Turbulence: The Order in Chaos
It’s the holiday season, so you decided to hop on a plane and move on to your favorite destination. For a few hours, it’s a rather calm journey, until a sudden jolt makes you jump out of your seat, the plane rattles for a few moments which feel like hours; disrupting the peace of your journey. The culprit behind all this? It’s turbulence.
Turbulence comes into play everywhere when there is a movement in fluid. For example, when an object like an airplane moves in air, air moving in our lungs, movement of gases in air, movements of various liquids in water. Despite being almost everywhere around us, turbulence has remained a rather mysterious phenomenon for scientists.
Turbulent flow is a chaotic flow which forms swirling patterns called “Eddies”. Note that these swirling patterns are chaotic but not random. And since they are chaotic, they are pretty hard to predict and monitor. This is mainly because turbulence is very sensitive to disruption.
Fluids have two opposing properties, viscosity and inertia. Inertia resists stationary fluids whereas viscosity is the amount of resistance given in a particular fluid. After extensive research it was found that turbulence occurs less with fluids which are highly viscous and with surfaces of greater lengths. This can be put in one formula which is represented by Reynolds’ Number.
Re = uL/V
Where, Re (dimensionless) = Reynolds’ number
u = Velocity of fluid, or the flow rate of the fluid
L = Characteristic length, such as the diameter or the length of the pip
v = Kinematic viscosity of the fluid.
For context, honey has an Re of about 1 whereas water has a Reynold’s number of about 10,000!
The main characteristics of turbulent flow are that it’s unpredictable and chaotic, can have eddies of various sizes, and is diffusive and mixes different substances. A higher Reynolds’ number results in more turbulence. Finally, turbulence is dissipative, which means it dies down and the eddies slowly dissipate to give off heat.
To conclude, turbulence plays a major role in everyday life; and knowing how this phenomenon works, will have a major effect on many aspects in our practical lives. Hopefully, there will be a scientific breakthrough soon, which can enhance our views on fluid mechanics and find a way to counteract turbulence.
And of course, it will also mean smoother rides for us, and all our fellow airplane passengers.
Smit Bachan, 10A