Investigation of Distribution of Velocity and Turbulence Intensity in Presence of Dunes and Vegetation in a Rectangular Open Channel

Document Type : Research Article

Authors

Abstract

Formation of bed forms, such as dunes, is a prominent feature in natural open channel flows with sediment transport. Knowledge of turbulent flow over sand dunes is needed to understand the interaction between the flow, the bed forms and the associated sediment transport. This study presents results of an experimental work aimed at investigating the effect of different dunes and vegetated banks on flow velocity, Reynolds stresses and turbulence intensities. Experimental measurements were made over fifth and sixth dunes in a series of ten of 2-dimensional asymmetric gravel dunes which had dune height of 4 and 8 cm, respectively. These dunes had a mean wavelength of 100 cm, mean lee slope angles of 28º, and width equal to the flume width. Rice stems with a median diameter of 2.7 mm and a stem distribution density of 400 stem/m were used to cover the flume banks for simulating vegetation on riverbanks. From experimental measurements, the effect of different heights of crest of gravel dunes on the characteristics of flow in vegetated flume; and the reattachment points for different heights of crest of gravel dunes were investigated.

Keywords

References

Allen, J. R. L., (1985). Principles of physical sedimentology, Chapman and Hall, New York, 272 pp.
Ashley, G. M. (1990). "Classification of large-scale subaquenous bed forms: a new look at an old problem", J. Sediment. Petrol. Vol. 60, pp. 160-172.
Bennett, S. J. and Best, J. L. (1995). "Mean flow and turbulence structures over fixed, two-dimentional dunes: Implication for sediment transport and bed form stability", Sedimentology. Vol. 42, pp. 491-513.
Bes., J. L. (1993). "On the interaction between turbulent flow structure, sediment transport and bed form development: some considerations from recent experimental research". In: N. J. Clifford, J. R. French, and J. Hardisty (Eds.), Turbulence: Perspectives on flow and sediment transport, John Wiley & Sons Ltd., New York, p. 360.
Best, J. and Kostaschuk, R., (2002). "An experimental study of turbulent flow over a low angle dune". J. Geophys. Res. 107(C9), 3135.
Carling, P. A., 1999, Subaqueous gravel dunes. J. Sediment. Res., 69: 534–545.
Carollo., F. G.; Ferro, V. and Termini, D. (2002). "Flow resistance law in channels with flexible submerged vegetation". J. Hydraul. Eng. Vol. 131, pp. 554-565.
Dingman, S. L. (1984). Fluvial hydrology. W. H. Freeman and Company, New York, p. 383.
Grass, A. J. (1971). "Structural features of turbulent flow over smooth and rough boundaries", J. Fluid Mech. Vol. 50, 233-255.
Guy, H. P., Simons, D. D. and Richardson, E. V., (1966). "Summary of alluvial channel data from flume experiments", 1956-1961. U.S. Geol. Surv. Prof. Pap. 462-I: 96.
Jerolmack, D. and Mohring, D. (2005). "Interactions between bed forms: topography, turbulence, and transport", J. Geophys. Res. 110: 1-13.
Leeder, M. R. (1983). "On the interaction between turbulent flow, sediment transport and bedform mechanics in channelized flows", PP 5-18. In: J. D. Collinson, and J. Lewin (Eds), Modern and Ancient Fluvial Systems: International Association of Sedimentologist Special Publication 6, Balckwell Scientific Publications, Oxford.
Lyn, D. A. (1993). "Turbulence measurements in open-channel flows over artificial bed forms", J. Hydraul. Eng. ASCE. Vol. 119, No. 3, pp. 306-326.
Mazumder, B. S. Pal, D. Ghoshal, K. and Ojha, S. P. (2009). "Turbulence statistics of flow over isolated scalene and isosceles triangular-shaped bedforms", J. Hydraul. Res. Vol. 47, No. 5, pp. 626-637.
McLean., S. R.; (1990). "The stability of ripples and dunes", Earth Sci. Rev. Vol. 29, pp. 131-144.
Mohajeri, S. H. Grizzi, S. Righetti, M. Romano, G. P., and Nikora, V. (2015). "The structure of gravel bed flow with intermediate submergence: A laboratory study". Water Resources Research, 51(11), 9232-9255.
Nasiri., E.; Afzalimehr, H.; and Singh, V. P.; (2010). "Effect of bedforms and vegetated banks on velocity distributions and turbulent flow structure. Journal of Hydrology Engineering", ASCE. pp. 1-41.
Nelson, J. M. Mclean, S. R. and Wolfe, S. R. (1993). "Mean flow and turbulence over two-dimensional bed form", Water Reasour. Res. Vol. 29, pp. 3935-3953.
Ojha, S. P.; and Mazumder, B. S. (2008). "Turbulence characteristics of flow region over a series of 2-D dune shaped structures", Adv. Water Res. Vol. 31, pp. 561-576.
Shiono, K. and Feng, T. (2003). "Turbulence measurements of dye concentration and effects of secondary flow on distribution in open channel flows", J. Hydraul. Eng. Vol. 129, No. 5, pp. 373-384.
Stoesser, T. M. Braun, C. Garcia-villalba M. and Rodi, W. M. (2008). "Turbulence structures in flow over two-dimensional dunes", J. Hydraul. Eng. ASCE. Journal of Hydrology Enginering. Vol. 134, No. 1, pp. 42-55.
Van Mierlo, M. C. L. M. and de Ruiter, J. C. C. (1988). "Turbulence measurements above artificial dunes", Technical Report, TOW A55 Q789, PP. 142. Delfut Hydraulics Laboratory, Delfut, Netherlands.
Venditti, J. G. (2007). "Turbulent flow and drag over fixed two- and three-dimensional dunes", J. Geophys. Res. 112, F04008, DOI: 10. 1029/2006JF000650.
Venditti, J. G. and Bennett, S. J., (2000). "Spectral analysisvof turbulent flow and suspended sediment transport over fixed dunes", J. Geophys. Res. 105: 22035-22047.
Xie, Z., Lin, B., and Falconer, R. A. (2014). "Turbulence characteristics in free-surface flow over two-dimensional dunes". Journal of Hydro-environment Research, 8(3), 200-209.
 
 
 

Files

History

  • Receive Date: 21 November 2015
  • Revise Date: 13 February 2016
  • Accept Date: 11 April 2016

Share

How to cite

Statistics