The enduring popularity of Kookslam videos, which document epic spills by beginner surfers, is proof that humans still have a lot to learn about catching the perfect wave. Fortunately for the kooks featured in the clips, there’s a lot physicists can do to help, and one surfer-slash-physicist has actually gone so far as to calculate how to hit a wave’s sweet spot.
In the Journal of Fluid Mechanics, Scripps Institution of Oceanography postdoctoral researcher Nick Pizzo, Ph.D., recently explained that by applying the principles of physics to the ocean’s surface, it’s possible to determine the area of the wave that experienced surfers call the “sweet spot” — the curl.
“My theory explains two things that surfers already know,” Pizzo tells Inverse. “First, to catch a wave you should be traveling near the speed of that wave. Secondly, the region where you accelerate the most, the sweet spot, occurs just underneath the lip of the breaking wave, that is, in the curl.”
Pizzo says that while he’s wondered whether the sweet spot was quantifiable during his own time on the water, emphasizes that the purpose of the study wasn’t to corroborate what surfers already know — even though that’s the result that emerged. This research relates to previous work he’s conducted with colleagues on the currents generated by breaking waves. Understanding the behavior of a wave when it breaks, he explains, isn’t just important for surfers but for oceanographers, too. It shows them how the atmosphere and ocean work together, which, in turn, helps them learn about the generation of currents, and the generation of bubbles — crucial vehicles for gas transfer.
“The reason why all of this matters is that the ocean and atmosphere talk to each other through the surface separating the two, and in particular the dynamics of that separation surface, namely waves,” says Pizzo. “A better description of breaking, like the one provided in this study, leads us to a better understanding of these transfers. The ideas from this paper may be put into coupled air-sea models, and lead to improved weather and climate models.”
Pizzo determined the mathematical sweet spotinside the curl using a formula called the “equation of John.” In plasma physics, there’s a related phenomenon describing wave speed called Landau damping, which is when a charged particle “surfs” on an underlying electric field. He hypothesized that a similar paradigm could be applied to water waves, and when he came across the equation of John, he applied it and determined that it’s “particles traveling near the phase speed of the wave, in a geometrically confined region on the forward face of the crest, increase in speed.”
As particles move towards the crest of a breaking wave (the curl), they travel at the same speed as the underlying wave. This causes the particles — and the surfer riding them — to increase in speed and hit the point of maximal acceleration. That’s good for scientists who want to know how a wave break’s mass, momentum, and energy alters along-shore current — and great for surfers who want to make sure they’re getting the most out of their barrels.