Turbulence is a challenge to model and simulate:
"When I meet God, I am going to ask him two questions: Why relativity? And why turbulence? I really believe he will have an answer for the first." -- Heisenberg, Werner (1901-1976)
An analytical method often used to investigate concepts is to find the most minimal possible example of the thing you are trying to understand, so my question is: what is the theoretical or empirically observed minimum required amount of fluid for turbulence to occur?