Problem 2 The Q-criterion is often used to define a vortex. This criterion highlights the vortical structure (core) where Q (1IR|12 - 1151 12) > 0, where R and S are the antisymmetric and symmetric components of the velocity deformation tensor. Show that the Q-criterion can be written solely in terms of pressure and density for incompressible flow. Explain why such expression can highlight the core of vortices (based on pressure arguments). [Ref: Jeong and Hussain, JFM1995]