A penalisation approach to simulate root compressors

The simulation of the unsteady flow field in root compressors requires to deal with several challenges related to the presence of moving parts and complex geometries. In the present work a penalisation approach applied to the compressible Navier- Stokes equations is investigated as a possible technique to perform this kind of simulations. In particular, the compressible Navier- Stokes equations are augmented by source terms which represent the effects of the body on the fluid and then they are integrated in both the fluid and solid domains. The presence of moving bodies is taken into account by a level set function. A validation based on a grid convergence study is performed on the flow around an impulsively started cylinder. A preliminary simulation of the flow field inside a root compressor is performed in order to predict the unsteady mass flow rate through the machine

A study on the statistical convergence of turbulence simulations around a cylinder

The turbulent flow around a circular cylinder at a Reynolds number equal to 3900 is studied by an implicit Large Eddy Simulation performed by means of a discontinuous Galerkin finite element solver. The average velocity field in the wake is evaluated and compared with experimental data from the literature. The focus of the present work is on the estimation of the statistical uncertainty which is related to the use of a finite time window for the averaging operation. This topic represents an open problem for both Direct Numerical Simulations and Large Eddy Simulations in which it is difficult to define a priori the size of the time window which gives statistically converged averaged quantities. Different techniques to estimate this uncertainty are compared in order to get a quantitative criterion for checking the convergence of statistics. In particular, the Non-Overlapping Batch Means and the Batch Means Batch Correlations techniques are applied to the present test case

Grooved stone tools from Calabria region (Italy): Archaeological evidence and research perspectives

Since the end of the 19th century the Calabria region in southern Italy has been known for an abundance of grooved stone axes and hammers used during late prehistory. These artefacts are characterized by a wide and often pronounced groove in the middle of the implement, thought to have aided securing the head to a wooden haft. Their widespread presence is known both in prehistoric archaeological literature and in the archaeological collections of various regional and extra-regional museums. At first, scholars did not relate these tools to the rich Calabrian ore deposits and to possible ancient mining activities; they were regarded simply as a variant of ground lithic industry of Neolithic tradition. However, between 1997 and 2012, about 50 tools were discovered in the prehistoric mine of Grotta della Monaca in northern Calabria where there are outcrops of copper and iron ore. This allowed us to recognize their specific mining value and to consider them as a sort of “guide fossil” for the identification of ancient mining districts. This paper presents the results of a study involving over 150 tools from the entire region, effectively demonstrating an almost perfect co-occurrence of grooved axes and hammers with areas rich in mineral resources, especially metalliferous ores

Macrolithic tools for mining and primary processing of metal ores from the site of Grotta della Monaca (Calabria, Italy)

Grotta della Monaca is a karst cave located in Calabria, the southernmost region of the Italian peninsula. About half a kilometre deep, the cavern has drawn the attention of people since the Palaeolithic period due to the abundance of metal ores within (mainly iron hydroxides but also copper carbonates). These easily reachable minerals were exploited during prehistory, especially between the late Neolithic and the early Copper Age.Research conducted from 2000 to 2012 has allowed us to understand various aspects of ancient mining activities performed within the site and to reconstruct a basic operational chain concerning the procurement and the primary processing of such resources, from the choice of tools to the various extractive techniques, from the disposal of mining debris to the early operations of ore processing.In this paper we focus on two categories of macrolithic tools: those used to extract minerals, and those used for their primary processing. The first group is composed of 51 artefacts divided into axes, hammers, and pickaxes with a central groove, found in the deeper areas of the cave, which represent the mining areas. Their morphological and dimensional variability indicates a significant functional diversification; furthermore, the choice of different very hard metamorphic rocks implies a high awareness in the selection of the raw materials used for making these implements. The second group includes 22 tools with different functions - mainly made of sandstone - classified as querns, grinders and crushers. They were found in an underground area adjacent to the entrance, which is characterized by large and comfortable spaces, with the widespread presence of natural light. A recent traceological study has clarified the function of such artefacts; they were used to grind mined blocks of iron hydroxides to obtain a powder. The multidisciplinary approach adopted in studying mining tools from Grotta della Monaca, including petrographic, typological and use-wear analysis, has allowed us to gain important knowledge about the general characteristics of these tools

Reynolds stress correction by machine learning methods with physical constraints

For the past three decade, Reynolds Average Navier-Stokes models have been widely used in the industry to simulate complex flows. However, these models suffer from limitations. Indeed there are still large discrepancies in the Reynolds stresses between the RANS model and high-fidelity data provided by DNS or experiments. This paper presents a strategy to correct the Menter SST model using an explicit algebraic model and two different neural networks: an multilayer perceptron (MLP) and a generative adversarial network (GAN). Moreover, in order to preserve the physical properties of the Reynolds stress tensor, we introduce a penalisation term in the loss of the GAN

Long-term persistence of poliovirus neutralizing antibodies in the era of polio elimination: An Italian retrospective cohort study.

Abstract Introduction The extensive use of oral and inactivated poliovirus (PV) vaccines has driven progress toward the global eradication of wild PV2 and PV3 and the elimination of PV1 in most countries, including Italy. Although the persistence of circulating neutralizing antibodies among the vaccinated is unclear, it is estimated that > 99% of the population vaccinated according to the recommended protocol should be protected for at least 18 years. Methods This study evaluated the seroprevalence of anti-PV neutralizing antibodies and the long-term immunogenicity of the oral poliovirus vaccine (OPV) in a sample of medical students and residents of the University of Bari who attended the Hygiene Department for a biological risk assessment between April 2014 and October 2020. Results The prevalence of protected vaccinated individuals was > 90% for PV1, PV2, and PV3. Specifically, >99% of the study group was protected against PV1, > 98% against PV2, and almost 93% against PV3. Protective antibodies against all three viruses persisted for at least up to 18 years after administration of the last OPV dose, with PV1 and PV2 antibodies detected in > 95% of the participants > 30 years after the last OPV dose. Conclusions The childhood series of four doses of OPV guarantees a long duration of protection, despite the elimination of the virus and therefore the absence of a natural booster. However, until PV1 is completely eradicated, maximum vigilance on the part of public health institutions must be maintained

Long time persistence of antibodies against Mumps in fully MMR immunized young adults: an Italian retrospective cohort study

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