Simulating Flows with SPH: Recent Developments and Applications

The chapter discusses recent theoretical developments and practical applications of the Smoothed Particle Hydrodynamics (SPH) method with specific concern to liquids. SPH is a meshless Lagrangian technique for the approximate integration of spatial derivatives, using particle interpolation over a compact support, without the usage of a structured grid. Its main related advantage is the capability of simulating the computational domain with large deformations and high discontinuities, bearing no numerical diffusion because advection terms are directly evaluated. SPH has recently become very popular for the simulation of fluid motion using computers, covering different fields, e.g. free surface flows, multiphase flows, turbulence modelling. In the following, recent theoretical achievements of SPH are firstly presented, concerning (1) numerical schemes for approximating governing equations, such as the Navier Stokes ones, most widely adopted in fluid dynamics, (2) smoothing or kernel function properties needed to perform the function approximation to the Nth order, (3) restoring consistency of kernel and particle approximation, yielding the SPH approximation accuracy. Secondly computation aspects related to the neighbourhood definition are discussed. Field variables, such as particle velocity or density, are evaluated by smoothing interpolation of the corresponding values over the nearest neighbour particles located inside a cut-off radius “rc”. The generation of a neighbour list at each time step takes a considerable portion of CPU time. Straightforward determination of which particles are inside the interaction range requires the computation of all pair-wise distances, a procedure whose computational time would be of the order O(N2), and therefore unpractical for large domains. Finally, some practical applications are presented, primariliy concerning free surface flows. The capability to easily handle large deformation is shown

Numerical wave interaction with tetrapods breakwater

ABSTRACT: The paper provides some results of a new procedure to analyze the hydrodynamic aspects of the interactions between maritime emerged breakwaters and waves by integrating CAD and CFD. The structure is modeled in the numerical domain by overlapping individual three-dimensional elements (Tetrapods), very much like the real world or physical laboratory testing. Flow of the fluid within the interstices among concrete blocks is evaluated by integrating the RANS equations. The aim is to investigate the reliability of this approach as a design tool. Therefore, for the results' validation, the numerical run-up and reflection effects on virtual breakwater were compared with some empirical formulae and some similar laboratory tests. Here are presented the results of a first simple validation procedure. The validation shows that, at present, this innovative approach can be used in the breakwater design phase for comparison between several design solutions with a significant minor cost. KEY WORDS: Volume of Fluid (VOF), Wave, Run up, Reflection, Rubble mound, Numerical simulations, Tetrapod Flow 3D®, RANS equation

A CFD approach to rubble mound breakwater design

The paper provides some developments of a numerical approach ("Numerical Calculation of Flow Within Armour Units", FWAU) to the design of rubble mound breakwaters. The hydrodynamics of wave induced flow within the interstices of concrete blocks is simulated by making use of advanced, but well tested, CFD techniques to integrate RANS equations.While computationally very heavy, FWAU is gaining ground, due to its obvious advantages over the "porous media", i.e. the possibility of accounting for the highly non stationary effects, the reduced need of ad hoc calibration of filtration parameters and also – in perspective – the evaluation of hydrodynamic forces on single blocks. FWAU however is a complex technique, and in order to turn it into a practical design tool, a number of difficulties have to be overcome.The paper presents recent results about this validation, as well as insight into fluid dynamical aspects. Keywords: Numerical simulation, Breakwaters, Run up, Reflection, Rubble moun

iga anticardiolipin in patients with gastroenteric tumor

Recently the presence of antiphospholipid antibodies in patients with cancer has been demonstrated, suggesting an involvement of autoimmune response in neoplastic conditions. The presence of antiphospholipid antibodies in tumor disease is highly correlated with the risk of developing thrombotic complications, which represents a significant cause of morbidity and mortality in cancer patients. Interestingly, it has been highlighted that high levels of IgM and IgG anticardiolipin antibodies are more often produced in patients with gastroenteric tumor than in patients with either ovarian or breast tumor. Thus far, there are no data looking into the role or measurements of IgA in patients with solid cancer. Our preliminary results, in this study, demonstrate that testing only for IgG and IgM anticardiolipin antibodies may increase the incidence of false positive because 44% who were IgA positive and IgG and IgM negative had high titres of CA19.9 and CEA. We suggest that taking into account the role of IgA could substantially improve the detection of antiphospholipids antibodies in subjects with solid cancer, and this detection may allow us for better prevention and management of thrombotic complications in these patients

Wave run-up prediction and observation in a micro-tidal beach

Abstract. Extreme weather events bear a significant impact on coastal human activities and on the related economy. Forecasting and hindcasting the action of sea storms on piers, coastal structures and beaches is an important tool to mitigate their effects. To this end, with particular regard to low coasts and beaches, we have developed a computational model chain based partly on open-access models and partly on an ad-hoc-developed numerical calculator to evaluate beach wave run-up levels and flooding. The offshore wave simulations are carried out with a version of the WaveWatch III model, implemented by CCMMMA (Campania Centre for Marine and Atmospheric Monitoring and Modelling – University of Naples Parthenope), validated with remote-sensing data. The waves thus computed are in turn used as initial conditions for the run-up calculations, carried out with various empirical formulations; the results were finally validated by a set of specially conceived video-camera-based experiments on a micro-tidal beach located on the Ligurian Sea. Statistical parameters are provided on the agreement between the computed and observed values. It appears that, while the system is a useful tool to properly simulate beach flooding during a storm, empirical run-up formulas, when used in a coastal vulnerability context, have to be carefully chosen, applied and managed, particularly on gravel beaches

Outcome of COVID-19 patients with haematological malignancies after the introduction of vaccination and monoclonal antibodies. Results from the HM-COV 2.0 study

Patients with haematological malignancies (HM) and SARS-CoV-2 infection present a higher risk of severe COVID-19 and mortality. The aim of the study was to investigate whether vaccination and monoclonal antibodies (mAbs) have modified the outcomes of HM patients with COVID-19. This is a single-centre retrospective study in HM patients hospitalized due to SARS-CoV-2 infection from March 2020 to April 2022. Patients were divided into PRE-V-mAb group (patients hospitalized before the introduction of vaccination and mAbs) and POST-V-mAb group (patients hospitalized after the use of vaccine and mAbs). A total of 126 patients were included (65 PRE-V-mAb and 61 POST-V-mAb). POST-V-mAb patients showed a significantly lower risk of intensive care unit (ICU) admission (8.2% vs. 27.7%, p = 0.005), shorter viral shedding [17 (IQR 10–28) vs. 24 days (IQR 15–50), p = 0.011] and shorter hospitalization length [13 (IQR 7–23) vs. 20 (IQR 14–41) days, p = 0.0003] compared to the PRE-V-mAb group. Nevertheless, both in-hospital and 30-day mortality rates did not significantly differ between the two groups (29.5% POST-V-mAb vs. 36.9% PRE-V-mAb and 21.3% POST-V-mAb vs. 29.2% PRE-V-mAb, respectively). At the multivariable analysis, an active malignancy (p = 0.042), a critical COVID-19 at admission (p = 0.025) and the need for high-level of oxygen support at respiratory worsening [either HFNC/CPAP (p = 0.022) or mechanical ven- tilation (p = 0.011)] were independently associated with in-hospital mortality. In the subgroup of POST-V-mAb patients, receiving therapy with mAbs was a protective factor (p = 0.033). Despite the new therapeutic and preventive strategies avail- able, HM patients with COVID-19 disease represent an extremely vulnerable group with still high mortality rates

Personalize, participate, predict, and prevent: 4Ps in inflammatory bowel disease

Inflammatory bowel disease (IBD), which includes Crohn's disease (CD) and ulcerative colitis (UC), is a complex, immune-mediated, disorder which leads to several gastrointestinal and systemic manifestations determining a poor quality of life, disability, and other negative health outcomes. Our knowledge of this condition has greatly improved over the last few decades, and a comprehensive management should take into account both biological (i.e., disease-related, patient-related) and non-biological (i.e., socioeconomic, cultural, environmental, behavioral) factors which contribute to the disease phenotype. From this point of view, the so called 4P medicine framework, including personalization, prediction, prevention, and participation could be useful for tailoring ad hoc interventions in IBD patients. In this review, we discuss the cutting-edge issues regarding personalization in special settings (i.e., pregnancy, oncology, infectious diseases), patient participation (i.e., how to communicate, disability, tackling stigma and resilience, quality of care), disease prediction (i.e., faecal markers, response to treatments), and prevention (i.e., dysplasia through endoscopy, infections through vaccinations, and post-surgical recurrence). Finally, we provide an outlook discussing the unmet needs for implementing this conceptual framework in clinical practice