Viscous drag reduction on a submerged surface can be obtained both in the limit of an unbroken gas film coating the solid and in the nanobubble or perhaps microbubble coating regime when an air layer is created with superhydrophobic coatings. We examine an intermediate bubble size regime with a trapped-bubble array (TBA) formed in a tap water environment using electrolysis to grow and maintain bubbles in thousands of millimeter-sized holes on a solid surface. We show that even though surface tension is sufficient to stabilize bubbles in a TBA against hydrostatic and shear forces beneath a turbulent boundary layer, no drag reduction is obtained. Drag measurements were acquired over Reynolds numbers based on plate length ranging from $7.2×104 using either a force balance for plates mounted in a vertical orientation, or by performing a momentum integral balance using a wake survey for a flat plate mounted in either vertical or horizontal orientation. In that the drag forces were small, emphasis was placed on minimizing experimental uncertainty. For comparison, the flow over a flat plate covered on one side by a large uninterrupted gas film was examined and found to produce large drag reductions of up to 32%.

1.
Matveev
,
K. I.
, 2003, “
On the Limiting Parameters of Artificial Cavitation
,”
Ocean Eng.
0029-8018,
30
(
9
), pp.
1179
1190
.
2.
Latorre
,
R.
, 1997, “
Ship Hull Drag Reduction Using Bottom Air Injection
,”
Ocean Eng.
0029-8018,
24
(
2
), pp.
161
175
.
3.
,
N. K.
,
Deutsch
,
S.
, and
Merkle
,
C. L.
, 1984, “
Reduction of Turbulent Skin Friction by Microbubbles
,”
Phys. Fluids
1070-6631,
27
(
2
), pp.
356
363
.
4.
,
N. K.
,
Deutsch
,
S.
, and
Merkle
,
C. L.
, 1985, “
Measurements of Local Skin Friction in a Microbubble-Modified Turbulent Boundary Layer
,”
J. Fluid Mech.
0022-1120,
156
, pp.
237
256
.
5.
Pal
,
S.
,
Deutsch
,
S.
, and
Merkle
,
C. L.
, 1988, “
Bubble Characteristics and Trajectories in a Microbubble Boundary Layer
,”
Phys. Fluids
1070-6631,
31
(
4
), pp.
744
751
.
6.
Sanders
,
W.
,
Winkel
,
E.
,
Dowling
,
D.
,
Perlin
,
M.
, and
Ceccio
,
S.
, 2006, “
Bubble Friction Drag Reduction in a High-Reynolds-Number Flat-Plate Turbulent Boundary Layer
,”
J. Fluid Mech.
0022-1120,
552
, pp.
353
380
.
7.
Balasubramanian
,
A.
,
Miller
,
A. C.
, and
Rediniotis
,
O. K.
, 2004, “
Microstructured Hydrophobic Skin for Hydrodynamic Drag Reduction
,”
AIAA J.
0001-1452,
42
(
2
), pp.
411
414
.
8.
Joseph
,
P.
,
Cottin-Bizone
,
C.
,
Benoît
,
J. M.
,
Ybert
,
C.
,
Journet
,
C.
,
Tabeling
,
P.
, and
Bocquet
,
L.
, 2006, “
Slippage of Water Past Superhydrophobic Carbon Nanotube Forests in Microchannels
,”
Phys. Rev. Lett.
0031-9007,
97
(
15
), p.
156104
.
9.
Ou
,
J.
,
Perot
,
B.
, and
Rothstein
,
J. P.
, 2004, “
Laminar Drag Reduction in Microchannels Using Ultrahydrophobic Surfaces
,”
Phys. Fluids
1070-6631,
16
(
12
), pp.
4635
4643
.
10.
Reed
,
J. C.
,
Bushnell
,
D. M.
, and
Weinstein
,
L. M.
, 1991, “
U.S. Patent for Hydrodynamic Skin-Friction Reduction
,” U.S. Patent No. 5,05,412.
11.
Stephani
,
K.
, and
Goldstein
,
D.
, 2007, “
The Effects of Trapped Bubbles on Viscous Drag Reduction for Submerged Surfaces
,” AIAA Paper No. 2007-4101.
12.
Stephani
,
K.
,
Marr
,
K.
,
Doctor
,
R.
and
Goldstein
,
D.
, 2006, “
Drag Reduction Using Trapped Bubbles on a Flat Plate Surface
,” AIAA Paper No. 2006-3193.
13.
Goldstein
,
D.
, 2006, “
U.S. Patent for Methods for Reducing the Viscous Drag on a Surface and Drag Reducing Device
,” U.S. Patent No. 7,044,073 B2.
14.
Barlow
,
J. B.
,
Rae
,
W. H.
, and
Pope
,
A.
, 1999,
Low Speed Wind Tunnel Testing
, 3rd ed.,
Wiley-Interscience
,
New York
.
15.
Phongikaroon
,
S.
,
Peter
,
J. K.
,
Smith
,
G.
, and
Handler
,
R.
, 2004, “
The Thermal Structure of a Wind-Driven Reynolds Ridge
,”
Exp. Fluids
0723-4864,
37
(
2
), pp.
153
158
.
16.
White
,
F. M.
, 2006,
Viscous Fluid Flow
, 3rd ed.,
McGraw-Hill
,
New York
.
17.
Feng
,
J. Q.
, and
Basaran
,
O. A.
, 1994, “
Shear Flow Over a Translationally Symmetric Cylindrical Bubble Pinned on a Slot in a Plane Wall
,”
J. Fluid Mech.
0022-1120,
275
, pp.
351
378
.
18.
Schlichting
,
H.
, 1987,
Boundary-Layer Theory
, 7th ed.,
McGraw-Hill
,
New York
.
19.
Stephani
,
K.
, 2006, “
Drag Reduction Using Trapped Bubbles on a Submerged Flat Plate Surface
,” MS thesis, Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin, Austin, TX.