2 questions about turbulence
 

Greetings,

I have 2 questions about turbulence:

- what is coherent structure and Lagrangian coherent structure? I read something about them, but I couldn't really understand them;

- what is phase space? I have seen many times in turbulence analysis, but I am not sure if I understand it correctly. So hope someboby could help me out.

Appreciate it.