On the Effect of an Aggressive Inlet Swirl Profile on the Aero-thermal Performance of a Cooled Vane

AbstractA high-pressure vane equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side while the leading edge is protected by a showerhead system. Steady three-dimensional Reynolds-Averaged Navier-Stokes (RANS) simulations have been performed. A preliminary grid sensitivity analysis has been performed (with uniform inlet flow) to quantify the effect of the spatial resolution. Turbulence model has been assessed in comparison with available experiment data. The effects of a realistic inlet swirl on the aero-thermal performance of the cooling system are then investigated by means of comparison between two different kinds of simulations. The first one using a uniform inlet flow while the second one with aggressive swirl derived from the EU-funded project TATEF2. Clocking effects are also accounted for. The effect of the swirling flow in determining the coolant transport are investigated, evidencing the key role that these phenomena have in determining the effectiveness of the cooling

Film Cooling Performance in a Transonic High-pressure Vane: Decoupled Simulation and Conjugate Heat Transfer Analysis☆

Abstract The continuous demand for increased performance and reliability of gas turbines leads to the improvement of prediction tools. Having regard to the effects of heat transfer on the residual life of gas turbine components, it is necessary to achieve a high level of accuracy in the evaluation of thermal loads. Computational fluid dynamics is able to provide reliable data in a limited lapse of time. In this paper, the numerical analysis of the cooled vane of the MT1 high-pressure turbine stage is presented. A grid dependence analysis based on the evaluation of the aero-thermal characteristics of the vane has been performed. Turbulence is modeled using the kT-kL-ω method whose performance in this kind of configuration is rarely debated in the scientific literature. Model parameters have been tuned to match the experimental data. The final objective of the present activity is to assess the capability of numerical methods to deal with an annular, transonic high-pressure vane with a realistic film cooling configuration. Adiabatic effectiveness, heat transfer coefficient and net heat flux reduction distributions have been evaluated, the latter providing relevant information on the performance of the cooling system. The coupled fluid-solid simulation of the cooled configuration has also been performed to evaluate the impact of conjugate heat transfer on the prediction of thermal loads. Results show a non-negligible difference in the wall temperature evaluation between the decoupled and the coupled approach, mainly caused by the heat conduction in the solid

Effects of realistic inflow conditions on the aero-thermal performance of a film-cooled vane

A high-pressure vane equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side while the leading edge is protected by a showerhead system of cylindrical holes. Steady three-dimensional Reynolds-Averaged Navier-Stokes simulations have been performed. A preliminary grid sensitivity analysis has been performed with uniform inlet flow to quantify the effect of the spatial resolution. Turbulence model has been assessed in comparison with available experimental data. The effects of a realistic inflow condition on the thermal behaviour of the cooled vane are then investigated by means of comparison between two conjugate heat transfer simulations. The first one is characterized by a uniform inlet flow while the second one presents a temperature distortion and a superimposed aggressive swirl derived from the EU- funded TATEF2 project. The effect of the swirling flow in determining the metal temperature distribution is investigated with particular attention to the consequences on the operation of the film cooling system

Stabilization of Arthrospira platensis with high-pressure processing and thermal treatments: Effect on physico-chemical and microbiological quality

Arthrospira platensis (Spirulina) is a cyanobacterium that has been recently studied for food applications due to its high biological and nutritional value. When A. platensis is used as an ingredient in food applications, proper treatments have to be applied in order to reduce microbial contamination. This work compared the effect of thermal treatments (sterilization at 121℃ and pasteurization at 90℃) and high-pressure processing (400, 600 MPa) on the chemical, physico-chemical, and microbial quality of 5% (wt/vol) A. platensis aqueous suspensions. Total antioxidant capacity, total polyphenols content, color, and pigments content were not strongly lowered/modified by the high-pressure processing (HPP) treatments. HPP at 400 MPa even improved the release of C-phycocyanin from the biomass because of the breakage of cell walls. HPP treatments were comparable to pasteurization in reducing yeasts, coliforms, Staphylococci, and total bacterial count. Conversely, sterilization was the only treatment that guaranteed the inactivation of spore-forming species but affecting the final quality. Novelty impact statement: High-pressure processing (HPP) treatments were found to be a good strategy to preserve or even improve some physical and chemical properties of Arthrospira platensis (Spirulina), in particular antioxidant capacity, polyphenols, color, and pigments content. Furthermore, HPP treatments were comparable to pasteurization in reducing microbial cell count, while sterilization was the only treatment able to ensure the inhibition of spore-forming species

A cost-effectiveness analysis of E/C/F/TAF vs three boosted regimens in the Italian context

BACKGROUND: Highly Active Antiretroviral Therapy (HAART) has transformed HIV into a lifelong condition. Following the chronicity of the disease, and significant increase in lifespan – the prevalence of comorbidities increased in HIV+ subjects that are exposed both to a higher risk of developing cardiovascular disease, renal disease, osteopenia/osteoporosis and diabetes, and to the risk of developing them early. Elvitegravir/Cobicistat/Emtricitabine/Tenofovir Alafenamide Fumarate (E/C/F/TAF), a complete, Single-Tablet antiretroviral Regimen (STR) that combines the effectiveness and tolerability of integrase inhibitors with an innovative backbone was recently introduced in Italy. Compared to Tenofovir Disoproxil Fumarate (TDF), TAF reaches the sites of action more efficiently, reducing tenofovir plasma concentration to more than 90% and the risk of off-target effects.OBJECTIVE: A patient-level micro-simulation model was adapted to the Italian context to evaluate E/C/F/TAF cost-effectiveness vs three boosted regimens for HIV+ patients treatment.METHODS: A Markov micro-simulation model was adapted to the Italian context for the evaluation of the cost-effectiveness in patients with HIV. The total cost per patient accounts for drug therapies and the management of adverse events and comorbidities. The quality-adjusted life expectancy (in QALYs) is calculated by weighing the years of life lived by the utility weights. A 70-year time horizon was adopted to simulate a lifetime analysis; shorter time horizons were considered in the sensitivity analyses. 3.5% discount rate was applied both for costs and future benefits. The rate of virologic suppression at 48 weeks with E/C/F/TAF is 92.3%; for the other treatments such proportion is calculated by applying to the reference rate the relative risks, as calculated in a recent network meta-analysis (NMA). Alternative treatments considered in this analysis are three boosted regimens commonly used in Italy: tenofovir disoproxil fumarate/emtricitabine/elvitegravir/cobicistat in STR; tenofovir disoproxil fumarate/emtricitabine + darunavir/ritonavir; tenofovir disoproxil fumarate/emtricitabine + atazanavir/ritonavir.RESULTS: E/C/F/TAF improves survival and quality of life (20.17 LY and 14.89 QALY), with the lowest total cost (€ 280,528), thus resulting dominant over three comparators considered as starting therapy. The sensitivity analysis confirms the results of the base case: at a willingness-to-pay threshold of € 30,000 per QALY, the E/C/F/TAF strategy is the most cost-effective, with a 90% probability and it is the most cost-effective even with a threshold of € 10,000 per QALY, with a 50% probability.CONCLUSION: E/C/F/TAF can be a sustainable alternative to currently available treatments, combining the advantage of the STR to lower risks of kidney and bone damage than observed in regimens based on TDF

A case-driven hypothesis for multi-stage crack growth mechanism in fourth-generation ceramic head fracture

Background Ceramic bearings are used in total hip arthroplasty due to their excellent wear behaviour and biocompatibility. The major concern related to their use is material brittleness, which significantly impacts on the risk of fracture of ceramic components. Fracture toughness improvement has contributed to the decrease in fracture rate, at least of the prosthetic head. However, the root cause behind these rare events is not fully understood. This study evaluated head fracture occurrence in a sizeable cohort of patients with fourth-generation ceramic-on-ceramic implants and described the circumstances reported by patients in the rare cases of head fracture. Methods The clinical survivorship of 29,495 hip prostheses, with fourth-generation ceramic bearings, was determined using data from a joint replacement registry. The average follow-up period was 5.2 years (range 0.1-15.6). Retrieval analysis was performed in one case for which the ceramic components were available. Results Clinical outcomes confirmed the extremely low fracture rate of fourth-generation ceramic heads: only two out of 29,495 heads fractured. The two fractures, both involving 36 mm heads, occurred without a concurrent or previous remarkable trauma. Considering the feature of the fractured head, a multi-stage crack growth mechanism has been hypothesized to occur following damage at the head-neck taper interface. Conclusions Surgeons must continue to pay attention to the assembly of the femoral head: achieving a proper head seating on a clean taper is a prerequisite to decrease the risk of occurrence of any damage process within head-neck junction, which may cause high stress concentration at the contact surface, promoting crack nucleation and propagation even in toughened ceramics

Numerical Prediction of Cavitation Inception in Centrifugal Impellers

Cavitation is a fundamental issue in pump design since it yields significant decrease of performances and pump life, damaging impeller surfaces and triggering harmful flow instabilities. This topic is usually addressed through costly experimental tests. The aim of this paper is to assess numerical methodologies for the correct evaluation and prediction of the cavitation inception in centrifugal impellers during the design phase. Preliminary analyses were performed to individuate the most promising approach by using two cavitation models on a 2D test case representing the NACA 0009 hydrofoil. Then, two CFD approaches were considered for the evaluation of the NPSHr in actual pumps. RANS two-phase calculations including the selected cavitation model were performed on a geometry provided by WEIR Gabbioneta srl. Monophase simulations have been performed as well and an in-house heuristic model has been proposed to evaluate the NPSHr curve from a non cavitating pressure field. The heuristic post-processor has been tuned using both the two-phase and the monophase data, and validated using the available experimental values provided by WEIR Gabbioneta srl

Transcriptome profiling of two olive cultivars in response to infection by the CoDiRO strain of Xylella fastidiosa subsp. pauca

Background: The recent Xylella fastidiosa subsp. pauca (Xfp) outbreak in olive (Olea europaea) groves in southern Italy is causing a destructive disease denoted Olive Quick Decline Syndrome (OQDS). Field observations disclosed that Xfp-infected plants of cv. Leccino show much milder symptoms, than the more widely grown and highly susceptible cv. Ogliarola salentina. To determine whether these field observations underlie a tolerant condition of cv. Leccino, which could be exploited for lessening the economic impact of the disease on the local olive industry, transcriptional changes occurring in plants of the two cultivars affected by Xfp were investigated. Results: A global quantitative transcriptome profiling comparing susceptible (Ogliarola salentina) and tolerant (Leccino) olive cultivars, infected or not by Xfp, was done on messenger RNA (mRNAs) extracted from xylem tissues. The study revealed that 659 and 447 genes were differentially regulated in cvs Leccino and Ogliarola upon Xfp infection, respectively, whereas 512 genes were altered when the transcriptome of both infected cultivars was compared. Analysis of these differentially expressed genes (DEGs) shows that the presence of Xfp is perceived by the plants of both cultivars, in which it triggers a differential response strongly involving the cell wall. Up-regulation of genes encoding receptor-like kinases (RLK) and receptor-like proteins (RLP) is the predominant response of cv. Leccino, which is missing in cv. Ogliarola salentina. Moreover, both cultivars react with a strong re-modelling of cell wall proteins. These data suggest that Xfp elicits a different transcriptome response in the two cultivars, which determines a lower pathogen concentration in cv. Leccino and indicates that this cultivar may harbor genetic constituents and/or regulatory elements which counteract Xfp infection. Conclusions: Collectively these findings suggest that cv. Leccino is endowed with an intrinsic tolerance to Xfp, which makes it eligible for further studies aiming at investigating molecular basis and pathways modulating its different defense response

Distribution Drivers of the Alien Butterfly Geranium Bronze (Cacyreus marshalli) in an Alpine Protected Area and Indications for an Effective Management

Cacyreus marshalli is the only alien butterfly in Europe. It has recently spread in the Gran Paradiso National Park (GPNP), where it could potentially compete with native geranium-consuming butterflies. Our study aimed to (1) assess the main drivers of its distribution, (2) evaluate the potential species distribution in GPNP and (3) predict different scenarios to understand the impact of climate warming and the effect of possible mitigations. Considering different sampling designs (opportunistic and standardised) and different statistical approaches (MaxEnt and N-mixture models), we built up models predicting habitat suitability and egg abundance for the alien species, testing covariates as bioclimatic variables, food plant (Pelargonium spp.) distribution and land cover. A standardised approach resulted in more informative data collection due to the survey design adopted. Opportunistic data could be potentially informative but a major investment in citizen science projects would be needed. Both approaches showed that C. marshalli is associated with its host plant distribution and therefore confined in urban areas. Its expansion is controlled by cold temperatures which, even if the host plant is abundant, constrain the number of eggs. Rising temperatures could lead to an increase in the number of eggs laid, but the halving of Pelargonium spp. populations would mostly mitigate the trend, with a slight countertrend at high elevations