Inertial circulation of the western Mediterranean sea

Summary The essential features of the steady circulation of the western Mediterranean are reproduced by means of a vertically integrated model. In the framework of barotropic theory, it is shown how the effects of the geometry of the basin, including the islands, of the variable bottom topography and of the forcing of the flow at the Gibraltar Strait concur in determining the circulation pattern. Some observed features in particular regions, such as the Ligurian Sea, which are not reproduced by the model, indicate where baroclinic and/or wind-driven dynamics are likely to dominate. Paper presented at the 1^o Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 19–22, 1984, Rome.     

Microscopic-scale simulations of macroscopic flow patterns in non-equilibrium two-dimensional systems

Summary We have used a molecular-dynamics simulation for reproducing the behaviour of a two-dimensional fluid flow submitted to external perturbations and embedded in a non-inertial reference frame. This simple model has been used to verify current hypotheses on the causes generating a cyclonic circulation in the North Tyrrhenian basin, provided one uses suitable perturbation strenghts scaled from the real-world dynamics. Results put in evidence that the onset of a stationary cyclonic circulation which superimposes to the S-N flow requires the simultaneous presence of an orthogonal and an anti-parallel stream. This finding is in agreement with the hypotheses suggested by a preliminary analysis of experimental data. The limits of such models are discussed together with possible extensions to reproduce mesoscopic systems, in order to simulate the coexistence of large- and small-scale dynamics. The model is particularly suited to deal with boundary conditions of general analytical shapes.     

The Vulcano 1994 summer campaign

Summary A set of measurements from various sources was collected for the Island of Vulcano (Aeolian Archipelago, South Tyrrhenian Sea) during summer 1994 with the scope of characterising the circulation pattern and the CO₂ natural volcanic emission of the island. Ground meteorological stations were activated, wind profiles from pilot balloons were obtained, ground temperature measurements were produced. Furthermore, temperature and humidity data from satellite (Landsat TM) were also derived. A critical analysis of the data on the gathered information was performed to quantify the volcanic risk related to the toxic-volcanic-gas release in foreseeable paroxysmal events.     

On the eigenperiods in the Tyrrhenian Sea level oscillations

Summary In this paper the eigenperiods of the Tyrrhenian Sea are examined by a hydrodinamical model in two dimensions. The knowledge of these eigenperiods is important to evaluate the seiches that often appear, in some point or circumstance, stronger than the tides. This investigation is performed by energizing the basin through the Sardinia channel, in the same way as it was already done for the tides. This excitation simulates a large set of waves inducing oscillations inside the basin. The periods of the waves are narrow and their amplitude equal. An analogous method of investigation is that of the fluorescence. In addition, the results are compared with those previously obtained leaving the basin swinging, after having increased the sea level by a uniform displacement. The response of the bidimensional model agrees with that of a monodimensional one as far as possible; thus the last one can give useful information, also for a sea that does not have a channel shape, like the Tyrrhenian Sea. Nevertheless, this basin has other openings, besides the Sardinia channel, it seems that they do not influence the eigenperiod behaviour. This has been confirmed by performing the same computations over a sea 500 m less deep: the uniform lowering of the sea surface is equivalent to close the four minor openings. The results carried out in this case agree with the previous one. Among all the periods pointed out by our investigation, one is always exhibited in every point and by each system. The period is that of 5.70 h and it can be considered a fundamental mode of the Tyrrhenian Sea.     

Mössbauer study of pelitic rocks from Ligurian Alps

Pelitic rocks of Val Lavagna and M. Antola formations (Lavagna and Graveglia Valley, Ligurian Alps) have been studied to investigate the behaviour of clay minerals at different metamorphic conditions using Mössbauer spectroscopy of⁵⁷Fe.     

Some simple solutions concerning the Ligurian Sea vortex and its stability

Summary The cyclonic vortex of the Ligurian Sea is a very persistent feature of the Mediterranean Sea, even if its intensity varies seasonally. In this paper we examine the barotropic component of this vortex. In particular we study the influence of the bottom topography and of the coastlines in shaping the cyclonic flow. Furthermore we show that the barotropic part of the vortex is stable to finite perturbations, which may explain its persistency. Paper presented at the IV Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 22–24, 1987, Rome.     

Thermoluminescence in sediments and historical supernovae explosions

Summary Thermoluminescence from the different layers of a recent core drilled in the Tyrrhenian Sea has been measured. The sedimentation rate of 0.115 cm y⁻¹ previously determined by the²¹⁰Pb−²²⁶Ra method allows the profile of TL to be obtained in the last 1500 years. We notice that sharp peaks in the TL intensity appear during the years in which records of hystorical supernovae explosions are given. A working model of the process based on the irradiation of dust in the upper atmosphere by γ-rays produced in the SN burst allows a satisfactory energy estimate of the observations to be done. Moreover, the profile shows the modulation of the irradiations of the Earth environment produced by the Sun in the past.     

On heat and moisture exchanges between the sea surface and the atmosphere during the Medalpex

Summary Data collected by a buoy, moored in the Ligurian Sea about 27 nautical miles off the coast during the period 1 March-31 May, 1982, are analysed. The buoy was equipped by the Institute for Naval Automation (IAN) of the Italian National Research Council (CNR) during the Mediterranean Alpine Experiment (Medalpex), joint program of the Alpine Experiment (Alpex). Exchanges of heat and mass across the air-sea interface are computed from the collected data and comparisons with existing values are made. The resulting agreement confirms the strong interaction between the sea and the atmosphere in some peculiar situations, and lends weight to the oceanographic hypothesis for the statistical occurrence of deepening of orographic cyclones in the Liguro-Provencal basin. Paper presented at the IV Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 22–24, 1987, Rome.     

Reversals of large-scale circulation in turbulent convection in rectangular cavities

The behavior of large-scale circulation appearing against the background of Rayleigh-Bénard turbulent convection in rectangular cavities of various geometries (from a thin layer to a cubic cell) has been experimentally investigated. It has been shown that the regimes of large-scale circulation with spontaneous reversals separated by long periods of quasistationary circulation appear both in a limited range of the Rayleigh number and in a limited range of the aspect ratio, which determines the ratio of the thickness of a cell to the side in the circulation plane. A regime without reversals is established in a thick layer, whereas a regime characterized by numerous changes in the direction of circulation, which are not separated by intervals with the stable direction of the large-scale flow, arises in a thin layer. The spectra of oscillations of the amplitude of large-scale circulation have been analyzed. It has been shown that a dominant frequency appears in the spectrum of oscillations of the cubic cell.     

Analysis of refrigerant-charged solar collectors with phase change

This paper presents a mathematical model for natural circulation refrigerant-charged solar collector plates with phase change. The model accounts for the thermal nonequilibrium vapor generation process along fully charged collector tubes.The local vapor generation rate is determined by solving the steady one-dimensional two-phase energy conservation equations in finite difference form along the flow path. The integral momentum balance around the circulation loop determines the circulation flow rate, which shows dependency on the solar flux and the pressure of the heat carrying refrigerant inside the loop. Calculations have been made for a system fully charged by R-11, with temperature-dependent thermophysical properties.The effect of solar insolation, for a controlled pressure system, on the vaquality, ad circulation rate is presented and discussed. Performance of the system is studied for a range of the independent variables, solar flux up to 1000 W m⁻², and refrigerant saturations temperatures up to 80°C.     

The structure and composition of novel electrodeposited Sn–Fe and Sn–Co–Fe alloys from a flow circulation cell system

This study involved the use of a flow circulation cell, using varying circulation rates as a room temperature process (20°C). Mössbauer and XRD analysis were conducted to ascertain whether amorphous or microcrystalline structures could be obtained at 20°C using a range of current densities. Amorphous or microcrystalline structures of Sn–Fe and Sn–Co–Fe have potentially important industrial applications for energy efficient cells, for use as high performance electrodes in lithium batteries, as environmentally acceptable corrosion resistant materials and are derived from an energy efficient environmentally friendly electrolyte process which would be acceptable as an industrial process. $^{\it 57}Fe$ and $^{\it 119}Sn$ Mössbauer investigations supported by XRD analysis confirmed that the room temperature flow circulation cell gave rise to previously unknown non-equilibrium amorphous structures which do not occur in the corresponding thermally prepared alloys as shown in the thermal equilibrium diagrams. Mössbauer analysis shows these alloys to be both amorphous and ferromagnetic. It is shown that the flow circulation cell used at 20°C based on the environmentally friendly gluconate bath reported gives amorphous based Sn–Fe and Sn–Co–Fe alloys over a useful range of current densities facilitated by using a range of circulation rates.     

Visualization of a rotating flow under large-deformed free surface using anisotropic flakes

This study aims to clarify the relationship between the deformation of a free surface and flow transition in a “switching phenomenon” process. In a flow driven by a rotating disk in a cylindrical open vessel, the free surface irregularly changes its shape from axisymmetric to nonaxisymmetric and vice versa with repeating up-and-down motion (so-called “switching phenomenon”). The flow under the free surface was visualized by anisotropic flakes. When the free surface assumes a parabolic shape, the flow is distinguished by three regions; local circulation region, rigid vortex region and meridional circulation region. The flow transition in the switching phenomenon was shown by snapshots and movies of the visualized flow; the flow near the free surface is laminar even if the shape of the free surface changes to nonaxisymmetric during the time at which the free surface attaches to the bottom of the vessel. After the free surface detaches from the disk, the flow near the free surface becomes turbulent. When the free surface changes to axisymmetric while descending to the bottom, the flow changes from turbulent to laminar flow and the local circulation region reemerges at the center of the vessel.     

基于RELAP5的池式研究堆自然循环瞬态计算

反应堆的自然循环能力是其固有安全性的一项重要特征参数,利用RELAP5/Mod 3.4程序计算了JRR-3M池式研究堆在无应急冷却系统和有应急冷却系统条件下失去场外电源的事故工况,分析了冷却剂流动方向反转过程中的瞬态自然循环能力,并得到了最大自然循环载热能力。计算结果表明:应急冷却系统的投入明显地降低了燃料和冷却剂的温度,提高了反应堆的安全性;当衰变功率降低至590 kW时关闭辅助泵,利用自然循环能力可使反应堆达到安全状态。通过此研究堆的自然循环能力计算,验证了计算模型、计算方法的可行性,可进一步应用于此类型的研究堆。     

A numerical simulation of the transport of surface ozone along a Mediterranean coastal area

Summary A simple numerical simulation of daily summer circulation in W-NW and E-SE directions was applied to a coastal area of Greater Ravenna in Northern Italy to assess the influence on ozone levels of the transport mechanism in the land-sea breeze system. Field measurements of ozone concentration and micrometeorological data collected over a ten-year period (1978–1989) by a coastal monitoring station were processed to identify meteorological and climatic situations. The diurnal pattern of a ?pure? off-shore-in-shore circulation system was reconstructed by applying a simple model in which data were considered or rejected as a function of the prevailing wind direction. Only data collected under W-NW and E-SE wind direction conditions became part of the ?reconstructed wind circulation system?. The findings show that the relative concentration values and the time duration of the simulated transport phenomenon are in good agreement with the recorded episodes of transport and of severe continuous fumigation, occurring during the night, at the polluted area.     

Turbulent convective heat transfer in an inclined tube filled with sodium

Turbulent free convection of liquid sodium in a straight thermally insulated tube with a length equal to 20 diameters and with end heat exchangers ensuring a fixed temperature drop is investigated experimentally. The experiments are performed for a fixed Rayleigh number Ra = 2.4 × 10⁶ and various angles of inclination of the tube relative to the vertical. A strong dependence of the power transferred along the tube on the angle of inclination is revealed: the Nusselt number in the angular range under investigation changes by an order of magnitude with a maximum at the angle of 65° with the vertical. The characteristics of large-scale circulation and turbulent temperature pulsations show that convective heat transfer is mainly determined by the velocity of large-scale circulation of sodium. Turbulent pulsations are maximal for small angles of inclination (α = 20°–30°) and reduce the heat flux along the channel, although in the limit of small angles (vertical tube), there is no large-scale circulation, and the convective heat flux, which is an order of magnitude larger than the molecular heat flux, is ensured only by small scale (turbulent) flow.     

自然循环预冷和低温热管耦合系统的初步实验研究

介绍的高效低温传热方法主要包括 :自然循环冷却法和基于自然循环预冷及低温热管的高效低温冷却方法。自然循环冷却法的特点是在大温差条件下实现物体的快速冷却。一旦被冷却物体到达或接近低温液体的温度 ,将产生循环动力不足的情况 ,必须采用诸如气体引射或容器自增压等方法加以解决。而低温热管的特点在于能在小温差条件下 ,传递大量的热能。文中将自然循环预冷法及低温热管技术有机结合 ,综合自然循环和低温热管的优点 ,取长补短 ,既可以在很短的时间内使被冷却物体的温度降低下来 ,又可以保证被冷却物体的温度波动较小。文中还详细给出了基于自然循环预冷及低温热管的高效低温传热单元的设计及试验结果     

Design and numerical analyses of the human greater circulatory system

The paper presents examinations of human's greater part of the circulatory system, modeled as an electric net. The similarities between human's greater circulation and the electric model have been evolved. The analysis of the greater circulation was performed in PSPICE – an environment of electric circuits modeling. The designed model allows to analyze human's greater circulation in physiological and pathological cases.