Turbulence and secondary motions in square duct flow

We study turbulent flows in pressure-driven ducts with square cross-section through direct numerical simulation in a wide enough range of Reynolds number to reach flow conditions which are representative of fully developed turbulence. Numerical simulations are carried out over extremely long integration times to get adequate convergence of the flow statistics, and specifically high-fidelity representation of the secondary motions which arise. The intensity of the latter is found to be in the order of 1-2% of the bulk velocity, and unaffected by Reynolds number variations. The smallness of the mean convection terms in the streamwise vorticity equation points to a simple characterization of the secondary flows, which in the asymptotic high-Re regime are found to be approximated with good accuracy by eigenfunctions of the Laplace operator. Despite their effect of redistributing the wall shear stress along the duct perimeter, we find that secondary motions do not have large influence on the mean velocity field, which can be characterized with good accuracy as that resulting from the concurrent effect of four independent flat walls, each controlling a quarter of the flow domain. As a consequence, we find that parametrizations based on the hydraulic diameter concept, and modifications thereof, are successful in predicting the duct friction coefficient

Heritage Cosmopolitics: Archaeology, Indigeneity and Rights in Bolivia and Argentina

This dissertation tackles the contemporary consensus on rights-based approaches to heritage management, conservation, and research through a multi-sited archaeology ethnography of two iconic sites of the south-central Andean region: the UNESCO World Heritage site of Tiwanaku (Bolivia), and the Sacred City of Quilmes in the Calchaquí Valleys (Tucumán, Argentina). The investigation is at the crossroads of archaeology, anthropology, and political sciences and aims to improve interdisciplinary methodology within the field of Critical Heritage Studies by showing conflictive, entangled configurations of memories and aspirations beneath the definition and exploitation of indigenous heritage in the present as much as in the past. The analytical assessment of what ties the fields of cultural heritage and human rights together in both field locations – in spite of national and academic demarcations – provided effective conceptual and evidentiary tools of translation across world-making practices, which I describe in terms of heritage cosmopolitics in this thesis. These assemblages shake taken-for-granted meanings of heritage/rights, while tangibly crafting my own fieldwork and questioning the logic and police of neoliberal multiculturalism

Numerical simulations of thermals with and without stratification

Abstrac

Phenological characteristics of different winegrape cultivars in Central Italy

Statistical models based on temperature accumulation are used to estimate grapevine phenology (e.g. bud break, flowering) through summation of daily heat requirements calibrated from a base temperature and a given date. This study was designed to define the grapevine agro-phenological behaviour through analysis of potential trends of some principal phenological phenomena, such as flowering, harvest, and berry sugar levels at harvest. The data utilized were recorded over a 13-year period (2000-2012) for different grape varieties in the Umbria wine region in central Italy. Moreover, to determine the more important relationships between meteorological variables and recorded data, partial least-squares regressions were carried out. The trend analysis for berry sugar accumulation shows increasing degrees during the study period that were linked more to the 'Grechetto' cultivar than to the 'Chardonnay' and 'Merlot' cultivars, and then to 'Cabernet'. The statistical model that was focused on the study of the relationships between mean annual berry sugar levels and meteorological variables showed that mean maximum temperatures in April and July are the most important predictive variables for berry sugar accumulation, through their positive influence on berry sugar degree

An observational and numerical case study of a flash sea storm over the Gulf of Genoa

International audienceDuring the night between the 8 and 9 December 2006 the seawall of the Savona harbour (Liguria Region in north west of Italy) was overtopped by waves. In this work the "Savona flash sea storm" has been studied by analyzing the data recorded by meteo-marine observing stations and the data produced by high resolution meteo-marine numerical models. The data show that, due to the presence of a fast moving low pressure system, the event was characterized by a rapid transition and interaction between two different regimes of winds and related sea states. The results of the study suggest that the most damaging dynamics of the event could be correlated to a bi-modal structure of the wave spectrum. Based on this the authors suggest that a deeper study of the spectral structure of sea storms could lead to define new operational forecasting tools for the preventive evaluation of sea storms damaging potential

Flow over the Mid Adriatic Pit

The influence of the Mid Adriatic Pit (MAP) on the general circulation of the Adriatic is explored through numerical simulations. The numerical code used is the DieCAST model specifically modified for application to the Adriatic Sea. A ten-year simulation is performed and the ability of the model to capture important features of the Adriatic circulation is demonstrated. A series of numerical experiments on the importance of the MAP on the general circulation is performed. It is demonstrated that the current over the northern flank of the MAP, which flows from the Croatian toward the Italian coast, is primarily a topographic current and that such a current would reverse direction if the gradient of the bathymetry were reversed