Experimental observation of chaos-chaos intermittency types in spherical Couette flow

TL;DR

This study experimentally investigates the transition to chaos in spherical Couette flow with small periodic boundary variations, identifying different intermittency types and providing a quantitative method to distinguish flow states.

Contribution

It is the first to experimentally observe chaos-chaos and cycle-chaos-chaos intermittency in spherical Couette flow with small boundary oscillations and to develop a quantitative identification procedure.

Findings

Identification of chaos-chaos and cycle-chaos-chaos intermittency in flow.

Development of a quantitative method to distinguish flow patterns.

Experimental validation of flow state transitions with boundary oscillations.

Abstract

Flows between concentric, counter rotating spherical boundaries are under investigation in the gap with size equal to inner sphere radius. Outer sphere rotational rate is fixed, while inner sphere rotational rate has time periodic variations. The amplitudes and frequencies of these variations are small relative to both spheres averaged rotational rates. With amplitude increase transition from initial periodical flow to chaos is occurred. To determine state of the flow time series of azimuthal velocity, taken with laser Doppler anemometry, were used. We demonstrate appearance of flow states in the form of chaos-chaos and cycle-chaos-chaos intermittency. A procedure is considered which allow quantitatively confirm distinct properties of different patterns of time alternating flow state with intermittency.