Scallops are distinguished from other bivalves in that they can rapidly swim. One species of the
scallop, Patinopecten yessoensis is known as inefficient swimmer or zigzag swimmer. Nevertheless P.
yessoensis can swim long distance quickly. The scallop has reversed airfoil-like shape, and low...
Scallops are distinguished from other bivalves in that they can rapidly swim. One species of the
scallop, Patinopecten yessoensis is known as inefficient swimmer or zigzag swimmer. Nevertheless P.
yessoensis can swim long distance quickly. The scallop has reversed airfoil-like shape, and low aspect
ratio (AR < 1.5). To investigated hydrodynamic characteristics of swimming scallop, swimming
motion of the scallop is recorded, and the three-dimensional kinematics of swimming motion is
analyzed. The scallop swims in the range of Reynolds number less than 45000. It also found that the
scallop is not always jump but swims touching the ground. Directly forces and moment are measured
by water tunnel experiment under 2 conditions, in ground effect and out of ground effect. Based on
the results of forces and moment measurement, expected trajectory of swimming scallop is computed
and compared with the trajectory of swimming actual scallop. By the comparison, quasi-steady state
assumption of swimming scallop is verified so water tunnel experiment is validated. 2 step stall
occurs out of ground effect. After first stall, lift is slightly decreased and increased again until second
stall. As angle of attack increased, nonlinear lift is increased so lift coefficient reaches maximum right
before second stall, because tip vortex helps the flow attach to the surface of the scallop. In case of
typical 3-dimensional wing, lift is increased, and drag is decreased in ground effect, but in case of
scallop, both lift and drag are increased. Multiple two-dimensional flow fields around the model out
of ground effect are measured by conducting particle image velocimetry. During first stall, separation
bubble from leading edge and wake region near the trailing edge encounter, so flow separation occurs
over all surface of the model. However, tip-vortex induced downwash make the leading-edge vortex
(LEV) attach to the surface, so lift is increased again. When angle of attack reaches 34°, tip-vortex
induced downwash no longer formed over the scallop, and second stall occurs. Compared with that of
level swimmer, hydrodynamic performance of zigzag swimmer is comparable to that of level
swimmer. Therefore, zigzag swimmer is enough applicable to engineering problem.
Scallops are distinguished from other bivalves in that they can rapidly swim. One species of the
scallop, Patinopecten yessoensis is known as inefficient swimmer or zigzag swimmer. Nevertheless P.
yessoensis can swim long distance quickly. The scallop has reversed airfoil-like shape, and low aspect
ratio (AR < 1.5). To investigated hydrodynamic characteristics of swimming scallop, swimming
motion of the scallop is recorded, and the three-dimensional kinematics of swimming motion is
analyzed. The scallop swims in the range of Reynolds number less than 45000. It also found that the
scallop is not always jump but swims touching the ground. Directly forces and moment are measured
by water tunnel experiment under 2 conditions, in ground effect and out of ground effect. Based on
the results of forces and moment measurement, expected trajectory of swimming scallop is computed
and compared with the trajectory of swimming actual scallop. By the comparison, quasi-steady state
assumption of swimming scallop is verified so water tunnel experiment is validated. 2 step stall
occurs out of ground effect. After first stall, lift is slightly decreased and increased again until second
stall. As angle of attack increased, nonlinear lift is increased so lift coefficient reaches maximum right
before second stall, because tip vortex helps the flow attach to the surface of the scallop. In case of
typical 3-dimensional wing, lift is increased, and drag is decreased in ground effect, but in case of
scallop, both lift and drag are increased. Multiple two-dimensional flow fields around the model out
of ground effect are measured by conducting particle image velocimetry. During first stall, separation
bubble from leading edge and wake region near the trailing edge encounter, so flow separation occurs
over all surface of the model. However, tip-vortex induced downwash make the leading-edge vortex
(LEV) attach to the surface, so lift is increased again. When angle of attack reaches 34°, tip-vortex
induced downwash no longer formed over the scallop, and second stall occurs. Compared with that of
level swimmer, hydrodynamic performance of zigzag swimmer is comparable to that of level
swimmer. Therefore, zigzag swimmer is enough applicable to engineering problem.
주제어
#Zigzag swimmer Ground effect Low aspect ratio Tip-vortex induced downwash
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