Velocity structure in interflow density currents

Document Type : Research Article

Authors

1 Department of Hydraulic structures, Shahid Chamran University,

2 department of water structurel engineering, faculty of water scienes engineering, shahid chamran university of ahvaz, ahvaz, iran

Abstract

Gravity currents, also known as density currents, or turbidity currents, are happened by the density difference between the flow and its ambient fluid. The density difference can be due to suspended particles, chemicals, soluble materials, and temperature differences. In dams reservoir ambient fluid, usually has a vertical stratification. When the gravity current arrived to ambient fluid, in the position that density of both gravity current and ambient fluid is equal the gravity current abandon the bed and flows in ambient fluid horizontally. Therefore the density current into this reservoir maybe intrude such as interflow density current. This study investigates the inter flow density current in a stratification ambient. For achieve to the objectives of this study, experiments were carried out at a flumes with 9 meters long by 4 discharge 1, 1.5, 2 and 2.5 l/s, and 4 concentration 5, 10, 15 and 20 mg/l, that created density 1003.2, 1006.3, 1009.4 and 1012.5 respectively. Stratification was made by mixture water and salt with vertical gradient. The investigation of velocity profiles showed that the flow is self-similar and velocity fluctuations Continues maximum up to 2.5 times greater than current thickness in the lower layer. The front velocity of currents in stratified environments increases at first then sizeable decreases. It shows that stratified can limited the flow movement. In each three slope, increasing of discharge and concentration increase velocity head of density current in stratified environment. As the slope increases, the current velocity increases at the underflow stage, and in the interflow stage, the slope does not have much effect on the current velocity. Interflow Travel Time decrease in increasing of discharge and concentration. Density current in weaker stratified can travel more distance in the slope and separate latter from the bed.

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References

[1] J. Imberger, R. Thompson, C. Fandry, Selective withdrawal from a finite rectangular tank, Journal of fluid mechanics, 78(3) (1976) 489-512.
[2] R.J. Lowe, P. Linden, J.W. Rottman, A laboratory study of the velocity structure in an intrusive gravity current, Journal of Fluid Mechanics, 456 (2002) 33-48.
[3] D. Ahlfeld, A. Joaquin, J. Tobiason, D. Mas, Case study: Impact of reservoir stratification on interflow travel time, Journal of hydraulic engineering, 129(12) (2003) 966-975.
[4] B.R. Sutherland, P.J. Kyba, M.R. Flynn, Intrusive gravity currents in two-layer fluids, Journal of Fluid Mechanics, 514 (2004) 327-353.
[5] M. Wells, P. Nadarajah, The intrusion depth of density currents flowing into stratified water bodies, Journal of Physical Oceanography, 39(8) (2009) 1935-1947.
[6] S. An, P.Y. Julien, Three-dimensional modeling of turbid density currents in Imha Reservoir, South Korea, Journal of hydraulic engineering, 140(5) (2014) 05014004.
[7] X.-f. Zhang, S. Ren, J.-q. Lu, X.-h. Lu, Effect of thermal stratification on interflow travel time in stratified reservoir, Journal of Zhejiang University-SCIENCE A, 16(4) (2015) 265-278.
[8] Z. He, L. Zhao, T. Lin, P. Hu, Y. lv, H.-C. Ho, Y.-T. Lin, Hydrodynamics of gravity currents down a ramp in linearly stratified environments, Journal of Hydraulic Engineering, 143(3) (2016) 04016085.
[9] T. Ellison, J. Turner, Turbulent entrainment in stratified flows, Journal of Fluid Mechanics, 6(3) (1959) 423-448
[10] M. Sadeghi Askari, M. Ghomeshi, Experimental investigation of velocity profile in interflow density current, Journal of Hydraulic, 13(1)  (1397) 58397, in Persian
[11] J.S. Turner, Buoyancy effects in fluids, Cambridge university press, 1979.
[12] M. Altinakar, W. Graf, E. Hopfinger, Flow structure in turbidity currents, Journal of Hydraulic Research, 34(5) (1996) 713-718.
[13] M. Garcia, G. Parker, Experiments on the entrainment of sediment into suspension by a dense bottom current, Journal of Geophysical Research: Oceans, 98(C3) (1993) 4793-4807.
[14] M. Sadeghi Askari, M. Ghomeshi, Experimental study of concentration profile in interflow density current, Journal of Irrigation Sciences and Engineering (JISE) 10.22055/ jise.2018.24246.1715, in Persian
[15] M.H. Garcia, Depositional turbidity currents laden with poorly sorted sediment, Journal of hydraulic engineering, 120(11) (1994) 1240-1263.
[16] S. Hosseini, A. Shamsai, B. Ataie-Ashtiani, Synchronous measurements of the velocity and concentration in low density turbidity currents using an Acoustic Doppler Velocimeter, Flow Measurement and Instrumentation, 17(1) (2006) 59-68.
[17] E. Khavasi, H. Afshin, B. Firoozabadi, Effect of selected parameters on the depositional behaviour of turbidity currents, Journal of Hydraulic Research, 50(1) (2012) 6069.
[18] Z. Nourmohammadi, H. Afshin, B. Firoozabadi, Experimental observation of the flow structure of turbidity currents, Journal of Hydraulic Research, 49(2) (2011) 168-177.
Amirkabir Journal of Civil Engineering
Volume 52, Issue 10
January 2021
Pages 2607-2620

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