Effect of Vegetation on Shear Stress and Flow Velocity in Compound Channels Using Flow3D Model

Document Type : Research Article

Authors

1 Assistant Professor, Department of Agriculture, Payame Noor University (PNU), Iran.

2 Associate Professor Department of Civil Engineering, Estahban Branch, Islamic Azad University, Estahban, Iran.

Abstract

Flow in a compound channel differs from a simple channel due to the strong interaction of flow between the main channel and the floodplain. In this research, flow pattern was investigated in a compound channel without vegetation and with vegetation by parallel arrangement. To study the effect of vegetation density on flow pattern, the ratio of inter-plant distance and plant diameter (L/D) was used, which was set to 3, 8, and 16. Results indicated that longitudinal velocity and depth-averaged velocity of flow in the main channel were lower in the non-vegetated condition than the vegetated one. However, this condition was reversed for the floodplain. Under the non-vegetated case, by moving from the center of the main channel to the floodplain, the depth-averaged velocity decreased until it increased at the interface between the main channel and the floodplain. Later the decreasing trend continued. In the parallel arrangement, with a reduction in L/D ratio, vegetation density increased while longitudinal velocity, depth-averaged velocity of flow, shear stress and flow rate at the floodplain decreased by about 65%.

Keywords

References

حمیدی­فر، ح.؛ امید، م. ح. و کشاورزی، ع. (1392). "ساختار جریان و آشفتگی در آبراهه­های مرکب تحت تأثیر پوشش گیاهی صلب سیلابدشت"، مجله تحقیقات مهندسی کشاورزی، دوره 14، شماره 3، ص.ص. 66-51.
Hamidifar, H. and Omid, M.H. (2013). “Floodplain vegetation contribution to velocity distribution in compound channels”. Journal of Civil Engineering and Urbanism. Vol. 3, No. 6, pp. 357-361.
Hubble, T., Docker, B. and Rutherfurd, I. (2010). “The role of riparian trees in maintaining riverbank stability: A review of Australian experience and practice”. Ecological Engineering, Vol. 36, No.3, pp. 292-304.
James, C.S. and Makoa, M. (2006). “Conveyance estimation for channels with emergent vegetation boundaries”. Proceedings of the Institution of Civil Engineers, Vol. 159, No. 4, pp. 235-243.
Knight, D.W. and Shiono, K. (1996). “River channel and floodplain hydraulics”. In Floodplain Processes. Anderson M.G. Walling D.E. Bates P.D. (ed). Chapter 5. J. Wiley.
Rajaratnam, N. and Ahmadi, R. (1981). “Hydraulics of channels with floodplains”. Journal of Hydraulic Research, Vol. 19, No. 1, pp. 43-60.
Shiono, K. and Knight, D.W. (1989). “Transverse and vertical Reynolds shear stress measurements in a shear layer region of a compound channel”. In Proc. 7th Int. Symp. on Turbulent Shear Flows, Stanford, USA., pp. 28.1.1-28.1.6.
Shiono, K. and Knight, D.W. (1991). “Turbulent open channel flow with variable depth across the channel”. Journal of Fluid Mechanics, Vol. 222, pp. 617-646.
Terrier, B. (2010). “Flow characteristics in straight
compound channels with vegetation along the main channel”. Ph.D Thesis. Department of Civil and Building Engineering, Loughborough University.
Tominaga, A. and Nezu, I. (1991). “Turbulent structure in compound open-channel
flows”. Journal of Hydraulic Engineering, Vol. 117, No. 1, pp. 21–41.
White, B. and Nepf, H. (2007). “Shear instability and coherent structures in shallow flow adjacent to a porous layer”, Journal of Fluid Mechanics, Vol. 593, No.1, pp. 1-32.
Yonesi, H.A., Omid, M.H. and Ayyoubzadeh, S.A. (2013). “The hydraulics of flow in non-prismatic compound channels”. Journal of Civil Engineering and Urbanism, Vol. 3, No. 6, pp. 342-356.

Files

History

  • Receive Date: 17 April 2017
  • Revise Date: 02 August 2017
  • Accept Date: 06 August 2017

Share

How to cite

Statistics