First published online January 5, 2005
Journal of Experimental Biology 208, 327-344 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01356
Body-induced vortical flows: a common mechanism for self-corrective trimming control in boxfishes
Ian K. Bartol1,*,
Morteza Gharib2,
Paul W. Webb3,
Daniel Weihs4 and
Malcolm S. Gordon5
1 Department of Biological Sciences, Old Dominion University, Nor folk, VA
23529-0266, USA
2 Options of Bioengineering and Aeronautics, California Institute of
Technology, Pasadena, CA 91125, USA
3 School of Natural Resources and Department of Biology, University of
Michigan, Ann Arbor, MI 48109, USA
4 Department of Aerospace Engineering, Technion, Haifa, 3200,
Israel
5 Department of Ecology and Evolutionary Biology, University of California,
Los Angeles, CA 90095-1606, USA
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Fig. 1. Anterior, posterior, and lateral views of a spotted boxfish, scrawled
cowfish, buffalo trunkfish, and smooth trunkfish. The smooth trunkfish was
examined in Bartol et al.
(2003 ). Some distinguishing
features of each boxfish are highlighted in the figure. Scale bars, 1 cm.
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Fig. 2. Vorticity contour fields around and in the wake of the spotted boxfish
(upper row), scrawled cowfish (middle row), and buffalo trunkfish (bottom row)
models positioned at a pitch angle of +10°. The data are viewed in
transverse planes at various locations along the body and in the wake. Each
plot is the mean result of 30 paired images (1 representative trial). From
left to right, the locations, which are highlighted in the upper corner of the
figures, are: eye ridge, maximum girth, midpoint between maximum girth and
posterior edge of the carapace, posterior edge of the carapace, caudal
peduncle, and wake. The shadows beneath the models represent areas that were
shielded from laser light. White dots in scrawled cowfish and buffalo
trunkfish figures are the tips of the ventral keel extensions. Mean
circulation magnitude and mean peak vorticity magnitude for a dorsal vortex
( D and P D, respectively) and
ventral vortex (V and PV,
respectively) are included beneath the plots. In the wake of the spotted
boxfish, ventral and dorsal vortices merge and thus dorsal and ventral
distinctions are not necessary.
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Fig. 3. Vorticity contour fields around and in the wake of the spotted boxfish
(upper row), scrawled cowfish (middle row) and buffalo trunkfish (bottom row)
models positioned at a pitch angle of -10°. The data are viewed in
transverse planes at various locations along the body and in the wake. Each
plot is the mean result of 30 image pairs (1 representative trial). From left
to right, the locations, which are highlighted in the upper corner of figures,
are: eye ridge, maximum girth, midpoint between maximum girth and posterior
edge of the carapace, posterior edge of the carapace, caudal peduncle, and
wake. The shadows on the sides of or beneath models represent areas that were
shielded from laser light. White dots in scrawled cowfish and buffalo
trunkfish figures are the tips of the ventral keels extensions. Mean
circulation magnitude and mean peak vorticity magnitude for a dorsal vortex
(D and PD, respectively) and a
ventral vortex (V and PV,
respectively) are included beneath the vorticity contour plots. In the
scrawled cowfish, mean circulation magnitude and mean peak vorticity magnitude
for a lateral vortex (L and PL,
respectively) also are included. In the wake, dorsal and ventral distinctions
are not necessary for the spotted boxfish and buffalo trunkfish since ventral
and dorsal vortices merge.
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Fig. 4. Vorticity contour fields around the posterior edge of the carapace of the
spotted boxfish (upper row), scrawled cowfish (middle row), and buffalo
trunkfish (bottom row) models positioned (from left to right) at pitch angles
of +20°, +10°, 0°, -10°, and -20°, and a yaw angle of
10°. The data are viewed in transverse planes, and sampling locations are
highlighted in the upper corner of figures. Each plot is the mean result of 30
image pairs (1 representative trial). The shadows underneath or to the side of
models represent areas that were shielded from laser light. White dots in
scrawled cowfish and buffalo trunkfish figures are the tips of the ventral
keels extensions. Mean circulation magnitude and mean peak vorticity magnitude
for a dorsal vortex (D, and PD,
respectively) and a ventral vortex (V and
PV, respectively are included beneath the vorticity
contour plots. For the yaw angles, circulation and peak vorticity values for
each side of the carapace are included (right side, in normal text =
far-field; left side, in italicized text = near-field).
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Fig. 5. Pressure coefficients (Cp) plotted as a function of location
along various dorso-ventral transects (A-F) on the spotted boxfish model
positioned at positive (left) and negative (right) pitch angles. The locations
of the pressure ports included in each graph are highlighted in images to the
left of the graphs. The location of each dorso-ventral transect is expressed
as a percentage of ventral keel length (measured from the anterior leading
edge) in the lower left-hand corner of each image. Ports in blue, red and
black are located on the dorsum, sides, and ventrum of the model,
respectively.  Denotes ports that were slightly out of alignment with
other ports along the dorso-ventral transect; * represent transects
that were considered in DPIV studies. Blue and red rectangles highlight ports
where local pressure minima were consistently detected at dorsal and ventral
locations, respectively. An ambient pressure line (Cp=0)
was included in the most posteriorly located transect (F).
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Fig. 6. Pressure coefficients (Cp) plotted as a function of
location along various dorso-ventral transects (A-F) on the scrawled cowfish
model positioned at positive (left) and negative (right) pitch angles. The
locations of the pressure ports included in each graph are highlighted in
images to the left of the graphs. The location of each dorso-ventral transect
is expressed as a percentage of ventral keel length (measured from the
anterior leading edge) in the lower left-hand corner of each image. Ports in
red and white are located on the sides and ventrum of the model, respectively.
Denotes ports that were slightly out of alignment with
other ports along the dorso-ventral transect; * represent transects
that were considered in DPIV studies. Blue and red rectangles highlight ports
where local pressure minima were consistently detected at dorsal and ventral
locations, respectively. An ambient pressure line (Cp=0)
was included in the most posteriorly located transect (F).
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Fig. 7. Pressure coefficients (Cp) plotted as a function of
location along various dorso-ventral transects (A-F) on the buffalo trunkfish
model positioned at positive (left) and negative (right) pitch angles. The
locations of the pressure ports included in each graph are highlighted in
images to the left of the graphs. The location of each dorso-ventral transect
is expressed as a percentage of ventral keel length (measured from the
anterior leading edge) in the lower left-hand corner of each image. Ports in
red and black are located on the sides and ventrum of the model, respectively.
Denotes ports that were slightly out of alignment with
other ports along the dorso-ventral transect; * represent transects
that were considered in DPIV studies. Blue and red rectangles highlight ports
where local pressure minima were consistently detected at dorsal and ventral
locations, respectively. An ambient pressure line (Cp=0)
was included in the most posteriorly located transect (F).
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© The Company of Biologists Ltd 2005
