An overview of DLR compound rotorcraft aerodynamics and aeroacoustics activities within the CleanSky2 NACOR Project

The challenge of increasing range and speed of a rotorcraft is encountered in the scope of the European CleanSky2 “Fast Rotorcraft” project by Airbus Helicopters with the compound helicopter design RACER (RapidAndCostEfficientRotorcraft) for which the box wing and the tail parts designs are respectively protected by patent. This paper presents the DLR contributions to the RACER development. This includes the aerodynamic design of the wing and tail section as well as an overall assessment of performance and noise. In a first step the aerodynamic properties of the configuration are evaluated both isolated and with consideration of the main rotor and lateral rotor interferences by the use of actuator discs. In the second step, the investigated possibilities to improve the configurations performance are described. These include airfoil design for improved high lift performance of the wing and tail section, an optimization of the box wing circulation distribution on the upper and lower wing. Additionally, the intersection fairings were improved and the efficiency of the trim flaps was evaluated. In this regard, it could be determined for which cases an isolated approach is appropriate and when the rotor interference should be considered. At the end the evaluation of the aero acoustics of the configuration is conducted. The applied configuration shows good aerodynamic characteristics with some further cruise and off design optimization potential

Validation of an unstructured CFD solver for complete helicopter configurations with loose CSD-Trim coupling

The present study addresses the applicability of the unstructured CFD solver TAU of the German Aerospace Center (DLR) for the simulation of isolated rotors and complete helicopter configurations. Rotor trim and elasticity of the rotorblades is taken into account by loose fluid-structure-trim coupling. Numerical results are presented and compared to experimental measurements of the GOAHEAD windtunnel campaign. The selected testcase of the GOAHEAD experimental database corresponds to a cruise flight condition at Ma=0.204 with an advance-ratio of m = 0:33. Validation results for the isolated mainrotor are in excellent agreement with CFD reference solutions and in good agreement with experimental data. CFD simulation for the rotor-fuselage configuration shows a good correlation with experimental data

Validation of the TAU-code for fuselage-rotorhead applications with moving meshes

In the SHANEL-L project in 2009 a simulation of the Eurocopter EC145 fuselage with a model rotorhead was performed with the block-structured solver FLOWer and the unstructured solver TAU 2007 by Eurocopter Deutschland. The results were compared to experimental data from a wind tunnel campaign at the university of Munich. While the results of FLOWer were comparable to the experiment, TAU suffered from an issue in the motion module. Since the solver was considerable improved in the last years, the simulation was repeated in order to demonstrate its applicability for fuselage-rotorhead simulations with moving meshes. The obtained results with the TAU 2011.1.0 release are validated against the experimental data and the FLOWer results

Towards Accurate Prediction of �Blade-Vortex-Interactions on Helicopter Rotors with Higher-Order Accurate Spatial Discretization Methods

In flow simulations of helicopter configurations the blade-vortex-interactions have a significant influence on the prediction of rotor blade loads and also on the trim state. To ensure accurate results, the vortex transport within the flow field has to be physically correct without a premature decay of vortical structures due to numerical dissipation. To realize a physically correct vortex transport in flow simulations with the unstructured DLR TAU code, very fine computational grids may be required to minimize the numerical dissipation, but this leads to an extensive computational effort. A more efficient simulation method for vortical flows is the fourth-order-accurate spatial discretization method implemented in the DLR-FLOWer code, commonly entitled as the FLOWer4 flow solver variant. This method implements a PADE scheme on structured rectilinear grid, so that grid generation for complex configurations may be difficult and costly. To overcome the disadvantages of these simulations methods, the TAU and the FLOWer4 code should be coupled for accurate rotor flow simulations by using an unstructured near-body grid associated to the TAU code and a Cartesian background grid associated to the FLOWer4 code. The transfer of the flow data at the coupling boundaries is realized by an external code coupling module. Additionally the trim state of the helicopter and the blade deformation has a significant impact on the rotor blade tip vortices, which should also be considered in this work, by a further coupling of the flow solution method to the comprehensive rotor code HOST. This code is coupled loosely to the flow solver, so that the rotor blade loads of a full revolution are used to calculate a new trim state and blade deformation data for the following rotor revolution, until a converged trim state is achieved. Within the DLR project DIGITAL-X both aspects of realistic rotor flow simulations are addressed by a coupled simulation approach allowing for accurate prediction of blade-vortex-interactions on helicopters

Coupled fluid-structure simulations of a trimmed helicopter rotor in forward flight

Coupled fluid-structure simulations of high fidelity tools enable an accurate prediction of the aerodynamic and structural properties of helicopters in forward flight. Within this paper the aeroelastic behavior of a trimmed helicopter rotor was investigated using strong and loose coupling approaches. Results of the coupling chains TAU-HOST and TAU-SIMPACK are compared to experimental data from the European GOAHEAD test campaign. The validation test case is a cruise flight condition at Ma=0.204 related to an advance ratio of m = 0:33. The comparison of pressure distributions along the blade and blade deflections are in good agreement with experimental results and amongst each other

An Adjoint-based Optimization Method for Helicopter Fuselage Backdoor Geometry

For utility and transport helicopters with rear loading backdoors, the afterbody area is usually one of the largest drag contributing areas of the fuselage. For this reason, numerical simulations have been performed to assess the possibilities of fuselage drag reduction by the means of local shape modification at the afterbody region. Within this study an automatic optimization chain with gradient-based optimization technique and surface parameterization/deformation tools has been established and applied to the backdoor geometry of a modified GOAHEAD configuration. This paper will present the first numerical results of the ongoing shape optimization studies. As it turns out, local shape modification on the backdoor geometry can lead to a reduction of the separation region there and to a drag reduction of the helicopter fuselage

DLR Project Digital-X: towards virtual aircraft design and flight testing based on high-fidelity methods

Numerical simulation is already an important cornerstone for aircraft design, although the application of highly accurate methods is mainly limited to the design point. To meet future technical, economic and social challenges in aviation, it is essential to simulate a real aircraft at an early stage, including all multidisciplinary interactions covering the entire flight envelope, and to have the ability to provide data with guaranteed accuracy required for development and certification. However, despite the considerable progress made there are still significant obstacles to be overcome in the development of numerical methods, physical modeling, and the integration of different aircraft disciplines for multidisciplinary analysis and optimization of realistic aircraft configurations. At DLR, these challenges are being addressed in the framework of the multicisciplinary project Digital-X (4/2012 - 12/2015). This paper provides an overview of the project objectives and presents first results on enhanced disciplinary methods in aerodynamics and stuctural analysis, the development of efficient reduced order methods for load analysis, the development of a multidisciplinary optimization process based on a multi-level/variable-fidelity approach, as well as the development and application of multidisciplinary methods for the analysis of maneuver loads

"DLR-Projekt Digital-X" Auf dem Weg zur virtuellen Flugzeugentwicklung und Flugerprobung auf Basis höherwertiger Verfahren

Die numerische Simulation stellt schon heute einen wichtigen Eckpfeiler im Flugzeugentwurf dar, obwohl der Einsatz hochgenauer Verfahren im Wesentlichen bisher noch auf den Entwurfspunkt beschränkt ist. Um den zukünftigen technischen, wirtschaftlichen und gesellschaftlichen Herausforderungen in der Luftfahrt begegnen zu können, wird es unverzichtbar sein, ein reales Flugzeug einschließlich aller multidisziplinären Wechselwirkungen im gesamten Flugbereich frühzeitig im Rechner zu simulieren oder entwicklungs- und zulassungsrelevante Daten mit garantierter Genauigkeit erstellen zu können. Trotz der bisher erzielten Fortschritte sind hierzu allerdings noch wesentliche Hürden im Bereich der Entwicklung numerischer Verfahren, der physikalischen Modellierung sowie der Zusammenführung der verschiedenen Flugzeugdisziplinen zur multidisziplinären Analyse und Optimierung für realistische Flugzeugkonfigurationen zu nehmen. Im DLR werden diese Herausforderungen im Rahmen des multidisziplinären Projektes Digital-X (4/2012-12/2015) angenommen. In diesem Übersichtsbeitrag werden neben der Zielsetzung des Projektes erste Ergebnisse hinsichtlich der weiterentwickelten disziplinären Verfahren in der Aerodynamik und der Strukturdynamik, der Entwicklung effizienter Methoden reduzierter Ordnung zu Lastanalyse, der Entwicklung eines multidisziplinären Optimierungsprozesses auf Basis eines "Multi-Level/Variable-Fidelity"-Ansatzes sowie der Entwicklung und Anwendung von multidisziplinären Verfahren zur Analyse von Manöverlasten gezeigt

New results on light nuclei, hyperons and hypernuclei from HADES (HADES collaboration)

International audienceIn March 2019 the HADES experiment recorded 14 billion Ag+Ag collisions at √sNN = 2.55 GeV as a part of the FAIR phase-0 physics program. In this contribution, we present and investigate our capabilities to reconstruct and analyze weakly decaying strange hadrons and hypernuclei emerging from these collisions. The focus is put on measuring the mean lifetimes of these particles