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Experimental Evidence of Nonlinear Resonance Effects Between Retrograde Precession and the Tilt-Over Mode Within a Spheroid

Wednesday, March 20, 2002 - 11:30am - 12:00pm
Keller 3-180
Dominique Jault (Centre National de la Recherche Scientifique (CNRS))
The Poincare flow (also known as the tilt-over mode) in a precessing cavity filled with water is investigated experimentally. Assuming that the flow is mainly a solid-body rotation, we have used three independent techniques to determine the rotation. Rapid changes in the direction of the axis of the rotation of the fluid for critical values of the rates of precession and rotation of the container are pointed out. A torque approach, which can be generalized to other forcings, shows that this effect is due to a nonlinear resonance between the frequencies of the Poincare mode and of precession. As a result, we can determine the validity domain of current theoretical models of nutations and precessions of planets enclosing a fluid core.