Abstract
The target of this paper is to measure the modifications that regular waves induce on the geometrical features and dilution of inclined negatively buoyant jets. In order to achieve this aim, we have carried out a set of experiments in a wavemaker-equipped flume, by measuring the concentration fields via light-induced fluorescence, a non-intrusive and full-field image analysis technique. The wave and jet parameters were selected in order to simulate the case of a typical discharge of brine, from a desalination plant, into the Mediterranean Sea, and compare it to a reference case, i.e., the same jet discharging into a stagnant water body. The mean concentration fields were obtained, as well as the geometrical features and dilution of the jets. The three main effects of waves on inclined negatively buoyant jets are the bifurcation (i.e., the separation in two branches), the rotation of the point of maximum height and the oscillation of the impact point around a fixed position different from the stationary one, and the reduction in size of the sea region interested by the discharge; this last effect increases with the wave period. As a consequence, under waves with high period and amplitude, the dilution of inclined negatively buoyant jets tends to decrease.
Highlights
A negatively buoyant jet (NBJ) is the phenomenon that develops when a fluid is discharged, with a non-negligible momentum, in a less dense fluid
The target of this paper is to measure the modifications that regular waves induce on the geometrical features and dilution of inclined negatively buoyant jets
The three main effects of waves on inclined negatively buoyant jets are the bifurcation, the rotation of the point of maximum height and the oscillation of the impact point around a fixed position different from the stationary one, and the reduction in size of the sea region interested by the discharge; this last effect increases with the wave period
Summary
A negatively buoyant jet (NBJ) is the phenomenon that develops when a fluid is discharged, with a non-negligible momentum, in a less dense fluid. Lin et al (2011, [23]), investigated experimentally the turbulent properties of horizontal NBJs and non-buoyant jets under regular progressive waves via Particle Image Velocimetry (PIV) They found that dilution is increased by the wave motion. The increase of the dilution of a jet has been measured in many experimental investigations, to the best of the authors’ knowledge the effects of regular waves on inclined (not horizontal or vertical) NBJs were never investigated before For this reason, Ferrari and Querzoli, 2015 [35], performed a preliminary series of experiments that highlighted significant differences among the behavior of simple or positively buoyant jets and the case of the inclined negatively buoyant jets. This paper is structured as follows: In Section 2, the experimental set-up, the run parameters and the data elaboration are briefly described; in Section 3, the results are shown and discussed; in Section 4, the conclusions are drawn
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