Note on the displacement effect in a spinning fluid

The interpretation of viscous effects in perturbations of rapid, solid-body rotation of a fluid in a cylindrical gyroscope is discussed. This is bound up with the explanation of the roots of those effects and aims to improve the foundation on which more sophisticated questions in this field can be addressed successfully. To help with the clarification of viscous displacement effects, their explanation in Section 3 is prefaced by a discussion of two examples displaying some of the salient features in a simpler setting.