A pump inspired by flapping bird wings

February 3, 2015

When a fluid is squeezed and expanded repeatedly between two sawtooth-like boundaries, a net flow is generated to the right (credit: B. Thiria & J. Zhang)

Two New York University researchers have taken inspiration from avian locomotion strategies and created a pump that moves fluid using vibration instead of a rotor. Their results were published today (February 3) in the journal Applied Physics Letters.

“When we use a household pump, that pump is very likely a centrifugal pump. It uses a high-speed rotor to move water by throwing it from the pump’s inlet to the outlet,” explained Benjamin Thiria, who carried out the work in collaboration with Jun Zhang.

Instead of a rotor, Thiria and Zhang’s design has teeth. Two asymmetrically sawtoothed panels, placed with their teeth facing each other, create a channel that can rapidly open and close. Water rushes into the channel when it expands and is forced out when it contracts.

The pump could be particularly useful in industrial situations where machinery is vibrating excessively and therefore operating inefficiently. Because it is powered by vibration, it could capture some of the wasted mechanical energy and instead use it for a productive task like circulating coolant. It would also dampen the noise that vibrating machinery tends to emit.

In the future, Thiria and Zhang hope to find other examples of similar pumps in nature — such as the human circulatory system — and use them to further optimize their design.

The authors of this paper are affiliated with New York University (Thiria and Zhang) and ESPCI ParisTech (Thiria).

Abstract for Ratcheting fluid with geometric anisotropy

We investigate a mechanism that effectively transports fluids using vibrational motion imposed onto fluid boundary with anisotropy. In our experiment, two asymmetric, sawtooth-like structuresare placed facing each other and form a corrugated fluid channel. This channel is then forced to open and close periodically. Under reciprocal motion, fluid fills in the gap during the expansion phase of the channel and is then forced out during contraction. Since the fluid experiences different impedances when flowing in different directions, the stagnation point that separatesflows of two directions changes within each driving period. As a result, fluid is transported unidirectionally. This ratcheting effect of fluid is demonstrated through our measurements and its working principle discussed in some detail.