدی معادل آن نشان می‌دهد که دبی تبادلات هایپریک و زمان ماندگاری به ترتیب 3 و 4 درصد افزایش می‌یابند

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Comparison of Hyporheic Exchanges in 2D and 3D Riffle-Pool bed form structures

نویسندگان [English]

  • Neshat Movahedi 1
  • Amir Ahmad Dehghani 2
  • Christian Schmidt 3
  • Nico Trauth 3
  • Mehdi Meftah Halaghi 4
1 PhD Student/Water and Soil Department, Gorgan University of Agricultural Sciences and Natural Resources,Gorgan, Iran
2 Water Engineering, Gorgan University of Agricultural Sciences and Natural Resources
3 Researcher, Helmholtz Center for Environmental Research (UFZ), Department of Hydrogeology, Leipzig, Germany
4 Associate Professor/Water and Soil Department, Gorgan University of Agricultural Sciences and Natural Resources,Gorgan, Iran
چکیده [English]

Exchanges of water and solute between stream flow and flow through river bed porous media are known as hyporheic exchanges. Hyporheic exchanges transfer water and nutrient to the organism lived in the hyporheic zone, so affect ecological conditions and food cycle. One of the important driving factors of these exchanges are pressure gradients along the bed form. Riffle-pools are geomorphic features of river beds which induce strong pressure gradient along the streambed, which control hyporheic exchanges and are therefore considered in river restoration projects. The goal of this study is to compare the hyporheic flux and residence time of flow within sediment bed underneath 2D and 3D riffle-pool structures. For reaching this goal, in a first step, the surface water flow is simulated by the CFD-software OpenFAOM, resulting in a detailed pressure distribution at the stream bed. In a second step, these pressure fields are then set as a top boundary condition of a groundwater model (MODFLOW software), for simulating the flow in porous media. The results show that, by increasing bed form amplitude, hyporheic exchanges flux increases by 26 % for both 2D and 3D models, and residence time decreases by 36 %for 2D and 41 % for 3D structures. Also, comparison of 3D riffle-pool with equal 2D model shows that hyporheic exchange flux and residence time increase by 2.9 % and 3.67 %, respectively.

کلیدواژه‌ها [English]

  • Riffle-Pool
  • OpenFOAM
  • MODFLOW
  • Hyporheic Exchanges
  • Residence Time
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