Pitt and University of Illinois Researchers Put Long-Sought Knowledge of Turbulence on Steady Ground; Has Potential for Reducing Friction in Oil Pipelines

Experiments performed at the University of Pittsburgh in partnership with the University of Illinois at Urbana-Champaign have led to a breakthrough in understanding fluid turbulence, the natural drag produced by flowing liquid that can hamper such processes as transporting oil through pipelines, according to a report recently featured on the cover of Nature Physics.

Walter Goldburg, a professor emeritus in the Department of Physics and Astronomy in Pitt’s School of Arts and Sciences, oversaw the experimental portion of a project that establishes a long-sought link between turbulence and “eddies,” microscopic swirls that impede smooth flow. The theoretical work underlying these experiments was conducted at the University of Illinois by Gustavo Gioia, Nigel Goldenfeld, Tuan Tran, Pinaki Chakraborty, and Nicholas Guttenberg. Experimental work also was performed by Hamid Kellay of the University of Bordeaux.

Any fluid that flows along any boundary­­–such as oil in a pipeline or water in a riverbank–encounters friction. This friction creates turbulence, which causes a lessened efficiency of flow. The team’s goal was to study the connection between frictional drag and the irregular motion of turbulent eddies in the flow’s interior.

In the experiments, Goldburg and undergraduate and graduate students in his laboratory induced turbulence in a soap film stretched between two wires. By probing the turbulent motion with lasers, they were able to measure the turbulent velocity changes and the frictional drag created at the two wires. This helped them identify how turbulence in a pipe generates the frictional force on the pipe and also how much force the pipe has on the flowing fluid.

The findings have such practical applications as helping to reduce friction in an oil pipeline, Goldburg said. Turbulence can be quite costly because friction leads to heat loss and a decreased flow rate. Understanding how to minimize energy loss by reducing friction and speeding up the process could lead to a reduced cost for delivering oil.

The next step in the project is to examine how the frictional energy loss depends on the roughness of the boundary’s interior wall, Goldburg said. Friction is greater when liquids flow over rough surfaces, a phenomenon the team aims to understand better.