Unsteady flow behaviour of multi-rotors in ground proximity
The unsteady flow behaviour of two side-by-side rotors in ground proximity is experimentally investigated. The rotors induce a velocity distribution interacting with the ground causing the radial expansion of the rotor wakes. In between the rotors, an interaction of the two wakes takes place, result...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Cambridge University Press
2023-01-01
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| Series: | Flow |
| Subjects: | |
| Online Access: | https://www.cambridge.org/core/product/identifier/S2633425923000211/type/journal_article |
| _version_ | 1797666526131650560 |
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| author | Hasse N.J. Dekker Woutijn J. Baars Fulvio Scarano Marthijn Tuinstra Daniele Ragni |
| author_facet | Hasse N.J. Dekker Woutijn J. Baars Fulvio Scarano Marthijn Tuinstra Daniele Ragni |
| author_sort | Hasse N.J. Dekker |
| collection | DOAJ |
| description | The unsteady flow behaviour of two side-by-side rotors in ground proximity is experimentally investigated. The rotors induce a velocity distribution interacting with the ground causing the radial expansion of the rotor wakes. In between the rotors, an interaction of the two wakes takes place, resulting in an upward flow similar to a fountain. Two types of flow topologies are examined and correspond to two different stand-off heights between the rotors and the ground: the first one where the height of the fountain remains below the rotor disks, and a second one where it emerges above, being re-ingested. The fountain unsteadiness is shown to increase when re-ingestion takes place, determining a location switch from one rotor disk to the other, multiple times during acquisition. Consequently, variable inflow conditions are imposed on each of the two rotors. The fountain dynamics is observed at a frequency that is about two orders of magnitude lower than the blade passing frequency. The dominant characteristic time scale is linked to the flow recirculation path, relating this to system parameters of thrust and ground stand-off height. The flow field is analysed using proper orthogonal decomposition, in which coupled modes are identified. Results from the modal analysis are used to formulate a simple dynamic flow model of the re-ingestion switching cycle. |
| first_indexed | 2024-03-11T19:59:38Z |
| format | Article |
| id | doaj.art-8ec19575f7074d4ca3febf906c3b90c7 |
| institution | Directory Open Access Journal |
| issn | 2633-4259 |
| language | English |
| last_indexed | 2024-03-11T19:59:38Z |
| publishDate | 2023-01-01 |
| publisher | Cambridge University Press |
| record_format | Article |
| series | Flow |
| spelling | doaj.art-8ec19575f7074d4ca3febf906c3b90c72023-10-04T09:54:39ZengCambridge University PressFlow2633-42592023-01-01310.1017/flo.2023.21Unsteady flow behaviour of multi-rotors in ground proximityHasse N.J. Dekker0https://orcid.org/0000-0001-5038-088XWoutijn J. Baars1https://orcid.org/0000-0003-1526-3084Fulvio Scarano2https://orcid.org/0000-0003-2755-6669Marthijn Tuinstra3Daniele Ragni4Faculty of Aerospace Engineering, Delft University of Technology, Delft, 2629 HS, The Netherlands Royal Netherlands Aerospace Centre, Marknesse, 8316 PR, The NetherlandsFaculty of Aerospace Engineering, Delft University of Technology, Delft, 2629 HS, The NetherlandsFaculty of Aerospace Engineering, Delft University of Technology, Delft, 2629 HS, The NetherlandsRoyal Netherlands Aerospace Centre, Marknesse, 8316 PR, The NetherlandsFaculty of Aerospace Engineering, Delft University of Technology, Delft, 2629 HS, The NetherlandsThe unsteady flow behaviour of two side-by-side rotors in ground proximity is experimentally investigated. The rotors induce a velocity distribution interacting with the ground causing the radial expansion of the rotor wakes. In between the rotors, an interaction of the two wakes takes place, resulting in an upward flow similar to a fountain. Two types of flow topologies are examined and correspond to two different stand-off heights between the rotors and the ground: the first one where the height of the fountain remains below the rotor disks, and a second one where it emerges above, being re-ingested. The fountain unsteadiness is shown to increase when re-ingestion takes place, determining a location switch from one rotor disk to the other, multiple times during acquisition. Consequently, variable inflow conditions are imposed on each of the two rotors. The fountain dynamics is observed at a frequency that is about two orders of magnitude lower than the blade passing frequency. The dominant characteristic time scale is linked to the flow recirculation path, relating this to system parameters of thrust and ground stand-off height. The flow field is analysed using proper orthogonal decomposition, in which coupled modes are identified. Results from the modal analysis are used to formulate a simple dynamic flow model of the re-ingestion switching cycle.https://www.cambridge.org/core/product/identifier/S2633425923000211/type/journal_articleAerodynamicsMulti-rotorGround proximityUnsteady fountain flowExperimental aerodynamics |
| spellingShingle | Hasse N.J. Dekker Woutijn J. Baars Fulvio Scarano Marthijn Tuinstra Daniele Ragni Unsteady flow behaviour of multi-rotors in ground proximity Flow Aerodynamics Multi-rotor Ground proximity Unsteady fountain flow Experimental aerodynamics |
| title | Unsteady flow behaviour of multi-rotors in ground proximity |
| title_full | Unsteady flow behaviour of multi-rotors in ground proximity |
| title_fullStr | Unsteady flow behaviour of multi-rotors in ground proximity |
| title_full_unstemmed | Unsteady flow behaviour of multi-rotors in ground proximity |
| title_short | Unsteady flow behaviour of multi-rotors in ground proximity |
| title_sort | unsteady flow behaviour of multi rotors in ground proximity |
| topic | Aerodynamics Multi-rotor Ground proximity Unsteady fountain flow Experimental aerodynamics |
| url | https://www.cambridge.org/core/product/identifier/S2633425923000211/type/journal_article |
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