اثر پوشش گیاهی ناهمگون در نوار کناری سیلابدشت بر ساختار جریان و تلاطم در آبراهه روباز مرکب

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه علوم و مهندسی آب، دانشکده کشاورزی، دانشگاه بوعلی سینا، همدان، ایران

2 گروه مهندسی آبیاری و آبادانی، دانشکدگان کشاورزی و منابع طبیعی، دانشگاه تهران، کرج، ایران.

3 گروه علوم و مهندسی آب، دانشکده کشاورزی، دانشگاه بوعلی سینا، همدان، ایران.

چکیده

پوشش گیاهی سیلابدشت می‌تواند خصوصیات جریان رودخانه را با اعمال یک نیروی کشانه اضافی تغییر دهد. در این پژوهش، ساختار جریان و خصوصیات تلاطم تحت اثر پوشش گیاهی دولایه ناهمگون در نوار کناری سیلابدشت‌های یک کانال مرکب مطالعه شد. در مطالعه این پدیده، از یک مدل عددی سه‌بعدی برای حل معادلات ناویر استوکس و ردیابی سطح آزاد استفاده شد. برای اطمینان از عملکرد مدل، نتایج عددی با استفاده از داده‌های مطالعات آزمایشگاهی پیشین اعتبارسنجی شد. نتایج اعتبارسنجی نشان داد که این مدل دقت بالایی در بازتولید خصوصیات دینامیکی جریان دارد. در گام بعدی، مدل در پیش‌بینی تغییرات سطح آزاد و میدان سرعت جریان ماندگار در ناحیه دارای پوشش گیاهی سیلابدشت مورد استفاده قرار گرفت. نتایج نشان داد که شکل‌گیری گرادیان سرعت در فصل مشترک بین کانال اصلی و سیلابدشت، منجر به توسعه جریان‌های ثانویه و انتقال جرم و مومنتوم در این ناحیه می‌شود. همچنین، انرژی جنبشی تلاطم و اتلاف انرژی جریان عبوری از ناحیه دارای پوشش گیاهی در سیلابدشت نسبتا زیاد است، بنابراین نتیجه‌گیری شد که پوشش گیاهی ناهمگون می‌تواند موجب افزایش تلاطم و اتلاف انرژی جنبشی جریان شود. مقادیر بیشینه پارامترهای انرژی جنبشی تلاطم و شدت تلاطم در فصل مشترک سیلابدشت و کانال اصلی رخ داد. بنابراین، تلاطم قابل ملاحظه در فصل مشترک سیلابدشت و کانال اصلی می‌تواند انتقال جرم و مومونتوم را در این ناحیه تقویت کند.

کلیدواژه‌ها

عنوان مقاله [English]

Flow and Turbulence Characteristics in a Compound Channel with Partially Layered Vegetated Floodplains

نویسندگان [English]

  • Fariba Ahmadi Dehrashid 1
  • majid heydari 1
  • mehdi yasi 2
  • alireza khoshkonesh 3
1 Department of Water Science and Engineering, Bu-Ali Sina University, Hamedan, Iran
2 Department of Irrigation and Reclamation Engineering, Faculty of Agricultural Engineering & Technology, University of Tehran, Karaj Campus, Iran
3 Department of Water Science and Engineering, Bu-Ali Sina University, Hamedan, Iran.
چکیده [English]

Floodplain vegetation can alter the flow characteristics of a river through the application of redundant drag forces. In this study, turbulence characteristics and flow structure were investigated under the influence of partially double-layered vegetation in a compound channel. To investigate the phenomenon, a three-dimensional numerical model was used to solve the Navier-Stokes equations and track the evolution of the free surface. To ensure the performance of the model, the numerical results were validated using data from previous experimental studies. The validation results showed that this model captured the flow dynamics with high accuracy. In the next step, the model was used to predict the free surface fluctuations and velocity field of the steady flow in the layered vegetated floodplains. The modeling results showed that the formation of a velocity gradient at the interface between the main channel and the floodplain can lead to the development of secondary flows and the mass and momentum exchange at this interface. In addition, turbulent kinetic energy and turbulent dissipation of the flow through vegetation in floodplains was observed in the numerical results. It was concluded that the layered vegetation can increase the flow turbulence and the dissipation rate of the flow energy. The maximum values of turbulence kinetic energy and turbulence intensity were observed at the interface between the floodplain and the main channel. Therefore, the flow disturbance at the interface between the floodplain and the main channel may increase the mass and momentum exchange in this region.

کلیدواژه‌ها [English]

  • Compound channel
  • Double-layer vegetation
  • Turbulence intensity
  • Turbulent kinetic energy
  • Velocity profile

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نشریه آبیاری و زهکشی ایران
دوره 17، شماره 3 - شماره پیاپی 99
مرداد و شهریور 1402
صفحه 479-491

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