Experimental Study of Concentration Profile in Interflow Density Current

Document Type : Research Article

Authors

1 Ph.D. Student, Department of Hydraulic Structures, Shahid Chamran University, Ahwaz, Iran

2 Professor, Department of Hydraulic Structures, Shahid Chamran University, Ahwaz, Iran

Abstract

Gravity currents, also called density currents or buoyancy currents, are flows driven by the density difference between the flow and its ambient environments. When a gravity current reaches the level of neutral buoyancy in a stratified water body, it can separate from the bed as an intrusion. Laboratory experiments are performed to investigate dense flow behavior in stratified ambient in this study. Experiments were carried out on 2.5%  bed slope by 4 discharges, 1, 1.5, 2 and 2.5 l/s, and 4 concentrations 5, 10, 15 and 20 mg/l, that created current with a density of 1003.2, 1006.3, 1009.4 and 1012.5 respectively. Stratification was made by mixture of water and salt with vertical gradient. For creating density flow, silica particles with 8 diameters in average and density of 2.673 g/cm3 was used. To investigate the concentration profile, density and concentration were measured in three sections along the flume with three centimeters interval in depth using siphon mechanism. Experimental observations showed that the currents would separate from the bed and then horizontally intrude into the ambience and the density of ambient fluids below the separation point decreases. The measurements in this study indicate that the maximum concentration depth and thickness of body current decreases with increasing concentration in interflow and body current thickness stabilize with increasing discharge.

Keywords


DE Rooij, F. Lindeny, P. F. and Dalziel, S. B. (2002). "Saline and particle-driven interfacial intrusions". Journal of Fluid Mechanics. Vol. 389, pp. 303-334.
Firoozabadi, B. Afshin, H. and Aram, E. (2009). “Three dimensional modeling of density current in a straight channel”. Journal of Hydraulic Engineering. Vol. 135, No. 5, pp. 393-402.
Guo, Y. Zhang, Z. and Shi, B. (2014). "Numerical simulation of gravity current descending a slope into a linearly stratified environment". Journal of Hydraulic Engineering. Vol. 140, No. 12, doi: 10.1061/(ASCE)HY.1943-7900.0000936.
Imberger, J. Thompson, R. and Fandry. C. (1976). "Selective withdrawal from a finite rectangular tank". Journal of Fluid Mechanics. Vol. 78, No. 03, pp. 489-512
Kaeo, B. (1997). "Density currents and their applications". Journal of the Hydraulics Division, ASCE, Vol. 103, No. HY5, pp. 543-555.
Kneller, B. C. Bennet, J. S. and McCaffrey, W. D. (1999). "Velocity structure, turbulence and fluid stresses in experimental gravity currents". Journal of Geophysical Research. Vol. 104, No.C3, pp. 5381-5391.
Lowe, R. Linden, P. F. and Rotman, J. W. (2002). "A laboratory study of the velocity structure in an intrusive gravity current". Journal of Fluid Mechanics. Vol. 456, pp. 33-48.
Marti, C. Mills, R. and Imberger, J. (2011). "Pathways of multiple inflows into a stratified reservoir Thomson reservoir Australia". Advances in Water Resources. Vol. 34, No. 05, pp. 551-561.
Snow, K. and Sutherland, B. R. (2014). "Particle-laden flow down a slope in uniform stratification". Journal of Fluid Mechanics. Vol. 755, pp. 251-273.
Sutherland, B. R. Kyba, P. J. and Flynn, M. R. (2004). "Intrusive gravity currents in two layer fluids". Journal of Fluid Mechanics. Vol. 514, pp. 327-353.
Wells, M. and Nadarajah, P. (2008). "The intrusion depth of density currents flowing into stratified water bodies". Journal of Physical Oceanography. Vol. 39, No. 8, pp. 1935-1947.
Zange, X. F. REN, S. Lu, J. Q. and LU, X. H. (2015). "Effect of thermal stratification on interflow travel time in stratified reservoir".
Journal of Zhejiang University Science A (Applied Physics and Engineering). Vol. 16, No. 4, pp. 265-278.
Samothrakis, P. and Cotel, A. J.(2006). "Propagation of a gravity current in a two-layer stratified environment". Journal of Geophysical Research. Vol. 111, No. C1, doi:10.1029/2005JC003125.
  • Receive Date: 27 July 2017
  • Revise Date: 27 November 2017
  • Accept Date: 29 November 2017
  • First Publish Date: 21 March 2018