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This paper reports on the first large-scale three-dimensional investigation of thermal convection inside a cylinder by time-resolved tomographic particle image velocimetry. Rayleigh-Bénard convection is one of the most intensely studied problems in fluid mechanics due to its relevance to several fields of application, ranging from the geophysics and astrophysics to industrial engineering. Despite the huge amount of works on this subject, only few works have focused on three-dimensional experimental measurement of convection inside a cylindrical sample. In the present study, Rayleigh-Bénard convection is investigated in a cylinder with one-half aspect ratio at Rayleigh and Prandtl numbers equal to about 2E-8 and 6.5, respectively. The behavior of the turbulent flow is analyzed both in the time-average and instantaneous evolution. Focus is given to the structure and dynamics of the large–scale circulation. The azimuthal motion of the large-scale circulation is instantaneously traced and its relationship with the time-averaged flow field is investigated. Proper orthogonal decomposition is also used to identify the characteristic modes of the thermal convection. The most energetic modes are strictly related to the existence of the large-scale circulation, but interestingly the third and fourth modes exhibit a double-roll configuration, which is found to be the dominant pattern in the instantaneous flow field at some time instants.

In the present work, a very compact reaction system thermally integrated for the distributed hydrogen production by natural gas reforming is reported. The system is based on hydrocarbon Auto-Thermal Reforming, followed by a Water-Gas Shift module. A compact heat exchanger was placed between the two catalytic stages, in order to assure an appropriate thermal integration that avoid any other external heat duties. Experimental results demonstrated that the integrated configuration assured a good management of thermal fluxes in the system, in which an effective heat recovery from ATR exhaust gas to reactants was realized. Preliminary tests showed very impressive performances of the system, both by processing methane and natural gas. Despite a quite slow WGS stage, the processor was able to produce up to 10 Nm3/h of hydrogen, assuring a thermal efficiency higher than traditional systems.

In this paper we describe the application of GPR and resistivity (dipole-dipole) methods to an archeological investigation. The aim of this study was to obtain information about buried pre-Roman structures below the Roman residence "Casa dell'Atrio a Mosaico", in the ancient town of Ercolano (Naples). A number of resistivity (dipole-dipole) and GPR profiles were carried out on the mosaic floor of the house. To perform resistivity profiles in a nondestructive way on the mosaic floor, special flatbase copper electrodes were used. The electrode spacing used was 1 m and 0.5 m. GPR data were collected using 100 MHz and 500 MHz antennas. The radar profiles were carried out primarily along the electrical profiles in order to obtain a direct comparison between the two methods. Both resistivity and GPR methods evidenced a number of structures buried at shallow depths. Both methods located a structure identified as a conductive body with electric parameters strongly contrasting those of the surrounding material. The archaeological interpretation of such structures is in terms of remnants of walls of pre-Roman houses and of a cistern used for collecting rain, connected to a pipe

The present work reports on the extended distribution of nineteen species in the Mediterranean. These are: Upeneus pori (Fish:Turkey), Bursatella leachii (Mollusca, Opisthobranchia: eastern coast of Spain), Sparisoma cretense (Fish: Ionian coast of Greece), Pseudobryopsis myura (Chlorophyta:Turkey), Aplysia dactylomela (Mollusca, Opisthobranchia: Karpathos island, and Kyklades Archipelago, Greece), Asparagopsis armata and Botryocladia madagascariensis (Rhodophyta: South Peloponnesos, Greece), Oxynotus centrina (Fish: Greece), Caulerpa racemosa var. cylindracea (Chlorophyta), Stypopodium schimperi (Phaeophyta) Siganus luridus and Stephanolepis diaspros (Fish) Percnon gibbesi (Decapoda, Brachyura) (Kyklades Archipelago, Greece), Cerithium scabridum (Mollusca, Prosobranchia: Anavissos: Greece) and Cerithium renovatum (Mollusca, Prosobranchia: N. Kriti), Cassiopea andromeda (Scyphomedusa: Rhodos Island, Greece), Abra tenuis (Mollusca Bivalvia: Vouliagmeni Lake, Greece) Lagocephalus lagocephalus (Fish: Calabrian coast, Italy) and Plocamopherus ocellatus (Mollusca, Opisthobranchia: Iskenderun Bay, Turkey).

This paper reports information about the presence of three allochthonous reptiles species in Calabria: Testudo marginata, Trachemys scripta elegans and Chamaeleo chamaeleon. The first one was found in three sites located in the Catena Costiera Massif and in the Crati Valley (Northern Calabria). The slider turtle was found in seven different sites throughout all the region. It massively colonised the Angitola artificial lake: here, this turtle lives in natural conditions and its reproduction was confirmed by the presence of nests, eggs and hatchlings. C. chamaeleon is present in sandy coastal habitats near Palmi and Gioia Tauro (Southern Calabria). From a conservationistic point of view, serious damages to autochtonous species could be caused by the spreading of T. scripta elegans: this species has already determined the local extinction of Angitola’s Emys orbicularis populations., Acta Herpetologica, Vol 5 No 2 (2010)

This paper reports on a parametric study of the impingement heat transfer from swirling jets issuing from a circular nozzle. The swirl velocity component is imparted to the flow via a tangential entry into a recirculation chamber located upstream of the nozzle; the degree of swirl is varied by changing the angle of the channels leading to the chamber with respect to the radial direction. The effects of the dimensionless impingement distance (H/D = 1, 2, 3, 4, 6, 8, 10, 12, 14 with D being the nozzle diameter), the swirl number (S = 0, 0 . 078, 0 . 22, 0 . 37, 0 . 54) and the Reynolds number (Re = 20,800 , 31,100 , 41,500) on the spatial distribution of the heat transfer are investigated by means of infrared thermography and the heated thin foil sensor. The present results show that the swirl number and the impingement distance significantly influence the structure of the heat transfer distribution, while the Reynolds number affects essentially the magnitude. Four distinct ranges with different behaviours can be identified by distinguishing between weakly or non swirling jets (0 ≤S ≤0 . 22) and moderately swirling jets (0 . 37 ≤S ≤0 . 54) and between short and long impingement distances (1 ≤H/D ≤4 and 6 ≤H/D ≤14 respectively). A comparative assessment of the performance of the swirling jets is carried out by focusing on the area-averaged Nusselt number distributions. It is found that in the range of short impingement distances and over relatively small target areas an enhancement of the heat transfer rates can be obtained at a small extent by adding a weak swirl with no detrimental effect on the uniformity of the distribution and at a larger extent by a moderate swirl with a deterioration of the uniformity. For long impingement distances no enhancement is observed, although swirl yields a significant reduction of the non-uniformity. Finally, correlation laws of the area-averaged Nusselt number as a function of the control parameters are derived in the four regimes identified.

Sweeping jets are oscillating jets generated by fluidic oscillators, i.e., devices designed to produce an oscillation of the flow without the use of any moving parts (Raghu, 2013). A typical configuration of such devices consists of an expansion chamber connected to a high-pressure supply via a converging nozzle and provided with feedback channels. The oscillating motion in the expansion chamber is triggered by an inherent flow instability and sustained by the flow rate across the feedback channels. Recently, sweeping jets have been studied in flow control applications for noise reduction, separation and circulation control over airfoils, control of resonant cavity oscillations and deflection of jets. The advantageous features of fluidic actuators, among which are the wide range of operating frequencies (up to kHz with meso-scale) and the distributed momentum addition, have also stimulated an increasing interest in their application to electronics cooling. Several recent studies on the convective heat transfer from impinging sweeping jets (e.g., Hossain et al., 2018; Park et al., 2018) have shown that, compared to conventional round jets, they offer higher cooling rates with better uniformity at least for small jet-to-plate spacings.

The present paper reports on a time-resolved three-dimensional experimental study of turbulent Rayleigh-Bénard convection inside a cylinder with one-half aspect ratio. The working fluid is water and the Rayleigh and Prandtl numbers are, respectively, and. Measurements are carried out via time-resolved particle tracking velocimetry for a relatively long time (approximately four hours) and due to the limited size of the convection cell (internal diameter of mm) the whole interior of the cylindrical sample is investigated. This allows a proper analysis of the statistical behaviour of the flow across the time. Proper orthogonal decomposition (POD) is used to extract the characteristic modes of the turbulent thermal convection. It is shown that the low-order POD modes are strictly related to the formation of a large scale circulation (LSC) and its organization in a single-roll state (SRS) or a double-roll state. Innovative criteria for the identification of the instantaneous flow state based on the POD analysis are also proposed. Such criteria are proved to overcome the limitations of methods commonly adopted in the previous literature and relying on the analysis of the azimuthal profiles of the temperature or the vertical velocity at three different heights (one quarter, one half and three quarters of the cell height). Compared with the latter methods, the POD-based criteria identify a larger frequency of occurrence of the SRS, which is recognized as the most frequent state of the LSC in the investigated conditions.

This work presents a comparison of the results from an experimental and numerical investigation of impinging swirling jets operating at Reynolds number and swirl number equal to 30’000 and 0.61, respectively. Measurements are carried out via InfraRed Thermography using a heated thin foil as heat flux sensor, varying the impingement distance from 1 to 10 nozzle diameters. Numerical simulations of the same configurations are performed with a commercial software (Ansys Fluent) to test the capability of different Reynolds-Averaged Navier-Stokes (RANS) equations-based turbulence models in predicting the heat transfer rates from wall to the swirling impinging jets.

The present paper aims at establishing the synthetic jet technology capabilities in controlling the von Kármán street behind a circular cylinder. The circular cylinder, placed in an open-circuit wind tunnel, presents a slot in its rear position, through which the synthetic jet is issued. The Reynolds number, based on the circular cylinder diameter and the free-stream velocity, is equal to 4600 and the von Kármán street is characterized, in the baseline configuration (i.e. without synthetic jet), by a shedding frequency of 16.2 Hz. Several synthetic jet operating conditions are tested. Therefore, the effects of the momentum coefficient (%, 10.8% and 21.6%) and the dimensionless frequency (, 0.98 and 1.96) on the von Kármán street behaviour can be analysed. Instantaneous two-dimensional in-plane velocity fields are measured in a plane containing the synthetic jet slot axis using multigrid/multipass cross-correlation digital particle image velocimetry. These measurements have been used to investigate the mean flow quantities and turbulent statistics of the phenomenon. In addition, the wake extent and behaviour (i.e. symmetric or asymmetric) are analysed as well as the drag coefficient, for each configuration. The extent of the wake region decreases as the momentum coefficient and/or the dimensionless frequency increase, while the symmetric/asymmetric wake behaviour is found to be governed by a different control parameter: the synthetic jet Reynolds number based on its impulse. As regards the drag coefficient, a maximum reduction, of approximately 35%, is found for the configuration at and.

In order to evaluate the usefulness of transcranial Doppler (TCD) in carotid artery surgery, 90 patients who underwent carotid endarterectomy were studied. Transcranial Doppler was performed preoperatively with digital compression of the carotid artery and intraoperatively at the time of cross-clamping, together with routine EEG monitoring. The percentage residual middle cerebral artery velocity (%MCAV) during carotid artery compression or cross-clamping was considered. The intraoperative %MCAV at cross-clamping was compared with the values obtained in the preoperative examination during the compression test and with the EEG data; the EEG records were blindly reviewed by a neurologist and divided into three groups: group A, normal; group B, moderate anomalies and group C, major anomalies. There were no significant differences between preoperative %MCAV (compression test) and intraoperative %MCAV (cross-clamping) by separate analysis of the data related to systolic, diastolic and mean velocity. The systolic, diastolic, mean %MCAV and the Gosling index after cross-clamping were then compared with the EEG data: no significant differences were seen between groups A and B; on the other hand, in all patients with major EEG anomalies (group C) the %MCAV at TCD was reduced to 0. In conclusion, preoperative TCD associated with carotid artery compression appears a safe and useful way of identifying patients at risk of cerebral ischaemia during carotid artery cross-clamping. Patients with no residual flow at intraoperative TCD need to be considered as presenting a very high risk of ischaemia and in this group the use of a shunt is mandatory.