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@ARTICLE{AR-CFD-22-76, author = {Duquesne, P. and Chanéac , J. and Mondin, G. and Dombard, J. }, title = {Topology Rule-Based Methodology for Flow Separation Analysis in Turbomachinery}, year = {2022}, number = {3}, volume = {7}, pages = {Article number 21}, doi = {10.3390/ijtpp7030021}, journal = {International Journal of Turbomachinery, Propulsion and Power}, abstract = {Boundary-layer flow separation is a common flow feature in many engineering applications. The consequences of flow separation in turbomachinery can be disastrous in terms of performance, stability and noise. In this context, flow separation is particularly difficult to understand because of its three-dimensional and confined aspects. Analyzing the skin friction lines is one key point to understanding and controlling this phenomenon. In the case of separation, the flow at the wall agglutinates around a manifold while the fluid from the boundary layer is ejected toward the flow away from the wall. The analysis of a three-dimensional separation zone based on topology is well addressed for a simple geometry. This paper aims at providing simple rules and methods, with a clear vocabulary based on mathematical background, to conduct a similar analysis with complex turbomachinery geometry (to understand a surface with a high genus). Such an analysis relies on physical principles that help in understanding the mechanisms of flow separation on complex geometries. This paper includes numerous typical turbomachinery surfaces: the stator row, vaneless diffuser, vaned diffuser, axial rotor and shrouded and unshrouded centrifugal impeller. Thanks to surface homeomorphisms, the generic examples presented can easily be converted into realistic shapes. Furthermore, classical turbomachinery problems are also addressed, such as periodicity or rotor clearance. In the last section, the proposed methodology is conducted on a radial diffuser of an industrial compressor. The flow at the wall is extracted from LES computations. This study presents the different closed separation zones in a high-efficiency operating condition}, keywords = {critical point, flow separation, topology rule, turbomachinery}}

@ARTICLE{AR-PA-22-78, author = {Lazzara, M. and Chevalier, M. and Colombo, M. and Garay Garcia, J. and Lapeyre, C. and Teste, O. }, title = {Surrogate modelling for an aircraft dynamic landing loads simulation using an LSTM AutoEncoder-based dimensionality reduction approach}, year = {2022}, volume = {126}, pages = {Article number 107629}, doi = {10.1016/j.ast.2022.107629}, journal = {Aerospace Science and Technology}, abstract = {Surrogate modelling can alleviate the computational burden of design activities as they rely on multiple evaluations of high-fidelity models. However, the learning task can be adversely affected by the high-dimensionality of the system, complex non-linearities and temporal dependencies, leading to an inaccurate surrogate model. In this paper we present an innovative dual-phase Long-Short Term Memory (LSTM) Autoencoder-based surrogate model applied in an industrial context for the prediction of aircraft dynamic landing response over time, conditioned by an exogenous set of design parameters. The LSTM-Autoencoder is adopted as a dimensionality-reduction tool that extracts the temporal features and the nonlinearities of the high-dimensional dynamical system response, and learns a low-dimensional representation of it. Then, a Fully Connected Neural Network is trained to learn the simplified relationship between the input parameters and the reduced representation of the output. For our application, the results demonstrate that our LSTM-AE based model outperforms both Principal Component Analysis and Convolutional-Autoencoder based surrogate models, in predicting the parameters-dependent high-dimensional temporal system response. }}

@ARTICLE{AR-CFD-22-61, author = {Crespo-Anadon , J. and Benito-Parejo, C.J. and Richard, S. and Riber, E. and Cuenot, B. and Strozzi, C. and Sotton, J. and Bellenoue, M. }, title = {Experimental and LES investigation of ignition of a spinning combustion technology combustor under relevant operating conditions}, year = {2022}, volume = {242}, pages = { 112204}, doi = {10.1016/j.combustflame.2022.112204}, journal = {Combustion and Flame}, abstract = {SAFRAN Helicopter Engines has developed the spinning combustion technology in which the burnt gases from one injector travel tangentially along the combustor annulus towards the neighboring injectors. Compared to a conventional design, this arrangement modifies the ignition process, which is a critical phase for aeroengines. In order to understand the ignition process in this technology, experiments and Large-Eddy Simulation (LES) have been performed in a cylindrical combustion chamber where the flow is injected tangentially (named Radius chamber). Three cases are considered with different strain and turbulence levels representative of real combustor flows. Micro calorimetry and the Background-Oriented Schlieren technique allows for detailed temporal measurements of energy deposited in the flame kernel. Pressure measurement and Schlieren imaging are used to study the flame propagation. LES are performed with a 19-species and 184-reactions analytically-reduced chemistry together with the thickened flame approach allowing the description of the first instants of ignition in a quasi-DNS mode and ensuing flame propagation. Both a static and dynamic formulations of the wrinkling factor to describe sub-grid scale chemistry-turbulence interaction are used. Results show that LES is able to capture the flame kernel formation and trajectory as well as the time to reach maximum pressure within an error of 10% when using a dynamic formulation. On the other hand, the static formulation of the wrinkling factor predicts the time for maximum pressure within a maximum error of 20%.}, keywords = {Ignition, Analytically Reduced Chemistry, LES, Spinning combustion technology}, pdf = {https://cerfacs.fr/wp-content/uploads/2022/06/CFD_Crespo_Comb_flame_AR_CFD_22_61.pdf}}

@ARTICLE{AR-CFD-22-67, author = {Di Renzo, M. and Cuenot, B. }, title = {A reduced chemical mechanism for the simulation of electrified methane/air flames}, year = {2022}, volume = {244}, pages = {112246}, doi = {10.1016/j.combustflame.2022.112246}, journal = {Combustion and Flame}, url = {https://www.sciencedirect.com/science/article/abs/pii/S0010218022002619}}

@ARTICLE{AR-CFD-22-71, author = {Sengupta, S. and Nadakkal-Appukuttan, S. and Mohanamuraly, P. and Staffelbach, G. and Gicquel, L.Y.M. }, title = {Global spectral analysis of the Lax–Wendroff-central difference scheme applied to Convection–Diffusion equation}, year = {2022}, volume = {242}, pages = {105508}, doi = {10.1016/j.compfluid.2022.105508}, journal = {Computers and Fluids}}