Application of Uncertainty Quantification techniques to CFD simulation of twin entry radial turbines

L'argomento principale della tesi \ue8 l'applicazione delle tecniche di quantificazione dell'incertezza (UQ) alla simulazione numerica (CFD) di turbine radiali twin entry impiegate nella turbosovralimentazione automobilistica. Lo studio approfondito di questo tipo di turbomacchine \ue8 affrontato nel capitolo 3, finalizzato alla comprensione dei principali parametri che caratterizzano e influenzano le prestazioni fluidodinamiche delle turbine twin scroll. Il capitolo 4 tratta di una piattaforma per l'analisi UQ sviluppata internamente tramite il set di strumenti open source \u2018Dakota\u2019. La piattaforma \ue8 stata testata dapprima su un caso di interesse industriale, ovvero un ugello de Laval supersonico (capitolo 5); l'analisi ha evidenziato l'utilizzo pratico delle tecniche di quantificazione dell'incertezza nella previsione delle prestazioni di un ugello affetto da condizioni di fuori progetto con complessit\ue0 fluidodinamica dovuta alla forte non linearit\ue0. L'esperienza maturata con l'approccio UQ ha agevolato l'identificazione di metodi idonei per applicare la propagazione dell\u2019incertezza alla simulazione CFD di turbine radiali twin scroll (capitolo 6). In tal caso sono state studiate e messe in pratica diverse tecniche di quantificazione dell'incertezza al fine di acquisire un'esperienza approfondita sull\u2019attuale stato dell'arte. Il confronto dei risultati ottenuti dai diversi approcci e la discussione dei pro e dei contro relativi a ciascuna tecnica hanno portato a conclusioni interessanti, che vengono proposte come linee guida per future applicazioni di quantificazione dell\u2019incertezza alla simulazione CFD delle turbine radiali. L'integrazione di modelli e metodologie UQ, oggi utilizzati solo da alcuni centri di ricerca accademica, con solutori CFD commerciali consolidati ha permesso di raggiungere l'obiettivo finale della tesi di dottorato: dimostrare all'industria l'elevato potenziale delle tecniche UQ nel migliorare, attraverso distribuzioni di probabilit\ue0, la previsione delle prestazioni relative ad un componente soggetto a diverse fonti di incertezza. Lo scopo dell\u2019attivit\ue0 di ricerca consiste pertanto nel fornire ai progettisti dati prestazionali associati a margini di incertezza che consentano di correlare meglio simulazione e applicazione reale. Per accordi di riservatezza, i parametri geometrici relativi alla turbina twin entry in oggetto sono forniti adimensionali, i dati sensibili sugli assi dei grafici sono stati omessi e nelle figure si \ue8 reso necessario eliminare le legende dei contours ed ogni eventuale riferimento dimensionale.The main topic of the thesis is the application of uncertainty quantification (UQ) techniques to the numerical simulation (CFD) of twin entry radial turbines used in automotive turbocharging. The detailed study of this type of turbomachinery is addressed in chapter 3, aimed at understanding the main parameters which characterize and influence the fluid dynamic performance of twin scroll turbines. Chapter 4 deals with the development of an in-house platform for UQ analysis through \u2018Dakota\u2019 open source toolset. The platform was first tested on a test case of industrial interest, i.e. a supersonic de Laval nozzle (chapter 5); the analysis highlighted the practical use of uncertainty quantification techniques in predicting the performance of a nozzle affected by off-design conditions with fluid dynamic complexity due to strong non-linearity. The experience gained with the UQ approach facilitated the identification of suitable methods for applying the uncertainty propagation to the CFD simulation of twin entry radial turbines (chapter 6). In this case different uncertainty quantification techniques have been investigated and put into practice in order to acquire in-depth experience on the current state of the art. The comparison of the results coming from the different approaches and the discussion of the pros and cons related to each technique led to interesting conclusions, which are proposed as guidelines for future uncertainty quantification applications to the CFD simulation of radial turbines. The integration of UQ models and methodologies, today used only by some academic research centers, with well established commercial CFD solvers allowed to achieve the final goal of the doctoral thesis: to demonstrate to industry the high potential of UQ techniques in improving, through probability distributions, the prediction of the performance relating to a component subject to different sources of uncertainty. The purpose of the research activity is therefore to provide designers with performance data associated with margins of uncertainty that allow to better correlate simulation and real application. Due to confidentiality agreements, geometrical parameters concerning the studied twin entry radial turbine are provided dimensionless, confidential data on axes of graphs are omitted and legends of the contours as well as any dimensional reference have been shadowed

Numerical Simulation of the Performance of a Twin Scroll Radial Turbine at Different Operating Conditions

Twin scroll radial turbines are increasingly used for turbocharging applications, to take advantage of the pulsating exhaust gases. In spite of its relevance in turbocharging techniques, scientific literature about CFD applied to twin scroll turbines is limited, especially in case of partial admission. In the present paper a CFD complete model of a twin scroll radial turbine is developed in order to give a contribution to literature in understanding the capabilities of current industrial CFD approaches applied to these difficult cases and to develop performance index that can be used for turbine design optimization purposes. The flow solution is obtained by means of ANSYS CFX \uae in a wide range of operating conditions in full and partial admission cases. The total-to-static efficiency and the mass flow parameter (MFP) have been calculated and compared with the experimental database in order to validate the numerical model. The purpose of the developed procedure is also to generate a database for twin scroll turbines useful for future applications. A comparison between performances obtained in different admission conditions was performed. In particular the analysis focused on the characterization of the flow at volute outlet/rotor inlet section. A flow distortion index at rotor inlet was introduced to correlate the turbine performance and the flow nonuniformities generated by the volute. Finally the influence of the backside cavity on the performance parameters is also discussed. The introduction of these new nonuniformity indices is proposed for volute design and optimization procedures

The new "Welding Machine" for the DUs integration in the KM3NeT experiment: Mechanical and Pneumatic parts

This note describes one of the tools used during Process-1 of the integration of the Detection Units (DUs) in the KM3NeT experiment. In particular, the device is designed to seal the Break-out-box (BOB). The BOB is a box interface between a Digital Optical Module (DOM) and the electro-optical cable (VEOC) for power and optical connection of each optical module (DOM) to the DU. The original manual version of the tool developed by NIKHEF was then automatized by INFN-LNS in order to guarantee a reproducible operation in the recursive process of the DU integration and two samples have been realized for the integration sites at LNS and Genova respectively

Reduction of Bacterial Proliferation by Zirconium Collar in Dental Implants

The peri-implant bacterial colonization is one of the current major problems facing dental implants with no actual protocols for prevention. The use of zirconium for bacterial eradication has already been reported and discussed in the dental literature. In this study we evaluated for the first time the ability of a "hybrid" dental implant model \u2013 where the implant collar is made out of titanium and zirconium - to reduce the peri-implant bacterial colonization, using traditional implants from the same manufacturer as controls. The results of microbiological analysis and the evaluation of the classic parameters of an implant success confirmed that, in all the 30 patients in this study, the zirconium collar had a vital role in reducing peri-implant bacterial colonization, and that the "hybrid" implants show lower plaque index values, less bleeding and less marginal bone loss than the traditional implants. Our data therefore suggest that a zirconium collar can effectively reduce the bacterial colonization around a titanium implant favoring a better long-term prognosis

The High Voltage Regulator Board for the BDX Experiment

In this note we describe the design and construction of SiPM High Voltage (HV) Regulator board for the BDX experiment. The board is used to provide bias voltage to the Silicon PhotoMultipliers (SiPMs) used in the BDX detector. It hosts four independent channels, each with a selectable output voltage in the range 37 V to 80 V: each channel is individually regulated by means of a variable resistor. In the note, after a brief introduction to the BDX experiment, we present the design of the board, discussing in particular the critical aspects that we identified during the circuit implementation phase. We also show the results obtained from the characterization of a first sample of 10 boards

Long-term home ventilation of children in Italy: A national survey.

BACKGROUND: Improved technology, as well as professional and parental awareness, enable many ventilator-dependent children to live at home. However, the profile of this growing population, the quality and adequacy of home care, and patients' needs still require thorough assessment. OBJECTIVES: To define the characteristics of Italian children receiving long-term home mechanical ventilation (HMV) in Italy. METHODS: A detailed questionnaire was sent to 302 National Health Service hospitals potentially involved in the care of HVM in children (aged <17 years). Information was collected on patient characteristics, type of ventilation, and home respiratory care. RESULTS: A total of 362 HMV children was identified. The prevalence was 4.2 per 100,000 (95% CI: 3.8-4.6), median age was 8 years (interquartile range 4-14), median age at starting mechanical ventilation was 4 years (1-11), and 56% were male. The most frequent diagnostic categories were neuromuscular disorders (49%), lung and upper respiratory tract diseases (18%), hypoxic (ischemic) encephalopathy (13%), and abnormal ventilation control (12%). Medical professionals with nurses (for 62% of children) and physiotherapists (20%) participated in the patients' discharge from hospital, though parents were the primary care giver, and in 47% of cases, the sole care giver. Invasive ventilation was used in 41% and was significantly related to young age, southern regional residence, longer time spent under mechanical ventilation, neuromuscular disorders, or hypoxic (ischemic) encephalopathy. CONCLUSIONS: Care and technical assistance of long-term HMV children need assessment, planning, and resources. A wide variability in pattern of HMV was found throughout Italy. An Italian national ventilation program, as well as a national registry, could be useful in improving the care of these often critically ill children