بررسی تأثیرتراکم زبری های مصنوعی مکعبی برآب‌راهه شیبدار روی عمق آبشستگی پایین دست آن

نوع مقاله : مقاله پژوهشی

نویسندگان

1 کارشناسی ارشد آب و سازه‌های هیدرولیکی، دانشکده مهندسی علوم آب، دانشگاه شهید چمران اهواز.

2 استادیار گروه سازه های آبی، دانشکده مهندسی علوم آب، دانشگاه شهید چمران اهواز

چکیده

عبور آب از شیب­های تند در مسائل مهندسی رودخانه و طرح سازه­های انتقال آب امری اجتناب ناپذیر است. به دلیل شیب تند بستر عمدتاً سرعت جریان ونرخ فرسایش سطحی بالا می­باشد. لذا توسعه حفره آبشستگی در پایین دست سازه­های انتقال آب که منجر به تخریب خود سازه می­گردد از دیر باز مورد توجه محققین بوده است.در این تحقیق، یک مدل آزمایشگاهی شامل سرریز با ارتفاع 60 سانتی‌متر وطول 180 سانتی مترساخته شد. سطح بستر سرریز پوشیده از زبری­های مصنوعی مکعبی در سه تراکم 5، 10 و15 درصد و آبشستگی داخل حوضچه در4 عدد آبشار مختلف از 0008/0 تا 003/0 بررسی شد. نتایج حاکی از آن است که در یک عدد آبشار ثابت با افزایش تراکم زبری­ها قدرت جریان عبوری از آبراهه شیبدار به دلیل مقاومت برشی تضعیف می­گردد. از این رو با تاثیرگذاری زبری بر کاهش قدرت گردابه­های بوجود آمده در جریان پرش هیدرولیکی پایین­دست آبراهه شیبدار از میزان عمق آبشستگی کاسته می­شود. در صورت افزایش تراکم به میزان 15 درصد عمق آبشستگی در عدد آبشار حداکثر 30 درصد کاهش می­یابد که این میزان کاهش در تراکم 5 درصد به حداکثر 10 درصد می­رسد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Examination of the Effect of Cubic Artificial Roughness Density inInclined Channel on Downstream Scour Depth

نویسندگان [English]

  • Fateme Farajzadeh 1
  • Ahmad Fathi 2
1 Master Student, Department of Hydraulic Structures, Shahid Chamran University of Ahvaz.
2 Assistant Professor in Hydraulic Structure of Shahid Chamran University of ahvaz
چکیده [English]

Water passage from  steep slopes in river engineering issues and the design of water transfer structures is inevitable. Because of the steep slope of the surface, the surface velocity and surface erosion rates are high. Energy control in high-speed flows is one of the challenges of designing hydraulic structures. These flows, for example, occur in places such as dam overhead structures, drainage systems of urban areas and Mountain Rivers with a steep slope. One of the ways to reduce dimensions or eliminate energy depreciating structures is to use methods to reduce the kinetic energy of flow over the weir, including using of stairs or blocks on the overflow. The use of large-sized stairs or blocks will cause the passing jets of flow to be separated and as a result turbulent, which can effectively deplete the kinetic energy of the current. The problem with using a staircase or block is a huge cost of built and a high risk of cavitation. Another method of energy depreciation is to apply roughness at the overflow bed, which may be an efficient way to reduce energy. Roughness can dramatically reduce the flow turbulence, and thus reduces the risk of cavitation. Also, roughness can reduce the flow power over the overflow and reduce the depth of the lower erosion pit by removing or reducing the dimensions of the relaxation basin. Most studies in this field have investigated the effect of these roughs on the amount of energy depletion, which in addition to energy depletion is also important for lowering the erosion of the structure. However, for the economic design of hydraulic structures, designers need to have full knowledge of the particle mechanics and the dimensions of the scour hole, so that they can consider the requirements for the stability of the structure, which has so far been  investigated insufficiently. Therefore, the present study aimed to investigate the effect of roughness density on sloped bed surface on its downstream scour depth.

کلیدواژه‌ها [English]

  • Artificial Roughness
  • Scour
  • Energy Depreciation
  • Inclined Channel
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