بررسی اثر پارامترهای مؤثر بر ضریب درگ در پوشش گیاهی صلب و انعطاف پذیر

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری، گروه سازه های آبی، دانشکده مهندسی آب و محیط زیست، دانشگاه شهید چمران اهواز، اهواز، ایران.

2 استاد، گروه سازه های آبی، دانشکده مهندسی آب و محیط زیست، دانشگاه شهید چمران اهواز، اهواز، ایران

3 استاد، گروه سازه های آبی، دانشکده مهندسی آب و محیط زیست، دانشگاه شهید چمران اهواز، اهواز، ایران.

4 دانشیار، گروه سازه های آبی، دانشکده مهندسی آب و محیط زیست، دانشگاه شهید چمران اهواز، اهواز، ایران.

چکیده

مسأله­ی مقاومت در مقابل جریان در مجاری روباز دارای پوشش گیاهی در دهه­های اخیر مورد توجه بسیاری از محققین قرار گرفته است. حضور پوشش گیاهی در مناطق مستعد سیلاب و حاشیه­ی رودخانه­ها تأثیر قابل توجهی بر پراکنش انرژی و کاهش خسارات دارد. در این مقاله به­منظور بررسی اثر پوشش گیاهی در آبراهه­ها، پوشش گیاهی صلب و انعطاف­پذیر با نمونه­های مصنوعی
 مدل­سازی شد. در شرایط آزمایشگاهی، نیروی درگ اعمال شده بر مدل پوشش گیاهی غیر مستغرق به­صورت مستقیم با استفاده از حس­گر نیرو در بخش متحرک فلوم اندازه­گیری شد­. در این مقاله، شاخص جدیدی با عنوان "شاخص تراکم" پوشش گیاهی معرفی شده­است. این شاخص به سطح مقابل جریان هر واحد پوشش گیاهی و مجموع تعداد واحدهای پوشش گیاهی در محدوده مورد مطالعه بستگی دارد. نتایج نشان داد در هر دو مدل صلب و انعطاف پذیر، با افزایش شاخص تراکم پوشش گیاهی و عمق نسبی، میزان جذب نیروی درگ افزایش می­یابد. بررسی اثر شاخص تراکم پوشش گیاهی نشان داد افزایش این شاخص تأثیر   به­سزایی در کاهش ضریب درگ دارد؛ به­طوریکه در بیشترین میزان افزایش شاخص تراکم، کاهش 8/19 درصد در ضریب درگ مشاهده گردید. افزایش عمق نسبی جریان تا رسیدن به مرحله­ای که پوشش گیاهی در آستانه­ی استغراق قرار گیرد، به­ترتیب در دو مدل صلب و انعطاف­پذیر موجب کاهش 81/ 12 درصد و 43/10 درصد ضریب درگ می­شود. در نهایت دو مدل ریاضی با ضریب رگرسیون 87/0 و 89/0 به­ترتیب به­منظور تخمین ضریب درگ پوشش گیاهی صلب و انعطاف­پذیر با در نظر گرفتن پارامترهای بدون بعد مؤثر ارائه گردید.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigation the Effective Parameters on the Drag Coefficient in Rigid and Flexible Vegetation

نویسندگان [English]

  • Samira Salmanzadeh 1
  • Manoochehr Fathi-Moghadam 2
  • Javad Ahadiyan 3
  • Seyed Mohsen Sajjadi 4
1 Ph.D. candidate, Hydraulic Structures Department, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
2 Professor, Hydraulic Structures Department, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
3 Professor, Hydraulic Structures Department, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
4 Assoiciated Professor, Hydraulic Structures Department, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
چکیده [English]

Rivers are known as the main sources of surface water in the world, which experience seasonal fluctuations in water level. These resources have severe damage to human societies and nature in flood conditions and have irreparable consequences in the drought seasons. Optimal utilization of these resources with maintaining the environmental conditions of the waterway and minimizing flood damage is considered one of the river engineering goals. Since the conventional methods of river management are imposed serious environmental threats on waterways and wetlands, consideration to these water resources requires attention to issues related to plant ecosystems, solving challenges of coastal bed erosion and predict the condition and management of the river in the future (Callow, 2012; Dawson and Haslam, 1983; Fan et al., 2013; Rose et al., 2010; Rowinski et al., 2018). One of the strategies that cause loss of flow energy in the river improves the hydrological system and river ecosystem is the presence of vegetation in the river banks and floodplains. Native vegetation in floodplains and coastal forests plays an important role in conserving waterway ecosystems, flood management, coastal protection in urban lands and agriculture adjacent to the river (Fathi-Moghadam, 1996). Vegetation will also control the width of the river and increase the stability of the shores by absorbing and settling suspended sediments in river banks. The plant species along rivers and waterways are composed of various vegetative components, mainly affected by the environmental conditions of their habitat, including the distance from the waterway bed, hydrological characteristics of the river, climatic and soil conditions. Obviously, the effect of each plant species in the ecosystem cycle varies and for each section of the river, a specific combination of plants will create optimal conditions.

کلیدواژه‌ها [English]

  • Density Index
  • Flow Resistance
  • Relative Depth
  • Non- Submerged
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