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@ARTICLE{AR-CFD-18-127, author = {Douasbin, Q. and Scalo, C. and Selle, L. and Poinsot, T. }, title = {Delayed-time domain impedance boundary conditions (D-TDIBC)}, year = {2018}, number = {October}, volume = {371}, pages = {50-66}, doi = {10.1016/j.jcp.2018.05.003}, journal = {Journal of Computational Physics}, abstract = {Defining acoustically well-posed boundary conditions is one of the major numerical and theoretical challenges in compressible Navier–Stokes simulations. We present the novel Delayed-Time Domain Impedance Boundary Condition (D-TDIBC) technique developed to impose a time delay to acoustic wave reflection. Unlike previous similar TDIBC derivations (Fung and Ju, 2001–2004 [1], [2], Scalo et al., 2015 [3] and Lin et al., 2016 [4]), D-TDIBC relies on the modeling of the reflection coefficient. An iterative fit is used to determine the model constants along with a low-pass filtering strategy to limit the model to the frequency range of interest. D-TDIBC can be used to truncate portions of the domain by introducing a time delay in the acoustic response of the boundary accounting for the travel time of inviscid planar acoustic waves in the truncated sections: it gives the opportunity to save computational resources and to study several geometries without the need to regenerate computational grids. The D-TDIBC method is applied here to time-delayed fully reflective conditions. D-TDIBC simulations of inviscid planar acoustic-wave propagating in truncated ducts demonstrate that the time delay is correctly reproduced, preserving wave amplitude and phase. A 2D thermoacoustically unstable combustion setup is used as a final test case: Direct Numerical Simulation (DNS) of an unstable laminar flame is performed using a reduced domain along with D-TDIBC to model the truncated portion. Results are in excellent agreement with the same calculation performed over the full domain. The unstable modes frequencies, amplitudes and shapes are accurately predicted. The results demonstrate that D-TDIBC offers a flexible and cost-effective approach for numerical investigations of problems in aeroacoustics and thermoacoustics.}, keywords = {COMB, Impedance boundary condition, Time delay, Characteristic boundary conditions ,NSCBC, Computational aeroacoustics, Thermoacoustics}, url = {https://www.sciencedirect.com/science/article/pii/S002199911830295X}}

@ARTICLE{AR-CMGC-18-132, author = {Lac, C. and Chaboureau, J.P. and Masson, V. and Pinty, J.-P. and Tulet, P. and Escobar, J. and Leriche, M. and Barthe, C. and Aouizerats, B. and Augros, C. and Aumond, P. and Auguste, F. and Bechtold, P. and Berthet, S. and Bielli, S. and Bosseur, F. and Caumont, O. and Cohard, J.-M. and Colin, J. and Couvreux, F. and Cuxart, J. and Delautier, G. and Dauhut, T. and Ducrocq, V. and Filippi, J.-B. and Gazen, D. and Geoffroy, O. and Gheusi, F. and Honnert, R. and Lafore, J.P. and Lebeaupin Brossier, C. and Libois, Q. and Lunet, T. and Mari, C. and Maric, T. and Mascart, P. and Mogé, M. and Molinié, G. and Nuissier, O. and Pantillon, F. and Peyrillé, P. and Pergaud, J. and Perraud, E. and Pianezze, J. and Redelsperger, J.-L. and Ricard, D. and Richard, E. and Riette, S. and Rodier, Q. and Schoetter, R. and Seyfried, L. and Stein, J. and Suhre, K. and Taufour, M. and Thouron, O. and Turner, S. and Verrelle, A. and Vié, B. and Visentin, F. and Vionnet, V. and Wautelet, P. }, title = {Overview of the Meso-NH model version 5.4 and its applications}, year = {2018}, volume = {11}, pages = {1929-1969}, doi = {10.5194/gmd-11-1929-2018}, journal = {Geoscientific Model Development}, pdf = {https://cerfacs.fr/wp-content/uploads/2018/09/Globc-Article-emili-gmd-11-1929-2018.pdf}}

@ARTICLE{AR-CFD-18-110, author = {Dupuis, R. and Jouhaud, J.-C. and Sagaut, P. }, title = {Surrogate Modeling of Aerodynamic Simulations for Multiple Operating Conditions Using Machine Learning}, year = {2018}, number = {9}, volume = {56}, pages = {3622-3635}, doi = {10.2514/1.J056405}, journal = {AIAA Journal}, abstract = {This paper describes a methodology, called local decomposition method, which aims at building a surrogate model based on steady turbulent aerodynamic fields at multiple operating conditions. The various shapes taken by the aerodynamic fields due to the multiple operation conditions pose real challenges as well as the computational cost of the high-fidelity simulations. The developed strategy mitigates these issues by combining traditional surrogate models and machine learning. The central idea is to separate the solutions with a subsonic behavior from the transonic and high-gradient solutions. First, a shock sensor extracts a feature corresponding to the presence of discontinuities, easing the clustering of the simulations by an unsupervised learning algorithm. Second, a supervised learning algorithm divides the parameter space into subdomains, associated to different flow regimes. Local reduced-order models are built on each subdomain using proper orthogonal decomposition coupled with a multivariate interpolation tool. Finally, an improved resampling technique taking advantage of the subdomain decomposition minimizes the redundancy of sampling. The methodology is assessed on the turbulent two-dimensional flow around the RAE2822 transonic airfoil. It exhibits a significant improvement in terms of prediction accuracy for the developed strategy compared with the classical method of surrogate modeling.}, keywords = {surrogate models, POD, aerodynamics, machine learning}, url = {https://arc.aiaa.org/doi/10.2514/1.J056405}}

@ARTICLE{AR-CMGC-18-6, author = {Menegoz, M. and Cassou, C. and Swingedouw, D. and Bretonnière, P.A. and Doblas-Reyes, F. }, title = {Role of the Atlantic Multidecadal Variability in modulating the climate response to a Pinatubo-like volcanic eruption}, year = {2018}, number = {5-6}, volume = {51}, pages = {1863-1883}, doi = {10.1007/s00382-017-3986-1}, journal = {Climate Dynamics}, pdf = {https://cerfacs.fr/wp-content/uploads/2018/09/GLOBC_Article_Cassou_et_al_Climdyn_Roleoftheatlanticvariability_092018.pdf}}

@ARTICLE{AR-CFD-18-123, author = {Rochette, B. and Riber, E. and Cuenot, B. }, title = {Effect of non-zero relative velocity on the flame speed of two-phase laminar flames}, year = {2018}, doi = {10.1016/j.proci.2018.07.100}, journal = {Proceedings of the Combustion Institute}, abstract = {A numerical study of one-dimensional n-heptane/air spray flames is presented. The objective is to evaluate the flame propagation speed in the case where droplets evaporate inside the reaction zone with possibly non-zero relative velocity. A Direct Numerical Simulation approach for the gaseous phase is coupled to a discrete particle Lagrangian formalism for the dispersed phase. A global two-step n-heptane/air chemical mechanism is used. The eects of initial droplet diameter, overall equivalence ratio, liquid loading and relative velocity between gaseous and liquid phases on the laminar spray flame speed and structure are studied. For lean premixed cases, it is found that the laminar flame speed decreases with increasing initial droplet diameter and relative velocity. On the contrary, rich premixed cases show a range of diameters for which the flame speed is enhanced compared to the corresponding purely gaseous flame. Finally, spray flames controlled by evaporation always have lower flame speeds. To highlight the controlling parameters of spray flame speed, approximate analytical expressions are proposed, which give the correct trends of the spray flame propagation speed behaviour for both lean and rich mixtures}, keywords = { Direct Numerical Simulation, Lagrangian particle tracking, Spray flame, Laminar flame}, url = {https://doi.org/10.1016/j.proci.2018.07.100}}