IAHR, founded in 1935, is a worldwide independent member-based organisation of engineers and water specialists working in fields related to the hydro-environmental sciences and their practical application. Activities range from river and maritime hydraulics to water resources development and eco-hydraulics, through to ice engineering, hydroinformatics, and hydraulic machinery.
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You are here : eLibrary : IAHR World Congress Proceedings : 34th Congress - Brisbane (2011) : THEME 5: Environmental Hydraulics and Hydrology : Time and space analysis of entrainment on density currents
Time and space analysis of entrainment on density currents
Author : H.I.S. Nogueira
In the governing equations of density currents, namely in the total mass balance equation, the entrainment rate of the ambient fluid through the upper interface becomes an explicit or source term requiring a closure model. The entrainment rate may be generally modelled as a function of the current longitudinal front velocity and it is usually evaluated through empirical relations. The aim of the present work is to experimentally investigate the entrainment of ambient fluid into unsteady density currents performed by lock-exchange release of saline water. The experiments were conducted in a 3.0 m long, 0.20 m wide and 0.30 m deep transparent Perspex flume, with horizontal smooth bed, and recorded with a 25 Hz CCD camera under controlled light conditions. An image analysis technique was applied to estimate time-space varying density of the current using dye concentration as a tracer. Temporal and spatial evolution of the current height and depth-averaged density, and temporal evolution of the front position, front velocity, mass balance and entrainment rate are thus assessed and discussed. The relation between entrainment rate and front velocity seems to converge asymptotically to a constant value.
File Size : 537,017 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 34th Congress - Brisbane (2011)
Article : THEME 5: Environmental Hydraulics and Hydrology
Date Published : 01/07/2011
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