[Flieger]

I am taking Fluid Mechanics 1 right now but turbulence is still not completely understood. Perhaps Fluid Mechanics 2 next quarter will explain more?

This course covers turbulent flow properties but not really what causes turbulence other than instabilities in the fluid as it enters a pipe which could be due to an abrupt opening. Turbulent flow is a little hard to define scientifically. It is a "I know it when I see it" thing. The Reynolds number definition is not fool proof, either. It is most accurate for saying that below and Re of 2000 the flow is laminar. Where turbulence sets in depends not only on Reynolds number but also factors that do not factor into the Reynolds number such as surface roughness and entry conditons- like a smooth bell mouth vs. an abrupt, thick walled pipe.

All fluid (and solids too) have random motion on the molecular scale. It must be a bit like certain types of rouge waves. They used some sort of Quantum Mechanics principles to show that in that distinctively random world of quantum mechanics where everything is possible (just maybe improbable) certain waves would begin taking energy from neighboring waves and several moderate waves would turn into one huge wave.

Perhaps a similar thing is going on here with the random fluid motion. Even static fluid has Brownian motion so there is always a certain random instability which can grow, even if the fluid is not swirling around in the first place due to windy conditions an aircraft is flying through or whatever.

This is a field that has great potential for growth. That randomness is very pesky. It would be nice to find a model that works every time to predict turbulence and then we can stop relying on average quantities.

Then there is the task of relating Navier-Stokes equations to turbulent flow. I am not sure whether average velocities can be used for that or if the equations are invalid due to some sort of thermodynamic effects (more and random energy dissipated due to turbulence). The Navier-Stokes only work for Newtonian, Incompressible fluids anyway so transsonic airflow is out.