Head Velocity and Entrainment of Density Current in an Expansion Reach

Document Type : Original Article

Authors

1 Ph.D. Student, School of Water Sciences and Engineering, Shahid Chamran, University, Ahwaz, Iran

2 Assistant Professor, School of Water Sciences and Engineering, Shahid Chamran, University, Ahwaz, Iran

3 Professor, School of Water Sciences and Engineering, Shahid Chamran, University, Ahwaz, Iran

Abstract

Velocity and Entrainment of density current in the expansion reach where a river enters into a dam reservoir, a lake, or open sea is of utmost importance. The present study investigates the head velocity  and entrainment of density currents in an Expansion Reach. The effects of discharge and bed slope on the head velocity and entrainment of the density current were evaluated by a physical and 3D mathematical model. Experiments were conducted in a flume, 6.0 meters long, 0.72 meters wide, and 0.6 meters in height. Head velocity was measured for an expansion degree of 8 in slopes of 0.0009 and 0.0016 for various discharges. Important parameters were normalized and a two-dimensional laser Doupler was used to develop the flow body velocity profile. The measurements showed that mixing values were higher in a divergent cross-section compared to a fixed cross-section. During some experiments a hydraulic jump was also detected depending upon the levels of the density current and slope of the bed in the divergent cross-section, which was investigated and the results are presented accordingly.

Keywords

References

قمشی، مهدی؛ بررسی آزمایشگاهی حرکت جریانهای غلیظ، مجموعه مقالات اولین کنفرانس هیدرولیک ایران، صص 260-249، 1376.
Altinakar, M.S., Graf, W.H. and Hopfinger, E.J. (1990), Weakly depositing turbidity current on a small slope, Journal of Hydraulic Research, Vol. 28, No.1.
Altinakar, M. S. (1988), Weakly depositing turbidity current on a small slope, Thesis No 738, Sciences Techniques, EPF Lausanne.
Britter, R.E., and Linden, P. (1980), The motion of the front of a gravity current traveling down an incline, Journal of Fluid Mechanics, Vol. 99, No.3, pp. 531-543.
Chikita, K. (1990),Sedimentation by river – induced Turbidity currents; field measurements and interpretation, Sedimentology, vol. 37, pp. 891-905.
De Cesare, G., Schleiss A. and Hermann, F. (2001), Impact of turbidity currents on reservoir sedimentation, Journal of Hydraulic Engineering, Vol. 127, No. 1.
De Cesare, G., Schleiss, A. and Hermann, F. (2002),Closure to: impact of turbidity currents on reservoir sedimentation, Journal of Hydraulic Engineering, Vol. 128, No. 6, pp.645-646.
Ghomeshi, M.  (1995), "Reservoir sedimentation modeling", Ph.D. Thesis, University of Wollongong, Australia.
Haghiabi, A. H. (2004), "The study of bed slope effect on velocity and concentration profiles of density currents", Ph.D. Thesis, ShahidChamranUniversity, Ahwaz,Iran.
Horsch, G. M. (2004),"The Structure of Two-Dimensional, Steady", Miscible Laminar Density Currents Flowing Down an Incline,Journal of Hydraulic Research, Vol. 42,No. 2.
Keulegan, G.H. (1957), "The motion of saline fronts in still water, Twelfth Progress Report on model laws for density currents", U.S.  Natl. Bur. Standards Rept.
King, S.E., Woods, A.W. (2003), Dipole solutions for viscous gravity currents: theory and experiments, Journal of Fluid Mechanics, Vol. 483, No.1, pp. 91– 109.
Middleton, G.V. (1966), Experiments on density and turbidity currents, motion of the head, Canadian Journal of Earth Science, No. 3, pp. 523-546.
Parker, G., Garcia M. and Fukushima, Y. (1987), Experiments on turbidity currents over an erodible bed, Journal of Hydraulic Research, Vol. 25, No. 1.
Ross, A.N., Linden, P.F. and Dalziel, S.B. (2002), A study of three-dimensional gravity currents on a uniform slope, Journal of Fluid Mechanics, Vol. 453, No.1, pp.239 – 261.
Turner, J.S. (1973), "Buoyancy effects in fluids", Cambridge University Press, London, England.
Turner, J.S. (1979), "Buoyancy effects in fluids", Cambridge University Press, London, England.
Iran-Water Resources Research
Volume 3, Issue 1
June 2007
Pages 56-67

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History

  • Receive Date: 08 July 2006
  • Revise Date: 14 April 2007
  • Accept Date: 30 June 2007

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