Rotating Wind Dynamic Stall: State of the Art and Future Directions

Dynamic stall has been studied for more than fifty years; in the last decade significant advances have been accomplished in the understanding, prediction, modeling and control of dynamic stall on rotors. In September 2019, an Army Research Office-funded workshop was held at the Georgia Institute of Technology to evaluate the state of the art and future directions in the understanding and control of dynamic stall found on rotors, specifically for vertical lift vehicles. Approximately forty attendees drawn from top experts in the field to graduate students convened to discuss experimental, computational, theoretical, and control research in the field over a two-day period. This paper provides a summary of the findings from this workshop, including a synopsis of best practices for experiments and first-principles-based computational prediction of rotor dynamic stall. Experimental data sets are discussed, as well the direction of research for empirical (non-first-principles) modeling and control of dynamic stall

Numerical Investigation of Three-Dimensional Static and Dynamic Stall on a Finite Wing

Three-dimensional numerical computations using ONERA’s structured elsA code and the unstructured DLR-TAU code are compared with the OA209 finite wing experiments in static stall and dynamic stall conditions at a Mach number of 0.16 and a Reynolds number of 1 × 10^6 . The DLR-TAU computations were run with the Spalart–Allmaras and Menter shear stress transport (SST) turbulence models, and the elsA computations were carried out using the Spalart–Allmaras and the k–ω Kok + SST turbulence models. Although comparable grids were used, the static simulations show large discrepancies in the stall region between the structured and unstructured approaches. Large differences for the three-dimensional dynamic stall case are obtained with the computations using the Spalart–Allmaras turbulence model showing trailing edge separation only in contrast to the leading edge stall in the experiment. The three-dimensional dynamic stall computations with the two- equation turbulence models are in good agreement with the unsteady pressure measurements and flow field visualizations of the experiment, but also show a shift in the stall angle compared to the experiment. The analysis of the flow field around the finite wing using the numerical simulations reveals the evolution of the -shaped vortex, generated by the interaction of the blade tip vortex

Numerical investigation of three-dimensional dynamic stall on an oscillating finite wing

Three-dimensional numerical computations using ONERA’s structured elsA code and the unstructured DLR-TAU code are compared with the OA209 finite wing experiments in static stall and dynamic stall conditions at a Mach number of 0.16 and a Reynolds number of 1x10^6. The DLR-TAU computations were run with the Spalart-Allmaras and Menter SST turbulence models, and the elsA computations were carried out using the Spalart-Allmaras and the k-w Kok + SST turbulence models. Although comparable grids were used the static simulations show large discrepancies in the stall region between the structured and unstructured approaches. Large differences for the three-dimensional dynamic stall case are obtained with the computations using the Spalart-Allmaras turbulence model showing no flow separation in contrast to the experiment. The three-dimensional dynamic stall computations with the two-equation turbulence models are in good agreement with the unsteady pressure measurements and flow field visualizations of the experiment, but also show a shift in the stall angle compared to the experiment. The analysis of the flow field around the finite wing using the numerical simulations reveals the evolution of the omega-shaped vortex, generated by the interaction of the blade tip vortex

Validation of Boundary-Layer-Transition Computations for a Rotor with Axial Inflow

Boundary-layer-transition computations are performed using the in-house finite-volume solvers elsA by ONERA and TAU by DLR. Reynolds-averaged Navier-Stokes simulations, using the Langtry-Menter model as well as semiempirical transition criteria, are presented using both solvers for a rotor in climb. The numerical results are compared to temperature-sensitive paint experiments conducted at DLR's rotor test facility. Concerning the Langtry-Menter computation, transition occurs with both solvers due to laminar separation close to the trailing edge, further downstream than seen in the experiment. Semi-empirical transition criteria predict transition within both codes due to laminar separation, which was not detected in the experiments. When only considering the AHD criterion, the transition locations within the numerical simulations and the experiment are in good agreement along the entire span in all three considered test cases. In addition, numerical results are presented for a test case with cyclic pitch. These unsteady boundary-layer transition computations are carried out using the semi-empirical transition criteria approach of DLR-TAU. In accordance with the static test cases, the results are promising, as long as the laminar-separation criterion is deactivated

Assessment of Boundary Layer Transition Prediction Methods for Rotating Blades

Boundary-layer-transition computations are performed using the in-house finite-volume solvers elsA by ONERA and TAU by DLR. Reynolds-averaged Navier-Stokes simulations, using the Langtry-Menter model as well as semiempirical transition criteria, are presented using both solvers for a rotor in climb. The numerical results are compared to temperature-sensitive paint experiments conducted at DLR's rotor test facility. Concerning the Langtry-Menter computation, transition occurs with both solvers due to laminar separation close to the trailing edge, further downstream than seen in the experiment. The transition locations using AHD semi-empirical transition criterion are in good agreement along the entire span in all three considered test cases. In addition, numerical results are presented for a test case with cyclic pitch. These unsteady boundary-layer transition computations are carried out using the semi-empirical transition criteria approach of DLR-TAU. In accordance with the static test cases, the results are promising, as long as the laminar-separation criterion is deactivated

Olegusella massiliensis gen. nov., sp nov., strain KHD7(T), a new bacterial genus isolated from the female genital tract of a patient with bacterial vaginosis

International audienceStrain KHD7(T), a Gram-stain-positive rod-shaped, non-sporulating, strictly anaerobic bacterium, was isolated from the vaginal swab of a woman with bacterial vaginosis. We studied its phenotypic characteristics and sequenced its complete genome. The major fatty acids were C16:0 (44%), C18:2n6 (22%), and C18:1n9 (14%). The 1,806,744 bp long genome exhibited 49.24% G+C content; 1549 protein-coding and 51 RNA genes. Strain KHD7(T) exhibited a 93.5% 16S rRNA similarity with Olsenella uli, the phylogenetically closest species in the family Coriobacteriaceae. Therefore, strain KHD7(T) is sufficiently distinct to represent a new genus, for which we propose the name Olegusella massiliensis gen. nov., sp. nov. The type strain is KHD7(T). (C) 2017 Elsevier Ltd. All rights reserved

Selectins impair regulatory T cell function and contribute to systemic lupus erythematosus pathogenesis

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by a loss of tolerance toward self-nucleic acids, autoantibody production, interferon expression and signaling, and a defect in the regulatory T (T(reg)) cell compartment. In this work, we identified that platelets from patients with active SLE preferentially interacted with T(reg) cells via the P-selectin/P-selectin glycoprotein ligand-1 (PSGL-1) axis. Selectin interaction with PSGL-1 blocked the regulatory and suppressive properties of T(reg) cells and particularly follicular T(reg) cells by triggering Syk phosphorylation and an increase in intracytosolic calcium. Mechanistically, P-selectin engagement on T(reg) cells induced a down-regulation of the transforming growth factor-β axis, altering the phenotype of T(reg) cells and limiting their immunosuppressive responses. In patients with SLE, we found an up-regulation of P- and E-selectin both on microparticles and in their soluble forms that correlated with disease activity. Last, blocking P-selectin in a mouse model of SLE improved cardinal features of the disease, such as anti-dsDNA antibody concentrations and kidney pathology. Overall, our results identify a P-selectin-dependent pathway that is active in patients with SLE and validate it as a potential therapeutic avenue

Improved survival in multiple myeloma during the 2005-2009 and 2010-2014 periods

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COVID-19 outcomes in patients with inflammatory rheumatic and musculoskeletal diseases treated with rituximab: a cohort study

International audienceBackground: Various observations have suggested that the course of COVID-19 might be less favourable in patients with inflammatory rheumatic and musculoskeletal diseases receiving rituximab compared with those not receiving rituximab. We aimed to investigate whether treatment with rituximab is associated with severe COVID-19 outcomes in patients with inflammatory rheumatic and musculoskeletal diseases.Methods: In this cohort study, we analysed data from the French RMD COVID-19 cohort, which included patients aged 18 years or older with inflammatory rheumatic and musculoskeletal diseases and highly suspected or confirmed COVID-19. The primary endpoint was the severity of COVID-19 in patients treated with rituximab (rituximab group) compared with patients who did not receive rituximab (no rituximab group). Severe disease was defined as that requiring admission to an intensive care unit or leading to death. Secondary objectives were to analyse deaths and duration of hospital stay. The inverse probability of treatment weighting propensity score method was used to adjust for potential confounding factors (age, sex, arterial hypertension, diabetes, smoking status, body-mass index, interstitial lung disease, cardiovascular diseases, cancer, corticosteroid use, chronic renal failure, and the underlying disease [rheumatoid arthritis vs others]). Odds ratios and hazard ratios and their 95% CIs were calculated as effect size, by dividing the two population mean differences by their SD. This study is registered with ClinicalTrials.gov, NCT04353609.Findings: Between April 15, 2020, and Nov 20, 2020, data were collected for 1090 patients (mean age 55·2 years [SD 16·4]); 734 (67%) were female and 356 (33%) were male. Of the 1090 patients, 137 (13%) developed severe COVID-19 and 89 (8%) died. After adjusting for potential confounding factors, severe disease was observed more frequently (effect size 3·26, 95% CI 1·66-6·40, p=0·0006) and the duration of hospital stay was markedly longer (0·62, 0·46-0·85, p=0·0024) in the 63 patients in the rituximab group than in the 1027 patients in the no rituximab group. 13 (21%) of 63 patients in the rituximab group died compared with 76 (7%) of 1027 patients in the no rituximab group, but the adjusted risk of death was not significantly increased in the rituximab group (effect size 1·32, 95% CI 0·55-3·19, p=0·53).Interpretation: Rituximab therapy is associated with more severe COVID-19. Rituximab will have to be prescribed with particular caution in patients with inflammatory rheumatic and musculoskeletal diseases