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Wake Characterization of a Free-Flying Model Helicopter in Ground Effect

Schwarz, Clemens and Bauknecht, Andre and Mailänder, Stephan and Raffel, Markus (2018) Wake Characterization of a Free-Flying Model Helicopter in Ground Effect. AHS International 74th Annual Forum & Technology Display, 14.-17. Mai 2018, Phoenix, Arizona, USA.

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Official URL: http://vtol.org

Abstract

Measurements of the flow field around a free-flying model helicopter in ground effect for both quasi-steady and unsteady maneuvering flights were performed using stereoscopic particle image velocimetry (PIV). The wake features for hover and forward flight at low advance ratios were characterized and changing flow patterns like recirculation and ground vortex flow were observed to be in good agreement with existing wind tunnel data. Parameters describing both general flow patterns and single blade tip vortices were extracted and showed significant dependence on the forward flight velocity. Landing approaches were performed and large vortical structures were observed close to the rotor disk, which contained high amounts of vorticity due to entrained blade tip vortices. The vortex structures developing for unsteady landing approaches contained distinctly higher velocities and momentum fluxes than expected from quasi-steady conditions at the same advance ratios. For a vertical takeoff maneuver with a rapid increase of collective pitch, the bundling of blade tip vortices into a "starting vortex" with circulation values up to 6 times higher than for a single blade tip vortex was observed. These results show the significance of experimental data on free-flying helicopters in unsteady maneuvering flight because the resulting flow fields cannot be predicted using steady-state experiments or simulations.

Item URL in elib:https://elib.dlr.de/120402/
Document Type:Conference or Workshop Item (Speech)
Title:Wake Characterization of a Free-Flying Model Helicopter in Ground Effect
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Schwarz, ClemensClemens.Schwarz (at) dlr.deUNSPECIFIED
Bauknecht, AndreUniversity of Maryland, USAUNSPECIFIED
Mailänder, StephanUniversität StuttgartUNSPECIFIED
Raffel, Markusmarkus.raffel (at) dlr.dehttps://orcid.org/0000-0002-3340-9115
Date:2018
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:Particle Image Velocimetry (PIV), Model Helicopter, Ground Effect, Maneuvering Flight, Free Flight Experiments, Blade-Tip Vortex
Event Title:AHS International 74th Annual Forum & Technology Display
Event Location:Phoenix, Arizona, USA
Event Type:international Conference
Event Dates:14.-17. Mai 2018
Organizer:AHS International Inc.
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:rotorcraft
DLR - Research area:Aeronautics
DLR - Program:L RR - Rotorcraft Research
DLR - Research theme (Project):L - The Virtual Aerodynamic Rotorcraft
Location: Göttingen
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > Helicopter, GO
Deposited By: Winkels, Elisabeth
Deposited On:15 Jun 2018 11:37
Last Modified:15 Nov 2018 10:50

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