Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamics of heavy and buoyant underwater pendulums   The humble pendulum is often invoked as the archetype of a simple, gravity
driven, oscillator. Under ideal circumstances, the oscillation frequency of the
pendulum is independent of its mass and swing amplitude. However, in most
real-world situations, the dynamics of pendulums is not quite so simple,
particularly with additional interactions between the pendulum and a
surrounding fluid. Here we extend the realm of pendulum studies to include
large amplitude oscillations of heavy and buoyant pendulums in a fluid. We
performed experiments with massive and hollow cylindrical pendulums in water,
and constructed a simple model that takes the buoyancy, added mass, fluid
(nonlinear) drag, and bearing friction into account. To first order, the model
predicts the oscillation frequencies, peak decelerations and damping rate well.
An interesting effect of the nonlinear drag captured well by the model is that
for heavy pendulums, the damping time shows a non-monotonic dependence on
pendulum mass, reaching a minimum when the pendulum mass density is nearly
twice that of the fluid. Small deviations from the model's predictions are
seen, particularly in the second and subsequent maxima of oscillations. Using
Time- Resolved Particle Image Velocimetry (TR-PIV), we reveal that these
deviations likely arise due to the disturbed flow created by the pendulum at
earlier times. The mean wake velocity obtained from PIV is used to model an
extra drag term due to incoming wake flow. The revised model significantly
improves the predictions for the second and subsequent oscillations.

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The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: eess
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg
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The categories of this paper are: chem-ph
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The categories of this paper are: cs
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The categories of this paper are: stat
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The categories of this paper are: acc-phys
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The categories of this paper are: math-ph
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The categories of this paper are: q-bio
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The categories of this paper are: cmp-lg
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The categories of this paper are: mtrl-th