University Student Solves a Simple Question Puzzling Physicists For Over 50 Years

A simple puzzle in physics that has confused physicists for over fifty years, was finally solved by a university student. According to a study published in the scientific journal Physical Review Fluids, Wassim Dhaouadi, an undergraduate engineering student working at the lab of his professor, John Kolinski, figured out why gas bubbles appear to get stuck inside narrow vertical tubes. Dhaouadi's findings just might provide a solution to understanding the behavior of natural gasses that get trapped in porous rocks. 

A long time ago, physicists noticed how gas bubbles in narrow tubes filled with liquids, did not move. Kolinski, an assistant professor in the Department of Mechanical Engineering at the Swiss Federal Institute of Technology Lausanne and the senior author of the research paper considered this a type of paradox. It was noted that the gas bubbles would get trapped in the narrow space because it was less dense than the liquid surrounding it. The bubbles would rise to the top of the tube. To solve this case, Dhaouadi and Kolinski used a method called "interference microscopy."

Interference microscopy is similar to the one used by the Laser Interferometer Gravitational-Wave Observatory detector that helps to find gravitational waves. The duo turned to a special microscope that would shine a light onto the sample and measure the intensity of the light that bounced back, according to Live Science. Dhaouadi directed the light at the side of the tube and then at the surface of the bubble stuck in it. Then he used the reflected rays of light to find out the thickness of the film. That was how he was able to observe that the bubble wasn't stuck. It was moving extremely slowly and its movements were affected by the film surrounding the bubble sticking to the tube.

"The alcohol allowed them to have a self-cleaning experiment which was necessary because the results would have been messed up by any kind of contamination or dirt," Kolinski explained per the outlet. The phenomenon was first looked into by a scientist named Bretherton in the 1960s. Earlier calculations suggested that the bubble was covered by a thin layer of liquid touching the sides of the tube. The layer would create friction and hinder the motion of the bubble to the surface. Understanding the way Bretherton's Buoyant Bubble moves would help experts study various ways to treat problems related to human blood vessels. Based on the measurements of the thin layer of fluid scientists were also able to calculate its velocity.

They found that the gas bubble isn't stuck at all but is rather moving extraordinarily slowly and at a pace invisible to the naked eye, due to the resistance caused by the thin layer," Kolinski mentioned. In another instance, Kolinski and Dhaouadi also figured that heating the liquid and bubble caused the thin layer of film to disappear. "Whenever you have a gas that's confined in a porous medium such as natural gas in porous rock, or if you're trying to go the opposite direction and trap carbon dioxide inside a rock, then you have lots of gas bubbles that are in confined spaces," Kolinski concluded, praising Dhaouadi for driving the project towards a successful outcome.