بررسی نحوه کارایی موانع نفوذپذیری بر هد جریان غلیظ نمکی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی عمران، واحد نجف آباد، دانشگاه آزاد اسلامی ، نجف آباد، ایران.

2 گروه سازه‌های آبی، دانشکده مهندسی آب و محیط زیست، دانشگاه شهید چمران اهواز، اهواز، ایران.

3 گروه مهندسی آب، دانشکده کشاورزی، دانشگاه صنعتی اصفهان، اصفهان، ایران.

چکیده

مقدمه: جریان­های غلیظ اغلب عامل اصلی انتقال رسوب در آب­های عمیق و مخازن می­باشند. برای جلوگیری از رسوب در مکان­های بحرانی سدها، روش­های مختلفی از جمله قرار دادن موانع در مسیر این جریان­ها ارائه شده است.
روش­: براین­اساس در این مطالعه اثر دبی، غلظت ورودی، شیب و ارتفاع موانع نفوذپذیر ذوزنقه­ای شکل بر رفتار جریان­های غلیظ نمکی به صورت آزمایشگاهی مورد بررسی قرار گرفته است. 72 آزمایش­  با دبی متغیر 7/0، 2/1و 7/1 لیتر برثانیه و غلظت متغیر 20 و 25 گرم بر لیتر، شیب 5/0، 1 و 5/1 درصد و ارتفاع مانع 1، 5/1 و 2 برابر بدنه جریان غلیظ انجام شد و  براساس شار هد جریان مقادیر درصدکاهش هد تعیین و اثر سایر پارامترها مورد ارزیابی قرار گرفت.
یافته­ها: نتایج نشان داد که سه پارامتر شیب، غلظت و دبی ورودی عوامل موثر بر مومنتم جریان بوده و با افزایش هر یک از این پارامترها، میزان کارایی موانع با نسبت بی­بعد ارتفاع 1 و 5/1 کاهش پیدا می­کند اما در مانع با نسبت بی­بعد ارتفاع 2 عملکرد مانع بهتر بوده و هنگام برخورد جریان با مانع اغتشاش زیاد ایجاد شده که سبب کاهش چشمگیر هد جریان غلیظ می­گردد.
نتیجه­گیری: به این صورت که نرخ متوسط کاهش شار هد برای نسبت بی­بعد ارتفاع 1 در حدود 38 درصد و برای نسبت بی­بعد ارتفاع 5/1 در حدود 52 درصد و برای نسبت بی­بعد ارتفاع 2 در حدود 86 درصد می­باشد. در انتها به برازش خطی و غیرخطی داده های درصد کاهش هد جریان غلیظ پرداخته شد.

کلیدواژه‌ها

عنوان مقاله [English]

Investigation of the effect of permeable obstacles on salt density current head

نویسندگان [English]

  • mehdi derakhshannia 1
  • mehdi ghomeshi 2
  • saied saeid Eslamian 3
  • seyed mahmood kashefipour 2
1 Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran.
2 Department of Water Structures, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
3 Department of Water Engineering, College of Agriculture, Isfahan University of Technology, Isfahan, Iran.
چکیده [English]

Density currents are often the main cause of sediment transport in deep water and reservoirs. To prevent sedimentation in critical locations of dams, various methods have been proposed, including placing obstacles in the path of these currents. in this study, the effect of discharge, inlet concentration, slope and height of trapezoidal permeable obstacle on the behavior of density current has been investigated . 72 experiments were performed with variable discharge of 1, 1.5, and 2 liters per second and variable concentrations of 10 and 15 g/l, slope of 0.5%, 1% and 1.5% and obstacle height of 1,1.5 and 2 times the body of density current. The percentage of flux reduction was determined and the effect of other parameters was evaluated. The results showed that slope, concentration and inlet discharge are the factors affecting the momentum and by increasing each of these parameters, the efficiency of obstacle with heights of 1 and 1.5 times body density current decreases. In case of obstacle with a height of 2 times the body, when the current collides with the obstacle, there is a lot of turbulence, which decreases the momentum of the current, and complete control is performed. Thus, the average percentage of flux reduction for the dimensionless ratio of height 1 is about 38%, for the dimensionless ratio of height 1.5 is about 52% and for the dimensionless ratio of height 2 is about 86%. Finally, linear and nonlinear regression of the average percentage of flux reduction data was obtained.

کلیدواژه‌ها [English]

  • Density currents
  • Permeable obstacle
  • Head flux
  • Momentum

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سابقه مقاله

  • تاریخ دریافت: 10 مهر 1399
  • تاریخ بازنگری: 30 دی 1399
  • تاریخ پذیرش: 04 آبان 1400

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