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  1. Article ; Online: Prediction of Liner Metal Temperature of an Aeroengine Combustor with Multi-Physics Scale-Resolving CFD.

    Bertini, Davide / Mazzei, Lorenzo / Andreini, Antonio

    Entropy (Basel, Switzerland)

    2021  Volume 23, Issue 7

    Abstract: Computational Fluid Dynamics is a fundamental tool to simulate the flow field and the multi-physics nature of the phenomena involved in gas turbine combustors, supporting their design since the very preliminary phases. Standard steady state RANS ... ...

    Abstract Computational Fluid Dynamics is a fundamental tool to simulate the flow field and the multi-physics nature of the phenomena involved in gas turbine combustors, supporting their design since the very preliminary phases. Standard steady state RANS turbulence models provide a reasonable prediction, despite some well-known limitations in reproducing the turbulent mixing in highly unsteady flows. Their affordable cost is ideal in the preliminary design steps, whereas, in the detailed phase of the design process, turbulence scale-resolving methods (such as LES or similar approaches) can be preferred to significantly improve the accuracy. Despite that, in dealing with multi-physics and multi-scale problems, as for Conjugate Heat Transfer (CHT) in presence of radiation, transient approaches are not always affordable and appropriate numerical treatments are necessary to properly account for the huge range of characteristics scales in space and time that occur when turbulence is resolved and heat conduction is simulated contextually. The present work describes an innovative methodology to perform CHT simulations accounting for multi-physics and multi-scale problems. Such methodology, named U-THERM3D, is applied for the metal temperature prediction of an annular aeroengine lean burn combustor. The theoretical formulations of the tool are described, together with its numerical implementation in the commercial CFD code ANSYS Fluent. The proposed approach is based on a time de-synchronization of the involved time dependent physics permitting to significantly speed up the calculation with respect to fully coupled strategy, preserving at the same time the effect of unsteady heat transfer on the final time averaged predicted metal temperature. The results of some preliminary assessment tests of its consistency and accuracy are reported before showing its exploitation on the real combustor. The results are compared against steady-state calculations and experimental data obtained by full annular tests at real scale conditions. The work confirms the importance of high-fidelity CFD approaches for the aerothermal prediction of liner metal temperature.
    Language English
    Publishing date 2021-07-15
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2014734-X
    ISSN 1099-4300 ; 1099-4300
    ISSN (online) 1099-4300
    ISSN 1099-4300
    DOI 10.3390/e23070901
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: A Simple Method to Quantify Outward Leakage of Medical Face Masks and Barrier Face Coverings: Implication for the Overall Filtration Efficiency.

    Chiera, Silvia / Cristoforetti, Alessandro / Benedetti, Luca / Nollo, Giandomenico / Borro, Luca / Mazzei, Lorenzo / Tessarolo, Francesco

    International journal of environmental research and public health

    2022  Volume 19, Issue 6

    Abstract: Face masking proved essential to reduce transmission of COVID-19 and other respiratory infections in indoor environments, but standards and literature do not provide simple quantitative methods for quantifying air leakage at the face seal. This study ... ...

    Abstract Face masking proved essential to reduce transmission of COVID-19 and other respiratory infections in indoor environments, but standards and literature do not provide simple quantitative methods for quantifying air leakage at the face seal. This study reports an original method to quantify outward leakage and how wearing style impacts on leaks and filtration efficiency. The amount of air leakage was evaluated on four medical masks and four barrier face coverings, exploiting a theoretical model and an instrumented dummy head in a range of airflows between 30 and 160 L/min. The fraction of air leaking at the face seal of the medical masks and barrier face coverings ranged from 43% to 95% of exhaled air at 30 L/min and reduced to 10-85% at 160 L/min. Filter breathability was the main driver affecting both leak fraction and total filtration efficiency that varied from 5% to 53% and from 15% to 84% at 30 and 160 L/min, respectively. Minor changes were related to wearing style, supporting indications on the correct mask use. The fraction of air leaking from medical masks and barrier face coverings during exhalation is relevant and varies according to design and wearing style. The use of highly breathable filter materials reduces air leaks and improve total filtration efficiency.
    MeSH term(s) COVID-19/prevention & control ; Filtration ; Humans ; Masks
    Language English
    Publishing date 2022-03-16
    Publishing country Switzerland
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2175195-X
    ISSN 1660-4601 ; 1661-7827
    ISSN (online) 1660-4601
    ISSN 1661-7827
    DOI 10.3390/ijerph19063548
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article: The role of air conditioning in the diffusion of Sars-CoV-2 in indoor environments: A first computational fluid dynamic model, based on investigations performed at the Vatican State Children's hospital

    Borro, Luca / Mazzei, Lorenzo / Raponi, Massimiliano / Piscitelli, Prisco / Miani, Alessandro / Secinaro, Aurelio

    Environmental research. 2021 Feb., v. 193

    2021  

    Abstract: About 15 million people worldwide were affected by the Sars-Cov-2 infection, which already caused 600,000 deaths. This virus is mainly transmitted through exhalations from the airways of infected persons, so that Heating, Ventilation and Air Conditioning ...

    Abstract About 15 million people worldwide were affected by the Sars-Cov-2 infection, which already caused 600,000 deaths. This virus is mainly transmitted through exhalations from the airways of infected persons, so that Heating, Ventilation and Air Conditioning (HVAC) systems might play a role in increasing or reducing the spreading of the infection in indoor environments.We modeled the role of HVAC systems in the diffusion of the contagion through Computational Fluid Dynamics (CFD) simulations of cough at the “Bambino Gesù” Vatican State Children's Hospital. Both waiting and hospital rooms were modeled as indoor scenarios. A specific Infection-Index (η) parameter was used to estimate the amount of contaminated air inhaled by each person present in the simulated indoor scenarios. The potential role of exhaust air ventilation systems placed above the coughing patient's mouth was also assessed.Our CFD-based simulations of the waiting room show that HVAC air-flow remarkably enhances infected droplets diffusion in the whole indoor environment within 25 s from the cough event, despite the observed dilution of saliva particles containing the virus. At the same time also their number is reduced due to removal through the HVAC system or deposition on the surfaces. The proper use of Local Exhaust Ventilation systems (LEV) simulated in the hospital room was associated to a complete reduction of infected droplets spreading from the patient's mouth in the first 0.5 s following the cough event. In the hospital room, the use of LEV system completely reduced the η index computed for the patient hospitalized at the bed next to the spreader, with a decreased possibility of contagion.CFD-based simulations for indoor environment can be useful to optimize air conditioning flow and to predict the contagion risk both in hospitals/ambulatories and in other public/private settings.
    Keywords Severe acute respiratory syndrome coronavirus 2 ; air ; air flow ; air pollution ; cough ; dynamic models ; heat ; hospitals ; mouth ; patients ; people ; research ; risk ; saliva ; viruses ; Vatican
    Language English
    Dates of publication 2021-02
    Publishing place Elsevier Inc.
    Document type Article
    Note NAL-AP-2-clean
    ZDB-ID 205699-9
    ISSN 1096-0953 ; 0013-9351
    ISSN (online) 1096-0953
    ISSN 0013-9351
    DOI 10.1016/j.envres.2020.110343
    Database NAL-Catalogue (AGRICOLA)

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  4. Article ; Online: The role of air conditioning in the diffusion of Sars-CoV-2 in indoor environments: A first computational fluid dynamic model, based on investigations performed at the Vatican State Children's hospital.

    Borro, Luca / Mazzei, Lorenzo / Raponi, Massimiliano / Piscitelli, Prisco / Miani, Alessandro / Secinaro, Aurelio

    Environmental research

    2020  Volume 193, Page(s) 110343

    Abstract: Background: About 15 million people worldwide were affected by the Sars-Cov-2 infection, which already caused 600,000 deaths. This virus is mainly transmitted through exhalations from the airways of infected persons, so that Heating, Ventilation and Air ...

    Abstract Background: About 15 million people worldwide were affected by the Sars-Cov-2 infection, which already caused 600,000 deaths. This virus is mainly transmitted through exhalations from the airways of infected persons, so that Heating, Ventilation and Air Conditioning (HVAC) systems might play a role in increasing or reducing the spreading of the infection in indoor environments.
    Methods: We modeled the role of HVAC systems in the diffusion of the contagion through Computational Fluid Dynamics (CFD) simulations of cough at the "Bambino Gesù" Vatican State Children's Hospital. Both waiting and hospital rooms were modeled as indoor scenarios. A specific Infection-Index (η) parameter was used to estimate the amount of contaminated air inhaled by each person present in the simulated indoor scenarios. The potential role of exhaust air ventilation systems placed above the coughing patient's mouth was also assessed.
    Results: Our CFD-based simulations of the waiting room show that HVAC air-flow remarkably enhances infected droplets diffusion in the whole indoor environment within 25 s from the cough event, despite the observed dilution of saliva particles containing the virus. At the same time also their number is reduced due to removal through the HVAC system or deposition on the surfaces. The proper use of Local Exhaust Ventilation systems (LEV) simulated in the hospital room was associated to a complete reduction of infected droplets spreading from the patient's mouth in the first 0.5 s following the cough event. In the hospital room, the use of LEV system completely reduced the η index computed for the patient hospitalized at the bed next to the spreader, with a decreased possibility of contagion.
    Conclusions: CFD-based simulations for indoor environment can be useful to optimize air conditioning flow and to predict the contagion risk both in hospitals/ambulatories and in other public/private settings.
    MeSH term(s) Air Conditioning ; Air Pollution, Indoor ; COVID-19 ; Child ; Hospitals ; Humans ; Hydrodynamics ; SARS-CoV-2 ; Ventilation
    Keywords covid19
    Language English
    Publishing date 2020-10-15
    Publishing country Netherlands
    Document type Journal Article
    ZDB-ID 205699-9
    ISSN 1096-0953 ; 0013-9351
    ISSN (online) 1096-0953
    ISSN 0013-9351
    DOI 10.1016/j.envres.2020.110343
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Uncertainty Quantification of Film Cooling Performance of an Industrial Gas Turbine Vane.

    Gamannossi, Andrea / Amerini, Alberto / Mazzei, Lorenzo / Bacci, Tommaso / Poggiali, Matteo / Andreini, Antonio

    Entropy (Basel, Switzerland)

    2019  Volume 22, Issue 1

    Abstract: Computational Fluid Dynamics (CFD) results are often presented in a deterministic way despite the uncertainties related to boundary conditions, numerical modelling, and discretization error. Uncertainty quantification is the field studying how these ... ...

    Abstract Computational Fluid Dynamics (CFD) results are often presented in a deterministic way despite the uncertainties related to boundary conditions, numerical modelling, and discretization error. Uncertainty quantification is the field studying how these phenomena affect the numerical result. With these methods, the results obtained are directly comparable with the experimental ones, for which the uncertainty related to the measurement is always shown. This work presents an uncertainty quantification approach applied to CFD: the test case consists of an industrial prismatic gas turbine vane with standard film cooling shaped holes system on the suction side only. The vane was subject of a previous experimental test campaign which had the objective to evaluate the film cooling effectiveness through pressure-sensitive paint technique. CFD analyses are conducted coherently with the experiments: the analogy between heat and mass transfer is adopted to draw out the adiabatic film effectiveness, solving an additional transport equation to track the concentration of CO
    Language English
    Publishing date 2019-12-22
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2014734-X
    ISSN 1099-4300 ; 1099-4300
    ISSN (online) 1099-4300
    ISSN 1099-4300
    DOI 10.3390/e22010016
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: The Role of Air Conditioning in the Diffusion of Sars-CoV-2 in Indoor Environments: a First Computational Fluid Dynamic Model, based on Investigations performed at the Vatican State Childrens Hospital.

    Borro, Luca / Mazzei, Lorenzo / Raponi, Massimiliano / Piscitelli, Prisco / Miani, Alessandro / Secinaro, Aurelio

    medRxiv

    Abstract: Background: About 15 million people worldwide were affected by the Sars-Cov-2 infection, which already caused 600,000 deaths. This virus is mainly transmitted through exhalations from the airways of infected persons, so that Heating, Ventilation and Air ... ...

    Abstract Background: About 15 million people worldwide were affected by the Sars-Cov-2 infection, which already caused 600,000 deaths. This virus is mainly transmitted through exhalations from the airways of infected persons, so that Heating, Ventilation and Air Conditioning (HVAC) systems might play a role in spreading the infection in indoor environments. Methods: We modelled the role of HVAC systems in the diffusion of the contagion through a Computational Fluid Dynamics (CFD) simulations of cough at the Vatican State childrens hospital Bambino Gesu. Both waiting rooms and hospital rooms were modeled as indoor scenarios. A specific Infection-Index parameter was used to estimate the amount of contaminated air inhaled by each person present in the simulated indoor scenarios. The potential role of exhaust air ventilation systems placed above the coughing patients mouth was also assessed. Results: Our CFD-based simulations show that HVAC air-flow remarkably enhance infected droplets diffusion in the whole indoor environment within 25 seconds from the cough event, despite the observed dilution of saliva particles containing the virus. In the waiting room simulation, Infection-Index parameter increases the faster the higher the HVAC airflow. Greater flows of air conditioning correspond to greater diffusion of the infected droplets. The proper use of Local Exhaust Ventilation systems (LEV) simulated in the hospital room was associated to a complete reduction of infected droplets spreading from the patient s mouth in the first 0.5 seconds following the cough event. In the hospital room, the use of LEV system completely reduced the index computed for the patient hospitalized at the bed next to the spreader, with a decreased possibility of contagion. Conclusions: CFD-based simulations for indoor environment can be useful to optimize air conditioning flow and to predict the contagion risk both in hospitals/ambulatories and in other public/private settings.
    Keywords covid19
    Language English
    Publishing date 2020-08-31
    Publisher Cold Spring Harbor Laboratory Press
    Document type Article ; Online
    DOI 10.1101/2020.08.25.20181420
    Database COVID19

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  7. Article ; Online: The Role of Air Conditioning in the Diffusion of Sars-CoV-2 in Indoor Environments

    Borro, Luca / Mazzei, Lorenzo / Raponi, Massimiliano / Piscitelli, Prisco / Miani, Alessandro / Secinaro, Aurelio

    Environmental Research

    a First Computational Fluid Dynamic Model, based on Investigations performed at the Vatican State Children’s Hospital

    2020  , Page(s) 110343

    Keywords Biochemistry ; General Environmental Science ; covid19
    Language English
    Publisher Elsevier BV
    Publishing country us
    Document type Article ; Online
    ZDB-ID 205699-9
    ISSN 1096-0953 ; 0013-9351
    ISSN (online) 1096-0953
    ISSN 0013-9351
    DOI 10.1016/j.envres.2020.110343
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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