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Behavioural and spatial distribution analyses were quantified during a phase of activity and lethargy in a wild population of the European pond turtle inhabiting a protected internal wetland area of the Venice lagoon. The marked individuals (13 males and 16 females) provided informative radiotracking data to study differential patterns of activity, dispersion and habitat use between the two study periods (“October-November both 2019 and 2020” and “June-July 2020”). The differences in the movements behaviours and habitat selection were affected by period. Movements were higher in the period of activity than lethargy, but they were not influenced by sex and size. The presence of the European pond turtle in the transitional woodland/shrubs and brackish water valley habitats was significantly higher in the period of activity than lethargy. During the latter one, pond turtles were observed to brumate gregariously in a small area for brumation, usually in shallow water. In contrast, all individuals have changed water bodies during the activity period. Part of those movements has occurred towards aquatic habitat with higher salinities 1-17 (mean: 10.64). These findings provide a set of information to better understand the behavioural ecology of Emys orbicularis in the lagoon area. This is of relevance for management actions and for the conservation of this threatened species.

Perforated plates are commonly used for flow control in pressurized systems. In different industrial applications, these devices are also used in series (multistage perforated plates) to manage high-pressure drop or reduce cavitation occurrence in industrial pipelines and enhance efficiency of gas turbines in power plants. In some specific conditions, the installation of perforated plates in series is a simple and cost-effective solution that increases plant efficiency. However, the large number of design parameters complicates the search for the optimal solution. With the aim of improving the knowledge of the most relevant design parameters, in the present investigation, the dissipation characteristics of multistage perforated plates are studied. Specifically, the analysis of the dependence of the pressure loss coefficient Eu on relative spacing and hole alignment for two subsequent identical plates is performed with CFD approach. Eight plates with different characteristics such as porosity, thickness, diameter, position, and number of holes are studied. The considered porosities vary in a range of 0.3–0.5, the ratio between plate thickness and hole diameter ranges between 0.7 and 1.3, and the number of holes between 4 and 26. A critical spacing between the plates, beyond which the pressure losses are independent of the alignment of the holes, has been calculated. The results obtained are relevant for a deeper understanding of the complex phenomenon of multistage perforated plates and can be used for the design and the installation of these devices commonly used in different engineering applications.

Salinity changes in transitional water ecosystems are a natural feature, but anthropogenic direct or indirect impacts are drastically altering their equilibrium and, therefore, their biological communities. Females of three species of Palaemonidae shrimps (the invasive Palaemon macrodactylus and the native P. adspersus and P. elegans) were collected in nature and kept in laboratory at salinities 20 and 30. For each species, the reproductive strategy (investment devoted to reproduction) and the reproductive performance (larval output and hatching success) were determined. Significant differences were observed comparing the three species, highlighting an opportunistic r-strategy in P. macrodactylus and P. elegans, while P. adspersus resulted to produce fewer and larger eggs. Palaemon elegans showed a lower hatching success than the other two species, and the size-adjusted larval output appeared to be highly sensitive to salinity variations, with a strong increase under euhaline conditions (salinity 30), while this increase was limited in the other two species. The selected species were used as model organisms to understand which could be the shift in biological communities due to salinity variations. Data suggest that a shift towards euhaline conditions will favor the native populations, while a shift towards mesohaline waters could determine an increase of the invasive shrimps.

Noise generation by low Mach number air flows through circular orifices in rectangular ducts is investigated. In particular, the influence of the number and position of the orifices maintaining a constant flow area is addressed. A review of the available theories suggests a certain importance of such parameters in the excitation of higher-order acoustic duct modes. A qualitative coefficient is proposed for a first characterization of the ability to enhance or lessen a given higher-order acoustic mode by the plate geometry. An experimental campaign is performed to measure the total emitted acoustic power by different plate geometries as well as its modal composition. It is found that the orifices' numbers and positions greatly influence the acoustic emissions while the flow pressure drop caused by the obstacles is similar. The proposed qualitative coefficient shows good agreement with the experimental results. A particle image velocimetry measurement campaign is performed to visualize the near-field average flow behavior upstream and downstream of the orifice plates. An increase in the turbulent velocity fluctuations in the vicinity of the orifices is observed on both sides, further validating previous studies on the subject.

Water demand in irrigation is expected to increase in the near future, and it will be seriously impacted by climate change, specifically in semi-arid areas. The increase of water demand, along with the reduction of water availability, can seriously intensify the frequency and magnitude of pressure deficits in pressurized irrigation networks, with dangerous consequences on the healthy crop growth and on the crop production. In this framework, the present paper investigates the contribution of a network of smart control valves, named GreenValve System (GVS, patented by the Politecnico di Milano), to improve the management of a pressurized irrigation system. The GVS is able to recover energy for its operation from the flow, to be remotely commanded and to introduce management logics based on real-time data in order to create a stand-alone real-time monitoring and control network. In the paper, specifically, a three-step general and replicable methodological approach for the definition of installation and operating conditions for these valves is proposed. The effectiveness of a specific management logic, allowed by the use of the GVS, to limit pressure deficit and failure occurrence in the network is discussed. Reference is made to a case study on a critical on-demand irrigation network. The results showed that the introduction of simple management rules can reduce and even avoid the occurrence of hydrant failure, creating the conditions for more effective use of the resources.

The aerodynamic noise emitted by a subsonic flow of dry air through an orifice plate is estimated in terms of internal sound power level and external sound pressure level (SPL) by application of the methodology described in the international standard IEC 60534-8-3. A shortcoming of the standard in defining the efficiency of the transformation of the mechanical energy of the flow into acoustic energy is discussed. Experimental evidence of the matter is also described. An alternative model employing the resolution of Reynolds Averaged Navier-Stokes equations (RANS) by means of Computational Fluid Dynamics (CFD) techniques for the calculation of the acoustic power generated by the turbulent flow through the orifice plate is applied so as to overcome the issue.

Vortex-induced vibrations (VIV) in systems with more than one degree of freedom often present complex synchronization among the motion components, also hidden by the randomness that characterizes the motion itself. A phase average method has been here developed and applied to the displacements of a tethered sphere, at low mass and damping, to analyze its xy trajectories over a wide range of reduced velocities, 5 ≤ U* ≤ 25 (Reynolds numbers, 5.1 × 103 ≤ Re ≤ 2.67 × 104). This method has allowed the identification of both the periodic and chaotic contribution of each motion component, accurately reconstructing the underlying trajectory periodic pattern. The two classical vibration modes, I and II, have been also observed. The method developed here was able to better rebuild the experimental data compared to other methods found in the relevant literature, providing useful insights into the study of the dynamic response of a freely-oscillating tethered sphere immersed in a steady flow.

Fluid-dynamic noise emissions produced by flow-control devices inside ducts are a concerning issue for valve manufacturers and pipeline management. This work proposes a modified formulation of Acoustic Perturbation Equations (APE) that is applicable to industrial frameworks where the interest is addressed to noise prediction according to international standards. This formulation is derived from a literature APE system removing two terms allowing for a computational time reduction of about 20%. The physical contribution of the removed terms is discussed according to the literature. The modified APE are applied to the prediction of the noise emitted by an orifice. The reliability of the new APE system is evaluated by comparing the Sound Pressure Level (SPL) and the acoustic pressure with the ones returned by LES and literature APE. The new formulation agrees with the other methods far from the orifice: moving over nine diameters downstream of the trailing edge, the SPL is in accordance with the other models. Since international standards characterize control devices with the noise measured 1 m downstream of them, the modified APE formulation provides reliable and faster noise prediction for those devices with outlet diameter, d, such that 9d < 1 m.

Water distribution networks (WDN) are going towards more sophisticated management strategies to save water and energy and to improve users’ service. The paper investigates experimentally the potent...

The brown meagre (Sciaena umbra) is a vulnerable vocal fish species that may be affected by boat noise. The breeding site distribution along the anthropized Venice sea inlets was investigated, by using the species' chorusing activity as a proxy of spawning. Passive acoustic campaigns were repeated at 40 listening points distributed within the three inlets during three-time windows in both summer 2019 and 2020. The role of temporal, morphological, and hydrodynamic variables explaining the observed distribution patterns was evaluated using a GLM approach, considering also human-induced pressures among the candidate predictors. The GLM analysis indicates a higher probability of recording S. umbra chorus after sunset in deeper areas of the inlets, characterized by low water current, while the underwater noise overlapping the species' hearing range and boat abundance did not play any role. This suggests that the species' breeding site choice in the inlets was not influences by boat-induced pressure.

The API Spec 6AV1 standard specifies the design requirements for valves operating in fields with sand production in order to reduce the risk of failure. In one of the validation tests, a valve is cyclically opened and closed under controlled conditions whilst a sand slurry is flowing in the loop. The carrier fluid is water with polymer viscosifiers to increase the viscosity up to about 55 cP. After completion of around 500 opening-closing cycles, high static pressure is applied upstream the valve to check for possible leakage. Objective of this study was to assess whether the occurrence of leakage might be affected by testing parameters that, being not specified by the standard, are decided by the experimenter; among them, particular attention was paid to the pressure and flow conditions during the valve operation. To this aim, numerical simulations were carried out combining different modelling approaches, and analyzing the failure of the valve from the point of view of the damage produced by impact wear. The difficulties inherent in the task of estimating erosion via numerical simulations are further enhanced in this work, since a number of complex case-specific issues had to be faced. First, the movement of the valve stem. Second, the co-existence of laminar and turbulent flow conditions due to the high viscosity of the carrier fluid. Third, the simulation of the valve as part of the entire loop. Fourth, the identification of a suitable indicator of valve leakage. Apart from the interest from a modelling point of view, the obtained results can help to improve the specification test procedures and acceptance criteria in the future.

Optical fiber sensors (OFSs) are nowadays widely adopted in many different fields and applications. Cavitation in pipeline systems is one of the main concerns of engineers because of its serious consequences for the lifetime of pipelines and on the performance of hydraulic devices. Among other useful parameters the incipient cavitation index is one of the most important because it represents the very beginning of the phenomenon. The present paper discusses the possibility of using optical fiber technology to detect cavitation in a pipeline. The experimental system exploits an interferometric fiber optical sensor based on a coherent demodulation scheme, avoiding the need for working point stabilization systems and coping with the polarization fading. Several dispositions and geometries for the sensors have been tested to select the most efficient solution. The results are then compared with cavitation indexes calculated following the standard procedure, using accelerometer measurements, to prove the optical fiber sensors’ effectiveness.

Divergence in acoustic traits between closely related species can be explained by phylogenetic history. In gobies, phylogenies reconstructed with acoustic signals primarily overlap with studies based on morphological or molecular data. Here, sound production of the two Ponto-Caspian gobies, Neogobius melanostomus and Ponticola kessleri, was recorded in controlled conditions and compared to determine the degree of interspecific acoustic variation across benthophilin gobies. Both species produced tonal-like sounds characterized by unique temporal and spectral properties during agonistic and reproductive intraspecific interactions, while the acoustic comparison revealed that the vocalizations of these two species differ in almost every acoustic property. N. melanostomus vocal structure was characterised by short (c. 100 ms), low-frequency (< 100 Hz) tonal sounds repeated at a relatively faster rate, while P. kessleri sounds appeared as a broadband, downward frequency modulated longer calls (c. 450 ms). Some acoustic features (sound rate and duration) proved to be stereotyped and could be considered a species-specific trait that could potentially be utilized to discriminate males or used by females for mate assessment. The tonal sounds appear to have a deeper origin within the Benthophilinae subfamily, as all acoustically investigated species to date have been able to produce this sound type. The recorded vocal repertoire represents a baseline for future comparative acoustic studies among the benthophilin gobies, aiming to gain additional information on the evolution of acoustic communication within Ponto-Caspian gobies and highlighting their importance in reconstructing phylogenetic relationships.

The number of farmed fish in the world has increased considerably. Aquaculture is a growing industry that will in the future provide a large portion of fishery products. Moreover, in recent years, the number of teleost fish used as animal models for scientific research in both biomedical and ecological fields has increased. Therefore, it is increasingly important to implement measures designed to enhance the welfare of these animals. Currently, a number of European rules exist as requirements for the establishment, care and accommodation of fish maintained for human purposes. As far as (teleost) fish are concerned, the fact that the number of extant species is much greater than that of all other vertebrates must be considered. Of further importance is that each species has its own specific physical and chemical requirements. These factors make it difficult to provide generalized recommendations or requirements for all fish species. An adequate knowledge is required of the physiology and ecology of each species bred. This paper integrates and discusses, in a single synthesis, the current issues related to fish welfare, considering that teleosts are target species for both aquaculture and experimental models in biological and biomedical research. We first focus on the practical aspects, which must be considered when assessing fish welfare in both research and aquaculture contexts. Next, we address husbandry and the care of fish housed in research laboratories and aquaculture facilities in relation to their physiological and behavioural requirements, as well as in reference to the suggestions provided by European regulations. Finally, to evaluate precisely which parameters described by Directive 2010/63/EU are reported in scientific papers, we analysed 82 articles published by European researchers in 2014 and 2015. This review found that there is a general lack of information related to the optimal environmental conditions that should be provided for the range of species covered by this directive.

Irrigated agriculture is currently one of the most water-consuming human activities at global level. Furthermore, in the next years, water demand for irrigation is expected to increase within a challenging framework characterized by the effects of climate change and dynamics such as the population increase. In this context and considering that up to now irrigation networks have experienced a limited access to innovation (such as e.g., several areas of the Mediterranean region, above all in the North African side), the opportunities offered by digitalization could be crucial in the next future. New technologies and IoT solutions can effectively improve the management of limited resources and the quality of service to users. In the present work, the advances in management of the irrigation networks that can be reached using a smart control valve, the GreenValveSystem (GVS), are discussed. The GVS is an innovative electro actuated control valve able to harvest part of the energy of the flow to enable high frequency monitoring of pressures and flow rate and real time operation on the valve, without the necessity of external power supply. It has been, up to now, positively tested and adopted in drinking water supply systems. A model of an on-demand pressurized irrigation network is used to provide, through hydraulic simulations, a proof-of-concept of the potential of such devices to support the selection and implementation of specific management strategies to limit (or even avoid) the occurrence of hydrant failures (i.e. an insufficient pressure or discharge ), and to guarantee an effective and sustainable use of water resources. In the study a procedure to find the best placement of the GVSs and some basilar management rules that limit failures is showed. This preliminary study demonstrates some of the improvement that the use of innovative devices based on IoT concepts, like cloud management of data and remote operations, can bring to water agencies and users.

Perforated plates are commonly used for flow control in pressurized systems. In different industrial applications, these devices are also used in series (multistage perforated plates) to manage high pressure drop or reduce cavitation occurrence in industrial pipes and enhance efficiency of gas turbines in power plants. Based on analysis of literature and modeling considerations, a functional relationship that describes the dimensionless pressure loss for multistage perforated plates is proposed in this paper. Moreover, numerical investigation of the influence of the spacing between perforated plates for two identical-stage plates with aligned and misaligned holes is carried out by simulating a wide range of Reynolds number in turbulent flow regime. The obtained results include the trend of the pressure loss coefficient as the spacing between the two perforated plates varies for both cases of aligned and misaligned holes. The numerical achievements also show that for small spacing, the pressure loss coefficient is very different from that caused by two independent plates and is strongly influenced by the alignment between the holes of the two plates. By increasing the spacing, the behavior of the losses caused by the two-stage plates tends to that of two independent plates. A critical spacing between the plates has also been defined, beyond which the pressure losses are independent from the alignment of the holes.

Boat noise is known to have a detrimental effect on a vulnerable Mediterranean sciaenid, the brown meagre Sciaena umbra. During summer 2019, two acoustic surveys were conducted at 40 listening points distributed within the inlet areas of Venice (northern Adriatic Sea). Two five-minute recordings were collected per each point during both the boat traffic hours and the peak of the species’ vocal activity with the aims of (1) characterizing the local noise levels and (2) evaluating the fish spatial distribution by means of its sounds. High underwater broadband noise levels were found (sound pressure levels (SPLs)50–20kHz 107–137 dB re 1 μPa). Interestingly, a significantly higher background noise within the species’ hearing sensibility (100–3150 Hz) was highlighted in the afternoon (113 ± 5 dB re 1 μPa) compared to the night (103 ± 7 dB re 1 μPa) recordings due to a high vessel traffic. A cluster analysis based on Sciaena umbra vocalizations separated the listening points in three groups: highly vocal groups experienced higher vessel presence and higher afternoon noise levels compared to the lower ones. Since the species’ sounds are a proxy of spawning events, this suggests that the reproductive activity was placed in the noisier part of the inlets.

A significant source of uncertainty in CFD-based erosion prediction is represented by the erosion model, used to turn the particle-wall impingement characteristics into an estimate of the removal of material. In engineering computations, frequent use is made of empirical erosion models obtained by fitting the experimental results of air-solid jet impingement tests. However, since the applicability conditions of these models are often unknown or unavailable to the users of CFD codes, they are frequently misapplied, producing not only uncertain, but at times also highly inaccurate wear estimates. As part of his PhD thesis defended at the University of Tulsa in 2016, Amir Mansouri proposed a methodology to calibrate the coefficients of an empirical erosion correlation by combining experimental data and CFD results of a slurry jet impingement test. This methodology provided an effective way to overcome the criticisms of using empirical erosion models taken from the literature without facing the complexity and the high computational burden of a multiscale, physically-based approach, in which the micro-scale mechanical interactions between the particles and the target surface are resolved according to the fundamental laws of damage mechanics. This paper presents an improved formulation of Mansouri's methodology, which not only increases the calibration accuracy of the empirical erosion equation, but also enhances the reliability of the CFD-based erosion prediction model as a whole. To this purpose, numerical simulations were supported by in-house slurry jet impingement experiments on an aluminum sample and curved Glass Reinforced Epoxy samples.

Transitional waters are fragile ecosystems with high ecological, social and economic values, that undergo numerous threats. According to the information provided by European Member States in the framework of the European Directive 92/43/EEC (Habitat Directive), the main threat to these ecosystems is represented by morphological and hydrological changes. The present work focuses on six lagoon fish species included in the Habitat Directive annex II (species requiring conservation measures: Aphanius fasciatus, A. iberus, Knipowitschia panizzae, Ninnigobius canestrinii, Valencia hispanica and V. letourneuxi) that spend their entire life cycle in the Mediterranean priority habitat 1150* “Coastal lagoons”. The overview of the current scientific literature allowed us to highlight how the presence and abundance of these species may provide important indications on the conservation status of coastal lagoon habitats. In fact, their occurrence, distribution and biology depend on the presence of peculiar structures, such as salt marshes, small channels, isolated pools and oligohaline areas. Coastal lagoon fragmentation and habitat loss have led to a significant reduction in genetic diversity or local population extinction. Although Aphanius and gobies have been shown to survive in eutrophic environments, it is clear that they cannot complete their life cycle without salt marshes (mainly Aphanius) and wetland areas (mainly gobies).

In recent years, water utilities have made worldwide investments targeted to the implementation of an effective monitoring system and the installation of pressure-reducing valves in strategic nodes of water distribution networks. In fact, these interventions are considered fast and effective solutions to address at least two main concerns of modern water utilities: leakage reduction and energy efficiency. The present paper, on the basis of a database of working conditions of installed pressure-reducing valves, discusses the range of applicability of the GreenValve system (GVS) as an alternative solution to improving standard pressure-reducing valve capabilities. The device is able to recover energy, and it can be used to create a stand-alone monitoring node with remote control ability, optimizing the network from an energetic, functional, and hydraulic point of view.

The larger anthropic pressure on the Water Supply Systems (WSS) and the increasing concern for the sustainability of the large energy use for water supply, transportation, distribution, drainage and treatment are determining a new perspective in the management of water systems [...]

Display of bright and striking color patterns is a widespread way of communication in many animal species. Carotenoid‐based coloration accounts for most of the bright yellow, orange, and red displays in invertebrates, fish, amphibians, reptiles, and birds, being widely considered a signal of individual health. This type of coloration is under the influence of several factors, such as sexual selection, predator pressure, pigment availability, and light transmission. Fish offer numerous examples of visual communication by means of color patterns. We used a small cyprinodontid fish, Aphanius fasciatus (Valenciennes, 1821), as a model species to assess habitat constraints on the color display in male caudal fin. Populations from natural and open/closed artificial habitats were tested for differences in the pigmentation of caudal fins. The most important factors explaining the intensity of coloration were the habitat type and the chlorophyll concentration in the sediment, followed by water turbidity; yellow fins were observed in natural habitats with low chlorophyll concentration and high water turbidity, while orange fins occurred in artificial habitats with high chlorophyll concentration and low turbidity. Furthermore, A. fasciatus in artificial habitats showed a higher somatic and a lower reproductive allotment with respect to natural habitats, according to the existing literature on the species. Furthermore, in closed artificial habitats, where the most intense reddish coloration of caudal fins was observed, a trade‐off between somatic growth and the coloration intensity of a carotenoid‐based sexual ornament has been observed; in these populations, intensity of caudal fin coloration was negatively related to the somatic allotment. Results of this study suggested how both the pigmentation of male's caudal fin and the life history strategies of the species are constrained by habitat characteristics.