Saving Energy in Turbulent Flows with Unsteady Pumping

TL;DR

This paper introduces a novel pulsed pumping technique that reduces energy losses in turbulent flows by cyclically transitioning between laminar-like and turbulent states, leading to significant net energy savings.

Contribution

The study proposes a simple pulsed pumping method that achieves energy savings in turbulent flows, supported by numerical simulations and physical analysis.

Findings

Pulsed pumping reduces overall energy consumption in turbulent flows.

Flow cyclically transitions between quasi-laminar and turbulent states.

Significant net energy savings are demonstrated through numerical results.

Abstract

Viscous dissipation causes significant energy losses in fluid flows; in ducts, laminar flows provide the minimum resistance to the motion, whereas turbulent currents substantially increase the friction at the wall and the energy requirement for pumping. Great effort is currently being devoted to find new ways of reducing the energy losses induced by turbulence. Here we propose a simple and novel drag-reduction technique which achieves substantial energy savings in internal flows, even after the energy cost of the control is accounted for. Our approach consists in driving the flow with a pulsed pumping, unlike the common practice of a constant pumping. We alternate "pump on" phases where the flow accelerates, and "pump off" phases where the flow decays freely. The flow cyclically enters a quasi-laminar state during the acceleration, and transitions to a more classic turbulent state during the deceleration. Our numerical results demonstrate that important net energy savings can be achieved by simply modulating the power injection in the system over time. The physical understanding we have achieved can help the industry in reducing the waste of energy, making it cheaper and preserving the environment by reducing harmful emissions.