Rogue waves—individual, isolated waves far larger than the surrounding waves—were reported for centuries by sailors. But their stories of massive walls of water appearing in the open ocean were not corroborated until 1995 when a rogue wave struck an offshore platform. How these giant waves form is still under active research, but one leading theory is that nonlinear interactions between waves allow one wave to sap energy from surrounding waves and focus it into one much larger, short-lived wave. I first learned of rogue waves during a seminar in graduate school. At the time, this idea of nonlinear focusing had only been explored in simulation, but a few years later a research group was able to demonstrate the effect in a wave tank, as shown in the video above. Wait for the end, and you’ll notice how the rogue wave that takes down the ship is much larger than its predecessors. For more on rogue waves and their mind-boggling behavior, be sure to check my previous post on the subject. (Video credit: A. Chabchoub, N. Hoffmann, and N. Akhmediev)
Tag: nonlinear wave amplification
Rogue Wave Recreated
For years, mariners have reported occurrences of rogue waves–sudden, isolated waves many times larger than the surrounding surface waves. Until 1995, when a rogue wave was first measured, debate raged as to whether such waves even existed. Scientists have since agreed that nonlinear models of wave interaction are the most likely source of the amplification necessary to create rogue waves. Since the Navier-Stokes equations that govern hydrodynamics are so difficult to solve, scientists have looked to simpler nonlinear wave equations, like the nonlinear Schroedinger equation that governs optics, to generate rogue-wave-like behavior. While the equation gives insight into how a given wave system will evolve, it is still necessary to determine what initial conditions can lead to the formation of a rogue wave. All manner of random conditions exist in the ocean, but to recreate the behavior in a simplified system, we must know which initial conditions are the right ones. Akhmediev et al presented a theoretical perspective on the initial conditions that might lead to rogue wave amplification, and now, for the first time, researchers have been able to create a rogue wave in a wave tank. That little blip that sinks the Lego pirate ship is a great accomplishment toward understanding a phenomenon whose very existence was in question less than twenty years ago. (Video credit: A Chabchoub, N Hoffmann, and N Akhmediev; via Gizmodo; for more, see APS Viewpoints and Akhmediev et al)