European Benchmark on Numerical Prediction of Stability and Control derivatives.

Reliable prediction of flight dynamic criteria is conditioned by a satisfactory prediction of aerodynamic static and dynamic derivatives. A numerical benchmark has been conducted within the framework of the European Project SimSAC “Simulating Aircraft Stability And Control Characteristics for Use in Conceptual Design”. The objective was to establish the ability as well as the productivity of different tools to predict stability and control derivatives. Different levels of fidelity have been included, from quasi-steady VLM to fully unsteady RANS solvers. The numerical data have been compared to experimental ones, on the DLR-F12 generic civil aircraft. It has been wind-tunnel tested during the project, with several forced-motion oscillations; the data base includes unsteady pressures (not analysed in this paper). The study confirms that an increase in fidelity level allows for a better estimation of dynamic derivatives. VLM tools can give very satisfactory results but are very sensitive to the geometry/mesh input data. All the quasi-steady CFD approaches give very comparable results (robustness) on steady dynamic derivatives. However, they do not allow for the prediction of unsteady components of the dynamic derivatives (so called damping derivatives): this can be done with either a fully unsteady approach (with a time-marching scheme) or with Frequency Domain solvers, both of them giving very comparable results

Accounting for Vertical Subgrid‐Scale Heterogeneity in Low‐Level Cloud Fraction Parameterizations

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Benchmarking the prediction of dynamic derivatives: wind tunnel tests, validation, acceleration methods

The dynamic derivatives are widely used in linear aerodynamic models which are considered to determine the flying qualities of an aircraft: the ability to predict them reliably, quickly and sufficiently early in the design process is more and more important, in order to avoid late and costly component redesigns. This paper describes some experimental and computational activities dealing with the determination of dynamic derivatives. The work has been carried out within the FP6 European project SimSAC. Numerical and experimental results are compared for two aircraft configurations: the generic civil transport aircraft, wing-fuselage-tail configuration DLR-F12 and a generic Transonic CRuiser (TCR), which is a canard configuration. Static and dynamic wind tunnel tests have been carried out for both configurations and are briefly described. The data base generated for the DLR-F12 configuration includes force and pressure coefficients obtained during small amplitude pitch, roll and yaw oscillations while the data base for the TCR configuration includes force coefficients for small amplitude oscillations, dedicated to the determination of dynamic derivatives, and large amplitude oscillations, in order to investigate the dynamic effects on nonlinear aerodynamic characteristics. The influence of the canard has been investigated too. Dynamic derivatives have been determined on both configurations with a large panel of tools, from linear aerodynamic (Vortex Lattice Methods) to CFD (unsteady Reynolds-Averaged Navier-Stokes solvers). The study confirms that an increase in fidelity level enables dynamic derivatives to be better calculated. Linear aerodynamics (VLM) tools can give satisfactory results but are very sensitive to the geometry/mesh input data. Although all the quasi-steady CFD approaches give very comparable results (robustness) on steady dynamic derivatives, they do not allow the prediction of unsteady components of the dynamic derivatives (angular derivatives w.r.t. time): this can be done with either a fully unsteady approach (with a time-marching scheme) or with Frequency Domain solvers, both of them giving very comparable results for the DLR-F12 test case. As far as the canard configuration is concerned; strong limitations of linear aerodynamic tools are observed. A specific attention is paid to acceleration techniques in CFD methods, which allow the computational time to be dramatically reduced while keeping a satisfactory accuracy

Validation of numerical prediction of dynamic derivatives: the DLR-F12 and the Transcruiser test cases

The dynamic derivatives are widely used in linear aerodynamic models in order to determine the flying qualities of an aircraft: the ability to predict them reliably, quickly and sufficiently early in the design process is vital in order to avoid late and costly component redesigns. This paper describes experimental and computational research dealing with the determination of dynamic derivatives carried out within the FP6 European project SimSAC. Numerical and experimental results are compared for two aircraft configurations: a generic civil transport aircraft, wing-fuselage-tail configuration called the DLR-F12 and a generic Transonic CRuiser, which is a canard configuration. Static and dynamic wind tunnel tests have been carried out for both configurations and are briefly described within this paper. The data generated for both the DLR-F12 and TCR configurations include force and pressure coefficients obtained during small amplitude pitch, roll and yaw oscillations while the data for the TCR configuration also include large amplitude oscillations, in order to investigate the dynamic effects on nonlinear aerodynamic characteristics. In addition, dynamic derivatives have been determined for both configurations with a large panel of tools, from linear aerodynamic (Vortex Lattice Methods) to CFD. This work confirms that an increase in fidelity level enables the dynamic derivatives to be calculated more accurately. Linear aerodynamics tools are shown to give satisfactory results but are very sensitive to the geometry/mesh input data. Although all the quasi-steady CFD approaches give comparable results (robustness) for steady dynamic derivatives, they do not allow the prediction of unsteady components for the dynamic derivatives (angular derivatives with respect to time): this can be done with either a fully unsteady approach i.e. with a time-marching scheme or with frequency domain solvers, both of which provide comparable results for the DLR-F12 test case. As far as the canard configuration is concerned, strong limitations for the linear aerodynamic tools are observed. A key aspect of this work are the acceleration techniques developed for CFD methods, which allow the computational time to be dramatically reduced while providing comparable results

Postoperative irinotecan in resected stage II-III rectal cancer: final analysis of the French R98 Intergroup trial

International audienceBACKGROUD:The R98 trial explores the addition of irinotecan to a 5-fluorouracil (5-FU) plus leucovorin (5-FU/LV) adjuvant regimen in optimally resected stages II-III rectal cancers. We report the updated long-term results. Disease-free survival (DFS) was the primary end point.PATIENST AND METHODS:Between March 1999 and December 2005, 357 patients were randomized: 178 in 5-FU/LV and 179 in LV5-FU2 + irinotecan arm. The trial was stratified by control arm: Mayo Clinic regimen or LV5-FU2 regimen.RESULTS:Three hundred and fifty-seven randomized patients were evaluable for efficacy. With a follow-up of 156 months, the DFS was in favour of experimental arm but did not reach statistical significance [hazard ratio (HR) = 0.80, P = 0.154]. The same was observed for overall survival (OS) (HR = 0.87, P = 0.433). The 5-year DFS was 58% in the control arm and 63% in the experimental arm. The 5-year OS was 74% in the control arm and 75% in the experimental arm. Patients allocated to the experimental arm had more grade 3-4 neutropenia when compared with the LV5-FU2 arm (33% versus 6%, P = 0.03), but not when compared with the Mayo Clinic arm (33% versus 36%, P = 0.84). Grade 3-4 diarrhoea tended to be higher in the experimental arm, but analyses stratified by control arm or by radiotherapy failed to show significant differences across strata (test for interaction P = 0.44).CONCLUSION:Even though a benefit of irinotecan in subgroups of patients cannot be excluded, due to early termination and lack of power, the study does not support the addition of irinotecan to 5-FU/LV in routine in patients with resected stage II-III rectal cancer

Adaptive Multiscale Methods for Flow Problems: Recent Developments

Abstract The concept of the new fully adaptive flow solver Quadflow has been developed within the SFB 401 over the past 12 years. Its primary novelty lies in the integration of new and advanced mathematical tools in a unified environment. This means that the core ingredients of the finite volume solver, the grid adaptation and grid generation are adapted to each others needs rather than putting them together as independent black boxes. In this paper we shall present recent developments and demonstrate their efficiency by numerical experiments for some representative basic configurations.