Researchers discover liquid spiral vortex

Researchers in Japan discovered a liquid spiral vortex at the intersection of two water pipes.

The goal of the scientists was to better understand how the geometry of piping systems and competing flow directions govern fluid dynamics. Researchers looked at the behavior of water in a cross-shaped device, with one pipe pumping in water from both directions and another pulling water out from both directions.

When the water met at the intersection it was forced to mix by the push of the pump. Dye inserted into one of the competing streams allowed researchers visualize the water's movement.

Researchers discovered that as they upped the flow rate of the two streams, a vortex appeared at the intersection. When they decreased the rate, the spiral vortex dissipated.

Scientists then manipulated the aspect ratio of the device by changing the size and length of the pipes. In doing so, the researchers were able to pick up on patterns and predict -- based on aspect ratio and flow rates -- where and when a vortex would appear within the intersection.

"In any channel we can predict when the spiral will form, how big it will grow, and the mixing quality that will result," Simon Haward, a researcher at the Okinawa Institute of Science and Technology Graduate University, said in a news release.

Haward and his colleagues recently shared their discovery in a paper published in the journal Physical Review E.

Researchers describe the type of behavior as a unique form of fluid instability.

"We are starting to think that this kind of instability would exist in any kind of intersecting geometry," Haward said.

Researchers say their findings may have important implications for researchers working on mixing fluids.

"In microfluidic devices it can be difficult to begin the mixing process," study author Amy Shen said. "Our results suggest that if we make the channel dimensions deeper than it is easier to induce mixing."