Abstract

We give a dynamical system analysis of the twisting somersaults using a reduction to a time-dependent Euler equation for nonrigid body dynamics. The central idea is that after reduction the twisting motion is apparent in a body frame, while the somersaulting (rotation about the fixed angular momentum vector in space) is recovered by a combination of dynamic phase and geometric phase. In the simplest “kick-model” the number of somersaults $m$ and the number of twists $n$ are obtained through a rational rotation number $W=m/n$ of a (rigid) Euler top. Using the full model with shape changes that take a realistic time we then derive the master twisting-somersault formula: an exact formula that relates the airborne time of the diver, the time spent in various stages of the dive, the numbers $m$ and $n$, the energy in the stages, and the angular momentum by extending a geometric phase formula due to Cabrera [J. Geom. Phys., 57 (2007), pp. 1405--1420]. Numerical simulations for various dives agree perfectly with this formula where realistic parameters are taken from actual observations.

Keywords

  1. nonrigid body dynamics
  2. geometric phase
  3. biomechanics
  4. rotation number

MSC codes

  1. 70E55
  2. 70E17
  3. 37J35
  4. 92C10

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Supplementary Material

Index of Supplementary Materials

Title of paper: Twisting Somersault

Authors: Holger R. Dullin and William Tong

File: M105509_01.mp4

Type: animation

Contents: Animation of a twisting somersault 5136D, 3/2 somersault, 6/2 twists as described by Theorem 6.

References

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Information & Authors

Information

Published In

cover image SIAM Journal on Applied Dynamical Systems
SIAM Journal on Applied Dynamical Systems
Pages: 1806 - 1822
ISSN (online): 1536-0040

History

Submitted: 4 January 2016
Accepted: 27 July 2016
Published online: 4 October 2016

Keywords

  1. nonrigid body dynamics
  2. geometric phase
  3. biomechanics
  4. rotation number

MSC codes

  1. 70E55
  2. 70E17
  3. 37J35
  4. 92C10

Authors

Affiliations

Funding Information

Australian Research Council : LP100200245

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