Comparison of RSM and LES Turbulence Models on Sharp Bend

Document Type : پژوهشی

Authors

• Javad Mozaffari ¹
• Amir Samadi ²
• Seyed Asadollah Mohseni Movahhed ¹
• Davoud Davoud-Maghami ¹

¹ Arak University

² Imam Khomeini International University

10.22067/civil.v27i1.38252

Abstract

Recognizing of river flow pattern, deposition and erosion areas in meanders is highly important. Despite the limitations of the physical models in laboratory investigation of flow pattern in meanders, mathematical models can be helpful. In this research, RSM and LES turbulence models have been compared on sharp river bend of a laboratory flume using Fluent Software. The Laboratory flume is a sharp river bend established in hydraulic laboratory of EPFL. In order to investigate turbulence models, depth-averaged parameters were used. Moreover, to quantitatively examine those models, some longitudinal velocity profiles were selected and compared with measured ones. Results of longitudinal depth averaged velocities showed that RSM model is not able to precisely determine the important flow points. This model shows flow separation region within 85 degree and maximum width of 40 percent, though measurements indicated it was located in the region with maximum width of 60 percent of total width and approximately 75 degree. On the contrary, LES model suitably shows separation region. Besides, it better determines maximum measured depth averaged velocity situations rather than RSM model. Investigation of transversal depth-averaged velocity distinguished LES model from RSM as the better model and finally quantitative comparison of velocity profiles showed LES model is more accurate and presents more valid authentic results.

Keywords

• Depth-Averaged velocity
• Fluent
• Sharp bend
• Turbulence model

---

References

1. Shettar, A.S., and Murthy, K.K., "A numerical study of division of flow in open channels", Journal of Hydraulic Research, Delft, The Netherlands, Vol. 34, No. 5, pp. 651-675, (1996).

2. صفرزاده گندشمین، ا.، و صالحی نیشابوری، ع.ا.، "مطالعه‌ی عددی الگوی جریان آشفته و بررسی کیفی انتقال رسوب و فرسایش در آبگیری جانبی از رودخانه"، مجله‌ی فنی و مهندسی مدرس، شماره‌ی 25، صص. 18-1، (1385).

3. امید بیگی، م.ع.، "مطالعه‌ی آزمایشگاهی و شبیه‌سازی عددی سهبعدی الگوی جریان در آبگیری جانبی از رودخانه در حضور صفحات مستغرق"، پایان‌نامه‌ی کارشناسی ارشد، دانشکده‌ی کشاورزی، دانشگاه تربیت مدرس، (1388).

4. شاملو، ح.، و پیرزاده، ب.، "بررسی اثرات پارامترهای هندسی و هیدرولیکی بر ابعاد ناحیه‌ی جدایی جریان در آبگیرهای جانبی به‌کمک نرم‌افزار فلوئنت"، نشریه‌ی مهندسی عمران و نقشه‌برداری، صص. 487-495، (1389).

5. Han, S.S., "Characteristics of flow around 90 open channel bends", PhD. Thesis. Dept. of Building, Civil and Environmental Engineering, Concordia University, Montreal, Quebec, (2010).

6. van Balen, W., Uijttewaal, W.S.J., and Blanckaert, K., "Large eddy simulation of a mildly curved open-channel flow", J. Fluid Mech., Vol. 630, pp. 413-442, (2009).

7. Booij, R., "Measurements and large eddy simulations of the flows in some curved flumes", J. Turbulence, Vol. 4, No. 1, pp. 8-16, (2003).

8. Dargahi, B., "Three-dimensional flow modelling and sediment transport in the river Klarälven", Earth Surface Processes and Landforms, Vol. 29, No. 7, pp. 821- 852, (2004).

9. Kang, H., and Choi, S., "Reynolds stress modelling of rectangular open-channel flow", Intl. J. Num. Meth. Fluids, Vol. 51, No. 11, pp. 1319-1334, (2006).

10. Khosronejad, A., Rennie, C.D., Neyshabouri, S.A.A.S., and Townsend, R.D., "3D numerical modeling of flow and sediment transport in laboratory channel bends", J. Hydraulic Eng., Vol. 133, No. 10, pp. 1123-1134, (2007).

11. Fluent Inc., "FLUENT 6.3 User's Guide", Lebanon, New Hampshire, United States of America, (2006).

12. Van Rijn, L.C., "Sediment transport, part 1: bed load transport", J. Hydr. Eng., Vol. 110, No. 10, pp. 1431-1456, (1984).

13. Montazeri, M., and Hashemi, R., "3D numerical simulation of supercritical flow in bends of channel", International conference on mechanical Engineering, Dubai, (2012).