نوع مقاله : مقاله پژوهشی
نویسندگان
1 دکتری آب و سازه های هیدرولیکی، دانشگاه آزاد اسلامی واحد استهبان، فارس، استهبان
2 استادیار گروه مهندسی آب و سازه های هیدرولیکی، دانشگاه آزاد اسلامی واحد استهبان، فارس، استهبان
چکیده
پیش‌بینی و تجزیه و تحلیل جریان در کانال با پوشش گیاهی و تالاب‌ها اصلی‌ترین مشکل چالش‌برانگیز در محیط زیست و هیدرولیک می‌باشد. دلیل این امر آن است که خصوصیات هیدرولیکی جریان در تالاب‌ها و کانال‌های انتقال‌دهنده جریان به شدت به ساختار فیزیکی، تراکم و نحوه توزیع پوشش گیاهی وابسته است. هدف از پژوهش حاضر، ارائه تحلیل جامعی از پروفیل‌های سرعت در کانال‌های با پوشش گیاهی غیر مستقرق در حضور گونه واقعی گیاهی و ارائه رابطه دقیق‌تری برای گونه گیاهی مورد آزمایش و گونه‌های مشابه آن است. بدین‌منظور، مطالعات در یک فلوم آزمایشگاهی با مقطع مستطیلی به طول 20 متر و عرض 1.5 متر با شیب کف ثابت 0.005 صورت گرفت که در آن از نوعی پوشش گیاهی به نام Eleocharis در سه نوع تراکم کم، متوسط و زیاد استفاده شده است. نتایج به‌دست آمده نشان داد که مقادیر سرعت در نواحی بالادست، کمترین مقدار را دارد که به‌طور میانگین سرعت متوسط در بالادست نسبت به پایین‌دست برای تراکم‌های مختلف حدود چهار الی 12 درصد کاهش را نشان می‌دهد. ضمناً مقدار سرعت متوسط نیز با افزایش تراکم گیاهی از تراکم 23 به 42 و از تراکم 42 به 72 به ترتیب حدود 12 و 4.5 درصد در بالادست و حدود 11 و چهار درصد در پایین‌دست کاهش پیدا می‌کند. در نهایت، برای برآورد سرعت متوسط جریان در ناحیه پوشش گیاهی یک رابطه ارائه شد که از دقت مناسبی برخوردار می‌باشد. لازم به ذکر است که کاربرد این رابطه در تالاب ها و کانال‌ها برای رفع مسئله آلودگی رواناب‌ها و مسئله رسوب‌گذاری حائز اهمیت می‌باشد.
کلیدواژه‌ها
عنوان مقاله [English]
Analysis of flow velocity distribution in vegetation channels with different densities
نویسندگان [English]
- Mohammad javad Rezaei 1
- Reza Mohammadpoor 2
1 PhD, Department of Civil Engineering, Estahban Branch, Islamic Azad University, Estahban, Iran
2 Assistant Professor, Department of Civil Engineering, Estahban Branch, Islamic Azad University, Estahban, Iran
چکیده [English]
Predicting and analysing flow in the vegetated channel and wetland is the main challenging environmental and hydraulic problem. It is due to the high dependency of the hydraulic properties of the flow to the physical structure, density, and distribution of vegetation in wetlands and channels In this study, velocity profiles are investigated in emerge vegetated channels with considering density effect. The experiments were performed in a laboratory flume with vegetation called Eleocharis and three different types of densities. This study aims to provide a comprehensive analysis of velocity profiles in emerged vegetation channels in the presence of real plant species and to provide a more accurate relationship. Therefore, studies were performed in a laboratory flume with a rectangular cross-section 20 meters long and 1.5 meters wide with a fixed floor slope of 0.005, in which a type of vegetation called Eleocharis was used in three types of low, medium, and high density. The results showed that the velocity in the upstream areas is the lowest which on average shows an average velocity in the upstream compared to the downstream for different densities of about 4 to 12 percent. Meanwhile, the average velocity decreases by increasing the plant density from 23 to 42 and from 42 to 72 about 12 and 4.5 percent in the upstream and about 11 and 4 percent in the downstream, respectively. Also, to estimate the average flow velocity in the vegetation area, a modified relationship was presented which has acceptable accuracy. The application and accuracy of this relationship in artificial wetlands and channels are important to eliminate runoff pollution and sedimentation.
کلیدواژه‌ها [English]
- Eleocharis
- Vegetated channel
- Vegetation density
- Velocity distribution
- Wetland
1.Afzalimehr, H., R. Moghbel, J. Gallichand and S.U.I. Jueyi. 2011. Investigation of turbulence characteristics in channel with dense vegetation. International Journal of Sediment Research, 26(3): 269-282.
2.Afzalimehr, H. and P. Setayesh. 2018. Investigation on logarithmic and coles laws under different emergent vegetation patches. Journal of Hydraulics, 13(1): 47-62.
3.Chakraborty, P. and A. Sarkar. 2018. Simulation of flow characteristics through emerged rigid vegetation over a perturbed bed. In Free Surface Flows and Transport Processes (pp. 155-165). Springer, Cham.
4.Choi, S.U. and H. Kang. 2006. Numerical investigations of mean flow and turbulence structures of partly-vegetated open-channel flows using the Reynolds stress model. Journal of Hydraulic Research, 44(2): 203-217
- Dijkstra, J.T. and R.E. Uittenbogaard. 2010. Modeling the interaction between flow and highly flexible aquatic vegetation. Water Resources Research, 46(12): 12-29.
6.Drikvandi, Kh., M. Fathi Moghadam, M. Masjedi and M. Bina. 2012. Investigating the effect of density and flexibility of vegetation on roughness coefficients on river banks and floodplains in non-submerged conditions. Water Resources Research, 8(2): 24-49 (in Persian).
7.Dupuis, V., S. Proust, C. Berni and A. Paquier. 2016. Combined effects of bed friction and emergent cylinder drag in open channel flow. Environmental Fluid Mechanics, 16(6): 1173-1193.
- Fischer-Antze, T., T. Stoesser, P. Bates and N.R.B. Olsen. 2001. 3D numerical modelling of open-channel flow with submerged vegetation. Journal of Hydraulic Research, 39(3): 303-310.
- Huai, W.X., Z.B Chen, H.A.N. Jie, L.X. Zhang and Y.H. Zeng. 2009. Mathematical model for the flow with submerged and emerged rigid vegetation. Journal of Hydrodynamics, 21(5): 722-729.
10.Huai, W.X., Y.H. Zeng, Z.G. Xu and Z.H. Yang. 2009. Three-layer model for vertical velocity distribution in open channel flow with submerged rigid vegetation. Advances in Water Resources, 32(4): 487-492.
11.Ikeda, S., T. Yamada and Y. Toda. 2001. Numerical study on turbulent flow and honami in and above flexible plant canopy. International Journal of Heat and Fluid Flow, 22(3): 252-258.
12.Jing, H.F., Y.J. Cai, W.H. Wang, Y.K. Guo, C.G. Li and Y.C. Bai. 2020. Investigation of open channel flow with unsubmerged rigid vegetation by the lattice Boltzmann method. Journal of Hydrodynamics, 32(4): 771-783.
13.Kouwen, N. and M. Fathi Moghadam. 1997. Nonrigid, nonsubmerged, vegetative roughness on floodplains. Journal of Hydraulic Engineering, 123(1): 51-57.
- Li, W.Q., D. Wang, J.L. Jiao and K.J. Yang. 2018. Effects of vegetation patch density on flow velocity characteristics in an open channel. Journal of Hydrodynamics, 31(5): 1052-1059.
15.Sajedi Sabegh, M., M. Saneie, M. Habibi, A. Abbasi and M. Ghadimkhani. 2011. Experimental investigation on the effect of river bank tree planting array, on shear velocity. Watershed Engineering and Management, 2(4): 206-210 (in Persian).
16.Wang, W., W.X. Huai and M. Gao. 2014. Numerical investigation of flow through vegetated multi-stage compound channel. Journal of Hydrodynamics, 26(3): 467-473.
17.Wu, F.C., H.W. Shen and Y.J. Chou. 1999. Variation of roughness coefficients for unsubmerged and submerged vegetation. Journal of Hydraulic Engineering, 125(9): 934-942.
18.Yang, W. and S.U. Choi. 2009. Impact of stem flexibility on mean flow and turbulence structure in depth-limited open channel flows with submerged vegetation. Journal of Hydraulic Research, 47(4): 445-454.
- Xia, J. and L. Nehal. 2013. Hydraulic features of flow through emergent bending aquatic vegetation in the riparian zone. Water, 5(4): 2080-2093.
20.Yang, Z.H., F.P. Bai, W.X. Huai and C.G. Li. 2018. Lattice Boltzmann method for simulating flows in open-channel with partial emergent rigid vegetation cover. Journal of Hydrodynamics, 31(4): 717-724.
21.Zhang, M., C.W. Li and Y. Shen. 2013. Depth-averaged modeling of free surface flows in open channels with emerged and submerged vegetation. Applied Mathematical Modelling, 37(1-2): 540-553.
)