Wave impact in sloshing flows: Hydroelasticity in shallow water condition

The hydroelastic interaction between a fluid (sloshing flow) and a flexible metal structure, as a consequence of a gravitational wave impact, has been investigated. When hydroelasticity occurs, the real stresses which the structure must overcome, may be underestimate if only the hydrodynamic pressure is taken in account. The knowledge of the stresses acting on the structure, as well as, the physical mechanisms which are able to trigger this kind of phenomena, are fundamental for a right design and the safety of a marine structures. The investigation has been performed following both the experimental and mathematical approach. An experimental set-up has been designed for the reproduction of the impact, during a two dimensional sloshing flow in low filling condition, against a flexible structure(, as well as, a rigid one). Two specific typologies of wave impacts have been considered, both of them, characterized by hydrodynamic loads which may activate hydroelastic effects on the structure: a) Flip-Through type wave impact b) Single Air-Bubble entrapment wave impact for the last one, the investigation has been extended also at the influence of the Euler number on the structural stress. The influence of the ullage pressure is an important topic related to the scaling procedure when model scale experiments are performed. For a better identification of the major physical features which play an active role in the hydroelastic phenomena, an hybrid “weak” hydroelastic and a fully hydroelastic methods have been developed. The three different sub-problems, that have been individuated from the experimental activities: 1a) sloshing stage with single phase flow, 1b) sloshing stage with two phase flow and 2) structural problem, have been modelled with a proper mathematical models, where the physical assumptions adopted, have been inspired by the experimental finding and also by the literature. The hybrid model combines a numerical model for the structural problem with hydrodynamic loads estimated during experimental tests with a fully rigid structure. More in detail, the Euler beam theory together with a model for the added mass have been used to describe the behavior of the structure. The hybrid model highlights how the added mass effect influence both the natural frequencies and the displacement of the structure. Anyway some differences on the structure displacement have been observed, especially on the higher peaks just after the impact, this suggests that a stronger hydroelastic interaction is present. For the fully hydroelastic model, also the sloshing sub-problem, which can be considered both as single phase of two phase flow, depending on the impact type, has been solved numerically. In particular, a mixed Eulerian-Lagrangian method has been applied for the evolution of the free surface, where for the liquid phase the hypotheses of incompressible and irrotational fluid have been considered. In that cases where the air cavity is present, the pressure inside the cavity has been modelled with ad-hoc semi-analytical model, such as the “lumped” model. The dynamic behaviour of the structure has been approximated as in the hybrid method. The coupling, during the numerical time integration scheme, of the cited sub-models gives the fully hydroelastic method

Wave-Impact in a sloshing tank: hydroelastic challenges

Wave-impact in sloshing flows is an important issue for the safety of the Liquefied Natural Gas (LNG) carriers. Although LNG tanks have filling restrictions, they must be able to operate at any filling depth. The full understanding of the physical phenomena and the accurate evaluation of the local loads in sloshing-induced slamming events occurring in completely, partially or barely filling conditions, is a challenge of the research field. Violent free-surface motions in a sloshing tank generally occur when the energy spectrum of the ship motion is focused in the frequency region close to the lowest sloshing mode of the tank. Slamming events may occur originating impulsive and large local loads that undermine the integrity of the structure. Depending on the local flow features before the impact, several and complex scenarios can characterize the physical evolutions of a wave impact in a sloshing flow. For example, when the impact angle between water and body is small, air entrapment may occur making important the compressibility of the air and its interaction with the free surface. In contrast, for an incipient breaking wave approaching a vertical wall, flip-through event may happen causing localized and large loads without any air-entrapment or flat-impact may occur. In all these cases, when the typical temporal duration of the local load is comparable with the lowest natural period of the structure, hydroelasticity matters affecting the integrity of the structure. Present research investigation pursues the experimental study about the kinematic and dynamic features of a wave impacting a rigid vertical wall of a 2D sloshing tank in shallow water conditions. Previous papers, have emphasized how the maximum pressure around the impact area is an unreliable indicator of the maximum load (with value of the standard deviation up to 50%), because of the stochastic behaviour of the impact phenomena. Here, the strain distribution along a deformable aluminum plate inserted in a rigid vertical wall of a sloshing tank has been measured to characterize the features of the local loads

Long-Term Drug Survival and Effectiveness of Secukinumab in Patients with Moderate to Severe Chronic Plaque Psoriasis: 42-Month Results from the SUPREME 2.0 Study

Purpose: SUPREME, a phase IIIb study conducted in Italy, demonstrated safety and high efficacy of secukinumab for up to 72 weeks in patients with moderate-to-severe plaque-type psoriasis. SUPREME 2.0 study aimed to provide real-world data on the long-term drug survival and effectiveness of secukinumab beyond 72 weeks. Patients and Methods: SUPREME 2.0 is a retrospective observational chart review study conducted in patients previously enrolled in SUPREME study. After the end of the SUPREME study, eligible patients continued treatment as per clinical practice, and their effectiveness and drug survival data were retrieved from medical charts. Results: Of the 415 patients enrolled in the SUPREME study, 297 were included in SUPREME 2.0; of which, 210 (70.7%) continued secukinumab treatment throughout the 42-month observation period. Patients in the biologic-naïve cohort had higher drug survival than those in the biologic-experienced cohort (74.9% vs 61.7%), while HLA-Cw6–positive and HLA-Cw6–negative patients showed similar drug survival (69.3% and 71.9%). After 42 months, Psoriasis Area and Severity Index (PASI) 90 was achieved by 79.6% of patients overall; with a similar proportion of biologic-naïve and biologic-experienced patients achieving PASI90 (79.8% and 79.1%). The mean absolute PASI score reduced from 21.94 to 1.38 in the overall population, 21.90 to 1.24 in biologic-naïve and 22.03 to 1.77 in biologic-experienced patients after 42 months. The decrease in the absolute PASI score was comparable between HLACw6–positive and HLA–Cw6-negative patients. The baseline Dermatology Life Quality Index scores also decreased in the overall patients (10.5 to 2.32) and across all study sub-groups after 42 months. Safety was consistent with the known profile of secukinumab, with no new findings. Conclusion: In this real-world cohort study, secukinumab showed consistently high long-term drug survival and effectiveness with a favourable safety profile

Italian Guidelines in diagnosis and treatment of alopecia areata

Alopecia areata (AA) is an organ-specific autoimmune disorder that targets anagen phase hair follicles. The course is unpredictable and current available treatments have variable efficacy. Nowadays, there is relatively little evidence on treatment of AA from well-designed clinical trials. Moreover, none of the treatments or devices commonly used to treat AA are specifically approved by the Food and Drug Administration. The Italian Study Group for Cutaneous Annexial Disease of the Italian Society of dermatology proposes these Italian guidelines for diagnosis and treatment of Alopecia Areata deeming useful for the daily management of the disease. This article summarizes evidence-based treatment associated with expert-based recommendations

SPH method for long-time simulations of sloshing flows in LNG tanks

The present work is dedicated to the numerical investigation of sloshing flows inside a ship LNG fuel tank. Long time simulations, involving 3-hours real-time duration with realistic severe sea-state forcing, have been performed using a parallel CFD solver running for several weeks on a dedicated cluster. The numerical model adopted is the Smoothed Particle Hydrodynamics model (SPH). This model has been chosen for its Lagrangian approach and for the intrinsic properties of mass and momenta conservation which makes it well adapted for the simulation of violent free-surface flows. The adopted SPH method relies on a Riemann Solver for the calculation of the particle interactions which increases the stability of the scheme and allows for accurate predictions of the pressure during water impact stages. Three different filling height conditions are considered. For all of them energetic sloshing flows are induced with the occurrence of several water impact events. The latter are focused on specific zones of the tank depending on the considered filling height. For some conditions the SPH pressure predictions are compared with experimental ones. A critical discussion of these predictions is performed, highlighting the cases in which the numerical solver is able to provide good local pressure estimations.(c) 2022 Elsevier Masson SAS. All rights reserved

Wave impact with air entrapped in shallow water sloshing flow

LNG carriers with prismatic membrane tanks are more exposed than other carriers to violent sloshing phenomena resulting large impact loads [1]. Because of the large and clean tanks used in LNG ship, low lling depth conditions are of concern for the maximum loads occurring on the walls