A discovery made by researchers from the Okinawa Institute of Science and Technology (OIST) and the Polytechnic University of Milan promises to cut the energy costs associated with fluid transportation by as much as 22%.

The team determined that when a fluid is pumped through a pipe intermittently, it reduces the cost of transport significantly.

A chaotic, turbulent flow. Source: OIST

Using numerical simulations, the team demonstrated that when periodically switching a pump on and off, the fluid flow continued to transition between a turbulent and laminar state, thereby reducing energy costs. This is due to fluid flow behaviors, according to the team. Because laminar flows are smooth and streamlined, they are considered more energy efficient flows than turbulent flows, which expend a lot of energy thanks to their chaotic nature.

"If you inject ink into a laminar flow, you'll see a clear line of ink moving down the pipe, but with a turbulent flow, the ink diffuses as each fluid particle takes an unpredictable path. This chaotic motion at the small scales results in a lot of energy being lost," explained Giulio Foggi Rota, first author and current Ph.D. student in the Complex Fluids and Flows Unit. "Laminar flows are ideal for fluid transport, but when viscous fluids move fast and over large scales, the system naturally evolves towards a turbulent state."

As such, the researchers created a code for simulating a standardized turbulent flow on a supercomputer, running different scenarios and altering the amount of time the pump was switched on, as well as the intensity of the pump, and the duration of time for each on-off pump cycle.

Their findings revealed that long cycles featuring a short, intense pump quickly accelerated the fluid flow, while a long phase where the pump was switched off and the fluid slowed, best kept the fluid in a laminar-like state for a longer duration of time.

This discovery, according to the team, could significantly reduce the costs of transporting fluids through pipes, which accounts for a significant portion of the final cost of fuel. As such, liquid hydrogen could become more affordable for developed countries to transition to, for instance. Likewise, developing countries not yet able to switch to green energy could have access to more affordable oil and natural gas, for example.

An article detailing the finding, Saving energy in turbulent flows with unsteady pumping, appears in the journal Scientific Reports.