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Parametric study of small-scale rotors in axial descent

Veismann, Marcel and Yos, Daniel and Gharib, Morteza (2022) Parametric study of small-scale rotors in axial descent. Physics of Fluids, 34 (3). Art. No. 035124. ISSN 1070-6631. doi:10.1063/5.0083761.

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Despite extensive research in multirotor aerodynamics in the recent past, axial descent, specifically the vortex ring state, still poses great challenges for multirotor configurations as this flight stage is typically accompanied by severe losses in rotor thrust and strong thrust fluctuations. This paper presents a parametric study to investigate the influence of relevant geometric parameters of a small-scale rotor blade on the rotor performance in axial descent. Design variables subject to variation were the collective pitch, chord length, taper ratio, number of blades, as well as the tip geometry. Custom rotors for each parameter modification were manufactured and experimentally evaluated in wind tunnel tests with mean thrust recordings and measurements of the thrust fluctuations serving as performance metrics. Results indicated that rotor blades with larger aspect ratio and higher blade loading coefficient are less affected by the adverse aerodynamics in the vortex ring state, experiencing lower thrust losses and vibrational loads. Particle image velocimetry flow visualization confirmed that the aerodynamic losses in the vortex ring state can be attributed to blade vortex interactions. Comparison of the rotor flow structure in hover of all investigated rotor designs suggested that improvements in the descent performance of a rotor stem from a combination of reduced tip vortex strength and increased axial tip vortex convection rate. Using the experimental findings of this study, a predictive model for approximating the maximum extent of mean thrust losses in axial descent for a given blade geometry and hover thrust coefficient could be established.

Item Type:Article
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URLURL TypeDescription
Veismann, Marcel0000-0001-8106-6738
Gharib, Morteza0000-0003-0754-4193
Additional Information:© 2022 Author(s). Published under an exclusive license by AIP Publishing. Submitted: 29 December 2021 . Accepted: 25 February 2022 . Published Online: 17 March 2022. This research was funded by the Center of Autonomous Systems and Technology (CAST) and the Summer Undergraduate Research Fellowship (SURF) at the California Institute of Technology. DATA AVAILABILITY. The data that support the findings of this study are available from the corresponding author upon reasonable request. The authors have no conflicts to disclose.
Group:GALCIT, Center for Autonomous Systems and Technologies (CAST)
Funding AgencyGrant Number
Center for Autonomous Systems and TechnologiesUNSPECIFIED
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Issue or Number:3
Record Number:CaltechAUTHORS:20220317-376350000
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Official Citation:Marcel Veismann, Daniel Yos, and Morteza Gharib, "Parametric study of small-scale rotors in axial descent", Physics of Fluids 34, 035124 (2022)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:113945
Deposited By: George Porter
Deposited On:18 Mar 2022 18:23
Last Modified:18 Mar 2022 18:23

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