Researchers Create a Wave Frozen in Time

San Diego, CA, July 22, 2013 -- Scientists at the Universidad Carlos III of Madrid (UC3M) and the University of California, San Diego have created, in a laboratory, a static “pipeline wave,” with a crest that moves neither forward nor backward. This research, published in the journal Experiments in Fluids, could lead to improvements in boat and seaport designs as well as analyses of how carbon dioxide exchange between the ocean and the atmosphere occurs. (This story is adapted from one written by the Universidad Carlos III of Madrid (UC3M))

 The static pipeline wave the researchers generated would not remain static in nature. Rendering the wave motionless in the laboratory provides the researchers time to study it in detail. Understanding how these waves are formed can be tremendously useful when predicting the intensity of the streams that form when waves hit marine structures including ports, off-shore oil rigs and ships. The work could also help researchers anticipate the damage that these streams of water might cause. The U.S. Office of Naval Research (ONR) partially financed this work due to its implications for improvements in naval hydrodynamics.

“A wave is a deformation in the surface of a liquid that moves at a speed that is independent of that liquid,” the researchers explain. For example: in the waves that are formed when a rock is thrown into a pond, the water remains still while the waves move away from the center at their own speed. “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 one of the authors of the research report, Javier Rodríguez, of UC3M’s Fluids and Thermal Engineering Department.

Every surfer’s dream

In the experiment described in Experiments in Fluids, the scientists used digital processing techniques and visualization techniques that used a laser to reconstruct the form of the wave in three dimensions in order to compare it with real waves, similar to those that are 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,” says Javier Rodríguez.

 In order to recreate this phenomenon, the scientists constructed a small canal in a laboratory at the University. The prototype is relatively simple, they say: it consists 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 Rodríguez.

In the theoretical part of the study, in which the UC3M scientists are currently collaborating with colleagues from the UC San Diego Jacobs School of Engineering and from the University of East Anglia (United Kingdom), they are using computer simulation techniques and asymptotic analysis to create an approximate description of this wave’s formation.

Structural and environmental applications

“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 out Pablo Martínez-Legazpi, a researcher from Juan C. Lasheras’ lab in the Department of Mechanical and Aerospace Engineering at the UC San Diego Jacobs School of Engineering. “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.”

From the oceanographic point of view, this is also a very useful tool, as it allows for the implementation of a great number of research techniques that would be very difficult to apply to a wave in motion. In addition, it has direct environmental applications: it allows 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 Rodríguez, who also spent time at UC San Diego as a postdoctoral researcher in the Lasheras lab. “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.

Further information:

Title: Plunging to spilling transition in corner surface waves in the wake of a partially submerged vertical plate (PDF)

Authors: Pablo Martinez Legazpi, P; Javier Rodriguez-Rodriguez, C. Marugan-Cruz; and Juan C. Lasheras

Journal: EXPERIMENTS IN FLUIDS. Volume: 54. Number: 1. Article number: 1437. DOI: 10.1007/s00348-012-1437-7. Published in January 2013.

Monday, July 22, 2013