Splendor
of Fluids in Motion
The world first flow visualization representation
below is a sketch of a free water jet issuing from a square hole
into a pool, drawn by the hands of Leonardo da Vinci; circa 1500.
In the view of John L. Lumley, Da Vinci might have prefigured the
now famous Reynolds turbulence decomposition nearly 400 years prior
to Osborne Reynolds' own pipe-flow visualization! In one of his notebooks,
da Vinci wrote (translated by Ugo Piomelli): "Observe the motion
of the surface of the water, which resembles that of hair, which
has two motions, of which one is caused by the weight of the hair,
the other by the direction of the curls; thus the water has eddying
motions, one part of which is due to the principal current, the other
to the random and reverse motion." For more details, click
here.
The three photographs below were taken close
to five centuries after that of da Vinci. The first one depicts a
top view of a turbulent spot growing by destabilizing the surrounding
laminar (vortical) flow. The second is a side view of the large eddies
in a turbulent boundary layer. And the last one is a side view of
a lifting surface undergoing a pitching maneuver. The top picture
was the first to appear in an archival publication (Journal of Fluid
Mechanics, vol. 110, p. 73, 1981) showing the utility of flow visualization
via laser-induced fluorescence (LIF), a technique which is now widely
used around the world for detailing the anatomy of three-dimensional
flow fields.
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