Modelling Open Channel Flows with Vegetation Using a Three-Dimensional Model
ABSTRACT
The effects of vegetation on the flow structure are investigated in this paper. In previous studies of modelling vegetated flows, two-equation turbulence models, such as the model, were often used. However, this approach involves a level of uncertainty since the empirical coefficients in these two equations have not yet been satisfactorily obtained for such flow conditions. In addition to this, two extra partial differential equations needing which will result in an increase in the computational cost. The main purpose of the study was therefore to try and acquire accurate velocity profiles without the more advanced two-equation turbulence models. A three-dimensional model using a simple two layer mixing length model was therefore used. The governing hydrodynamic equations were refined to include the effects of drag force induced by vegetation on the flow structure. The model was applied to an experiment flume to study the flow field with vegetations, where experiment data are available. Distributions predicted by the model were compared with laboratory measured ones, with very good agreements being obtained. The results showed that the simple mixing length model could produce accurate complex velocity profile predictions requiring fewer coefficient data and less computation.
The effects of vegetation on the flow structure are investigated in this paper. In previous studies of modelling vegetated flows, two-equation turbulence models, such as the model, were often used. However, this approach involves a level of uncertainty since the empirical coefficients in these two equations have not yet been satisfactorily obtained for such flow conditions. In addition to this, two extra partial differential equations needing which will result in an increase in the computational cost. The main purpose of the study was therefore to try and acquire accurate velocity profiles without the more advanced two-equation turbulence models. A three-dimensional model using a simple two layer mixing length model was therefore used. The governing hydrodynamic equations were refined to include the effects of drag force induced by vegetation on the flow structure. The model was applied to an experiment flume to study the flow field with vegetations, where experiment data are available. Distributions predicted by the model were compared with laboratory measured ones, with very good agreements being obtained. The results showed that the simple mixing length model could produce accurate complex velocity profile predictions requiring fewer coefficient data and less computation.
Cite this paper
nullG. Gao, R. Falconer and B. Lin, "Modelling Open Channel Flows with Vegetation Using a Three-Dimensional Model," Journal of Water Resource and Protection, Vol. 3 No. 2, 2011, pp. 114-119. doi: 10.4236/jwarp.2011.32013.
nullG. Gao, R. Falconer and B. Lin, "Modelling Open Channel Flows with Vegetation Using a Three-Dimensional Model," Journal of Water Resource and Protection, Vol. 3 No. 2, 2011, pp. 114-119. doi: 10.4236/jwarp.2011.32013.
References
[1] C. A. M. E. Wilson, T. Stoesser and P. D. Bates, “Modelling of Open Channel through Vegetation,” In: P. D. Bates, S. N. Lane and R. I. Ferguson, Eds., Computational Fluid Dynamics: Applications in Environmental Hydraulics, John Wiley & Sons Ltd., 2005. doi:10.1002/0470015195.ch15 [2] S. Choi and H. Kang, “Numerical Investigations of Mean Flow and Turbulence Structures of Partly-Vegetated Open-Channel Flows Using the Reynolds Stress Model,” Journal of Hydraulic Research, Vol. 44, No. 3, 2006, pp. 203-217. doi:10.1080/00221686.2006.9521676 [3] C. W. Li and K. Yan, “Numerical Investigation of Wave- Current-Vegetation Interaction,” Journal of Hydraulic Engineering, Vol. 33, No. 7, 2007, pp. 794-803. doi:10.1061/(ASCE)0733-9429(2007)133:7(794) [4] N. R. Wilson and R. H. Shaw, “A Higher Order Closure Model for Canopy Flow,” Journal of Applied Meteology, Vol. 16, No. 11, 1977, pp. 1198-1205. doi:10.1175/1520-0450(1977)016<1197:AHOCMF>2.0.CO;2 [5] F. Lopez and M. Garcia, “Open Channel Flow through Simulated Vegetation: Turbulence Modelling and Sediment Transport,” Hydrosystems Laboratory, Department of Civil Engineering, University of Illinois, 1997. [6] T. Tsujimoto, Y. Shimizu, T. Kitamura and T. Okada, “Turbulent Open Channel Flow over Bed Covered by Rigid Vegetation,” Journal of Hydroscience and Hydraulic Enigineering, Vol. 10, No. 2, 1992, pp. 13-25. [7] T. Fischer-Antze, T. Stoesser, P. Bates and N. R. B. Olsen, “3D Numerical Modelling of Open Channel Flow with Submerged Vegetation,” Journal of Hydraulich Research, Vol. 39, No. 3, 2001, pp. 303-310. doi:10.1080/00221680109499833 [8] S. Choi and W. Yang, “CFD Modelling Vegetated Channel Flows: A State-Of-Art Review,” Water Engineering Research, Vol. 6, No. 3, 2005, pp. 101-112. [9] A. Murota, T. Fukuhara and M. Sato, “Turbulence Structure in Vegetated Open Channel Flows,” Journal of Hydrologic and Hydraulic Engineering, Vol. 2, No. 1, 1984, pp. 47-61. [10] H. M. Nepf and E. R. Vivoni, “Flow Structure in Depth- Limited Vegetated Flow,” Journal of Geophysical Research, Vol. 105, No. 12, 2000, pp. 547-557. doi:10.1029/2000JC900145 [11] W. Rodi, “Turbulence Models and Their Application in Hydraulics,” 2nd Edition, International Association for Hydraulics Research, Delft, the Netherlands, 2000, pp. 104. [12] B. Lin and R. A. Falconer, “Three-Dimensional Layer- integrated Modelling of Estuarine Flows with Flooding and Drying,” Journal of Estuarine, Coastal and Shelf Science, Vol. 44, No. 6, 1997, pp. 737-751. doi:10.1006/ecss.1996.0158 [13] S. A. M. Dorcheh, Effect of Rigid Vegetation on the Velocity, Turbulence and Wave Structure in Open Channel Flows, PhD Thesis, Cardiff University, 2007.
[1] C. A. M. E. Wilson, T. Stoesser and P. D. Bates, “Modelling of Open Channel through Vegetation,” In: P. D. Bates, S. N. Lane and R. I. Ferguson, Eds., Computational Fluid Dynamics: Applications in Environmental Hydraulics, John Wiley & Sons Ltd., 2005. doi:10.1002/0470015195.ch15 [2] S. Choi and H. Kang, “Numerical Investigations of Mean Flow and Turbulence Structures of Partly-Vegetated Open-Channel Flows Using the Reynolds Stress Model,” Journal of Hydraulic Research, Vol. 44, No. 3, 2006, pp. 203-217. doi:10.1080/00221686.2006.9521676 [3] C. W. Li and K. Yan, “Numerical Investigation of Wave- Current-Vegetation Interaction,” Journal of Hydraulic Engineering, Vol. 33, No. 7, 2007, pp. 794-803. doi:10.1061/(ASCE)0733-9429(2007)133:7(794) [4] N. R. Wilson and R. H. Shaw, “A Higher Order Closure Model for Canopy Flow,” Journal of Applied Meteology, Vol. 16, No. 11, 1977, pp. 1198-1205. doi:10.1175/1520-0450(1977)016<1197:AHOCMF>2.0.CO;2 [5] F. Lopez and M. Garcia, “Open Channel Flow through Simulated Vegetation: Turbulence Modelling and Sediment Transport,” Hydrosystems Laboratory, Department of Civil Engineering, University of Illinois, 1997. [6] T. Tsujimoto, Y. Shimizu, T. Kitamura and T. Okada, “Turbulent Open Channel Flow over Bed Covered by Rigid Vegetation,” Journal of Hydroscience and Hydraulic Enigineering, Vol. 10, No. 2, 1992, pp. 13-25. [7] T. Fischer-Antze, T. Stoesser, P. Bates and N. R. B. Olsen, “3D Numerical Modelling of Open Channel Flow with Submerged Vegetation,” Journal of Hydraulich Research, Vol. 39, No. 3, 2001, pp. 303-310. doi:10.1080/00221680109499833 [8] S. Choi and W. Yang, “CFD Modelling Vegetated Channel Flows: A State-Of-Art Review,” Water Engineering Research, Vol. 6, No. 3, 2005, pp. 101-112. [9] A. Murota, T. Fukuhara and M. Sato, “Turbulence Structure in Vegetated Open Channel Flows,” Journal of Hydrologic and Hydraulic Engineering, Vol. 2, No. 1, 1984, pp. 47-61. [10] H. M. Nepf and E. R. Vivoni, “Flow Structure in Depth- Limited Vegetated Flow,” Journal of Geophysical Research, Vol. 105, No. 12, 2000, pp. 547-557. doi:10.1029/2000JC900145 [11] W. Rodi, “Turbulence Models and Their Application in Hydraulics,” 2nd Edition, International Association for Hydraulics Research, Delft, the Netherlands, 2000, pp. 104. [12] B. Lin and R. A. Falconer, “Three-Dimensional Layer- integrated Modelling of Estuarine Flows with Flooding and Drying,” Journal of Estuarine, Coastal and Shelf Science, Vol. 44, No. 6, 1997, pp. 737-751. doi:10.1006/ecss.1996.0158 [13] S. A. M. Dorcheh, Effect of Rigid Vegetation on the Velocity, Turbulence and Wave Structure in Open Channel Flows, PhD Thesis, Cardiff University, 2007.