TY - JOUR

T1 - Dynamics of an axisymmetric body spinning on a horizontal surface. I. Stability and the gyroscopic approximation

AU - Moffatt, H. K.

AU - Shimomura, Y.

AU - Branicki, M.

PY - 2004/12/8

Y1 - 2004/12/8

N2 - The general spinning motion of an axisymmetric rigid body on a horizontal table is analysed, allowing for slip and friction at the point of contact P. Attention is focused on the case of spheroids (prolate or oblate), and particularly on spheroids whose density distribution is such that the centre-of-mass and centre-of-volume coincide. Four classes of fixed points (i.e. steady states) are identified, and the linear stability properties in each case are determined, assuming viscous friction at P. The governing dynamical system is six-dimensional. Trajectories of the system are computed, and are shown in projection in a three-dimensional subspace; these start near unstable fixed points and (in the case of viscous friction) end at stable fixed points. It is shown inter alia that a uniform prolate spheroid set in sufficiently rapid spinning motion with its axis horizontal is unstable, and its axis rises to a stable steady state, at either an intermediate angle or the vertical, depending on the initial angular velocity. These computations allow an assessment of the circumstances under which the condition described as 'gyroscopic balance' is realized. Under this condition, the evolution from an unstable to a stable state is greatly simplified, being described by a first-order differential equation. Oscillatory modes which are stable on linear analysis may be destabilized during this evolution, with consequential oscillations in the normal reaction R at the point of support. The computations presented here are restricted to circumstances in which R remains positive.

AB - The general spinning motion of an axisymmetric rigid body on a horizontal table is analysed, allowing for slip and friction at the point of contact P. Attention is focused on the case of spheroids (prolate or oblate), and particularly on spheroids whose density distribution is such that the centre-of-mass and centre-of-volume coincide. Four classes of fixed points (i.e. steady states) are identified, and the linear stability properties in each case are determined, assuming viscous friction at P. The governing dynamical system is six-dimensional. Trajectories of the system are computed, and are shown in projection in a three-dimensional subspace; these start near unstable fixed points and (in the case of viscous friction) end at stable fixed points. It is shown inter alia that a uniform prolate spheroid set in sufficiently rapid spinning motion with its axis horizontal is unstable, and its axis rises to a stable steady state, at either an intermediate angle or the vertical, depending on the initial angular velocity. These computations allow an assessment of the circumstances under which the condition described as 'gyroscopic balance' is realized. Under this condition, the evolution from an unstable to a stable state is greatly simplified, being described by a first-order differential equation. Oscillatory modes which are stable on linear analysis may be destabilized during this evolution, with consequential oscillations in the normal reaction R at the point of support. The computations presented here are restricted to circumstances in which R remains positive.

KW - Dynamical systems

KW - Gyroscopic approximation

KW - Instability

KW - Jellett constant

KW - Rigid body dynamics

KW - Spinning spheroid

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U2 - 10.1098/rspa.2004.1329

DO - 10.1098/rspa.2004.1329

M3 - Article

AN - SCOPUS:17144412150

SN - 1364-5021

VL - 460

SP - 3643

EP - 3672

JO - Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

JF - Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

IS - 2052

ER -