Evaluation de méthodes CFD avec prise en compte de la transition laminaire-turbulent pour l'aéroélasticité des voilures laminaires

International audienceHigh fidelity aeroelastic simulations of laminar wings require an accurate prediction of the aerodynamic forces taking into account non-linear phenomena due to the laminar-turbulent transition. This paper proposes an evaluation of CFD RANS based methods associated with transition criteria or models for flight conditions of interest from an aeroelastic point of view (low and high incidences, transonic Mach numbers). This evaluation is carried out through comparisons with wind tunnel tests. The first step consists in assessing different models for steady transonic flow fields around a 2D laminar airfoil. The influence of crossflow transition on the aerodynamic response to a 3D wing oscillating in pitch is addressed in a second step for low speed flight conditions

Structural optimization of an aeroelastic wind tunnel model for unsteady transonic testing

The reduction of loads, ultimately leading to a weight reduction and thus an increase in aircraft performance, plays an important role in the design of modern aircraft. To this end, two aeroelastic tailoring methodologies, independently developed at ONERA and DLR and aiming at load reduction by means of a sophisticated application of composite materials, were applied to a common model geometry. A choice was made in favor of the publicly available NASA Common Research Model (CRM) wing, featuring a comprehensive database with respect to geometry, as well as analytical and experimental research results. The span of the wing half to be investigated was set to 0.55 m, limited by the test section dimensions. While wind tunnel testing was part of ONERA's workshare, the model building was performed by DLR. This paper at hand focuses on the structural, aeroelastic optimization of the DLR wing. It is based on an optimization framework developed and constantly being enhanced and extended at the DLR - Institute of Aeroelasticity (DLR-AE). The paper describes the consideration of different structural objective functions, structural and aeroelastic constraint combinations, design field considerations, as well as the application of an aero load correction applied in the course of the optimization. The final results consist of the selection of an appropriate fiber type, optimized fiber layers represented as stacking sequence tables for the upper and lower wing skins, and the corresponding optimized jig twist distribution, required for manufacturing the lamination molds; in summary, all data required to start the construction of the wind tunnel model

Aeroelastic-tailoring of a wind-tunnel model for passive alleviation of static and dynamic loads

Composite materials allow to tailor the elastic properties of a structure. In aeroelasticity, this opens up the possibility to passively enhance the coupled aerostructural characteristics. In this work, the design of a composite wing is addressed with the aim to alleviate static and dynamic aeroelastic loads; these two objectives are quantified by the root-bending-moment in a high load-factor condition and the deformation amplitude of the wing under gust. A two-step approach of the optimal design of the structure is adopted. A Pareto front is computed via an aeroelastic model of the wing; the aerodynamic loads are modelled, depending on the load-case, either via the DLM or the RANS equations. The best-compromise design is chosen via a criterion based on the jig-shape and, finally, the stacking-sequences are computed via a specialised evolutionary algorithm

Capnocytophaga canimorsus endocarditis with root abscess in a patient with a bicuspid aortic valve

Infective endocarditis caused by a zoonotic micro organism is a rare clinical condition. Capnocytophaga canimorsus is a commensal bacterium living in the saliva of dogs and cats which produces rarely reported endocarditis whose incidence may be underestimated, considering its failure to grow on standard media. We reported the case of a 65-year-old man with bicuspid aortic valve endocarditis and multiple abscesses of the aortic wall caused by the canine bacteria C. canimorsus

Unitarity Bounds in AdS_3 Higher Spin Gravity

We study SL(N,R) Chern-Simons gauge theories in three dimensions. The choice of the embedding of SL(2,R) in SL(N,R), together with asymptotic boundary conditions, defines a theory of higher spin gravity. Each inequivalent embedding leads to a different asymptotic symmetry group, which we map to an OPE structure at the boundary. A simple inspection of these algebras indicates that only the W_N algebra constructed using the principal embedding could admit a unitary representation for large values of the central charge.Comment: 1+23 pages, Version 3 Appendix B revise

Silicon photonics frequency shifter based on I&Q dual Mach-Zehnder modulator

We present a fully CMOS compatible frequency shifter device, in a I&Q dual Mach-Zehnder architecture. Frequency shift up to 410 MHz are obtained, with carrier and image sideband extinction from 27 to 51 dB

MRI-Based Radiomics Input for Prediction of 2-Year Disease Recurrence in Anal Squamous Cell Carcinoma

International audiencePurpose: Chemo-radiotherapy (CRT) is the standard treatment for non-metastatic anal squamous cell carcinomas (ASCC). Despite excellent results for T1-2 stages, relapses still occur in around 35% of locally advanced tumors. Recent strategies focus on treatment intensification, but could benefit from a better patient selection. Our goal was to assess the prognostic value of pre-therapeutic MRI radiomics on 2-year disease control (DC). Methods: We retrospectively selected patients with non-metastatic ASCC treated at the CHU Bordeaux and in the French FFCD0904 multicentric trial. Radiomic features were extracted from T2-weighted pre-therapeutic MRI delineated sequences. After random division between training and testing sets on a 2:1 ratio, univariate and multivariate analysis were performed on the training cohort to select optimal features. The correlation with 2-year DC was assessed using logistic regression models, with AUC and accuracy as performance gauges, and the prediction of disease-free survival using Cox regression and Kaplan-Meier analysis. Results: A total of 82 patients were randomized in the training (n = 54) and testing sets (n = 28). At 2 years, 24 patients (29%) presented relapse. In the training set, two clinical (tumor size and CRT length) and two radiomic features (FirstOrder_Entropy and GLCM_JointEnergy) were associated with disease control in univariate analysis and included in the model. The clinical model was outperformed by the mixed (clinical and radiomic) model in both the training (AUC 0.758 versus 0.825, accuracy of 75.9% versus 87%) and testing (AUC 0.714 versus 0.898, accuracy of 78.6% versus 85.7%) sets, which led to distinctive high and low risk of disease relapse groups (HR 8.60, p = 0.005). Conclusion: A mixed model with two clinical and two radiomic features was predictive of 2-year disease control after CRT and could contribute to identify high risk patients amenable to treatment intensification with view of personalized medicine