GARTEUR Helicopter Cooperative Research

This paper starts with an overview about the general structure of the Group for Aeronautical Research and Technology in EURope (GARTEUR). The focus is on the activities related to rotorcraft which are managed in the GARTEUR Helicopter Group of Responsables (HC GoR). The research activities are carried out in so-called Action Groups. Out of the 5 Action Groups which ended within the last four years results generated in the Helicopter Action Groups HC(AG14) “Methods for Refinement of Structural Dynamic Finite Element Models”, HC(AG15) “Improvement of SPH methods for application to helicopter ditching” and HC(AG16) “Rigid Body and Aeroelastic Rotorcraft-Pilot Coupling” are briefly summarized

Generation of an Advanced Helicopter Experimental Aerodynamic Database for CFD Code Validation (GOAHEAD)

During the last ten years considerable progress has been made in the development of aerodynamic prediction capabilities by means of CFD for isolated helicopter components such as an isolated main rotor or an isolated fuselage. Today leading edge CFD software systems are available which are capable of predicting the viscous flow around complete helicopters. The greatest shortcoming in Europe for qualifying RANS methods as design tools in the industrial design process for helicopters is the lack of detailed experimental validation data for the aerodynamics of complete helicopters. This issue was addressed by the European GOAHEAD research project (Generation of Advanced Helicopter Experimental Aerodynamic Database for CFD code validation). The presentation will give an overview over the results obtained in GOAHEAD: Within the project a wind tunnel experiment for a complete helicopter configuration consisting of fuselage, main and tail rotor was conducted. The wind tunnel set-up, the extensive model instrumentation and the wind tunnel test matrix were chosen to satisfy the requirements for validation of CFD methods. Results of the campaign in the DNW-LLF wind tunnel include unsteady pressures and loads, laminar/turbulent transition lines, blade deformation data and flow field visualization by means of PIV. The data were analysed in detail and a comprehensive documentation was generated for the experimental data base. In parallel to the wind tunnel experiment six European CFD codes were applied by 11 partners from industry, research organizations and universities in a blind test and post test exercise. The comparison of the computational results provides an assessment of different code features, allows to evaluate the reliability of the codes and gives directions for further code developments. The progress made within GOAHEAD is a big step forward having in mind that the first successful RANS helicopter simulations in Europe have been published in 2002

CHANCE: A FRENCH-GERMAN HELICOPTER CFD-PROJECT

The paper gives an overview of the CHANCE research project (partly supported by the French DPAC and DGA and the German BMWA) which was started in 1998 between the German and French Aerospace Research Centres DLR and ONERA, the University of Stuttgart and the two National Helicopter Manufacturers, Eurocopter and Eurocopter Deutschland. The objective of the project was to develop and validate CFD tools for computing the aerodynamics of the complete helicopter, accounting for the blade elasticity by coupling with blade dynamics. The validation activity of the flow solvers was achieved through intermediate stages of increasing geometry and flow modelling complexity, starting from an isolated rotor in hover, and concluding with the time-accurate simulation of a complete helicopter configuration in forward-flight. All along the research program the updated versions of the CFD codes were systematically delivered to Industry. This approach was chosen to speed up the transfer of capabilities to industry and check early enough that the products meet the expectations for applicability in the industrial environment of Eurocopter

The GOAHEAD Project

The 6th Framework Programme EU-Project GOAHEAD is presented. The consortium is described and the project structure is explained. The main objective of GOAHEAD is to create an experimental database for the validation of 3D CFD and comprehensive aeromechanics methods for the prediction of unsteady viscous flows including rotor dynamics for complete helicopter configurations. The wind tunnel model integration is ongoing. On the CFD side first results were obtained for trimmed Unsteady Reynolds Averaged Navier Stokes (URANS) simulations of a complete helicopter including fluid structure coupling. The wind tunnel experiment is scheduled for January 2008 in the DNW LLF

Application of the Standard Aeronautical CFD Method FLOWer to ETR500 Tunnel Entry

The time-accurate 3D Euler/Navier-Stokes code FLOWer of DLR is applied to a symmetric and a non-symmetric train entering a tunnel test case. The computed pressure signals are compared with full scale measurements of an ETR500 high speed train entering the north portal of the Terranuova Le Ville Tunnel. It is shown that FLOWer is able to compute tunnel entry configurations qualitatively correct

Application of the Standard Aeronautical CFD Method FLOWer to Trains Passing on Open Track

The time-accurate 3D Euler/Navier-Stokes code FLOWer of DLR is applied to trains passing on open track test cases. One test case with the German ICE and three test cases with the Italian ETR500 high speed train were selected. It turned out that the accuracy requirements for train passing applications are very high because absolutely and relatively small pressure differences, compared to typical aeronautical applications, have to be resolved. In order to reach the required accuracy the grid quality in terms of grid fineness and smoothness (cell stretching, cell distortion) on the surfaces and in the flow field is of primary importance. The paper addresses the numerical problems encountered during these applications. Computed pressure signals are compared with full scale measurements. It is shown that FLOWer is able to accurately compute train passing configuration but with a high computational effort

New Technologies for Green Rotorcraft

The paper presents main results obtained in the DLR rotorcraft program within the last years such as computational tools (e.g. CFD development and validation for aerodynamics and aeroacoustic), noise studies, environmental studies such as all weather issues, new technologies for active rotor control and active blades, flight mechanics and handling quality studies, recent developments for tiltrotor applications, crash analysis and modelling and helicopter flight tests including studies for noise abatement procedures. The DLR rotorcraft research program is closely connected to the Onera rotorcraft program and is part of international networks of cooperation with many partner organizations. DLR and Onera have been designing rotorcraft airfoils for many years. Almost all Eurocopter helicopters use these airfoils. One important asset to improve the aerodynamic efficiency (i.e. reduce the fuel consumption and the exhaust) of rotorcraft or rotorcraft components is the access to accurate prediction tools. Therefore a large effort was spent during the last two decades to develop so called Computational Fluid Dynamics (CFD) methods which are able to compute the flow around a complete rotorcraft. In order to validate such methods the GOAHEAD (Generation of Advanced Helicopter Experimental Aerodynamic Database for CFD code Valication) project was carried out. One of the main factors restricting the use of rotorcaft in civil and partly in military missions, is the noise emission of these vehicles. Therefore ongoing research concerns itself with the development and validation of methods for the prediction of external and internal noise and specific solutions for noise reduction. This includes the main and tail rotor/Fenestron noise, as well as the engine noise. The successful application of helicopters in Emergency Medical Services (EMS), in rescue operations (Save and Rescue: SAR) and in specific military missions is limited by bad weather conditions, especially degraded visual environments and icing conditions. Helicopters are frequently operated in close proximity to the ground at short distances from obstacles (trees, power poles, etc.). The workload of the pilot and the accident risk in such difficult missions is considerably higher than that of a typical fixed wing aircraft. Therefore research is for flight control, man-machine-interface, sensor development, information display, pilot assistance and navigation systems. At the same time new operational procedures and redundancy concepts under safety- and certification aspects are developed. The results achieved with the flight test aircraft Flying Helicopter Simulator (FHS) of DLR are of specific importance. A complete test environment for the FHS has been developed (system identification, real time simulation, ground simulator, model following control system (MFCS), integration of an active sidestick including the required software in the aircraft and the ground simulator)

Compressibility Effects in Rotorcraft Applications

Compressibility effects play an important role in rotorcraft applications. They limit the high speed performance of rotorcraft because of wave drag and they are the reason for the emission of high speed impulsive noise. Furthermore compressibility triggers flow separation on highly loaded rotors in forward flight (dynamic stall)

Generation of an advanced helicopter experimental aerodynamic data base for CFD validation – The European GOAHEAD project

An introduction into the European GOAHEAD Project is given. The project considered a wind tunnel experiment for a complete helicopter configuration (fuselage, main and tail rotors). CFD analysis was applied in a blind- and post-test phase before and after the experiment

New Technologies for Efficient Rotorcraft

Onera and DLR are both national research centres involved in aeronautic research since early 1900. In 1998, Onera and DLR signed an agreement to join their competencies and manpower in the helicopter and tilt rotor domain, following in this matter the helicopter manufacturer Eurocopter. Furthermore, DLR and Onera have a strong partnership with industry and intensive links with academia. Together or by their own Onera and DLR are cooperating with many other research centres worldwide. The paper presents selected results obtained in the cooperation within the last years such as computational tools (e.g. CFD development and validation for aerodynamics and aeroacoustic), noise studies (e.g. noise abatement flight procedures), new technologies for active rotor control and active blades, flight mechanics and handling quality studies, recent developments for tiltrotor applications, ballistic protection and helicopter flight tests