Boundary Element and Finite Element Coupling for Aeroacoustics Simulations

We consider the scattering of acoustic perturbations in a presence of a flow. We suppose that the space can be split into a zone where the flow is uniform and a zone where the flow is potential. In the first zone, we apply a Prandtl-Glauert transformation to recover the Helmholtz equation. The well-known setting of boundary element method for the Helmholtz equation is available. In the second zone, the flow quantities are space dependent, we have to consider a local resolution, namely the finite element method. Herein, we carry out the coupling of these two methods and present various applications and validation test cases. The source term is given through the decomposition of an incident acoustic field on a section of the computational domain's boundary.Comment: 25 page

Lorentz Transform and Staggered Finite Differences for Advective Acoustics

38 pagesWe study acoustic wave propagation in a uniform stationary flow. We develop a method founded on the Lorentz transform and a hypothesis of irrotationality of the acoustic perturbation. After a transformation of the space-time and of the unknown fields, we derive a system of partial differential equations that eliminates the external flow and deals with the classical case of non advective acoustics. A sequel of the analysis is a new set of perfectly matched layers equations in the spirit of the work of Berenger and Collino. The numerical implementation of the previous ideas is presented with the finite differences method HaWAY on cartesian staggered grids. Relevant numerical tests are proposed

Model of Intention for the model specification verification during the simulation architecture design process

International audienceNowadays, simulation technologies are becoming indispensable to support the design process, and notably during the verification and optimization phases. However, when building a simulation architecture that has to provide the systems architects with answers, simulations architects have to correctly specify the corresponding models required. In a MBSE concept, we propose to extend the concept of model of intention, to verify the specification of these models, to model suppliers by providing them with a Model Request Package. Models of Intention will allow an executable verification of the simulation architecture before the integration of the final models of realization

Heterogeneity in defining multiple trauma: a systematic review of randomized controlled trials

Abstract Introduction While numerous randomized controlled trials (RCTs) have been conducted in the field of trauma, a substantial portion of them are yielding negative results. One potential contributing factor to this trend could be the lack of agreement regarding the chosen definitions across different trials. The primary objective was to identify the terminology and definitions utilized for the characterization of multiple trauma patients within randomized controlled trials (RCTs). Methods A systematic review of the literature was performed in MEDLINE, EMBASE and clinicaltrials.gov between January 1, 2002, and July 31, 2022. RCTs or RTCs protocols were eligible if they included multiple trauma patients. The terms employed to characterize patient populations were identified, and the corresponding definitions for these terms were extracted. The subsequent impact on the population recruited was then documented to expose clinical heterogeneity. Results Fifty RCTs were included, and 12 different terms identified. Among these terms, the most frequently used were “multiple trauma” (n = 21, 42%), "severe trauma" (n = 8, 16%), "major trauma" (n = 4, 8%), and trauma with hemorrhagic shock" (n = 4, 8%). Only 62% of RCTs (n = 31) provided a definition for the terms used, resulting a total of 21 different definitions. These definitions primarily relied on the injury severity score (ISS) (n = 15, 30%), displaying an important underlying heterogeneity. The choice of the terms had an impact on the study population, affecting both the ISS and in-hospital mortality. Eleven protocols were included, featuring five different terms, with "severe trauma" being the most frequent, occurring six times (55%). Conclusion This systematic review uncovers an important heterogeneity both in the terms and in the definitions employed to recruit trauma patients within RCTs. These findings underscore the imperative of promoting the use of a unique and consistent definition

Weaning-Related Shock in Patients With ECMO: Incidence, Mortality, and Predisposing Factors

International audienceObjective: Venoarterial extracorporeal membrane oxygenation (VA-ECMO) commonly is used to manage refractory cardiogenic shock after cardiac surgery, with 31% to 76% of patients successfully weaned off their ECMO. However, it is associated with high mortality rates, and 20% to 65% of weaned patients do not survive to hospital discharge. This study aimed to assess the incidence of ECMO weaning-related shock, the risk factors, and prognosis in the intensive care unit (ICU).Design: Retrospective observational cohort study.Setting: Surgical ICU of Cardiology Institute of Pitié-Salpêtrière University Hospital (Paris-France).Participants: Patients who were assisted with a peripheral VA-ECMO from January 2015 to December 2017 were included. Patients with venovenous, central, or right ECMO were excluded.Measurements: The authors collected data on patients' characteristics, during and after surgery. The indications for VA-ECMO implantation were ventricular dysfunction, primary graft dysfunction, and refractory cardiac arrest. Weaning-related shock was defined as the need to introduce or increase the dose of catecholamine at ECMO explantation or in the following week.Results: After weaning off VA-ECMO, 56 of 146 patients (38.4%) presented weaning-related shock: 55% were septic shocks, 12.5 % were caused by right ventricle failure, and 7.1% by hemorrhage. ICU mortality was 42% versus 8% in patients who did not present shock. Multivariate analysis showed that patients with pulmonary hypertension and those with norepinephrine before weaning were more likely to develop shock.Conclusion: ECMO weaning-related shock is frequent in patients with refractory cardiogenic shock after cardiac surgery. This is most commonly caused by sepsis and causes higher mortality rates, calling for further evaluation