laminar flow

it's about layers. layers and fluid dynamics, viscosity and surface friction. laminar flow is known more for its disruption than its existence. moving fluids have laminar flow, layers. shear flows are where some layers moving faster than others. in tubes or pipes, the fluid near the center moves faster than the fluid near outside. friction causes this. it's all governed by physics. cars and airplanes are aerodynamically designed because air is a fluid. to move through it at high speeds, you want to cause the least disruption possible. disruption causes turbulence, turbulence requires energy to overcome. it reduces the efficiency of the system. such a drag, really.

so what's the point? well, turbulence was always considered a static property of a system. if you have flow, you are bound to have turbulence. but a recent study has shown that given time, turbulence will disappear. like a plucked guitar string, it vibrates but eventually returns to a taut, still state. because the vibration uses energy, its dissipation marks the transition from a high energy state to a lower energy state, which is always favorable. turbulence is the vibration, the disruption of smooth flow. and in this way, it is also transient.

so now there is the potential to design systems so the decay time of turbulence is reduced, instead of simply trying to reduce the turbulence itself. a new way to approach an old problem, and with it new possibilities. never a bad thing.

references:

Hof B, Westerweel J, Schneider TM, Eckhardt B. 2006. Finite lifetime of turbulence in shear flows. Nature 443:59-62

Lathrop DP. 2006. Turbulence lost in transience. Nature 443:36-37