The present study investigates bubbly two-phase flow in a hydraulic jump using a flow visualization technique. Bubbly two-phase flow is encountered in many engineering problems; however, mainly because of experimental difficulties, little is known on the internal structure of these flows, although such knowledge is clearly essential to a thorough understanding of the mass transfer between the two component phases. In the past, some authors measured the distribution of void ratio in a hydraulic jump using hot-film anemometry. Nowadays this interesting technique may be improved using a flow visualization technique, which enables one to obtain the percentage of air across each vertical section of the jump. This is possible by evaluating the gray levels of the first principal axes of transformed images starting from RGB images. The experiments considered the phenomenon of air concentration in a hydraulic jump, which was studied and analyzed using image processing techniques, aimed at obtaining reliable quantitative measurements. To achieve this, the processing system was planned and tested at the hardware level and a procedure for managing the processing was set up. The calibration curve was obtained using the McCorquodale and Khalifa law (1983). The results permit the visualization of flow structures and the estimation of air concentration of the flow along all the jump and to show the position in which the air concentration reaches the maximum value versus time.

An experimental study on long local scouring downstream of bed sills in a monogranular sand bed was carried out in the hydraulic laboratory flume at the Mediterranean Agronomic Institute of Bari (Italy). The main objectives of this study were to determine scour hole dimension, with its maximum scour depth as a function of time and at the equilibrium stage, the scour hole shapes and the investigation of the influence of sills on the distribution of the three-velocity components through the scour hole at the same stage. Four experimental configurations were tested, the main difference between them being the distance between sills. Based on experimental data, the classical dimensional analysis of the variables that influence the development of the scour hole has been carried out in order to obtain two empirical formulas predicting the maximum scour depth and the length of the scour hole at the equilibrium stage. Moreover, it was observed that the distance between sills influences the scour hole dimension and shape. The three-velocity components of the flow, measured with an acoustic Doppler velocimeter, show that in the scour hole, at the equilibrium stage, the three components of the flow turbulence intensities are very high. Near-bed flow vortexes in addition to secondary currents are also observed. RÉSUMÉUne étude expérimentale sur l'affouillement local à long terme à l'aval des seuils le long d'un lit à sable mono-granulaire a été élaborée dans un canal d'essai au laboratoire d'hydraulique de l'Institut Agronomique Méditerranéen de Bari (Italie). Les objectifs principaux de cette étude sont; la détermination des dimensions de l'affouillement, à savoir, l'évolution de sa profondeur maximale en fonction du temps et à la phase d'équilibre, sa forme et l'analyse de l'influence du seuil sur la distribution des trois composantes de la vitesse d'écoulement lors de la même phase. Quatre configurations expérimentales ont été réalisées, la différence entre ces dernières étant l'écartement entre les seuils. Sur la base des résultats expérimentaux, l'analyse dimensionnelle classique des variables influençant le développement de l'affouillement a induit à l'obtention de deux formules empiriques permettant la détermination de la profondeur maximale et de la longueur d'affouillement à l'équilibre. En outre, il a été observé que l'écartement entre les seuils présente une influence aussi bien sur les dimensions que sur la forme de l'affouillement. Les mesures de la vitesse d'écoulement tridimensionnelle par le biais d'un Acoustic Doppler Velocimeter (ADV) a montré que dans l'affouillement, durant la phase d'équilibre, les trois composantes de l'intensité de la turbulence de l'écoulement sont très élevées. Une circulation de fluide en vortex à proximité du lit ainsi qu'un développement d'écoulement secondaire ont été observés.

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A forest of the black coral Antipathella subpinnata was found from 52 to 80 m depth in three different sites at Tremiti Islands Marine Protected Area (MPA; Mediterranean Sea), with two of them hosting a monospecific forest on horizontal and vertical substrates. Colonies of A. subpinnata showed a mean density between 0.22 ± 0.03 and 2.40 ± 0.26 colonies m −2 (maximum local values of 2.4-7.2 colonies m −2). The link between the local distribution of A. subpinnata and the main oceanographic features confirmed the fundamental role of the currents in shaping the distribution of the species in presence of hard substrata. This black coral forest represents the only one known thus far in the Adriatic Sea, but it could be linked with other unseen forests all over the Mediterranean Sea. The associated megafauna highlights the importance of these forests as habitat for species of both conservation and commercial importance but, at the same time, makes such habitat a target for fishing practices, as many lost fishing gears were found within the coral forest. The enlargement of the MPA borders and the enforcement of controls in the area of the A. subpinnata forest is urgently needed for the proper conservation of this protected species.

Despite the many studies on flow in partly obstructed open channels, this issue remains of fundamental importance in order to better understand the interaction between flow behavior and the canopy structure. In the first part of this study we suggest a new theoretical approach able to model the flow pattern within the shear layer in the unobstructed domain, adjacent to the canopy area. Differently from previous studies, the new analytical solution of flow momentum equations takes into account the transversal velocity component of the flow, which is modelled as a linear function of the streamwise velocity. The proposed theoretical model is validated by different experiments carried out on a physical model of a very large rectangular channel by the research group of the Department of Civil, Environmental, Building Engineering and Chemistry of the Technical University of Bari. An array of vertical, rigid, and circular steel cylinders was partially mounted on the bottom in the central part of the flume, leaving two lateral areas of free flow circulation near the walls. The three-dimensional flow velocity components were measured using a 3D Acoustic Doppler Velocimeter. A comparison of the measured and predicted data of the present study with those obtained in other previous studies, carried out with different canopy density, show a non-dependence of this analytical solution on the array density and the Reynolds number. In the second part of the paper, detailed observations of turbulent intensities and spanwise Reynolds stresses in the unobstructed flow are analyzed and discussed. Differently from some earlier studies, it was observed that the peak of the turbulence intensity and that of the spanwise Reynolds stress are significantly shifted toward the center of the shear layer.

Abstract. SANIFS (Southern Adriatic Northern Ionian coastal Forecasting System) is a coastal-ocean operational system based on the unstructured grid finite-element threedimensional hydrodynamic SHYFEM model, providing short-term forecasts. The operational chain is based on a downscaling approach starting from the large-scale system for the entire Mediterranean Basin (MFS, Mediterranean Forecasting System), which provides initial and boundary condition fields to the nested system.The model is configured to provide hydrodynamics and active tracer forecasts both in open ocean and coastal waters of southeastern Italy using a variable horizontal resolution from the open sea (3-4 km) to coastal areas (50-500 m).Given that the coastal fields are driven by a combination of both local (also known as coastal) and deep-ocean forcings propagating along the shelf, the performance of SAN-IFS was verified both in forecast and simulation mode, first (i) on the large and shelf-coastal scales by comparing with a large-scale survey CTD (conductivity-temperature-depth) in the Gulf of Taranto and then (ii) on the coastal-harbour scale (Mar Grande of Taranto) by comparison with CTD, ADCP (acoustic doppler current profiler) and tide gauge data.Sensitivity tests were performed on initialization conditions (mainly focused on spin-up procedures) and on surface boundary conditions by assessing the reliability of two alternative datasets at different horizontal resolution (12.5 and 6.5 km).The SANIFS forecasts at a lead time of 1 day were compared with the MFS forecasts, highlighting that SANIFS is able to retain the large-scale dynamics of MFS. The largescale dynamics of MFS are correctly propagated to the shelfcoastal scale, improving the forecast accuracy (+17 % for temperature and +6 % for salinity compared to MFS). Moreover, the added value of SANIFS was assessed on the coastalharbour scale, which is not covered by the coarse resolution of MFS, where the fields forecasted by SANIFS reproduced the observations well (temperature RMSE equal to 0.11 • C).Furthermore, SANIFS simulations were compared with hourly time series of temperature, sea level and velocity measured on the coastal-harbour scale, showing a good agreement. Simulations in the Gulf of Taranto described a circulation mainly characterized by an anticyclonic gyre with the presence of cyclonic vortexes in shelf-coastal areas. A surface water inflow from the open sea to Mar Grande characterizes the coastal-harbour scale.

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