Biomechanics and Medicine in Swimming XI

BiomechanicsandmedicineinswimmingXi
As an example of multi agents (multiple swimmers) simulation, simple
synchronized swimming by three swimmers was simulated. In this simulation,
three swimmers performed the flutter kick in order to obtain
thrust and fluid force, which lifts the lower limbs. In order to represent
hands grasping each other, virtual springs and dampers were employed.
Animation images as the simulation results are shown in Fig.4. Note
that the time t is nondimensional. At the initial stage (Fig.4(a)), all the
swimmers swam in the same direction. Due to the virtual springs and
dampers attached to their hands, they gradually gathered (Fig.4(b)(c)).
Finally, the swimmers’ upper limbs stably formed a hexagon (Fig.4(d)).
This simulation was very simple since it was conducted for the demonstration.
By carefully configuring the interactions among a larger
number of swimmers, an entire simulation of a complicated team performance
in synchronized swimming will become possible in the near
future.
As an example of multi objects (a swimmer and multiple objects),
monofin swimming was simulated. The monofin was divided into five
rigid plates in this simulation in order to represent its elastic deformation
in the sagittal plane. The truncated elliptic cones were employed
in order to model the five rigid plates, and the plates were represented
by flattening the cones. Virtual springs and dampers were employed in
order to represent connections among the plates. In addition to these,
rotational springs and dampers were also employed in order to represent
the elasticity of the monofin itself. The animation images of the simulation
results are shown in Fig.5. It was found that large fluid forces were
acting on the monofin. In the near future, detailed simulation of the
monofin swimming will be carried out.
Figure 5. Simulation results of monofin swimming.
As the third example of the multi agent/object simulation, the shooting
motion in water polo was simulated. Animation images of the simulation
results are shown in Fig.6. In this simulation, the swimmer’s hand
and the ball were connected by a virtual spring and damper before the
release of the ball. From the moment of release (t = 0.68), the spring and
damper coefficients were set as zero. The ball was modeled as a series of
four segments of truncated cones. From Fig.6, it can be found that the
ball was smoothly released and flew in an appropriate direction. It was
also found that a large fluid force was acting on the swimmer’s feet due
to the breaststroke kick at the moment of release. The velocity of the
shot ball was 13.5m/s.
conclusIon
In this paper, three extensions of the swimming human simulation model
SWUM to the optimizing calculation, musculoskeletal simulation,
and multi agent/object simulation were explained and various recent
results were presented. The usefulness of the extensions was confirmed
since many reasonable results were obtained. More detailed quantitative
validation will be the future task. In future studies, various mechanical
problems in swimming and aquatic activities will be analyzed by the
present extensions.
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Figure 6. Simulation results of shooting motion in water polo.
reFerences
Nakashima, M. (2005). Development of computer simulation software
“Swumsuit” to analyze mechanics of human swimming, Proc 10th Int
Symp on Comp Sim in Biomech (ISCSB2005): 65-66.
Nakashima, M. (2006). “SWUM” and “Swumsuit” -a modeling technique
of a self-propelled swimmer. Biomechanics and Medicine in
Swimming X: 66-68.
Nakashima, M. (2007a). Mechanical study of standard six beat front
crawl swimming by using swimming human simulation model. J
Fluid Sci & Tech, 2(1): 290-301.
Nakashima, M. (2007b). Analysis of breast, back and butterfly strokes
by the swimming human simulation model SWUM, In: Bio-mechanisms
of Swimming and Flying -Fluid Dynamics, Biomimetic Robots,
and Sports Science-: Springer, 361-372.
Nakashima, M. (2009). Simulation analysis of the effect of trunk undulation
on swimming performance in underwater dolphin kick of
human. J Biomech Sci & Eng, 4(1): 94-104.
Nakashima, M, Motegi, Y. (2007a). Proc 11th Int Symp on Comp Sim
in Biomech (ISCSB2007): 59-60.
Nakashima, M., Satou, K., Miura, Y. (2007b). Development of swimming
human simulation model considering rigid body dynamics and
unsteady fluid force for whole body. J Fluid Sci & Tech, 2(1): 56-67.
Nakashima, M., Motegi, Y. (2008). Musculoskeletal simulation to estimate
muscle activity in swimming. Proc 1st Int Sci Conf Aquatic
Space Activities: 327-332.
Nakashima, M., Sato, Y. (2009). Optimization of arm stroke in
freestyle swimming by simulation, The Impact of Technology
on Sport III (APCST2009): 207-211.