Turbulence Models Could Save Billions in Fuel Costs

Professor Beverley McKeon

New models of turbulence could reduce ships' fuel costs by allowing for new ways to counteract drag, according to engineers studying the topic.

Ati Sharma of the University of Southampton in the United Kingdom and Beverley McKeon of the California Institute of Technology in the U.S. have developed a new model to predict the composition of turbulence near walls.

Wall turbulence involves the kinds of motions that develop when liquid or gas flows past a solid surface, including in the motion of a ship or airplane.

Reducing drag created by these types of motion could save the global economy billions of dollars in fuel costs and slash emissions, the scientists said.

"The interesting puzzle has always been how to predict the seemingly chaotic motion of a turbulent fluid," Sharma said.

"Although very complicated, scientists have always observed recurring patterns in turbulence.

"The great red spot on Jupiter would be one well-known example.

"Somehow these motions must be encouraged more than others, so we started by asking the question, 'what motions of the fluid does the flow amplify the most?'"

Sharma and McKeon's models break down large-scale flow into simpler "blocks" that can be combined to build simulations comparable to an expensive laboratory or supercomputer experiment on a laptop computer.

"We now have a low-cost way of looking at the 'skeleton' of wall turbulence," McKeon said.

"It was surprising to find that turbulence condenses to these essential building blocks so easily."

The research could allow scientists to improve their understanding of how turbulence is formed so they can modify it to control flow and reduce drag on an object moving through air or water.

"Imagine being able to shape not just an aircraft wing but the characteristics of the turbulence in the flow over it to optimise aircraft performance," McKeon said.

"It opens the doors for entirely new capabilities in vehicle performance."

With fuel prices representing a large part of vessel operating costs, ship owners such as Maersk Line are increasingly focused on improving ships' fuel efficiency.