The multislope concept has been recently introduced in the literature to deal with MUSCL reconstructions on triangular and tetrahedral unstructured meshes in the finite volume cell-centered context. ...Dedicated scalar slopes are used to compute the interpolations on each face of a given element, in opposition to the monoslope methods in which a unique limited gradient is used. The multislope approach reveals less expensive and potentially more accurate than the classical gradient techniques. Besides, it may also help the robustness when dealing with hyperbolic systems involving complex solutions, with large discontinuities and high density ratios. However some important limitations on the mesh topology still have to be overcome with the initial multislope formalism. In this paper, a generalized multislope MUSCL method is introduced for cell-centered finite volume discretizations. The method is freed from constraints on the mesh topology, thereby operating on completely general unstructured meshes. Moreover optimal second-order accuracy is reached at the faces centroids. The scheme can be written with nonnegative coefficients, which makes it L∞-stable. Special attention has also been paid to equip the reconstruction procedure with well-adapted dedicated limiters, potentially CFL-dependent. Numerical tests are provided to prove the ability of the method to deal with completely general meshes, while exhibiting second-order accuracy.
•A novel numerical strategy is proposed for the modeling of primary atomization in an unstructured finite volume platform.•An experimental device of a cryogenic flame with subcritical oxygen ...injection is reproduced by Large-Eddy Simulation.•The behavior of physical phenomena from primary atomization of the liquid jet to the combustion of the spray are highlighted.•Both the dynamics of the two-phase flow and the features of the flame are in good agreement with experimental measurements.
Atomization of liquid jets is a key feature of many propulsion systems, such as jet engines, internal combustion engines or liquid-propellant rocket engines (LRE). As it controls the characteristics of the spray, atomization has a great influence on the complex interaction between phenomena such as evaporation, turbulence, acoustics and combustion. In this context, Computational Fluid Dynamics is a promising way to bring better understanding of dynamic phenomena involving atomization, such as e.g. high-frequency combustion instabilities in LRE. However the unsteady simulation of primary atomization in reactive compressible two-phase flows is very challenging, due to the variety of the spatial and temporal scales, as well as to the high density, velocity and temperature gradients which require robust and efficient numerical methods. To address this issue, a numerical strategy is proposed in this paper, which is able to describe the dynamics of the whole chain of mechanisms from the liquid injection to its atomization and combustion. Primary atomization is modeled by a coupling between a homogeneous diffuse interface model and a kinetic-based Eulerian model for the spray. This strategy is successfully applied to the unsteady simulation of an operating point of the Onera’s Mascotte test bench, representative of one coaxial injector of LRE operating under subcritical conditions. The dynamics of the liquid core is retrieved and the flame shape as well as Sauter mean diameters are in good agreement with experimental results. These results demonstrate the ability of the strategy to deal with the harsh conditions of cryogenic combustion, and provide a promising framework for future studies of combustion instabilities in LRE.
In this paper, we tackle the issue of the accurate simulation of evaporating and reactive polydisperse sprays strongly coupled to unsteady gaseous flows. In solid propulsion, aluminum particles are ...included in the propellant to improve the global performances but the distributed combustion of these droplets in the chamber is suspected to be a driving mechanism of hydrodynamic and acoustic instabilities. The faithful prediction of two-phase interactions is a determining step for future solid rocket motor optimization. When looking at saving computational ressources as required for industrial applications, performing reliable simulations of two-phase flow instabilities appears as a challenge for both modeling and scientific computing. The size polydispersity, which conditions the droplet dynamics, is a key parameter that has to be accounted for. For moderately dense sprays, a kinetic approach based on a statistical point of view is particularly appropriate. The spray is described by a number density function and its evolution follows a Williams–Boltzmann transport equation. To solve it, we use Eulerian Multi-Fluid methods, based on a continuous discretization of the size phase space into sections, which offer an accurate treatment of the polydispersion. The objective of this paper is threefold: first to derive a new Two Size Moment Multi-Fluid model that is able to tackle evaporating polydisperse sprays at low cost while accurately describing the main driving mechanisms, second to develop a dedicated evaporation scheme to treat simultaneously mass, moment and energy exchanges with the gas and between the sections. Finally, to design a time splitting operator strategy respecting both reactive two-phase flow physics and cost/accuracy ratio required for industrial computations. Using a research code, we provide 0D validations of the new scheme before assessing the splitting technique's ability on a reference two-phase flow acoustic case. Implemented in the industrial-oriented CEDRE code, all developments allow to simulate realistic solid rocket motor configurations featuring the first polydisperse reactive computations with a fully Eulerian method.
Purpose
Erectile dysfunction (ED) is one of the most prevalent male sexual dysfunctions. ED has been in the past mistakenly considered a purely psycho-sexological symptom by patients and doctors. ...However, an ever-growing body of evidence supporting the role of several organic factors in the pathophysiological mechanisms underlying ED has been recognized.
Methods
The Italian Society of Andrology and Sexual Medicine (SIAMS) commissioned an expert task force involving several other National Societies to provide an updated guideline on the diagnosis and management of ED. Derived recommendations were based on the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system.
Results
Several evidence-based statements were released providing the necessary up-to-date guidance in the context of ED with organic and psychosexual comorbidities. Many of them were related to incorrect lifestyle habits suggesting how to associate pharmacotherapies and counseling, in a couple-centered approach. Having the oral therapy with phosphodiesterase type 5 inhibitors as the gold standard along with several other medical and surgical therapies, new therapeutic or controversial options were also discussed.
Conclusions
These are the first guidelines based on a multidisciplinary approach that involves the most important Societies related to the field of sexual medicine. This fruitful discussion allowed for a general agreement on several recommendations and suggestions to be reached, which can support all stakeholders in improving couple sexual satisfaction and overall general health.
The accurate simulation of polydisperse sprays undergoing coalescence in unsteady gaseous flows is a crucial issue. In solid rocket motors, the internal flow depends strongly on the alumina droplet ...size distribution, which spreads up with coalescence. Yet solving for unsteady two-phase flows with high accuracy on the droplet sizes is a challenge for both modeling and scientific computing. As an alternative to Lagrangian approaches, a wide range of Eulerian models have been recently developed to describe the disperse liquid phase at a lower cost, with an easier coupling to the gaseous phase and with massively parallel codes. Among these models, the multi-fluid model allows the detailed description of polydispersity and size/velocity correlations by separately solving fluids of size-sorted droplets, the so-called sections. The existing one size moment method, which describes the size distribution with one size moment per section, provides simple and fast resolution for coalescence. On the other hand, a two size moment method has been suggested to reduce the number of sections but it lacks an efficient coalescence resolution method. After introducing a new strategy for two size moment coalescence, the two methods are compared on various configurations in a research code and an industrial-oriented code, in order to conclude on computational accuracy and cost. Then the paper aims at describing the most efficient approach for multi-dimensional unsteady and eventually coalescing rocket chamber simulations. Its objective is threefold: first, to validate the two size moment method by comparing simulations to reference solutions and dedicated experimental measurements conducted at ONERA, second to study the efficiency and robustness of both methods, third, to draw some firm conclusions about the necessity to use the one size moment or two size moment method to simulate solid propellant alumina sprays. We finally perform the first simulations of coalescence in realistic 2D boosters with the two size moment method, implemented in the industrial-oriented code CEDRE.
Elevated serum uric acid (sUA) concentrations have been associated with worse prognosis in heart failure (HF) but little is known about elderly patients. We aimed to assess long-term additive ...prognostic value of sUA in elderly patients hospitalized for HF.
Clinical and echocardiographic characteristics of 310 consecutive elderly patients hospitalized for HF were collected. During index period, 206 had sUA concentrations available, which were obtained within 24 h prior to discharge; 10 patients were lost to follow-up, leaving 196 patients available. Patients had a median age of 77 (IQR 69–83) years, and were mostly male (64.5%). sUA ranges for tertiles I–III were: 1.5–6.1, 6.2–8.3, and 8.4–18.9 mg/dl, respectively. During a median follow-up of 27 months (IQR 10.5–39.5), 122 combined events occurred (87 deaths and 73 HF rehospitalizations). Four-year event-free survival for the combined endpoint was 46 ± 7% for tertile I, 34 ± 7% for tertile II, and 21 ± 5% for tertile III (P = 0.001). By multivariable Cox backward analysis, sUA was retained as a significant predictor. Compared with the lowest sUA tertile, tertile III showed a strong association with outcome, also after adjustment for other predictors (HR 1.84, 95% CI 1.16–2.93; P = 0.01). Importantly, addition of sUA to the other significant predictors of outcome resulted in improved risk classification (net reclassification improvement 0.19, P = 0.017).
High sUA at discharge is a strong predictor of adverse outcome in elderly hospitalized for HF, and it significantly improves risk classification. Measuring sUA can be a simple and useful tool to identify high-risk elderly hospitalized for HF.
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