Numerical simulation of bedform effect on flow structure in shallow rivers

Document Type : Original Research

Authors
M. Sharifi 1
S. H. Ghoraishi Najafabadi 2
M. majdzadeh tabatabaie 3
S. Beheshti 4
1 Graduate Master Student of Shahid Beheshti University
2 Assistant professor of Shahid Beheshti University
3 Assistant professor of Shahid Beheshti university
4 Instructor of Shahid Beheshti University
Abstract
On way to understand the behavior of rivers is to study of flow structures and bedforms. Most rivers have rough beds, that are called bedforms. These shapes have different types depending on the hydraulic conditions that cause the resistance to flow, so sufficient knowledge of the hydraulic resistance of the flow is necessary to calculate discharge, depth, water velocity, flood prediction and sediment transport to reduce the damages that are caused by rivers. Despite years of research and experimentation on bedforms, there is still no adequate and accurate equation to predict the geometry of bedforms and their interaction with flow. The RANS turbulence model is not sufficiently accurate in detecting flow separation in high-altitude and high-angel lee side dunes, but it is more appropriate in other dunes. The LES turbulence model can be more appropriate in detecting flow separation in the vicinity of the bed. But in the layers away from the dune, it produces relatively severe turbulences. The DES turbulence model is more accurate in detecting the flow separation in large-scale dunes and has less execution time than the LES, but this model produces irregular vortices in smaller dunes near the bed. In this research, with the aim of investigating the effect of dune geometry on flow structure, numerical simulation of flow motion on dunes in open channel duct was investigated. In this regard, 29 simulations were performed to study the effect of the geometry of five types of dune with different angles and heights in different hydraulic conditions and different bed roughnesses with RANS and DES turbulence models. The STAR-CCM+ was used in order to simulate the numerical model in this research. This software provides highly realistic results by providing a seamless environment with high network production capability and extensive simulation tools, which helps professionals in the process of working with fluids.In this research, VOF method is used to calculate free surface area, and the solution method is Implicit Unsteady. In order to sensitize the numerical model to the number of computational cells as well as to optimize the runtime and output accuracy, several blocks of lattice dimensionality change in data points and dune locations were used. To select the appropriate networking dimensions, 8 models were run to optimize the time and accuracy of the model. To evaluate the accuracy of the simulations, the numerical model results were compared with those of previous researchers. The results of comparison of the numerical model and the experimental model showed that only about 9.5%, 15.5%, 14.5%, 9.4%, 12.2% and 7.4% were different. This error rate indicates good numerical model accuracy. Also the results of numerical model + STAR-CCM were compared with SSIIM numerical model. then, by using the dimensional analysis, effective factors on the interaction of dune geometry and flow structure were investigated and finally, a formula was developed to predict this interaction. The results of the evaluation of the obtained formula for investigating the effect of dune geometry on the hydraulic flow showed that the presented formula with error of 11.25% and 0.86 R2, due to the completely random nature of bedform formation, is very accurate.

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Subjects

Bathurst, J.C. 1985. Flow Resistance Estimation in Mountain Rivers, Journal of Hydraulic Engineering ASCE, Vol 111, pp 625-641.
Gilbert, G. K.1914. The transition of debris by running water. U.S. Geol. Surv. Prof. Pap. 86, pp 263 .
Soulsby, R. L.1989. Bedform migration in sandy estuaries. H.R Wallingford Res. Rep. No. SR 208, pp 16.
Thélusmond, J., Chevalier, L., & DeVantier, B. 2013. The use of plastic media in a movable bed model to study sedimentary processes in rivers. International Journal Of Hydrology Science And Technology, 3(2), pp 93.
Engelund, F., & Hansen, E.1967. A Monograph on Sediment Transport in Alluvial Streams. Teknisk Vorlag, Copenhagen, Denmark.
Julien, P. 2010. Erosion and sedimentation. Cambridge: Cambridge University Press, 2nd ed, 148 (4), pp 175-176.
Athaullah, M. 1968. Prediction of Bedforms in Erodible Channels. PhD Thesis. Colorado State University, Fort Collins, USA.
Reisenbüchler, M., Bui, M., Skublics, D., & Rutschmann, P. 2019. An integrated approach for investigating the correlation between floods and river morphology: A case study of the Saalach River, Germany. Science Of The Total Environment, Vol. 647, pp 814-826.
Van Rijn, L.C. 1984c. Sediment Transport, Part III: Bed Forms and Alluvial Roughness. Journal of Hydraulic Engineering, ASCE, Vol. 110, No. 12.
Hafez, Y.I., El-Gamal, F.S., and Soliman, W.R., 2001. " River Nile bed forms, resistance to flow and discharge prediction" Water Science, the 28th – 29th issue, October 2000-April 2001.
Balachandar, R. & Patel, V.C. 2002. Rough Wall Boundary Layer on a Plate in an Open Channel. J. Hydr. Engrg., ASCE (12810), pp 947–951.
Venditi, J. G. 2007. Turbulent flow & drag over fixed two- and three-dimensional dunes. J. Geophys. Res. 112 F04008.
Omid, M., Karbasi, M., & Farhoudi, J. 2010. Effects of bed-load movement on flow resistance over bed forms. Sadhana, 35(6), pp 681-691.
Yaseen, M., Afzal, M., & Khan, K. 2015. Effect of Different Bed Configuration on Flow Resistance under Different Flow Regimes in an Open Channel Effect of Different Bed Configuration on Flow Resistance under Different Flow Regimes in an Open Channel. Global Journal Of Researches In Engineering: E Civil And Structural Engineering, 15(1).
Niazkar, M., Talebbeydokhti, N., & Afzali, S. 2019. Development of a New Flow-dependent Scheme for Calculating Grain and Form Roughness Coefficients. KSCE Journal Of Civil Engineering, 23(5), pp 2108-2116.
Kostaschuk, R., & Venditti, J. 2019. Why do large, deep rivers have low-angle dune beds?. Geology, 47(10), 919-922.
Schippa, L., Cilli, S., Ciavola, P., & Billi, P. 2019. Dune Contribution to Flow Resistance in Alluvial Rivers. Water, 11(10), 2094.
Van Mierlo, M. C. L. M. & de Ruiter, J. C. C. 1988. Turbulence measurements above artificial dunes, Report on measurements. Report Q789, WL | Delf Hydraulic, Delf, The Nederlands.
Yue, W., Lin, C., & Patel, V. 2005. Large eddy simulation of turbulent open-channel flow with free surface simulated by level set method. Physics Of Fluids, 17(2), 025108.
Paarlberg, A., Dohmen-Janssen, C. M., Termes, A. P. P., & Hulscher, S. J. M. H. 2005. Model for river dune development including a paramerization for flow separation. 231.
Tjerry, S., & Fredsøe, J. 2005. Calculation of dune morphology. Journal Of Geophysical Research: Earth Surface, 110(F4).
Yue, W., Lin, C., & Patel, V. 2006. Large-Eddy Simulation of Turbulent Flow over a Fixed Two-Dimensional Dune. Journal Of Hydraulic Engineering, 132(7), 643-651.
Kubtako, E. J., & Westerink, J. J. 2007. Exact Discontinuous Solutions of Exner’s Bed Evolution. Journal of Hydraulic Engineering, 133(3), pp 305-311.
Motamedi, A., Afzalimehr, H. Singh, V., & Dufresne, L.2012 Experimental Study on the Influence of Dune Dimensions on Flow Separation. Journal of Hydrologic Engineering, 19(1), pp.78-86.
Abbaspour A., & Kia S.H. 2014. Numerical Investigation of Turbulent Open Channel Flow with Semi-cylindrical Rough Beds, KSCE Journal of Civil Engineering, 18(7), pp: 2252- 2260.
Doré, A., Bonneton, P., Marieu, V., & Garlan, T. 2016. Numerical modeling of subaqueous sand dune morphodynamics. Journal of Geophysical Research: Earth Surface, 121(3), pp.565-587.
Lefebvre, Alice. 2019. Three‐Dimensional Flow Above River Bedforms: Insights From Numerical Modeling of a Natural Dune Field (Río Paraná, Argentina). Journal Of Geophysical Research: Earth Surface, 124(8), 2241-2264.
Spalart, P.R., & Allmaras, S.R. 1994. A one-equation turbulence model for aerodynamic flows. La RechercheA_erospatiale, Vol. 1, pp. 5-21.
Mustaffa, N., Ahmad, N., & Razi, M. 2016. Variations of Roughness Coefficients with Flow Depth of Grassed Swale. IOP Conference Series: Materials Science And Engineering, 136, 012082.Shur M., Spalart P.R., Strelets M., & Travin A. 1999. Detached-eddy simulation of an airfoil at highangle of attack. Engineering Turbulence Modeling and Experiments, Vol. 4, pp. 669-678.
Bunge U., Mockett C., & Thiele F. 2007. Guidelines for implementing Detached-Eddy Simulation using different models. Aerospace Science and Technology, Vol. 11, pp. 376-385.
Viswanathan A.K., & Tafti D.K. 2006. Detached eddy simulation of turbulent flow and heat transfer in a two-pass internal cooling duct. International Journal of Heat and Fluid Flow, Vol. 27, pp. 1-20.
Nelson, J. M., McLean, R. & Wolfe,S. 1993. Mean flow and turbulence over fixed, two-dimensional bed form. Water Resour. Res. 29: 3935-3953.
[34] Allen, J. R. L. 1985. Principles of Physical Sedimentology. Chapman and Hall, PP. 272
Nasiri DehSorkhi, A., 2010, Interaction of vegetation cover, bed forms and flow structure on distributions of velocity and turbulent intensities, Master’s Thesis, Faculty of Agriculture, Isfahan University of Technology, Isfahan, Iran. (In Persian)
DavarPanah, Sh. 2011. Investigation of Interaction of Straight Crested Gravel Bedforms and Vegetated Banks on Turbulent Flow Components, Master’s Thesis, Faculty of Agriculture, Isfahan University of Technology, Isfahan, Iran. (in Persian)
Balachandar, R., & Patel, V.2008. Flow over a fixed rough dune. Canadian Journal of Civil Engineering, 35(5), pp.511-520.
Yue, W., Lin, C., & Patel, V. 2003. Numerical investigations of turbulent free surface flows using level set method and large eddy simulation, Tech. Rep. 435, 170 pp., Iowa Inst. of Hydraul. Res., Iowa City.
Modares Civil Engineering journal
Volume 20, Issue 5
November and December 2020
Pages 103-115