Abstract
This chapter derives the relations between Eulerian and Lagrangian descriptions of displacement and velocity fields, relations between the time derivatives of system properties, variations, and introduces Jourdain’s variational Jourdain’s Principle. Jourdain’s Jourdain’s Principle is then applied to viscous incompressible fluids, and the derivation of the energy rate equation. These equations will be utilized in the subsequent chapter for the derivation of the flow-Flow oscillator model for vortex-induced vibration.