July 23, 2013
Researchers Create A Wave That Is Frozen In Time
April Flowers for redOrbit.com - Your Universe Online
A team of scientists from the Universidad Carlos III of Madrid (UC3M) and the University of California - San Diego (UC San Diego) have created a static pipeline wave in a laboratory. The wave has a crest that moves neither forward nor backward, which will allow improvements in boat and seaport designs. The wave will also allow analysis of how carbon dioxide exchange between the ocean and the atmosphere occurs. The study findings are described in a recent issue of Experiments in Fluids."A wave is a deformation in the surface of a liquid that moves at a speed that is independent of that liquid," the scientists said. For example: the water remains still while the waves move away from the center at their own speed in the waves that are formed when a rock is thrown into a pond. "In our case, what occurs is actually the opposite: the water moves very rapidly (at several meters per second), but the wave moves at a speed of zero. That is, it remains still, "frozen" in time for any observer who sees it from outside of the water," explains Javier Rodriguez, of UC3M's Fluids and Thermal Engineering Department.
The scientific team used digital processing techniques, along with visualization techniques that used a laser, to reconstruct the form of the wave in three dimensions. This allowed the team to compare it with real waves, similar to those ridden by surfers. "The most remarkable thing is to observe a pipeline wave that remains still, to the point that we can put our fingers under the crest for as long as we want and not get wet, because this wave never breaks," describes Javier Rodriguez.
The scientists constructed a small canal in a laboratory in order to recreate this phenomenon. The team says the prototype is relatively simple, consisting of a semi-submerged panel with a square corner that partially obstructs the flow in a tank of water that is approximately the length of a van. "This is the simplest and cheapest way to produce different heights in a very rapidly moving current of water," states Professor Rodriguez.
The UC3M scientists are collaborating with a team from UC San Diego and the University of East Anglia, UK, in the theoretical part of the study. The researchers are using computer simulation techniques and asymptotic analysis to create an approximate description of this wave's formation. "This description is precise enough to enable us to understand its behavior; we are taking advantage of the fact that the wave is very slender. That is, as we move away from its starting point, its size slowly increases," points Pablo Martinez-Legazpi, a researcher at UC San Diego. "As we investigate further into this subject," he adds, "we realize that this formation process is representative of and common to other waves that are of great interest to civil and naval engineering, such as waves that crash into ports, bridges or off-shore oil rigs during rough sea conditions."
The scientists are able to generate a wave that would never be static in nature, thanks to this experiment. They are able to render the wave motionless in the laboratory for the time necessary to study it in detail. The knowledge gained from this experiment can be tremendously useful when predicting the intensity of the streams that appear when waves impact against marine structures (ports, off-shore oil rigs, ships, etc.) and it could help to anticipate the damage they might cause. The US Navy suggested and partially financed this study due to its implications for improvements in naval hydrodynamics.
The wave study will also be a very useful tool from an oceanographic point of view. It will allow for the implementation of a great number of research techniques that would be very difficult to apply to a wave in motion. It also has direct environmental applications, such as allowing for a better response to what occurs on the marine surface when a wave breaks, which in turn can help scientists understand how carbon dioxide exchange between the ocean and atmosphere occurs. "And although it has nothing to do with science, we also think this research can be of interest when it comes to creating decorative fountains or rides in water parks," notes Javier Rodriguez. "If, in addition to being interesting because it can help us understand the ocean, you can also have fun with it, why not do it?" he concludes.