Sviluppo di strumenti per l'ottimizzazione del progetto aerodinamico di turbomacchine assiali

La tesi propone un modello throughflow inverso da impiegare durante la fase assialsimmetrica del processo di progetto di una turbomacchina. Il modello risolve con tecnica time marching le equazioni meridiane di Eulero, nelle quali un campo di forza volumica normale alle superfici medie delle pale ("blade force") ne riproduce l'azione sul flusso. La geometria delle superfici è ricavata dalla condizione di tangenza, in accordo con la componente tangenziale della "blade force" imposta come dato di progetto. La distribuzione meridiana della blade force sulle regioni palettate del flowpath è definibile attraverso un processo di ottimizzazione inversa. Le equazioni di Eulero contengono anche altri termini destinati a riprodurre gli effetti del bloccaggio delle pale e delle perdite di profilo. La tesi affronta in particolare il problema delle alte deflessioni (pale di turbina), sia sotto l'aspetto fisico, individuando le più opportune condizioni al contorno da associare alle equazioni di Eulero, sia sotto l'aspetto numerico, introducendo uno schema upwind di tipo implicito per contrastare le instabilità che quelle condizioni comportano. Lo schema si rivela molto efficiente e robusto nel generare singole schiere di apertura infinita, non altrettanto se applicato a stadi di turbina completi. Per questa ragione, la tesi indaga anche la variante diretta del modello throughflow, che valuta la "blade force" (e perciò le prestazioni della macchina) a partire da un'assegnata geometria delle superfici medie. Pur con le sue limitazioni, il solutore inverso è ugualmente introdotto in ottimizzatori esistenti, allo scopo di illustrare alcuni esempi di ottimizzazione inversa per configurazioni fortemente defless

Two years of flight of the Pamela experiment: results and perspectives

PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range (protons: 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV-190 GeV), positrons (50 MeV-270 GeV) and search for antinuclei with a precision of the order of $10^{-8}$). The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June, $15^{th}$ 2006 in a $350\times 600 km$ orbit with an inclination of 70 degrees. In this work we describe the scientific objectives and the performance of PAMELA in its first two years of operation. Data on protons of trapped, secondary and galactic nature - as well as measurements of the December $13^{th}$ 2006 Solar Particle Event - are also provided.Comment: To appear on J. Phys. Soc. Jpn. as part of the proceedings of the International Workshop on Advances in Cosmic Ray Science March, 17-19, 2008 Waseda University, Shinjuku, Tokyo, Japa

Launch of the Space experiment PAMELA

PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range protons: 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV-190 GeV), positrons (50 MeV-270 GeV) and search for antimatter with a precision of the order of 10^-8). The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June, 15, 2006 in a 350*600 km orbit with an inclination of 70 degrees. The detector is composed of a series of scintillator counters arranged at the extremities of a permanent magnet spectrometer to provide charge, Time-of-Flight and rigidity information. Lepton/hadron identification is performed by a Silicon-Tungsten calorimeter and a Neutron detector placed at the bottom of the device. An Anticounter system is used offline to reject false triggers coming from the satellite. In self-trigger mode the Calorimeter, the neutron detector and a shower tail catcher are capable of an independent measure of the lepton component up to 2 TeV. In this work we describe the experiment, its scientific objectives and the performance in the first months after launch.Comment: Accepted for publication on Advances in Space Researc

Colorectal Cancer Stage at Diagnosis Before vs During the COVID-19 Pandemic in Italy

IMPORTANCE Delays in screening programs and the reluctance of patients to seek medical attention because of the outbreak of SARS-CoV-2 could be associated with the risk of more advanced colorectal cancers at diagnosis. OBJECTIVE To evaluate whether the SARS-CoV-2 pandemic was associated with more advanced oncologic stage and change in clinical presentation for patients with colorectal cancer. DESIGN, SETTING, AND PARTICIPANTS This retrospective, multicenter cohort study included all 17 938 adult patients who underwent surgery for colorectal cancer from March 1, 2020, to December 31, 2021 (pandemic period), and from January 1, 2018, to February 29, 2020 (prepandemic period), in 81 participating centers in Italy, including tertiary centers and community hospitals. Follow-up was 30 days from surgery. EXPOSURES Any type of surgical procedure for colorectal cancer, including explorative surgery, palliative procedures, and atypical or segmental resections. MAIN OUTCOMES AND MEASURES The primary outcome was advanced stage of colorectal cancer at diagnosis. Secondary outcomes were distant metastasis, T4 stage, aggressive biology (defined as cancer with at least 1 of the following characteristics: signet ring cells, mucinous tumor, budding, lymphovascular invasion, perineural invasion, and lymphangitis), stenotic lesion, emergency surgery, and palliative surgery. The independent association between the pandemic period and the outcomes was assessed using multivariate random-effects logistic regression, with hospital as the cluster variable. RESULTS A total of 17 938 patients (10 007 men [55.8%]; mean [SD] age, 70.6 [12.2] years) underwent surgery for colorectal cancer: 7796 (43.5%) during the pandemic period and 10 142 (56.5%) during the prepandemic period. Logistic regression indicated that the pandemic period was significantly associated with an increased rate of advanced-stage colorectal cancer (odds ratio [OR], 1.07; 95%CI, 1.01-1.13; P = .03), aggressive biology (OR, 1.32; 95%CI, 1.15-1.53; P < .001), and stenotic lesions (OR, 1.15; 95%CI, 1.01-1.31; P = .03). CONCLUSIONS AND RELEVANCE This cohort study suggests a significant association between the SARS-CoV-2 pandemic and the risk of a more advanced oncologic stage at diagnosis among patients undergoing surgery for colorectal cancer and might indicate a potential reduction of survival for these patients

The impact of surgical delay on resectability of colorectal cancer: An international prospective cohort study

AIM: The SARS-CoV-2 pandemic has provided a unique opportunity to explore the impact of surgical delays on cancer resectability. This study aimed to compare resectability for colorectal cancer patients undergoing delayed versus non-delayed surgery. METHODS: This was an international prospective cohort study of consecutive colorectal cancer patients with a decision for curative surgery (January-April 2020). Surgical delay was defined as an operation taking place more than 4 weeks after treatment decision, in a patient who did not receive neoadjuvant therapy. A subgroup analysis explored the effects of delay in elective patients only. The impact of longer delays was explored in a sensitivity analysis. The primary outcome was complete resection, defined as curative resection with an R0 margin. RESULTS: Overall, 5453 patients from 304 hospitals in 47 countries were included, of whom 6.6% (358/5453) did not receive their planned operation. Of the 4304 operated patients without neoadjuvant therapy, 40.5% (1744/4304) were delayed beyond 4 weeks. Delayed patients were more likely to be older, men, more comorbid, have higher body mass index and have rectal cancer and early stage disease. Delayed patients had higher unadjusted rates of complete resection (93.7% vs. 91.9%, P = 0.032) and lower rates of emergency surgery (4.5% vs. 22.5%, P < 0.001). After adjustment, delay was not associated with a lower rate of complete resection (OR 1.18, 95% CI 0.90-1.55, P = 0.224), which was consistent in elective patients only (OR 0.94, 95% CI 0.69-1.27, P = 0.672). Longer delays were not associated with poorer outcomes. CONCLUSION: One in 15 colorectal cancer patients did not receive their planned operation during the first wave of COVID-19. Surgical delay did not appear to compromise resectability, raising the hypothesis that any reduction in long-term survival attributable to delays is likely to be due to micro-metastatic disease

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic

An actuator disk model of incidence and deviation for RANS-based throughflow analysis

Reynolds-averaged Navier-Stokes (RANS) equations with blade blockage and blade force source terms are solved in the meridional plane of complete axial flow turbomachinery using a finite-volume scheme. The equations of the compressible actuator disk (AD) are introduced to modify the evaluation of the convective fluxes at the leading and trailing edges (LEs and TEs). An AD behaves as a compact blade force which instantaneously turns the flow with no production of unphysical entropy. This avoids unphysical incidence loss across the LE discontinuity and allows for application of all of the desired deviation at the TE. Unlike previous treatments, the model needs no handmade modification of the throughflow (TF) surface and does not discriminate between inviscid and viscous meridional flows, which allows for coping with strong incidence gradients through the annulus wall boundary layers and with secondary deviation. This paper derives a generalized blade force term that includes the contribution of the LE and TE ADs in the divergence form of the TF equations and leads to generalized definitions of blade load, blade thrust, shaft torque, and shaft power. In analyzing a linear flat plate cascade with an incidence of 32 deg and a deviation of 21 deg, the proposed model provided a 105 reduction of unphysical total pressure loss compared to the numerical solution with no modeling. The computed mass flow rate, blade load, and blade thrust showed excellent agreement with the theoretical values. The complete RANS TF solver was used to analyze a four-stage turbine in design and off-design conditions with a spanwise-averaged incidence of up to 2 deg and 43 deg, respectively. Compared to a traditional streamline curvature solution, the RANS solution with incidence and deviation modeling provided a 0.1 to 0.7% accurate prediction of mass flow rate, shaft power, total pressure ratio, and adiabatic efficiency in both the operating conditions. It also stressed satisfactory agreement concerning the spanwise distributions of flow angle and Mach number at LEs and TEs. In particular, secondary deviation was effectively predicted. The RANS solution with no modeling showed acceptable performance prediction only in design conditions and could introduce no deviation

Euler-based throughflow method for inverse design and optimization of turbomachinery blades

An inviscid model for complete axial flow turbomachinery is adopted, which replaces the blades with throughflow surfaces. The main effects of the real blades on the flow are modelled by blade forces. The inverse method predicts the axisymmetric flow field and throughflow surface geometry for a specified distribution of azimuthal inviscid force. This quantity drives the meridional distribution of rotor shaft power. Euler equations are solved by an implicit upwind finite-volume scheme. The time-marching computation includes an evolutionary equation for each throughflow surface, which is solved by implicit finite differences. Standard optimisation algorithms are used to find distributions of azimuthal force that minimise some sample cost functions. The optimal blade shapes are given by the corresponding geometrical solutions of the inverse problem. Since the cost function evaluation is reduced to an inviscid two-dimensional computation, the entire process is significantly less time-consuming than those based on three-dimensional CFD solver