On the generation of a helicopter aerodynamic database

Abstract

NOMENCLATURE a speed of sound, ms -1 c blade chord, m u′ 2 root mean square of velocitiy longitudinal component v′ 2 root mean square of velocitiy spanwise component w′ 2 root mean square of velocitiy vertical component M WT Mach number of wind-tunnel flow, M WT = V WT /a M MR Mach number of blade tip in hover, main rotor, M MR = (ΩR) MR /a M TR Mach number of blade tip in hover, tail rotor, M TR = (ΩR) TR /a R blade radius, m α S rotor shaft angle-of-attack α fus fuselage angle-of-attack μ advance ratio M WT /M MR ψ MR main rotor azimuth angle (0° = reference blade above the fuselage) Ω rotor rotational frequency, rad/s ABSTRACT The GOAHEAD (Generation of an Advanced Helicopter Experimental Aerodynamic Database for CFD code validation) consortium was created in the frame of an EU-project in order to create an experimental database for the validation of 3D-CFD and comprehensive aeromechanics methods for the prediction of unsteady viscous flows. This included the rotor dynamics for complete helicopter configurations, i.e. main rotor -fuselage -tail rotor configurations with emphasis on viscous phenomena like flow separation and transition from laminar to turbulent flow. The wind tunnel experiments have been performed during two weeks in the DNW-LLF on a Mach-scaled model of a modern transport helicopter consisting of the main rotor, the fuselage, control surfaces and the tail rotor. For the sake of controlled boundary conditions for later CFD validation, a closed test section has been used. The measurement comprised global forces of the main rotor and the fuselage, steady and unsteady pressures, transition positions, stream lines, position of flow separation, velocity profiles at the test section inlet, velocity fields in the model wake, vortex trajectories and elastic deformations of the main and tail rotor blades.

CFD prediction of air flow past a full helicopter configuration

“…Three-dimensional velocity field PIV data were gathered during the experimental campaign [25] in several cross-planes, described in Fig. 15.…”

A comprehensive PIV measurement campaign on a fully equipped helicopter model

“…The experiments comprised measurements of the global forces of the main rotor and fuselage, normal force and bending moments acting on the horizontal stabiliser, axial force and torque of the tail rotor, steady and unsteady pressures, and boundary layer transition positions. Furthermore, the position of flow separation, the velocity fields of the model wake, around the fuselage and on the upper surface of the advancing and retreating rotor blades, the vortex trajectories and the elastic deformations of the main and tail rotor blades were investigated (Raffel et al 2009. This paper summarises the flow field measurements of the GOAHEAD test campaign jointly performed by CIRA, DLR and DNW.…”

Differential Infrared Thermography for Unsteady Boundary-Layer Transition Measurements

“…Sophisticated experimental techniques for the determination of the skin-friction distribution (thereby also detecting transition) have to be developed in order to improve and validate numerical prediction and design methods. The complex hot-film anemometry has successfully been used in order to investigate the unsteady boundary-layer transition on pitching airfoils [1,2] and large-scale helicopter rotor models in forward-flight configurations [3]. Recently, considerable efforts have been focused toward optical techniques for their high spatial resolution and relative ease of use.…”