A separated vortex ring is the main aerodynamic feature of the dandelion seed which enables its flight. However, recent research on simply modeled dandelion seeds with a pappus angle of 180° (flat porous disk) shows that the vortex ring is not entirely separated from the pappus. This significantly differs from what is observed in a real dandelion seed and would prevent us from fully understanding its flight mechanism. In this work, the two key structural features of the pappus that are considered in the work of others, i.e., the circular disk-like geometry and the porosity, were expected to be insufficient to form an entirely separated vortex ring. Therefore, refined numerical simulations were conducted on model pappi with different pappus angles, which are more similar to real dandelion seeds than flat porous disks. A stable and entirely separated vortex ring and a small vortex ring above the central disk were observed. The lower pappus angle increases the radial pressure gradient toward the central axis between the root of the filaments. When the net effect of this pressure gradient is large enough to overcome the effect of the pressure gradient away from the central axis below the pappus, the streamlines near the root of the filaments deflect to the central axis and the vortex ring is lifted and separates entirely. It is concluded that an appropriate pappus angle is another key feature for forming an entirely separated vortex ring. This more in-depth flow mechanism is of considerable reference value for future research.
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The pappus angle as a key factor in the entire separation of a vortex ring from a dandelion seed’s pappus
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August 2022
Research Article|
August 01 2022
The pappus angle as a key factor in the entire separation of a vortex ring from a dandelion seed’s pappus
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Fu-Sheng Qiu (邱福生)
;
Fu-Sheng Qiu (邱福生)
a)
(Project administration, Resources, Supervision, Writing – review & editing)
College of Aerospace Engineering, Shenyang Aerospace University
, Shenyang 110136, People’s Republic of China
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Hui-Yuan Qian (钱会元);
Hui-Yuan Qian (钱会元)
(Writing – original draft, Writing – review & editing)
College of Aerospace Engineering, Shenyang Aerospace University
, Shenyang 110136, People’s Republic of China
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Yi-Ming Du (杜一鸣)
;
Yi-Ming Du (杜一鸣)
a)
(Writing – original draft, Writing – review & editing)
College of Aerospace Engineering, Shenyang Aerospace University
, Shenyang 110136, People’s Republic of China
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Cheng-Jun Li (李承骏)
Cheng-Jun Li (李承骏)
(Writing – original draft)
College of Aerospace Engineering, Shenyang Aerospace University
, Shenyang 110136, People’s Republic of China
Search for other works by this author on:
Fu-Sheng Qiu (<span class='lang' lang='zh'>邱福生</span>)
Project administration, Resources, Supervision, Writing – review & editing
a)
College of Aerospace Engineering, Shenyang Aerospace University
, Shenyang 110136, People’s Republic of China
Hui-Yuan Qian (<span class='lang' lang='zh'>钱会元</span>)
Writing – original draft, Writing – review & editing
College of Aerospace Engineering, Shenyang Aerospace University
, Shenyang 110136, People’s Republic of China
Yi-Ming Du (<span class='lang' lang='zh'>杜一鸣</span>)
Writing – original draft, Writing – review & editing
a)
College of Aerospace Engineering, Shenyang Aerospace University
, Shenyang 110136, People’s Republic of China
Cheng-Jun Li (<span class='lang' lang='zh'>李承骏</span>)
Writing – original draft
College of Aerospace Engineering, Shenyang Aerospace University
, Shenyang 110136, People’s Republic of China
Physics of Fluids 34, 083101 (2022)
Article history
Received:
May 11 2022
Accepted:
July 06 2022
Citation
Fu-Sheng Qiu, Hui-Yuan Qian, Yi-Ming Du, Cheng-Jun Li; The pappus angle as a key factor in the entire separation of a vortex ring from a dandelion seed’s pappus. Physics of Fluids 1 August 2022; 34 (8): 083101. https://doi.org/10.1063/5.0098730
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