بررسی سرعت تغییرات شرایط مرزی بر مدل ‌سازی پدیده تداخل آب ‌شور و شیرین در آبخوان‌های ساحلی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشگاه ارومیه

2 گروه مهندسی آب - استاد

10.22034/hydro.2023.56782.1292

چکیده

دریاها دارای تغییرات تراز سطح آب تدریجی و طولانی ‌مدت می‌باشند. شبیه‌سازی عددی رفتار سفره‌های زیرزمینی ساحلی با دوره‌ی زمانی طولانی، می‌تواند بسیار زمان‌بر باشد. در این مقاله به بررسی اثر افزایش و یا کاهش زمان تغییرات تراز آب دریاها بر مدل‌سازی عددی رفتار آب‌های زیرزمینی پرداخته‌شده است. بدین منظور از مدل عددی GeoStudio مبتنی بر روش اجزای محدود استفاده شد. ابتدا مدل موردنظر بر اساس داده‌های آزمایشگاهی منتشرشده در منابع معتبر واسنجی و اعتبارسنجی شد و در ادامه تغییرات پنجه آب‌شور تحت حالت‌های تغییر تراز سریع و تدریجی مورد بررسی قرار گرفت. نتایج بررسی نشان داد که مدت‌زمان  تغییر تراز سطح آب‌شور تأثیری در  برآورد ابعاد نهایی گوه آب‌شور ندارد. اما در حالت افزایش آنی تراز آب‌شور، مقدار طول پنجه 4% بیشتر از حالات افزایش تدریجی برآورد می‌شود. همچنین نتایج این تحقیق نشان داد سریع‌ترین زمان به تعادل رسیدن سیستم (TR_min) در حالت افزایش و یا کاهش آنی تراز سطح آب رخ می‌دهد. با این‌حال نتایج نشان داد که اگر طول مدت تغییرات تدریجی شرایط مرزی کمتر از نصف TR_min  باشد، تغییری در زمان تعادل رخ نمی‌دهد. علاوه بر این، نتایج حاصله نشان داد که زمان رسیدن به 50%  طول پیشروی پنجه آب‌شور مستقل از سرعت تغییرات شرایط مرزی آب‌شور است. درصورتی‌که مقدار حداقل زمان به تعادل رسیدن در حالت افزایش آنی تراز آب‌شور TA_min باشد و زمان افزایش تراز سطح آب‌شور برابر یا بیشتر از TA_min 4/1 باشد، زمان به تعادل رسیدن پنجه تقریباً منطبق بر زمان توقف تغییرات سطح آب‌شور خواهد بود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Analyzing the Impact of Rapid Boundary Condition Changes on Salt and Fresh Water Interaction in Coastal Aquifers

نویسندگان [English]

  • Zahra Yazdi 1
  • Hojjat Ahmadi 2
1 Department of water engineering
2 Department of Water Engineering
چکیده [English]

This article investigates the impact of sea level fluctuations on numerical modeling of groundwater behavior. The study employs GeoStudio, a finite element numerical model, to calibrate and validate the model using benchmark data from reliable sources. The investigation focuses on changes in saltwater levels under varying rates of increase and decrease. Results indicate that reducing saltwater levels in the numerical model does not affect the estimation of the final dimensions of the saltwater wedge. However, a sudden increase in saltwater levels results in an estimated wedge length that is 4% greater than gradual increases. Furthermore, the research reveals that the system reaches equilibrium fastest when water levels increase or decrease instantaneously. If the minimum time to reach equilibrium during a sudden decrease in water levels is denoted as TR_min, gradual changes in boundary conditions lasting less than half of this time do not impact the equilibrium time. The study also demonstrates that the time required to reach 50% of the advancing length of the saltwater wedge remains independent of the rate of change in saltwater boundary conditions. If the minimum time to reach equilibrium following an instantaneous increase in saltwater levels is denoted as TA_min, and the duration of saltwater level increase is equal to or greater than 1.4TA_min, the time to reach equilibrium of the wedge will be approximately the same as the duration of the saltwater level stabilization.

کلیدواژه‌ها [English]

  • groundwater
  • numerical modeling
  • saltwater wedge
  • time scale
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