Author(s): B. Perez-Diaz; P. Palomar; S. Castanedo
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Keywords: No keywords
Abstract: ABSTRACT: Saline density currents are horizontal flows driven by the density difference between the environmental fluid and the density current. In recent years, as the problems related to environmental conservation and coastal development have become more serious and complicated, it has become important to understand the behaviour of these flows. This work carries out an experimental characterization of saline density currents through advanced non-intrusive laser optical techniques PIV (Particle Image Velocimetry) and PLIF (Planar Laser Induced Fluorescence). By means of synchronized PIV-PLIF techniques, high-quality accurate instantaneous measurements of velocity and concentration are obtained. The aim of these experiments is to study the quasi-steady flow properties of the current body generated by a constant flux release. Seeking elucidation about the most influential variables in the behaviour of density currents, different experimental set-up varying the initial conditions (flow rate, thickness, slope, excess density) were carried out in a 3×3×1 m tank. Through PIV-PLIF result analysis, important conclusions about the influence of these variables on the mixing at the interface between fluids have been obtained. To carry out a quantitative comparison between currents, the stable mixing rate along each current is evaluated, which is commonly known as Entrainment (E) in scientific literature. As an example, keeping constant the rest of variables, steeper slopes and higher flow rates favour mixing, i.e. dilution, reaching stable mixing rates (E) values two times higher than values obtained in the corresponding base case (E～2·10 -2). In addition, a high resolution and quality experimental database has been generated, which will allow to calibrate/validate hydrodynamic modelling tools.
Year: 2016