D. Malcangio

Experimental study of a vertical jet in a vegetated crossflow.

Aquatic ecosystems have long been used as receiving environments of wastewater discharges. Effluent discharge in a receiving water body via single jet or multiport diffuser, reflects a number of complex phenomena, affecting the ecosystem services. Discharge systems need to be designed to minimize environmental impacts. Therefore, a good knowledge of the interaction between effluents, discharge systems and receiving environments is required to promote best environmental management practice. This paper reports innovative 3D flow velocity measurements of a jet discharged into an obstructed crossflow, simulating natural vegetated channel flows for which correct environmental management still lacks in literature. In recent years, numerous experimental and numerical studies have been conducted on vegetated channels, on the one hand, and on turbulent jets discharged into unvegetated crossflows, on the other hand. Despite these studies, however, there is a lack of information regarding jets discharged into vegetated crossflow. The present study aims at obtaining a more thorough understanding of the interaction between a turbulent jet and an obstructed crossflow. In order to achieve such an objective, a series of laboratory experiments was carried out in the Department of Civil, Environmental, Building Engineering and Chemistry of the Technical University of Bari - Italy. The physical model consists of a vertical jet discharged into a crossflow, obstructed by an array of vertical, rigid, circular and threaded steel cylinders. Analysis of the measured flow velocities shows that the array of emergent rigid vegetation significantly affects the jet and the ambient flow structures. It reduces the mean channel velocity, allowing the jet to penetrate higher into the crossflow. It significantly increases the transversal flow motion, promoting a major lateral spreading of the jet within the crossflow. Due to the vegetation array effects, the jet undergoes notable variations in its vortical structure. The variation of the flow patterns affects the mixing process and consequently the dilution of pollutants discharged in receiving water bodies.

Vertical dense jet in flowing current

The discharge of brackish water, as a dense jet in a natural water body, by the osmotic power plants, undergoes complex mixing processes and has significant environmental impacts. This paper focuses on the mixing processes that develop when a dense round jet outfall perpendicularly enters a shallow flowing current. Extensive experimental measurements of both the salinity and the velocity flow fields were conducted to investigate the hydrodynamic jet behavior within the ambient current. Experiments were carried out in a closed circuit flume at the Coastal Engineering Laboratory (LIC) of the Technical University of Bari (Italy). The salinity concentration and velocity fields were analyzed, providing a more thorough knowledge about the main features of the jet behavior within the ambient flow, such as the jet penetration, spreading, dilution, terminal rise height and its impact point with the flume lower boundary. In this study, special attention is given to understand and confirm the conjecture, not yet experimentally demonstrated, of the development and orientation of the jet vortex structures. Results show that the dense jet is almost characterized by two distinct phases: a rapid ascent phase and a gradually descent phase. The measured flow velocity fields definitely confirm the formation of the counter-rotating vortices pair, within the jet cross-section, during both the ascent and descent phases. Nevertheless, the experimental results show that the counter-rotating vortices pair of both phases (ascent and descent) are of opposite rotational direction.

Physical modelling of buoyant effluents discharged into a cross flow

This study focuses on physical modelling of turbulent vertical buoyant jets, discharged into a transversal current and interacting with localized background turbulence. The physical model was developed in the Coastal Engineering Laboratory of the Technical University of Bari. The physical model consists of a sophisticated system that allows to monitor and adjust all the characteristic parameters of both the channel flow (e.g. discharge, flow depth) and the buoyant jets (e.g. flow rate, temperature, salinity). Positively and negatively buoyant jets are realized by discharging water respectively at a temperature and salinity higher than that of the receiving environment. Due to the complexity of the jet-current hydrodynamic phenomena, a set of sophisticated instruments to measure the jet spreading within the cross flow is used. The average jet dilution is measured by (i) four different Resistance Temperature Detectors (RTD) for the positively buoyant jet, and (ii) a MicroScale Conductivity Temperature Instrument (MSCTI) of high resolution for the negatively buoyant jet. Whereas, a Nortek Acoustic Doppler Velocimeter (ADV) system is used to measure the field flow velocities, together with CollectV software for data acquisition and ExploreV software for data analysis. The measured scalar and vector fields will be illustrated in this paper, with the aim to emphasize that a well-set physical model is able to explain the behavior of buoyant jets in an open channel with ambient factors, such as cross flow and vegetation.

Modelling Circulation In A Southern ItalyCoastal Basin

The purpose of the present work is the study of particular hydrodynamic aspects of Mar Piccolo, a basin located in the Northern side of the Gulf of Taranto in the Ionio Sea (Italy), by means of mathematical modelling. A first analysis has been driven, thus realizing a test case with simple hypothesis, referring to data from the literature, in order to validate two 3D hydrodynamic models, i.e. the Princeton Ocean Model and the MIKE 3. Once a quite good agreement wasobserved between the outputs of the tested models, a further comparison was considered. The results of the two models have been compared with some circulation structures proposed in the literature, in analogous conditions. Successively, both models have been forced by a further input, in order to observe the response of the circulation to input modifications. The direct comparison between simulation results and field measurements collected during surveys is the future development of the ongoing research.