A new adaptive-passive control device is introduced to optimally reduce the drag on a sphere over a wide range of Reynolds numbers, Re = 0.4 × 105–4.4 × 105. The device, called an adaptive moving ring (AMR), is designed to change its size (i.e., protrusion height) adaptively depending on the wind speed (i.e., the Reynolds number) without energy input. An empirical model is formulated to accurately predict the drag coefficient as a function of the size of AMR and the Reynolds number. Based on the model, we estimate how the optimal size of AMR should vary with the Reynolds number to maximize the drag reduction. Following the estimation of the optimal size, the optimally tuned AMR reduces its protrusion height with increasing Reynolds number, and the drag decreases monotonically by up to 74% compared to that of a smooth sphere. The drag reduction by AMR is attributed to different mechanisms depending on the Reynolds number. For low Reynolds numbers, the locally separated flow at large AMR is energized by the disturbance induced by AMR and reattaches to the sphere surface, forming a large recirculation region. Then, the main separation is delayed downstream due to the increased near-wall momentum. On the other hand, at high Reynolds numbers, no recirculation zone is formed at AMR due to its low protrusion height, but a secondary separation bubble is generated on the rear sphere surface. Therefore, the boundary-layer flow becomes turbulent, and the main separation is significantly delayed, resulting in more drag reduction than for low Reynolds numbers.
REFERENCES
1.
P. W.
Bearman
and J. K.
Harvey
, “Golf ball aerodynamics
,” Aeronaut. Q.
27
, 112
–122
(1976
).2.
R. D.
Mehta
, “Aerodynamics of sports balls
,” Annu. Rev. Fluid. Mech.
17
, 151
–189
(1985
).3.
J.
Choi
, W.-P.
Jeon
, and H.
Choi
, “Mechanism of drag reduction by dimples on a sphere
,” Phys. Fluids
18
, 041702
(2006
).4.
E.
Achenbach
, “The effects of surface roughness and tunnel blockage on the flow past spheres
,” J. Fluid Mech.
65
, 113
–125
(1974
).5.
T.
Maxworthy
, “Experiments on the flow around a sphere at high Reynolds numbers
,” J. Appl. Mech.
36
, 598
–607
(1969
).6.
K.
Son
, J.
Choi
, W.-P.
Jeon
, and H.
Choi
, “Mechanism of drag reduction by a surface trip wire on a sphere
,” J. Fluid Mech.
672
, 411
–427
(2011
).7.
H.
Choi
, W.-P.
Jeon
, and J.
Kim
, “Control of flow over a bluff body
,” Annu. Rev. Fluid. Mech.
40
, 113
–139
(2008
).8.
W. S.
Saric
, H. L.
Reed
, and E. J.
Kerschen
, “Boundary-layer receptivity to freestream disturbances
,” Annu. Rev. Fluid. Mech.
34
, 291
–319
(2002
).9.
K.
Aoki
, A.
Ohike
, K.
Yamaguchi
, and Y.
Nakayama
, “Flying characteristics and flow pattern of a sphere with dimples
,” J. Visualization
6
, 67
–76
(2003
).10.
A. J.
Smits
and S.
Ogg
, “Aerodynamics of the golf ball
,” in Biomedical Engineering Principles in Sports
(Springer
, Boston
, 2004
), pp. 3
–27
.11.
E.
Achenbach
, “Experiments on the flow past spheres at very high Reynolds numbers
,” J. Fluid Mech.
54
, 565
–575
(1972
).12.
D.
Terwagne
, M.
Brojan
, and P. M.
Reis
, “Smart morphable surfaces for aerodynamic drag control
,” Adv. Mater.
26
, 6608
–6611
(2014
).13.
M.
Guttag
and P. M.
Reis
, “Active aerodynamic drag reduction on morphable cylinders
,” Phys. Rev. Fluids
2
, 123903
(2017
).14.
J.
Kim
and S.
Chae
, Korea patent 10-1907582 (5 October 2018
).15.
D. F.
James
and Q. S.
Truong
, “Wind load on cylinder with spanwise protrusion
,” Proc. ASCE, J. Eng. Mech. Div.
98
, 1573
–1589
(1972
).16.
M. M.
Zdravkovich
, Flow Around Circular Cylinders
(Oxford University Press
, New York
, 1997
), pp. 769
–771
.17.
A. K.
Norman
and B. J.
McKeon
, “The effect of a small isolated roughness element on the forces on a sphere in uniform flow
,” Exp. Fluids
51
, 1031
–1045
(2011
).18.
E.
Achenbach
, “Vortex shedding from spheres
,” J. Fluid Mech.
62
, 209
–221
(1974
).19.
H. J.
Kim
and P. A.
Durbin
, “Observations of the frequencies in a sphere wake and of drag increase by acoustic excitation
,” Phys. Fluids
31
, 3260
(1988
).20.
H.
Sakamoto
and H.
Haniu
, “A study on vortex shedding from spheres in a uniform flow
,” J. Fluids Eng.
112
, 386
–392
(1990
).21.
A. K.
Norman
and B. J.
McKeon
, “Unsteady force measurements in sphere flow from subcritical to supercritical Reynolds numbers
,” Exp. Fluids
51
, 1439
–1453
(2011
).22.
K.
Son
, J.
Choi
, W.-P.
Jeon
, and H.
Choi
, “Effect of free-stream turbulence on the flow over a sphere
,” Phys. Fluids
22
, 045101
(2010
).23.
J.
Kim
and H.
Choi
, “Aerodynamics of a golf ball with grooves
,” Proc. - Inst. Mech. Eng. Part P, J. Sports Eng. Technol.
228
, 233
–241
(2014
).24.
J.
Kim
, H.
Choi
, H.
Park
, and J. Y.
Yoo
, “Inverse Magnus effect on a rotating sphere: When and why
,” J. Fluid Mech.
754
, R2
(2014
).25.
D.
Choi
and H.
Park
, “Flow around in-line sphere array at moderate Reynolds number
,” Phys. Fluids
30
, 097104
(2018
).26.
H.
Kim
, J.
Kim
, and H.
Choi
, “Flow structure modifications by leading-edge tubercles on a 3D wing
,” Bioinspiration Biomimetics
13
, 066011
(2018
).27.
J. B.
Barlow
, W. H.
Rae
, and A.
Pope
, Low-Speed Wind Tunnel Testing
(Wiley
, New York
, 1999
), pp. 196
–197
.28.
M.
Kuss
, F.
Jäkel
, and F. A.
Wichmann
, “Bayesian inference for psychometric functions
,” J. Vision
5
, 478
–492
(2005
).29.
D. P.
Hart
, “Super-resolution PIV by recursive local-correlation
,” J. Visualization
3
, 187
–194
(2000
).30.
31.
S.
Taneda
, “Visual observations of the flow past a sphere at Reynolds numbers between 104 and 106
,” J. Fluid Mech.
85
, 187
–192
(1978
).32.
G. K.
Suryanarayana
and G. E. A.
Meier
, “Effect of ventilation on the flowfield around a sphere
,” Exp. Fluids
19
, 78
–88
(1995
).33.
S.
Jeon
, J.
Choi
, W.-P.
Jeon
, H.
Choi
, and J.
Park
, “Active control of flow over a sphere for drag reduction at a subcritical Reynolds number
,” J. Fluid Mech.
517
, 113
–129
(2004
).34.
R.
Deshpande
, V.
Kanti
, A.
Desai
, and S.
Mittal
, “Intermittency of laminar separation bubble on a sphere during drag crisis
,” J. Fluid Mech.
812
, 815
–840
(2017
).35.
M.
Lang
, U.
Rist
, and S.
Wagner
, “Investigations on controlled transition development in a laminar separation bubble by means of LDA and PIV
,” Exp. Fluids
36
, 43
–52
(2004
).36.
S.
Burgmann
, C.
Brücker
, and W.
Schröder
, “Scanning PIV measurements of a laminar separation bubble
,” Exp. Fluids
41
, 319
–326
(2006
).37.
S.
Burgmann
, J.
Dannemann
, and W.
Schröder
, “Time-resolved and volumetric PIV measurements of a transitional separation bubble on an SD7003 airfoil
,” Exp. Fluids
44
, 609
–622
(2008
).38.
T.
Michelis
, S.
Yarusevych
, and M.
Kotsonis
, “Response of a laminar separation bubble to impulsive forcing
,” J. Fluid Mech.
820
, 633
–666
(2017
).39.
J.
Choi
, Ph.D. thesis, Seoul National University
, 2006
.40.
R. F.
Huang
, C. M.
Hsu
, and Y. T.
Chen
, “Modulating flow and aerodynamic characteristics of a square cylinder in crossflow using a rear jet injection
,” Phys. Fluids
29
, 015103
(2017
).41.
Y.
Cao
and T.
Tamura
, “Supercritical flows past a square cylinder with rounded corners
,” Phys. Fluids
29
, 085110
(2017
).42.
A.
Sanyal
and A.
Dhiman
, “Wake interactions in a fluid flow past a pair of side-by-side square cylinders in presence of mixed convection
,” Phys. Fluids
29
, 103602
(2017
).43.
H.
Bai
and M. M.
Alam
, “Dependence of square cylinder wake on Reynolds number
,” Phys. Fluids
30
, 015102
(2018
).44.
C.
Yue
, S.
Guo
, and L.
Shi
, “Hydrodynamic analysis of the spherical underwater robot SUR-II
,” Int. J. Adv. Rob. Syst.
10
, 247
(2013
).45.
M.
Purcell
, C.
von Alt
, B.
Allen
, T.
Austin
, N.
Forrester
, R.
Goldsborough
, and R.
Stokey
, in Proceedings of the OCEANS 2000 MTS/IEEE Conference 11–14 September 2000
(IEEE
, Providence, RI, USA
, 2000
), pp. 147
–151
.46.
B.
Hobson
, B.
Schulz
, J.
Janet
, M.
Kemp
, R.
Moody
, C.
Pell
, and H.
Pinnix
, in Proceedings of the OCEANS 2001 MTS/IEEE Conference 5–8 November 2001
(IEEE
, Honolulu, HI, USA
, 2001
), pp. 2043
–2045
.47.
S. A.
Cambone
, K. J.
Krieg
, P.
Pace
, and L.
Wells
, Unmanned Aircraft Systems (UAS) Roadmap 2005-2030
(Office of the Secretary of Defense
, Washington, DC
, 2005
), pp. 26
–29
.© 2019 Author(s).
2019
Author(s)
You do not currently have access to this content.
