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BOS-based three-dimensional reconstruction of rotor blade tip vortices

Debernardis, Nicola (2020) BOS-based three-dimensional reconstruction of rotor blade tip vortices. Master's, Politecnico di Malano.

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Official URL: https://www.politesi.polimi.it/handle/10589/153023

Abstract

A research topic of the Institute of Aerodynamics and Flow Technology in Göttingen is the investigation of blade tip vortices created by helicopter rotors. These vortices are investigated both on free-flying helicopters in different flight situations and on a rotor test stand. A measurement technique that is used to visualize these vortices is the density based background-oriented schlieren (BOS) method. The subject of this work is the three-dimensional vortex reconstruction based on stereoscopic BOS measurements. Therefore, a reconstruction scheme based on epipolar geometry was developed and applied to vortex filaments that were recorded in two different experiments. First, a model helicopter in free flight was investigated and it was possible to reconstruct significant parts of the vortex system up to a maximum vortex age Ψv above 600° during an unsteady takeoff maneuver in ground effect. The developed evaluation scheme was subsequently adapted and applied to the vortex system generated by a rotor test stand with cyclic pitch control. Vortex filaments of the rotor in cyclic pitch conditions were reconstructed and the vortex convection was investigated. The evaluation of a larger sample number of 200 measurement images in quasi-steady conditions showed a significant scatter in the vortex locations, which is in agreement with previous findings. The developed reconstruction scheme allows an automated extraction of vortex positions for a multitude of test conditions at the rotor test stand for future investigations.

Item URL in elib:https://elib.dlr.de/135806/
Document Type:Thesis (Master's)
Title:BOS-based three-dimensional reconstruction of rotor blade tip vortices
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Debernardis, NicolaPolitecnico di MalanoUNSPECIFIED
Date:29 April 2020
Refereed publication:No
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:3D reconstruction, epipolar geometry, BOS
Institution:Politecnico di Malano
Department:Dipartimento di Scienze e Tecnologie Aerospaziali
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 (old)
Location: Göttingen
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > Helicopter, GO
Deposited By: Carter, Beatrice
Deposited On:08 Sep 2020 10:02
Last Modified:08 Sep 2020 10:02

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