Ship Motions and Added Resistance with a BEM in frequency and time domain

This thesis is focused on the calculation of ship motions and on the evaluation of added resistance in waves. A partial desingularized panel method based on potential theory has been developed. Rankine sources are distributed on the hull and at small distance above the free surface. In such way only the free surface is desingularized. This choice allows to consider also thin hull shapes at the bow where desingularization could cause numerical problems. The main advantage of this approach leads to reduce the computational time, especially when non linear effects are considered, provided an adequate source-panel center vertical distance is selected. The fluid domain boundaries have been represented as a structured grid consisting of flat quadrilater panels. In the linear case the boundary conditions have been applied on the mean body wetted surface and the free-surface is considered at the calm water level. By using an Eulerian timestepping integration scheme the kinematic and dynamic boundary conditions are updated on the free-surface at every time-step. After the potential is obtained, the pressure on the mean hull surface can be calculated and forces and moments can be determined by integrating the pressure on the body surface. Therefore in two-dimensional environment an introduction of non-linear effects has been analysed. In particular a 2D body exact method has been developed. The added resistance is determined by a near field method integrating the second-order pressure on the body surface. Then it is corrected using a semi-empirical method to allow to consider the wave reflection of short waves. The adequacy of the results has been verified applying the code to different test cases and comparing the numerical output with experimental data available in literature. Furthermore in order to discuss the improvements obtained with this present method the results have been compared with another numerical method in frequency domain

A Boundary Element Method for Motions and Added Resistance of Ships in Waves

The accurate prediction of ship resistance in waves is nowadays of increased importance since it greatly influences ship performance regarding sustainable service speed and fuel consumption in seaways. Added resistance is considered as the longitudinal component of the second order mean force acting on a ship in waves and can be calculated from the first order ship motions by integrating the corresponding second-order pressure on the body surface. The purpose of this paper is to present a methodology for the prediction of motions and added resistance by a three dimensional Rankine panel method and to discuss and validate its results by comparing them with experimental data. The prediction in the short wave range, where forces due to wave reflection dominate, has been made applying semi-empirical corrections proposed by Kuroda. Experimental data for the heave, pitch, and added resistance of an ITTC benchmark KRISO container ship have been compared with numerical ones, and the applicability of the proposed method is discussed

Lopinavir/Ritonavir and Darunavir/Cobicistat in Hospitalized COVID-19 Patients: Findings From the Multicenter Italian CORIST Study

Background: Protease inhibitors have been considered as possible therapeutic agents for COVID-19 patients. Objectives: To describe the association between lopinavir/ritonavir (LPV/r) or darunavir/cobicistat (DRV/c) use and in-hospital mortality in COVID-19 patients. Study Design: Multicenter observational study of COVID-19 patients admitted in 33 Italian hospitals. Medications, preexisting conditions, clinical measures, and outcomes were extracted from medical records. Patients were retrospectively divided in three groups, according to use of LPV/r, DRV/c or none of them. Primary outcome in a time-to event analysis was death. We used Cox proportional-hazards models with inverse probability of treatment weighting by multinomial propensity scores. Results: Out of 3,451 patients, 33.3% LPV/r and 13.9% received DRV/c. Patients receiving LPV/r or DRV/c were more likely younger, men, had higher C-reactive protein levels while less likely had hypertension, cardiovascular, pulmonary or kidney disease. After adjustment for propensity scores, LPV/r use was not associated with mortality (HR = 0.94, 95% CI 0.78 to 1.13), whereas treatment with DRV/c was associated with a higher death risk (HR = 1.89, 1.53 to 2.34, E-value = 2.43). This increased risk was more marked in women, in elderly, in patients with higher severity of COVID-19 and in patients receiving other COVID-19 drugs. Conclusions: In a large cohort of Italian patients hospitalized for COVID-19 in a real-life setting, the use of LPV/r treatment did not change death rate, while DRV/c was associated with increased mortality. Within the limits of an observational study, these data do not support the use of LPV/r or DRV/c in COVID-19 patients

Seakeeping and Added Resistance of a Fast Semi-Swath Ship

Multi-hull vessels, including SWATH vehicles, are interesting design solutions for a number of marine applications, from coastal ferries to workboats. Some hybrid and unconventional configurations, able to combine good quality of more classic designs, appear to be also attractive. This is the case of Semi-SWATHs, that merge the stern shapes of high speed catamarans with the bow shapes of conventional SWATHs. The aim of the proposed work is to go deeper into its seakeeping behavior also evaluating the added resistance. The analysis is carried out by means of a three dimensional Boundary Element Method (BEM), that makes use of a Rankine source distribution over the hull and the free surface. Incoming head waves only are considered in this study. Both the response amplitude operators of heave and pitch motions and the added resistance of the high speed catamaran are compared with available experimental data. The same analysis is carried out on the proposed Semi-SWATH vessel and results are critically discussed

Numerical simulation of Added Resistance in Head waves: a RANS and BEM approach

Nowadays with the increase of the importance of the green aspect, related to fuel con- sumption, also engine emissions are an important issue to consider in ship design. From the hydrodynamic point of view, in addition to the well known ship resistance optimization, ship performance in waves should be taken into account not only in terms of safety and comfort due to motions, but also in terms of added resistance in waves. The aim of this article is to compare the evaluation of added resistance deriv- ing from the prediction of motions obtained from a three dimensional boundary element method based on Rankine sources with the corresponding added resistance results coming from a viscous method. In particular it is desired to overview on the ability of a RANSE solver on this particular field. The methods are applied considering only regular head waves for the test case, MOERI Container Ship (KCS)

A STUDY ON THE ADDED RESISTANCE PERFORMANCE OF CATAMARANS IN WAVES

The added resistance of a catamaran advancing in waves is investigated in the framework of a non-viscous potential theory. A linear Boundary Element Method (BEM) is used for the first order seakeeping prediction and the mean longitudinal component of the second-order steady-state force is computed by using a near-field method. Both methods are briefly presented and preliminary validations on both a mono-hull and a catamaran are shown. A systematic analysis of the added resistance of the so-called DUT catamaran is presented highlighting the effects of the advancing speed and those of the ship-wave heading angle

Relationship between regulatory T cells subsets and lipid profile in dyslipidemic patients: A longitudinal study during atorvastatin treatment

Background: The CD4+ T-lymphocytes and their subtype CD4 + CD25highFoxP3+ regulatory T cells are receiving growing interest as major regulators of atherogenesis. We sought to investigate 1) whether the CD4 + cell subsets were expressed differently in dyslipidemic patients (Pts) and healthy subjects (HS) and 2) whether atorvastatin treatment could be associated in-vivo and in-vitro with cell changes in expression and functional response. Methods: CD4+ subsets frequency (CD4 + CD25highFoxP3+, CD4 + CD25-FoxP3+) and mRNA expression for FoxP3, IL-10 and TGF-\u3b2 were evaluated in 30 consecutive Pts at baseline and after a 3-month atorvastatin therapy, and in 17 HS. Results: The % of CD4 + cells did not differ between HS and Pts. The % of CD4 + CD25highFoxP3+ was higher in Pts than HS and did not change during treatment. The CD4 + CD25-FoxP3+ cells were similar between the two groups and were lower in Pts at visit 2. Cytokine expression and FoxP3 did not differ in HS and Pts and no substantial change was observed during treatment. At visit 1, CD4 + CD25highFoxP3+ cells were significantly correlated with both total-cholesterol (r = 0.570, P = 0.0002), LDL-cholesterol (r = 0.715, P = 0.0001), Apolipoprotein B (r = 0.590, P = 0.0001). In-vitro atorvastatin (up to 5 \u3bcM) failed to induce any significant modulation of cell functions. Conclusion: CD4 + CD25highFoxP3+ regulatory cells seem to be over-stimulated in the early pre-clinical phase of atherosclerosis and a relationship exists between their frequency and circulating lipids. A potential immuno-modulation by statin treatment is not achieved through a normalization in peripheral CD4 + cell subsets

Relationship between low Ankle-Brachial Index and rapid renal function decline in patients with atrial fibrillation: a prospective multicentre cohort study

OBJECTIVE: To investigate the relationship between Ankle-Brachial Index (ABI) and renal function progression in patients with atrial fibrillation (AF). DESIGN: Observational prospective multicentre cohort study. SETTING: Atherothrombosis Center of I Clinica Medica of 'Sapienza' University of Rome; Department of Medical and Surgical Sciences of University Magna Græcia of Catanzaro; Atrial Fibrillation Registry for Ankle-Brachial Index Prevalence Assessment-Collaborative Italian Study. PARTICIPANTS: 897 AF patients on treatment with vitamin K antagonists. MAIN OUTCOME MEASURES: The relationship between basal ABI and renal function progression, assessed by the estimated Glomerular Filtration Rate (eGFR) calculated with the CKD-EPI formula at baseline and after 2 years of follow-up. The rapid decline in eGFR, defined as a decline in eGFR >5 mL/min/1.73 m(2)/year, and incident eGFR<60 mL/min/1.73 m(2) were primary and secondary end points, respectively. RESULTS: Mean age was 71.8±9.0 years and 41.8% were women. Low ABI (ie, ≤0.90) was present in 194 (21.6%) patients. Baseline median eGFR was 72.7 mL/min/1.73 m(2), and 28.7% patients had an eGFR<60 mL/min/1.73 m(2). Annual decline of eGFR was -2.0 (IQR -7.4/-0.4) mL/min/1.73 m(2)/year, and 32.4% patients had a rapid decline in eGFR. Multivariable logistic regression analysis showed that ABI ≤0.90 (OR 1.516 (95% CI 1.075 to 2.139), p=0.018) and arterial hypertension (OR 1.830 95% CI 1.113 to 3.009, p=0.017) predicted a rapid eGFR decline, with an inverse association for angiotensin converting enzyme (ACE) inhibitors/angiotensin receptor blockers (OR 0.662 95% CI 0.464 to 0.944, p=0.023). Among the 639 patients with AF with eGFR >60 mL/min/1.73 m(2), 153 (23.9%) had a reduction of the eGFR <60 mL/min/1.73 m(2). ABI ≤0.90 was also an independent predictor for incident eGFR<60 mL/min/1.73 m(2) (HR 1.851, 95% CI 1.205 to 2.845, p=0.005). CONCLUSIONS: In patients with AF, an ABI ≤0.90 is independently associated with a rapid decline in renal function and incident eGFR<60 mL/min/1.73 m(2). ABI measurement may help identify patients with AF at risk of renal function deterioration

Common cardiovascular risk factors and in-hospital mortality in 3,894 patients with COVID-19: survival analysis and machine learning-based findings from the multicentre Italian CORIST Study

There is poor knowledge on characteristics, comorbidities and laboratory measures associated with risk for adverse outcomes and in-hospital mortality in European Countries. We aimed at identifying baseline characteristics predisposing COVID-19 patients to in-hospital death