تاثیر شکل مقطع بر ضریب تصحیح انرژی جنبشی و مومنتوم و مقایسه با نرم‌افزار CES

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری گروه مهندسی آب دانشگاه لرستان

2 استادیار/دانشگاه شهرکرد

3 گروه مهندسی آب دانشگاه لرستان

چکیده

در ناحیه اندرکنش کانال اصلی و سیلابدشت در یک کانال مرکب به دلیل تبادل مومنتوم و تنش‌های برشی موجود اتلاف انرژی جریان وکاهش ظرفیت انتقال رخ می‌دهد. به دلیل اغتشاش جریان در این محل برآورد انرژی جنبشی و میزان مومنتم جریان با خطا روبرو خواهد بود. بنابراین تعیین مقادیر پارامترهای مهم هیدرولیکی قابل اطمینان نخواهد بود. برای تصحیح این خطا و تعیین دقیق‌تر پارامترهای هیدرولیکی از جمله پروفیل سطح آب، روندیابی سیلاب و یا انتقال رسوب و آلودگی تعیین ضرایب تصحیح انرژی جنبشی (α یا ضریب کوریولیس) و مومنتوم (ß یا بوزینسک) از اهمیت بالایی برخوردار است. در این مطالعه با استفاده از داده‌های کانال FCF ، تاثیر شیب دیواره کانال اصلی (0:1، 1:1 و 2:1)، عرض سیلابدشت (1/4 و 75/0 متر) و عدم تقارن مقطع، بر ضرایب α و ß بررسی شده است. طبق نتایج با افزایش عرض سیلابدشت بیشینه مقادیر α و ß افزایش یافته است بطوری که مقدار α و ß در سیلابدشت با بیشترین عرض به ترتیب 36/1 و 13/1 برابر مقدار α و ß در سیلابدشت با کمترین عرض بوده است. البته اثر افزایش شیب دیواره کانال اصلی بر مقادیر این ضرایب قابل صرفنظر کردن است. زیرا با افزایش شیب از 2:1 به 0:1 بیشینه ضرایب α و ß به ترتیب 015/1 و 01/1 برابر شده است. بیشینه مقادیر ضریب α در کانال نامتقارن همواره کمتر از کانال‌های متقارن (با مجموع عرض کمتر یا بیشتر سیلابدشت) بوده است. بیشینه مقادیر ضریب ß در کانال نامتقارن از کانال‌های متقارن با عرض سیلابدشت بیشتر، کمتر است و از کانال‌های متقارن با عرض سیلابدشت کمتر، بیشتر است. همچنین با استفاده از نرم‌افزار CES مقادیر ضرایب α، ß و دبی، برآورد شده و با داده‌های آزمایشگاهی کانال FCF مقایسه شده است. نتایج نشان دهنده قابلیت بالای CESدر تعیین پارامترهای هیدرولیکی جریان در مقاطع مرکب متقارن و نامتقارن می‌باشد.

کلیدواژه‌ها


عنوان مقاله [English]

The Effect of Cross-section Shape on Kinetic and Momentum Correction Coefficient and Compare with CES Model

نویسندگان [English]

  • jalil kermannezhad 1
  • Elham GhanbariAdivi 2
  • hojat alah yonesi 3
1 Ph.D Student, Department of Water Engineering, College of Agriculture, Lorestan University of Khoram-Abad.
2 Water engineering,Shahrekord university
3 Associated Professor, Department of Water Science Engineering, Lorestan University
چکیده [English]

Momentum exchange and tensions at the main channel–flood plain interface in a compound channel will losses the energy flow, reduce conveyance and makes error in estimating the water surface profile, flood routing and sediment and pollutant transport. So, determining the kinetic energy correction coefficients (α or Coriolis coefficient) and momentum coefficients (B or Boussinesq coefficient) is very important in estimating kinetic energy loss and momentum exchange. In this study, using FCF (Flood Channel Facility) channel data, the effects of floodplain width (4.1, 2.25 and 0.75 m), main channel bank slop (0:1, 1:1 and 2:1) and asymmetric cross section on the coefficients α and B are investigated. According to the results, with increasing floodplain width, the maximum values of α and B increased, so that the values of α and B in the floodplain with the highest width are 1.36 and 1.13 times the values of α and B in the floodplain with the lowest width respectively. Of course, the effect of increasing the main channel bank slope on the values of these coefficients can be discarded. Because with increasing slope from 2:1 to 0:1, the maximum coefficients α and B were 1.015 and 1.01 respectively. The maximum values of the coefficient α in the asymmetric channel are always less than symmetric channels (with less or more total width in the floodplain). The maximum value of the B coefficient in the asymmetric channel is lower than the symmetrical channels with wider floodplain, and it is higher than the symmetrical channels with narrower floodplain. Also, using the CES (Conveyance Estimation System) software, the coefficients a, b and discharge are estimated and compared with actual FCF channel data. The results show that the high performance of the CES in determining the hydraulic parameters of flow in symmetric and asymmetric composite sections

کلیدواژه‌ها [English]

  • Compound channel
  • CES
  • Floodplain
  • Kinetic energy correction coefficients
  • momentum correction coefficients
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