Boundary conditions and SGS models for LES of wall-bounded separated flows: an application to engine-like geometries

The implementation and the combination of advanced boundary conditions and subgrid scale models for Large Eddy Simulations are presented. The goal is to perform reliable cold flow LES simulations in complex geometries, such as in the cylinders of internal combustion engines. The implementation of an inlet boundary condition for synthetic turbulence generation and of two subgrid scale models, the local Dynamic Smagorinsky and the Wall-Adapting Local Eddy-viscosity SGS model (WALE) is described. The WALE model is based on the square of the velocity gradient tensor and it accounts for the effects of both the strain and the rotation rate of the smallest resolved turbulent fluctuations and it recovers the proper y(3) near-wall scaling for the eddy viscosity without requiring dynamic pressure; hence, it is supposed to be a very reliable model for ICE simulation. Model validation has been performed separately on two steady state flow benches: a backward facing step geometry and a simple IC engine geometry with one axed central valve. A discussion on the completeness of the LES simulation (i.e. LES simulation quality) is given

GPU-accelerated Linear Algebra for Coupled Solvers in Industrial CFD Applications with OpenFOAM

The present work describes the development of heterogeneous GPGPU implicit CFD coupled solvers, encompassing both density- and pressure- based approaches. In this setup, the assembled linear matrix is offloaded onto multiple GPUs using specialized external libraries to solve the linear problem efficiently. These coupled solvers are applied to two industrial test cases representing common scenarios: the NASA CRM in a transonic regime and the external aerodynamics study of the DriveAER car. Significant performance enhancements are evident when compared to their CPU counterparts. Specifically, the NASA CRM case achieves an overall speedup of more than 4x, while the DriveAER test case demonstrates improved stability and reduced computational time compared to segregated solvers. All calculations were carried out utilizing the GPU-based partition of the davinci-1 supercomputer at the Leonardo Labs, featuring 82 GPU-accelerated nodes

VOF Simulation of The Cavitating Flow in High Pressure GDI Injectors

[EN] The paper describes the development in the OpenFOAM® technology of a dynamic multiphase Volume-of-Fluid (VoF) solver, supporting mesh handling with topological changes, that has been used for the study of the physics of the primary jet breakup and of the flow disturbance induced by the nozzle geometry during the injector opening event in high-pressure Gasoline Direct Injection (GDI) engines. Turbulence modeling based on a scale-resolving approach has been applied, while phase change of fuel is accounted by means of a cavitation model that has been coupled with the VOF solver. Simulations have been carried out on a 6-hole prototype injector, especially developed for investigations in the framework of the collaborative project FUI MAGIE and provided by Continental Automotive SAS. Special attention has been paid to the domain decomposition strategy and to the code development of the solver, to ensure good load balancing and to minimize inter-processor communication, to achieve good performance and also high scalability on large computing clusters.Giussani, F.; Montorfano, A.; Piscaglia, F.; Onorati, A.; Helie, J. (2017). VOF Simulation of The Cavitating Flow in High Pressure GDI Injectors. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 1009-1018. https://doi.org/10.4995/ILASS2017.2017.4989OCS1009101

Imaging of Liver Tumors in Patients with Chronic Liver Disease

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A three-phase VOF solver for the simulation of in-nozzle cavitation effects on liquid atomization

The development of a single-fluid solver supporting phase-change and able to capture the evolution of three fluids, two of which are miscible, into the sharp interface capturing Volume of Fluid (VOF) approximation, is presented. The transport of each phase-fraction is solved independently by a flux-corrected transport method to ensure the boundedness of the void fraction over the domain. The closure of the system of equations is achieved by a cavitation model, that handles the phase change between the liquid and the fuel vapor and it also accounts for the interaction with the non-condensable gases. Boundedness and conservativeness of the solver in the transport of the volume fraction are verified on two numerical benchmarks: a two-dimensional bubble rising in a liquid column and a cavitating/condensing liquid column. Finally, numerical predictions from large-eddy simulations are compared against experimental results available from literature; in particular, validation against high-speed camera visualizations and Laser Doppler Velocimetry (LDV) measurements of cavitating microscopic in-nozzle flows in a fuel injector is reported

Circulating hematopoietic stem cells and putative intestinal stem cells in coeliac disease

Background: The intestinal stem cells (ISC) modulation and the role of circulating hematopoietic stem cells (HSC) in coeliac disease (CD) are poorly understood. Our aim was to investigate the longitudinal modifications in peripheral blood HSC traffic and putative ISC density induced by gluten-free diet (GFD) in CD. Methods: Thirty-one CD patients and 7 controls were enrolled. Circulating CD133+ and CD34+ HSC were measured by flow cytometry, at enrolment and after 7 days and 1, 3, 6, 12, and 24 months of GFD. Endoscopy was performed at diagnosis and repeated at 6, 12, and 24 months following GFD. We used the Marsh-Oberhuber score to evaluate the histological severity of duodenal damage; immunohistochemistry was employed to measure the intraepithelial lymphoid infiltrate (IEL, CD3+ lymphoid cells) and the putative ISC compartment (CD133+ and Lgr5+ epithelial cells). Results: At enrolment, circulating HSCs were significantly increased in CD patients and they further augmented during the first week of GFD, but progressively decreased afterwards. CD patients presented with villous atrophy, abundant IEL and rare ISC residing at the crypt base. Upon GFD, IEL progressively decreased, while ISC density increased, peaking at 12 months. After 24 months of GFD, all patients were asymptomatic and their duodenal mucosa was macroscopically and histologically normal. Conclusions: In active CD patients, the ISC niche is depleted and there is an increased traffic of circulating HSC versus non-coeliac subjects. GFD induces a precocious mobilization of circulating HSC, which is followed by the expansion of the local ISC compartment, leading to mucosal healing and clinical remission

Real-Life Clinical Data of Cabozantinib for Unresectable Hepatocellular Carcinoma

Introduction: Cabozantinib has been approved by the European Medicine Agency (EMA) for hepatocellular carcinoma (HCC) previously treated with sorafenib. Cabozantinib is also being tested in combination with immune checkpoint inhibitors in the frontline setting. Real-life clinical data of cabozantinib for HCC are still lacking. Moreover, the prognostic factors for HCC treated with cabozantinib have not been investigated. Methods: We evaluated clinical data and outcome of HCC patients who received cabozantinib in the legal context of named patient use in Italy. Results: Ninety-six patients from 15 centres received cabozantinib. All patients had preserved liver function (Child-Pugh A), mostly with an advanced HCC (77.1%) in a third-line setting (75.0%). The prevalence of performance status (PS) > 0, macrovascular invasion (MVI), extrahepatic spread, and alpha-fetoprotein (AFP) >400 ng/mL was 50.0, 30.2, 67.7, and 44.8%, respectively. Median overall survival (OS) and progression-free survival were 12.1 (95% confidence interval 9.4-14.8) and 5.1 (3.3-6.9) months, respectively. Most common treatment-related adverse events (AEs) were fatigue (67.7%), diarrhoea (54.2%), anorexia (45.8%), HFSR (43.8%), weight loss (24.0%), and hypertension (24.0%). Most common treatment-related Grade 3-4 AEs were fatigue (6.3%), HFSR (6.3%), and increased aminotransferases (6.3%). MVI, ECOG-PS > 0, and AFP >400 ng/mL predicted a worse OS. Discontinuation for intolerance and no new extrahepatic lesions at the progression were associated with better outcomes. Conclusions: In a real-life Western scenario (mostly in a third-line setting), cabozantinib efficacy and safety data were comparable with those reported in its registration trial. Data regarding the prognostic factors might help in patient selection and design of clinical trials

Real-Life Clinical Data of Cabozantinib for Unresectable Hepatocellular Carcinoma

Introduction: Cabozantinib has been approved by the European Medicine Agency (EMA) for hepatocellular carcinoma (HCC) previously treated with sorafenib. Cabozantinib is also being tested in combination with immune checkpoint inhibitors in the frontline setting. Real-life clinical data of cabozantinib for HCC are still lacking. Moreover, the prognostic factors for HCC treated with cabozantinib have not been investigated. Methods: We evaluated clinical data and outcome of HCC patients who received cabozantinib in the legal context of named patient use in Italy. Results: Ninety-six patients from 15 centres received cabozantinib. All patients had preserved liver function (Child-Pugh A), mostly with an advanced HCC (77.1%) in a third-line setting (75.0%). The prevalence of performance status (PS) > 0, macrovascular invasion (MVI), extrahepatic spread, and alpha-fetoprotein (AFP) >400 ng/mL was 50.0, 30.2, 67.7, and 44.8%, respectively. Median overall survival (OS) and progression-free survival were 12.1 (95% confidence interval 9.4–14.8) and 5.1 (3.3–6.9) months, respectively. Most common treatment-related adverse events (AEs) were fatigue (67.7%), diarrhoea (54.2%), anorexia (45.8%), HFSR (43.8%), weight loss (24.0%), and hypertension (24.0%). Most common treatment-related Grade 3–4 AEs were fatigue (6.3%), HFSR (6.3%), and increased aminotransferases (6.3%). MVI, ECOG-PS > 0, and AFP >400 ng/mL predicted a worse OS. Discontinuation for intolerance and no new extrahepatic lesions at the progression were associated with better outcomes. Conclusions: In a real-life Western scenario (mostly in a third-line setting), cabozantinib efficacy and safety data were comparable with those reported in its registration trial. Data regarding the prognostic factors might help in patient selection and design of clinical trials

Adverse Events as Potential Predictive Factors of Activity in Patients with Advanced HCC Treated with Atezolizumab Plus Bevacizumab

Background In the context of patients with hepatocellular carcinoma (HCC) treated with systemic therapy, the correlation between the appearance of adverse events (AEs) and reported efficacy outcomes is well-known and widely investigated. From other pathological settings, we are aware of the prognostic and predictive value of the occurrence of immune-related AEs in patients treated with immune-checkpoint inhibitors. Objective This retrospective multicenter real-world study aims to investigate the potential prognostic value of AEs in patients with HCC treated with atezolizumab plus bevacizumab in the first-line setting. Patients and methods The study population consisted of 823 patients from five countries (Italy, Germany, Portugal, Japan, and the Republic of Korea). Results Of the patients, 73.3% presented at least one AE during the study period. The most common AEs were proteinuria (29.6%), arterial hypertension (27.2%), and fatigue (26.0%). In all, 17.3% of the AEs were grade (G) 3. One death due to bleeding was reported. The multivariate analysis confirmed the appearance of decreased appetite G < 2 [versus G >= 2; hazard ratio (HR) 0.60; 95% confidence interval (CI) 0.13-0.90; p < 0.01] and immunotoxicity G < 2 (versus G >= 2; HR: 0.70; 95% CI 0.24-0.99; p = 0.04) as independent prognostic factors for overall survival, and the appearance of decreased appetite G < 2 (versus G >= 2; HR: 0.73; 95% CI 0.43-0.95; p = 0.01), diarrhea (yes versus no; HR: 0.57, 95% CI 0.38-0.85; p = 0.01), fatigue (yes versus no; HR: 0.82, 95% CI 0.65-0.95; p < 0.01), arterial hypertension G < 2 (versus G >= 2; HR: 0.68, 95% CI 0.52-0.87; p < 0.01), and proteinuria (yes versus no; HR: 0.79, 95% CI 0.64-0.98; p = 0.03) as independent prognostic factors for progression-free survival. Conclusions As demonstrated for other therapies, there is also a correlation between the occurrence of AEs and outcomes for patients with HCC for the combination of atezolizumab plus bevacizumab

Trends in chronic hepatitis B virus infection in Italy over a 10-year period: Clues from the nationwide PITER and MASTER cohorts toward elimination

Objectives: The study measures trends in the profile of patients with chronic hepatitis B virus linked to care in Italy. Methods: A cross-sectional, multicenter, observational cohort (PITER cohort) of consecutive patients with hepatitis B surface antigen (HBsAg) over the period 2019-2021 from 46 centers was evaluated. The reference was the MASTER cohort collected over the years 2012-2015. Standard statistical methods were used. Results: The PITER cohort enrolled 4583 patients, of whom 21.8% were non-Italian natives. Compared with those in MASTER, the patients were older and more often female. The prevalence of hepatitis B e antigen (HBeAg) declined (7.2% vs 12.3; P <0.0001) and that of anti-hepatitis D virus (HDV) remained stable (9.3% vs 8.3%). In both cohorts, about 25% of the patients had cirrhosis, and those in the PITER cohort were older. HBeAg-positive was 5.0% vs 12.6% (P <0.0001) and anti-HDV positive 24.8% vs 17.5% (P <0.0017). In the logistic model, the variables associated with cirrhosis were anti-HDV-positive (odds ratio = 10.08; confidence interval 7.63-13.43), age, sex, and body mass index; the likelihood of cirrhosis was reduced by 40% in the PITER cohort. Among non-Italians, 12.3% were HBeAg-positive (vs 23.4% in the MASTER cohort; P <0.0001), and 12.3% were anti-HDV-positive (vs 11.1%). Overall, the adherence to the European Association for the Study of the Liver recommendations for antiviral treatment increased over time. Conclusion: Chronic hepatitis B virus infection appears to be in the process of becoming under control in Italy; however, HDV infection is still a health concern in patients with cirrhosis and in migrants