NEWS | FEATURES
712 10 NOVEMBER 2017 • VOL 358 ISSUE 6364 sciencemag.org SCIENCE
If similar wave pools are built around
the globe, as Surf Ranch backers hope, they
could fundamentally alter the surf world. On
the surfing blogosphere, loud worries have
already surfaced that “Kelly’s wave” strips
out surfing’s natural allure and could breed
obnoxious hordes of newbies who will further crowd ocean breaks. But the awestruck
far outnumber the naysayers. “I see the day
when the world’s best surfer is from Little
Rock, Arkansas,” says 1968 world champion
Fred Hemmings of Kailua, Hawaii. “This is
the start of a huge revolution.”
WAVE POOLS FOR SURFING date back more
than 50 years, but even the best pale in com-
parison to a good ocean surf spot. In the
ocean, storms create surface gravity waves
that roll along in deep water and only inter-
act with the bottom, or shoal, when the water
depth is about half the length of the distance
between successive crests (the wavelength).
Three things then happen: The wavelength
shortens, the height increases, and the crest
moves faster than the wave’s lowest point,
the trough. When the height of the wave
is about the same as the water’s depth, the
wave breaks and surfers surf.
If the bottom has just the right contour
and the wind blows from land to sea or is
still, a swell is transformed into a breaking wave that peels evenly to the left or the
right, with the white water moving across
the wave’s face like a steadily closing curtain. Steeper waves can pitch into a tube,
allowing more skilled surfers to ride for a
few seconds inside the barrel. A 30-second
ride on an ocean wave is remarkably long,
and few spots consistently offer barrels.
In 2006, Slater, the world’s most famous
surfer, approached Fincham, who took on
the challenge of mimicking nature in a tank.
“I had no idea who he was,” says Fincham,
who grew up in Jamaica and began surfing
only when he came to USC. To develop the
wave, Slater founded his own epony-
mously named company, which
promptly hired Fincham.
Fincham is, by several ac-
counts, wildly creative and
dogged. He’s published works
on such esoteric-sounding top-
ics as digital particle imaging
velocimetry for laser diagnostics
to decaying grid turbulence in a
rotating stratified fluid. But Slater
jokes that he and Fincham both have a
touch of obsessive-compulsive disorder.
“If you don’t have someone who’s passion-
ate about things, they’re not going to do
it differently than someone who’s done it
before,” Slater says.
Tanks in labs typically make waves a few
centimeters tall, which can be modeled
with linear equations: What you put in re-liably predicts what’s produced. But trying
to mimic a larger swell by generating steep
waves unleashes nonlinear forces, including turbulence; a thin, slow-moving layer
atop the swell (“the boundary layer”); and
oscillations of the entire water body called
seiching. “Nonlinearity is everywhere,” Eiff
says—which makes it fiendishly difficult to
plot out an artificial wave.
The scientific literature on wave sculpting doesn’t run deep. Fincham and Slater’s
U.S. patent applications reference just two
scientific papers about waves, both written
by prominent physicists/mathematicians in
the 1870s. So aside from other patent filings
on surfing waves, Fincham and Slater were
largely on their own.
They began in a laboratory wave tank.
Whereas many wave pools use paddles,
plungers, caissons, or other strategies to ef-
fectively throw water into the air, Fincham’s
team designed a hydrofoil that is partially
submerged in water. As it cuts through the
pool, the hydrofoil moves water to the side
(but not upward) and then pulls back on the
forming wave to “recover” some of the water
it pushed away. The result is what physicists
call a solitary wave, or soliton, that mimics
an individual swell in the open ocean.
Then Slater’s surfing experience came in.
“It was [Fincham’s] job to figure out how to
make that swell, and it was my job to figure
out how to break that swell,” he says. It takes
a shallow “reef” of just the right shape to
turn a swell into a surfing wave. To fine-tune
the shape of the pool bottom, the team relied
on Slater’s input and on massively parallel
supercomputers that often had to run for
weeks at a time to complete a simulation. In
silico, a wave is a mesh of millions of cells
that represent air and fluid. Computations
3. The dampers
The making and breaking of each wave cause
the entire pool to oscillate. Water also bounces
off the sides. Gulleys serve as dampers to
calm the water before a new wave is made.
4. The reefs
The pool’s bottom has carefully
calculated contours of different
depths and dimensions that give
the wave its shape.
A scientist teamed up with a world-famous surfer
to engineer the most alluring artificial surfing wave
2. The hydrofoil
A huge metal contraption pulled along
a track that runs the length of the pool both
pushes and pulls the water to form a swell.
1. The quest
They aimed to sculpt a surfing wave that
alternated between having a large “face”
to make turns on and a “barrel” that
surfers could ride inside.