Pope's vortex-stretching parameter for two-dimensional, planar, compressible flows
 

Hello everyone,

How do you prove that that the Pope's vortex-stretching parameter Xp≠0 in general two-dimensional, planar, compressible flows? This is a question (5.10) from Wilcox (2006) Turbulence Modeling for CFD textbook. The book did not mention a bit about it. And I cannot find the solution manual for this book neither. Please help, thanks!