A static wave created by researchers could allow major allow improvement in boat and seaport designs.
Scientists at the Universidad Carlos III of Madrid (UC3M) and the University of California - San Diego (UC San Diego) have created, in a laboratory, a static pipeline wave, with a crest that moves neither forward nor backward.
The experiment makes it possible to generate a wave, that would never be static in nature, and render it motionless in the laboratory for the time that is necessary to study it in detail.
Understanding how these waves are formed could vastly improve researchers’ ability to predict the intensity of the streams that appear when waves impact against marine structures like ports, off-shore oil rigs and ships and help anticipate the damage they might cause.
The research was suggested and partially financed by the US Navy due to its implications for improvements in naval hydrodynamics.
“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,” said Javier Rodríguez of UC3M’s Fluids and Thermal Engineering Department.
In waves that are formed when a rock is thrown into a pond, the water remains still while the waves move away from the centre at their own speed, but in the wave created by the researchers the water moves very rapidly, at several meters per second, but the wave moves at a speed of zero, keeping it frozen in time.
In order to recreate the phenomenon, the scientists constructed a small canal in a laboratory at the university with 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,” said Rodríguez.
In an article published in the journal Experiments in Fluids, the scientists explain how they used digital processing and visualization techniques using 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.
In the theoretical part of the study, in which the UC3M scientists are collaborating with colleagues from UC San Diego and from the University of East Anglia, they are using computer simulation techniques and asymptotic analysis to create an approximate description of the wave’s formation.
“This description is precise enough to enable us to understand its behaviour; 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,” said Pablo Martínez-Legazpi, a researcher at UC San Diego.
“As we investigate further into this subject,” he added, “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.”