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Brian Polagye

Adjunct Investigator

Assistant Professor, Mechanical Engineering

Email

bpolagye@apl.uw.edu

Phone

206-543-7544

Research Interests

Tidal Energy Site and Device Characterization

Biosketch

Brian Polagye specializes in the characterization of tidal energy sites and devices through his work with the Northwest National Marine Renewable Energy Center. He works closely with Dr. Jim Thomson to develop instrumentation and methodologies to characterize the physical and biological environments at tidal energy sites. A combination of shipboard and stand-alone surveys monitor current velocity, turbulence, water quality, underwater noise, and marine mammal behavior. These activities are essential to the effective siting of tidal energy devices.

Publications

2000-present and while at APL-UW

Comparison of cross-flow turbine performance under torque-regulated and speed-regulated control

Polagye, B., B. Strom, H. Ross, D. Forbush, and R.J. Cavagnaro, "Comparison of cross-flow turbine performance under torque-regulated and speed-regulated control," J. Renewable Sustainable Energy, 11, 044501, doi:10.1063/1.5087476, 2019.

More Info

13 Aug 2019

When experimentally evaluating the performance of a wind or water current turbine, one must impose a regulating torque on the turbine rotor by electrical or mechanical means. Some options limit this controlling torque to a purely resistive quantity, while servomotors and stepper motors allow torque to be applied in the direction of turbine rotation. Any control mode that results in net positive power for a turbine may be of interest for energy harvesting, and all of these are net "fluid-driven." Here, we present experiments that characterize the power, torque, and force coefficients of a cross-flow turbine operated at a constant rotational speed or under a constant imposed control torque. Time- and phase-average performance coefficients are largely equivalent for the two strategies although torque-regulated control is restricted to a narrower range of rotational speeds and the two strategies result in slightly different blade kinematics.

Noise correction of turbulent spectra obtained from acoustic Doppler velocimeters

Durgesh, V., J. Thomson, M. Richmond, and B. Polagye, "Noise correction of turbulent spectra obtained from acoustic Doppler velocimeters," Flow Meas. Instrum., 37, 29-41, doi:10.1016/j.flowmeasinst.2014.03.001, 2014.

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1 Jun 2014

Velocity spectra are essential in characterizing turbulent flows. The Acoustic Doppler Velocimeter (ADV) provides three-dimensional time series data at a single point in space which are used for calculating velocity spectra. However, ADV data are susceptible to contamination from various sources, including instrument noise, which is the intrinsic limit to the accuracy of acoustic Doppler processing. This contamination results in a flattening of the velocity spectra at high frequencies (O(10)Hz).

This paper demonstrates two elementary methods for attenuating instrument noise and improving velocity spectra. First, a "Noise Auto-Correlation" (NAC) approach utilizes the correlation and spectral properties of instrument noise to identify and attenuate the noise in the spectra. Second, a Proper Orthogonal Decomposition (POD) approach utilizes a modal decomposition of the data and attenuates the instrument noise by neglecting the higher-order modes in a time-series reconstruction. The methods are applied to ADV data collected in a tidal channel with maximum horizontal mean currents up to 2 m/s. The spectra estimated using both approaches exhibit an f-5/3 slope, consistent with a turbulent inertial sub-range, over a wider frequency range than the raw spectra. In contrast, a Gaussian filter approach yields spectra with a sharp decrease at high frequencies.

In an example application, the extended inertial sub-range from the NAC method increased the confidence in estimating the turbulent dissipation rate, which requires fitting the amplitude of the f-5/3 region. The resulting dissipation rates have smaller uncertainties and are more consistent with an assumed local balance to shear production, especially for mean horizontal currents less than 0.8 m/s.

Flow-noise and turbulence in two tidal channels

Bassett, C., J. Thomson, P. H. Dahl, and B. Polagye, "Flow-noise and turbulence in two tidal channels," J. Acoust. Soc. Am., 135(4), 1764-1774, doi:10.1121/1.4867360, 2014.

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13 May 2014

Flow-noise resulting from oceanic turbulence and interactions with pressure-sensitive transducers can interfere with ambient noise measurements. This noise source is particularly important in low-frequency measurements (f < 100 Hz) and in highly turbulent environments such as tidal channels. This work presents measurements made in the Chacao Channel, Chile, and in Admiralty Inlet, Puget Sound, WA. In both environments, peak currents exceed 3 m/s and pressure spectral densities attributed to flow-noise are observed at frequencies up to 500 Hz. At 20 Hz, flow-noise exceeds mean slack noise levels by more than 50 dB. Two semi-empirical flow-noise models are developed and applied to predict flow-noise at frequencies from 20 to 500 Hz using measurements of current velocity and turbulence. The first model directly applies mean velocity and turbulence spectra while the second model relies on scaling arguments that relate turbulent dissipation to the mean velocity. Both models, based on prior formulations for infrasonic (f < 20 Hz) flow-noise, agree well with observations in Chacao Channel. In Admiralty Inlet, good agreement is shown only with the model that applies mean velocity and turbulence spectra, as the measured turbulence violates the scaling assumption in the second model.

More Publications

In The News

UW engineers test tidal energy turbines on Lake Washington

KING5 News, Laura Fattaruso

A team of engineers are testing turbines in Lake Washington that are designed to turn tides into usable energy.

17 Aug 2019

Eyes Underwater Watching Aquatic Wildlife

Environmental Monitor, Karla Lant

Recent work from researchers at the University of Washington offers a promising new way to harvest energy from waves at sea and use that energy to power an Adaptable Monitoring Package.

9 Jul 2019

Converting ocean waves into electricity poses challenges—and promise

Columns Magazine, Jon Marmor

In the glorious Pacific Ocean waters off the windward coast of O’ahu, waves crash along the Kailua coast. But it isn’t just surfers who salivate over those ocean jewels. Scientists believe the motion of the ocean could bring the promise of something even more important: clean energy.

3 Jun 2019

More News Items

Inventions

An Adaptable Monitoring Package for Marine Environmental Monitoring

Record of Invention Number: 47352

Brian Polagye, James Joslin, Ben Rush, Andy Stewart

Disclosure

21 May 2015

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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