Summer 2016 Test Results
Over the course of July-August 2016, the Leading Edge team conducted tests with
two of the Leading Edge Oscillating Wings in inline configuration. The test
platform consists of a custom designed pontoon boat with two Leading Edge
Oscillating Wings mounted along the centerline.
Each Leading Edge Oscillating Wing consists of two staggered hydrofoils, which oscillate 90 degrees out of phase and drive a generator. The following movie shows the kinematics of each device superimposed on the simulations from computational fluid dynamics.
Results from single device tests
A 1kW prototype was tested in August 2015 on the Taunton River in Somerset, MA. The device was attached to the underside of a modified pontoon boat to facilitate testing at controlled flow speeds. The device generated up to 1.15kW of power at 4 knots, exceeding its nameplate capacity.
With a design that utilized two hydrofoils operating out of phase, our device was able start up and maintain operation passively in flow speeds of 1 knot or greater without any additional energy input. See how the design worked in in practice:
The characteristics of a single device are described in terms of the reduced frequency and the energy conversion efficiency. The reduced frequency (f* = fc/U) represents the frequency of oscillations the foils and the generator assembly dynamically chooses, non-dimensionalized in terms of the foil chord and the freestream speed. The device efficiency is also a non-dimensional number that compare the electric power generated as a fraction of the fluid kinetic energy incident on the swept area of the foils.
Further description here …
Results from tandem device tests
In an array of devices, each device sheds a wake similar to a shadow, where the kinetic energy of the flow is depleted. The tandem device tests are interesting because devices are directly in the shadow of upstream devices. The figure below shows results from two devices arranged in tandem with a spacing of 6 foil chords.
The power extracted by the downstream device is plotted against that extracted by the upstream device in the left panel. Similarly the frequency of oscillations of the two devices in plotted in the panel on the right.
Examining the panel on the left, we see that the power extracted by the downstream device is 68-80% of the power extracted by the upstream device. This is remarkable, because rotary turbines placed downstream of other turbines are able to extract at most 30-40% of the power extracted by upstream turbines.
For more information contact Dr. Shreyas Mandre.