1,783 research outputs found
Periodic and Chaotic Flapping of Insectile Wings
Insects use flight muscles attached at the base of the wings to produce
impressive wing flapping frequencies. The maximum power output of these flight
muscles is insufficient to maintain such wing oscillations unless there is good
elastic storage of energy in the insect flight system. Here, we explore the
intrinsic self-oscillatory behavior of an insectile wing model, consisting of
two rigid wings connected at their base by an elastic torsional spring. We
study the wings behavior as a function of the total energy and spring
stiffness. Three types of behavior are identified: end-over-end rotation,
chaotic motion, and periodic flapping. Interestingly, the region of periodic
flapping decreases as energy increases but is favored as stiffness increases.
These findings are consistent with the fact that insect wings and flight
muscles are stiff. They further imply that, by adjusting their muscle stiffness
to the desired energy level, insects can maintain periodic flapping
mechanically for a range of operating conditions
Stability of Underwater Periodic Locomotion
Most aquatic vertebrates swim by lateral flapping of their bodies and caudal
fins. While much effort has been devoted to understanding the flapping
kinematics and its influence on the swimming efficiency, little is known about
the stability (or lack of) of periodic swimming. It is believed that stability
limits maneuverability and body designs/flapping motions that are adapted for
stable swimming are not suitable for high maneuverability and vice versa. In
this paper, we consider a simplified model of a planar elliptic body undergoing
prescribed periodic heaving and pitching in potential flow. We show that
periodic locomotion can be achieved due to the resulting hydrodynamic forces,
and its value depends on several parameters including the aspect ratio of the
body, the amplitudes and phases of the prescribed flapping. We obtain
closed-form solutions for the locomotion and efficiency for small flapping
amplitudes, and numerical results for finite flapping amplitudes. We then study
the stability of the (finite amplitude flapping) periodic locomotion using
Floquet theory. We find that stability depends nonlinearly on all parameters.
Interesting trends of switching between stable and unstable motions emerge and
evolve as we continuously vary the parameter values. This suggests that, for
live organisms that control their flapping motion, maneuverability and
stability need not be thought of as disjoint properties, rather the organism
may manipulate its motion in favor of one or the other depending on the task at
hand.Comment: 15 pages, 15 figure
Optimal Motion of an Articulated Body in a Perfect Fluid
An articulated body can propel and steer itself in a
perfect fluid by changing its shape only. Our strategy for motion
planning for the submerged body is based on finding the optimal
shape changes that produce a desired net locomotion; that
is, motion planning is formulated as a nonlinear optimization
problem
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