Approximately 10% of global electricity consumption is for pumping water, oil, natural gas and other fluids through pipes. Researchers at the Institute of Science and Technology Austria have discovered a technique which could reduce the energy required for this by up to 95%.
The major part of this energy is lost through turbulence which leads to a drastic increase of frictional drag and much more energy being required to pump the fluid
Until now, it had been assumed that, once a flow of a fluid has become turbulent, turbulence would persist. The researchers have now shown that this is not the case.
In their experiments, they managed to eliminate turbulence so that the flow turned to a laminar state and the flow remained laminar thereafter. Eliminating turbulence can save as much as 95% of the energy required to pump a fluid through a pipe.
The secret lies in the velocity profile of the fluid – that is, in the variation of the flow velocity at different positions in the pipe’s cross section. The flow is fastest in the middle of the pipe while it is much slower near the walls. This difference in flow rates creates turbulence.
The researchers were able to produce a “flatter” profile, and eliminate turbulence, in three ways:
- by placing rotors in the flow that reduced the velocity difference between the fluid in the center and that close to the wall,
- by moving the walls of part of pipe quickly over a stretch of the pipe and
- by injecting liquid from the wall.
The concept has been proven for relatively small velocities and in computer simulations of large pipelines at high velocities. The next step is to prove that it works at high velocities in the field.