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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

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.

More Info

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.

More Info

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.

Integrated instrumentation for marine energy monitoring

Polagye, B., J. Joslin, A. Stewart, and A. Copping, "Integrated instrumentation for marine energy monitoring," Proc., 2nd International Conference on Environmental Interactions of Marine Renewable Energy Technologies (EIMR 2014), 28 April - 2 May, Stornaway, Isle of Lewis, Scotland (2014).

More Info

28 Apr 2014

Integrated instrumentation packages designed for operation at marine renewable energy sites have the potential to reduce the risk uncertainty around high- priority interactions between stressors and receptors. Such packages can leverage the competitive strengths of individual instruments and reduce risk in a rapid, cost-effective manner. One emerging example of environmental infrastructure to achieve these objectives, the Adaptable Monitoring Package, is presented and its capabilities described. The development and adoption of such packages requires close coordination between resource managers, technology developers, and researchers.

More Publications

In The News

Underwater sensors for monitoring sea life (and where to find them)

UW News, Sarah McQuate

Harvesting power from the ocean, through spinning underwater turbines or bobbing wave-energy converters, is an emerging frontier in renewable energy.

Researchers have been monitoring how these systems will affect fish and other critters that swim by. But with most available technology, scientists can get only occasional glimpses of what’s going on below.

13 Dec 2018

AMPing up underwater environmental monitoring

UW News, Chelsea Yates

Researchers have long been interested in better understanding how marine energy affects underwater environments, and thanks to UW engineers, they may be a big step closer.

26 Jul 2017

"Millennium Falcon" launches "X-Wing" into marine world

Marine Technology News, Eric Haun

The long-term effect of renewable energy installations on marine animals is to be investigated by researchers at Washington University. APL-UW Ocean Engineers Andy Stewart, Ben Rush, Paul Gibbs, Trina Litchendorf, Tim McGinnis, and Chris Siani are involved in this R&D project.

5 May 2015

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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