معرفی مدل توسعه یافته KDW-VG و بررسی کارایی آن در شبیه‌سازی عددی جریان ترجیحی آب در خاک

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری آبیاری و زهکشی دانشگاه شهید چمران اهواز، اهواز، ایران

2 استاد دانشکده مهندسی علوم آب،گروه آبیاری و زهکشی دانشگاه شهید چمران اهواز، اهواز، ایران

3 استادیار گروه مهندسی آب، دانشکده علوم کشاورزی دانشگاه گیلان، رشت، ایران

چکیده

جریان­های ترجیحی سریع در خلل و فرج درشت خاک، مانند سوراخ و کانال­های زیرزمینی که با فعالیت کرم­ها و یا رشد ریشه گیاهان به وجود می­آید، رخ می­دهند. برای پیش­بینی روند و توضیح این نوع جریان­ها در خاک، دی پترو و همکاران (2003)، مدل موج سینماتیک، انتشار (4KDW) را توسعه و پیشنهاد دادند. نام­بردگان این مدل را با اضافه کردن ترم انتشار به معادله موج سینماتیک (5KW) که به شدت توده­ای است و توسط جرمن در سال 1985 ارائه شده بود، توسعه دادند (Di pietro et al., 2003)، (German., 1985). فرض­های اساسی این مدل، این است که فلاکس جریان به تنهایی تابعی از مقدار آب متحرک است. ولی در مدل موج سینماتیک، انتشار با اضافه شدن بخش انتشار به معادله قبلی،فرض می­شود که فلاکس جریان یک تابع غیر خطی از مقدار آب متحرک و مشتق اول آن نسبت به زمان می­باشد. بخش اول این فرض یک تابع توانی است که در آن فلاکس جریان به رطوبت متحرک وابسته است. این معادله توانی تنها یک معادله ریاضی است و از معنی و مفهوم فیزیکی چندانی برخوردار نیست. در این پژوهش این معادله توانی با صورت ظاهری معادله وان گنوختن که معنی فیزیکی قابل قبولی دارد، جایگزین شد و مدل ریاضی موج سینماتیک، انتشار- وان گنوختن (6KDW-VG) برای اولین بار معرفی شد. ابتدا ضرایب مدل با استفاده از روش بهینه­سازی تراکم ذرات(7PSO) به دست آمد و سپس مدل با استفاده از داده­های آزمایشگاهی مربوط به هیدروگراف حاصل از بارندگی و گذار آب از مسیرهای ترجیحی مدل فیزیکی که از انتهای ستون خاک برداشت شده بود، مورد صحت سنجی قرار گرفت. برای ایجاد مسیر ترجیحی در خاک، یک ستون ماسه درشت به قطر 4/1 سانتی­متر در مرکز ستون خاکی به قطر خارجی 160 و ارتفاع 300 میلی­متر ایجاد شد. نتایج این پژوهش نشان از تطابق بسیار خوب مدل با مشاهدات آزمایشگاهی داشت و مقادیر RMSE بین مشاهدات و پیش­بینی­های مدل حاضر نسبت به مطالعات پیشین کم­تر بوده است.

کلیدواژه‌ها

عنوان مقاله [English]

Introducing Developed KDW-VG Model and Its Performance Iinvestigation to Numerical Simulation of Preferential Water Flow in Soil

نویسندگان [English]

  • Mostafa Moradzadeh 1
  • Hadi Moazed 2
  • Saeid Boroomandnasab 2
  • Mohammad reza Khaledian 3
1 PhD student of Irrigation and Drainage Engineering, Faculty of Water Sciences Engineering, Shahid Chamran University of Ahvaz,., Ahvaz., Iran
2 - Professor at Faculty of Water Sciences Engineering, Shahid Chamran University of Ahvaz., Ahvaz., Iran
3 Faculty of Agricultural Sciences, Department of Water Engineering, University of Guilan., Rasht., Iran
چکیده [English]

Rapid preferential water flow occurs in soil macropores such as underground channels formed by worm activity and root plants growth. For process predicting and describing of these types of water flow in soil, Di Pietro et al., (2003) developed and proposed kinematic–dispersive wave (KDW) model. They proposed this model by adding dispersive term to kinematic wave model which is strictly convective and was presented by German (1985). The fundamental assumption of this model is that the flux is exclusively a function of the mobile water content but in kinematic–dispersive wave model with its aditional dispersive term, it is assumed that the flux is some non-linear function of the mobile water content and its first time derivative. The first term of this assumption is a power function where the flux is depended to mobile water content .This equation is just a mathematic equation and has not the strong physical meaning. In this research, this power function is substituted by the shape of van Genuchten equation which has an acceptable physical meaning and the kinematic dispersive wave- van Genuchten (KDW-VG) is introduced for the first time. At first the model coefficients were optimized using particle swarm optimization (PSO) method and after that the model was validated by experimental observation of hydrograph of rainfall which was passed through the preferential routes of physical model and was recorded from the bottem of soil column. For creating the preferential pathways in the soil profile, a soil column of coarse sand with diameter of 1.4 cm was embedded in the center of a soil column with diameter of 160 mm and height of 300 mm.The results showed that the numerical model has very good agreement with the experimental observations and the RMSE amount between observations and the model prediction was lesser compared with last researches.

کلیدواژه‌ها [English]

  • Physical Model
  • Porous media
  • Mathematical Modeling
  • optimization
  • Rainfall hydrograph

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نشریه آبیاری و زهکشی ایران
دوره 9، شماره 6 - شماره پیاپی 54
بهمن و اسفند 1394
صفحه 960-972

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