scale adaptive simulations of a swirl stabilized spray flame using flamelet generated manifold

Abstract The present work describes the main findings derived from CFD simulations of the swirl stabilized spray flame experimentally investigated by Sheen [1] . Scale Adaptive Simulations (SAS) have been performed using Flamelet Generated Manifold (FGM) for combustion modelling and a Eulerian-Lagrangian approach for liquid phase description. Results highlight the capabilities of SAS in predicting the main characteristics of the analysed turbulent spray flame, leading to appreciable enhancements with respect to RANS results in terms of both velocity and temperature distributions

modelling soot production and thermal radiation for turbulent diffusion flames

Abstract This paper presents a systematic investigation on the strategies required for modelling soot when performing CFD simulations of turbulent flames. The first test case consists in a 3D enclosure containing a mixture of N 2 , CO 2 , H 2 O and soot (Coelho, 2003). Results obtained with the gray implementation of the Discrete Ordinate Method in ANSYS Fluent are compared against literature data, assessing different formulations for the absorption coefficient of soot. These considerations are exploited through reactive RANS simulations accounting for radiative heat transfer, with the purpose to test different models for soot formation process on a turbulent non-premixed kerosene-air flame (Young et al., 1994)

methane swirl stabilized lean burn flames assessment of scale resolving simulations

Abstract The reliable prediction of the turbulent combustion process in lean flames is of paramount importance in the design of gas turbine combustors. The present work presents an assessment of the capabilities of Flamelet Generated Manifold (FGM) in the framework of Reynolds-Averaged Navier-Stokes (RANS) and Large-Eddy Simulation (LES) At this purpose the TECFLAM swirl burner consisting of a strongly swirling, unconfined natural gas flame was chosen. Results highlight that RANS-FGM succeeds in predicting the main characteristics of the reacting flow field and species concentrations. However, only LES is capable of reproducing the actual turbulent mixing between swirling flow and co-flow, thus leading to appreciable enhancements with respect to RANS results

numerical analyses of a high pressure sooting flame with multiphysics approach

Abstract The development of a new standard for soot emissions proposed by ICAO-CAEP to reduce the environmental impact of civil aviation is moving increasingly research effort on the investigation of sooting flames. Formation and oxidation of the particulate matter are strongly affected by gas temperature, requiring an accurate prediction of the flow field from a numerical point of view. On the other hand, the temperature distribution within the combustor is modified by radiation, which depends on the soot concentration, leading to a very challenging coupled problem. In this work, a series of sensitivity analyses in RANS context are performed on soot, radiation and heat transfer modelling to assess their impact on the prediction of soot emission, gas temperature as well as wall heat fluxes distribution in the context of a high pressure sooting flame which is representative of a RQL combustor. These results are employed to set up a CHT (Conjugate Heat Transfer) simulation, using the multiphysics THERM3D procedure in a loosely-coupled manner where reactive CFD, radiation and heat conduction calculations are computed sequentially with a separate solver in a dedicated framework. These sensitivities can provide useful information for the numerical setup in high-fidelity simulations, as Scale Resolving Simulations

Active infective endocarditis: Clinical characteristics and factors related to hospital mortality

Background: Little information exists on the clinical characteristics and factors related to hospital mortality in patients with active infective endocarditis referred for surgery. Methods: Between January 1, 2003 and December 31, 2006, 86 patients (56 males, 30 females, mean age 59.2 years) with active infective endocarditis were referred to our Department (2.8% of overall hospitalizations). The relation of several clinical, laboratory and echocardiographic findings at admission with hospital mortality was evaluated. Results: A native valve (NVE) was involved in 50/86; the other 30 had a prosthetic valve endocarditis (PVE). Six had pacemaker endocarditis. The aortic valve was involved more frequently than the mitral valve, both in NVE and PVE. The tricuspid valve was involved in four drug addicts; 51% of patients were in NYHA class III–IV. Staphylococci and streptococci were isolated in 69% of patients (39% vs 30%). Blood cultures were negative in 24%. Overall hospital mortality has been 11.6%. Two patients died before surgery, eight in the perioperative period. Hospital mortality was closely related to age, clinical and laboratory evidence of advanced septic condition (temperature > 38°C, leukocytosis and creatinine > 2.0 mg/dL) and hemodynamic impairment. Conclusions: Active infective endocarditis is a significant cause of referral to heart surgery departments and hospital mortality is still > 10%. Clinical and laboratory parameters easily available at admission suggest that severe sepsis and/or hemodynamic impairment may be helpful in predicting the clinical outcome in this group of high risk patients. (Cardiol J 2010; 17, 6: 566-573

Subgrid Liquid Flux and interface modelling for LES of Atomization

[EN] Traditional Discrete Particle Methods (DPM) such as the Euler-Lagrange approaches for modelling atomization, even if widely used in technical literature, are not suitable in the near injector region. Indeed, the first step of atomization process is to separate the continuous liquid phase in a set of individual liquid parcels, the so-called primary break-up. Describing two-phase flow by DPM is to define a carrier phase and a discrete phase, hence they cannot be used for primary breakup. On the other hand, full scale simulations (direct simulation of the dynamic DNS, and interface capturing method ICM) are powerful numerical tools to study atomization, however, computational costs limit their application to academic cases for understanding and complementing partial experimental data. In an industrial environment, models that are computationally cheap and still accurate enough are required to meet new challenges of fuel consumption and pollutant reduction. Application of DNS-ICM methods without fairly enough resolution to solve all length scales are currently used for industrial purpose. Nevertheless, effects of unresolved scales are generally cast aside. The Euler-Lagrange Spray Atomization model family (namely, ELSA, also call, Σ − �� or Ω − ��) developed by Vallet and Borghi pioneering work [1], and [2], at the contrary aims to model those unresolved terms. This approach is actually complementary to DNS-ICM method since the importance of the unresolved term depends directly on mesh resolution. For full interface resolution the unclosed terms are negligible, except in the far-field spray when the unresolved terms become dominant. Depending on the complexity of the flow and the available computational resources, a Large Eddy Simulation (LES) formalism could be employed as modelling approach. This work focus on the two main terms that drive these different modelling approaches namely the subgrid turbulent liquid flux and the resolved interface. Thanks to the open source library OpenFoam® this work is an attempt to review and to release an adapted modelling strategy depending on the available mesh resolution. For validation, these solvers are tested against realistic experimental data to see the overall effect of each model proposal.This work was partly supported European Union’s Horizon 2020 research and innovation program under the Sklodowska-Curie grant agreement No. 675676. Simulations were carried out at TGCC (The Curie supercomputer, owned by GENCI and operated into the TGCC by CEA), and at CRIHAN (Centre de Ressources de Haute Normandie).Anez, J.; Ahmed, A.; Puggelli, S.; Reveillon, J.; Brändle De Motta, JC.; Demoulin, F. (2017). Subgrid Liquid Flux and interface modelling for LES of Atomization. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 385-393. https://doi.org/10.4995/ILASS2017.2017.4694OCS38539

Where does the drop size distribution come from?

[EN] This study employs DNS of two-phase flows to enhance primary atomization understanding and modelling to be used in numerical simulation in RANS or LES framework. In particular, the work has been aimed at improving the information on the liquid-gas interface evolution available inside the Eulerian-Lagrangian Spray Atomization (ELSA) framework. Even though this approach has been successful to describe the complete liquid atomization process from the primary region to the dilute spray, major improvements are expected on the establishment of the drop size distribution (DSD). Indeed, the DSD is easily defined once the spray is formed, but its appearance and even the mathematical framework to describe its creation during the initial breakup of the continuous liquid phase in a set of individual liquid parcels is missing. This is the main aim of the present work to review proposals to achieve a continuous description of the DSD formation during the atomization process. The attention is here focused on the extraction from DNS data of the behaviour of geometrical variable of the liquidgas interface, such as the mean and Gauss surface curvatures. A DNS database on curvature evolution has been generated. A Rayleigh-Plateau instability along a column of liquid is considered to analyse and to verify the capabilities of the code in correctly predicting the curvature distribution. A statistical analysis on the curvatures data, in terms of probability density function, was performed in order to determine the physical parameters that control the curvatures on this test case. Two different methods are presented to compute the curvature distribution and in addition, the probability to be at a given distance of the interface is studied. This approach finally links the new tools proposed to follow the formation of the spray with the pioneering work done on scale distribution analysis.Canu, R.; Dumouchel, C.; Duret, B.; Essadki, M.; Massot, M.; Ménard, T.; Puggelli, S.... (2017). Where does the drop size distribution come from?. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 605-612. https://doi.org/10.4995/ILASS2017.2017.4706OCS60561