Faculty Papers and Data, Mechanical Engineering

Permanent URI for this collectionhttps://digital.lib.washington.edu/handle/1773/34910

Browse

Now showing 1 - 20 of 29

Data-driven modeling of an oscillating surge wave energy converter using dynamic mode decomposition
(2025-03-26) Lydon, Brittany; Polagye, Brian; Brunton, Steven
Modeling wave energy converters (WECs) to accurately predict their hydrodynamic behavior has been a challenge for the wave energy field. Often, this results in either low-fidelity linear models or high-fidelity numerical models that are too computationally expensive for operational use. To bridge this gap, we propose the use of dynamic mode decomposition (DMD) as a purely data-driven technique that can generate an accurate and computationally efficient model of WEC dynamics. Specifically, we model and predict the behavior of an oscillating surge wave energy converter (OSWEC) in mono- and polychromatic seas without an equation of motion or knowledge of the incident wave field. We generate data with the open-source code WEC-Sim, then evaluate how well DMD can describe past dynamics and predict future behavior. We consider realistic challenges including noisy sensors, nonlinear dynamics, and irregular wave forcing. Specifically, by using an extension of DMD we reduce the effect of noise on our system and significantly increase model accuracy outside the training region. Additionally, by introducing time delays we accurately describe weakly nonlinear dynamics, even though DMD is a linear algorithm. Finally, we use Optimized DMD (optDMD) to model OSWEC behavior in response to irregular waves. While optDMD accurately models training data, future prediction was inaccurate, demonstrating the limits of modeling efforts without access to information about the incident wave field. These findings provide insight into the use of DMD, and its extensions, on systems with limited time-resolved data and present a framework for applying similar analysis to lab- or field-scale experiments.
Performance of a Drifting Acoustic Instrumentation SYstem (DAISY) for Characterizing Radiated Noise from Marine Energy Converters
(2024-11-29) Polagye, Brian; Crisp, Corey; Jones, Lindsey; Murphy, Paul; Noe, Jessica; Calandra, Gemma; Bassett, Christopher
Marine energy converters can generate electricity from energetic ocean waves and water currents. Because sound is extensively used by marine animals, the radiated noise from these systems is of regulatory interest. However, the energetic nature of these locations poses challenges for performing accurate passive acoustic measurements, particularly with stationary platforms. The Drifting Acoustic Instrumentation SYstem (DAISY) is a modular hydrophone recording system purpose-built for marine energy environments. Using a flow shield in currents and mass-spring-damper suspension system in waves, we demonstrate that DAISYs can effectively minimize the masking effect of flow noise at frequencies down to 10 Hz. In addition, we show that groups of DAISYs can utilize time-delay-of-arrival post-processing to attribute radiated noise to a specific source. Consequently, DAISYs can rapidly measure radiated noise at all frequencies of interest for prototype marine energy converters. The resulting information from future operational deployments should support regulatory decision-making and allow technology developers to make design adjustments that minimize the potential for acoustic impacts as their systems are scaled up for utility-scale power generation.
Performance data for an axial-flow turbine with passive adaptive blades
(2024) Van Ness, Katherine; Polagye, Brian; Crisp, Corey
Passive adaptive blades for axial-flow marine current turbines offer the potential for blade load reductions without introducing failure modes inherent to active pitch mechanisms. To support the development of simulation tools for passive adaptive turbine rotors, an experimental data set from a laboratory-scale axial-flow turbine with passive adaptive blades is provided. The blades were fabricated with unidirectional off-axis carbon fiber, resulting in a coupling between flapwise deflection and spanwise twisting. The 0.45-meter diameter turbine was tested in an open-channel, recirculating flume at three flow speeds over tip-speed ratios 2-8. Blade and rotor loads were measured at 1 kHz using six-axis force/torque sensors at the root of a blade and on the drive shaft in the rotor hub, while deflection and twist at the blade tip were tracked using a high-speed camera. Frequency analysis of the blade loads revealed no evidence of flutter instability, with dominant frequencies identified only at the blade passing frequency and associated harmonics.
Experimental data from "An experimental evaluation of the interplay between geometry and scale on cross-flow turbine performance"
(2023) Hunt, Aidan; Strom, Benjamin; Talpey, Gregory; Ross, Hannah; Scherl, Isabel; Brunton, Steven; Wosnik, Martin; Polagye, Brian
The provided MATLAB file contains data from 223 cross-flow turbine experiments conducted at the University of Washington and University of New Hampshire, which are described in detail in "A parametric evaluation of the interplay between geometry and scale on cross-flow turbine performance" by Hunt et al. The "data" struct in the provided file includes time-average and phase-median performance, rotor geometry specifications, and flow properties for each experiment. The "comments" struct describes each field of the "data" struct in detail. Please contact Aidan Hunt at ahunt94@uw.edu or Brian Polagye at bpolagye@uw.edu if you have questions about the data.
Variable Speed of Light Cosmology and Electromagnetism
(KDP, 2022) Devasia, Santosh
This work explores modifications of electromagnetism models to allow variable speed of light (VSL) without violating current observations and investigates the utility of VSL to explain anomalies (unexplainable observations) in cosmology. Such a variable speed of light (VSL) approach, where the source speed augments the speed of light, is controversial since it violates Maxwell’s equations that requires the speed of light to be independent of the source speed. Therefore, relative-velocity (RV) based modifications of Maxwell’s equations are proposed to facilitate a VSL-based cosmology, that predicts (rather than assume) the Hubble law and explains current cosmological anomalies such as the apparent lack of time dilation in quasar observations. It is shown also that the proposed RV-based model matches current observations in electromagnetism and optics, such as the transverse Doppler effect and the Fresnel drag. Finally, a method to potentially validate/refute the proposed approach using high speed ion experiments is proposed.
Algebraic Skeleton Transform: A symbolic computation challenge
(2022-05-04) Storti, Duane
We introduce an algebraic formulation for the shape skeleton transform (also known as the medial axis transform) and present a concrete low-degree example. While we can now construct an algorithmic approach and provide a proof-of-concept example, small increases in algebraic degree or geometric complexity cause the algebraic computations to become intractable, and we propose the algebraic skeleton transform as a challenge problem for algebraic computation.
Experimental comparison of blade pitch and speed control strategies for horizontal-axis current turbines
(Journal of Ocean Engineering and Marine Energy, 2021-03-11) Van Ness, Katherine; Polagye, Brian; Hill, Craig; Aliseda, Alberto; Burnett, Justin
The majority of utility-scale horizontal-axis current turbines use either speed or pitch control to maintain a constant power output once the currents exceed a certain threshold: the turbine-specific “rated speed”. In this study, we experimentally characterized power performance and turbine loading over a range of blade pitch settings and tip-speed ratios for a threebladed horizontal-axis turbine. We then implemented a control strategy to maintain power output in time-varying currents using blade pitch control and compare the turbine performance under this control strategy to “overspeed” and “underspeed” control strategies for a fixed pitch turbine. The experiments were conducted with a laboratory-scale 0.45-m diameter turbine in an open channel flume with a 35% blockage ratio. During pitch characterization experiments, inflow velocity was maintained at 0.8m/s with 4% turbulence intensity. During time-varying inflow experiments, currents varied from 0.7 to 0.8m/s over a 20- min period, while a proportional controller regulated either blade pitch or rotor speed, and we recorded turbine power output and turbine loads. In this velocity range, where turbine performance is independent of Reynolds number, we demonstrated that pitch control substantially reduced torque requirements relative to underspeed control and turbine loads relative to overspeed control. Additional tests were conducted for underspeed control and pitch control in a Reynolds-dependent regime with time-varying inflow between 0.4–0.5 and 0.5–0.6 m/s. These cases suggest that blade pitch control could provide even greater benefits relative to speed control in small-scale applications.
Supplementary material for "Effects of dimensionless parameters on the performance of a cross-flow current turbine"
(2021) Ross, Hannah; Polagye, Brian
These files accompany the manuscript "Effects of dimensionless parameters on the performance of a cross-flow current turbine". The files include turbine performance data collected in the Alice C. Tyler recirculating water flume at the University of Washington's Harris Hydraulics Laboratory. The data contain turbine power coefficients and tip-speed ratios used to compare performance across a range of dimensionless parameters, in addition to channel depth upstream and downstream of the turbine. Information about turbine and channel geometry and the processing codes used to produce the results in the manuscript are included as well. The data are described in the README file.
Data (coming) to support a paper on mechanical prosthetics
(2021-05-24) Ledoux, William R.
High-Productivity Parallelism with Python Plus Packages (but without a Cluster)
(2021) Bartlett, John; Storti, Duane; Chris, Uchytil
We present two computing projects, peridynamics simulation and numerical integration on implicit domains, for which we realized high performance implementations using Python with appropriate packages. The problems are sufficiently compute-intensive that a straightforward serial implementation is prohibitively slow. While conventional wisdom suggests moving such problems onto a computing cluster, we very directly produced high-performance parallel implementations that effectively perform the computing tasks on a single GPU. For the peridynamics application, the only package needed in addition to Numpy is Numba whose just-in-time compiler allows us to write kernel functions in Python and compile them to run in parallel on a CUDA-enabled GPU. Our approach to numerical integration on implicit domains invokes two additional packages to support interval arithmetic and dynamic parallelism to enable tree-structured recursive refinement. Use of Python (with only kernels requiring dynamic parallelism written in C) enabled rapid development of concise code that successfully achieves significant performance enhancement.
A SINGLE-CARD GPU IMPLEMENTATION OF PERIDYNAMICS
(2021) Bartlett, John; Storti, Duane
The rapid development of parallelization technology over the recent decades has provided a promising avenue for the acceleration of meshfree simulation methods. One such method, peridynamics, is particularly well-suited for parallelization due to the simplicity of the operations which must occur at each material point. However, while MPI-based parallelization (Message- Passing Interface; a method for CPU-based parallelization) of peridynamic problems is commonplace, GPU parallelization of peridynamics has received far less attention. While GPU technology may have once been an inferior option to MPI parallelization for peridynamics, modern GPU cards are more than capable of handling substantially sized peridynamics problems. This paper presents the parallelization of the peridynamic method for single - card GPU computing, providing a schematic for a compact parallel approach. The resulting method is tested with CUDA on a NVIDIA Tesla P100 card with 16 GB of memory. The per - node memory requirements for each data structure used are evaluated, as well as the per - node execution times for each operation in a million - node benchmark test. This setup is shown to provide speedup factors over 200 for problems sized up to several million nodes, therefore indicating such a GPU is more than adequate for the single - card parallelization of the peridynamic method.
Detection and Classification Capabilities of Two Multibeam Sonars
(2020-09-07) Cotter, Emma D
Supplemental data for: Detection and Classification Capabilities of Two Multibeam Sonars, by Emma Cotter and Brian Polagye, accepted for publication in Limnology and Oceanography Methods (2020)
Supplementary material for "Effect of Aspect Ratio on Cross-Flow Turbine Performance"
(Journal of Renewable and Sustainable Energy, 2020) Hunt, Aidan; Stringer, Carl; Polagye, Brian
These files support the manuscript "Effect of Aspect Ratio on Cross-Flow Turbine Performance". They include time-average turbine efficiency and non-dimensional parameter datasets for each of the associated turbine experiments, which were conducted at the University of Washington Harris Hydraulics Laboratory. Additionally, they also include a video showing an example of the rotor ventilation we observed in our experiments. Both of these files are described in further detail in the README file.
Adaptable Monitoring Package Development and Deployment: Lessons Learned for Integrated Instrumentation at Marine Energy Sites
(MDPI, 2020) Polagye, Brian; Joslin, James; Murphy, Paul; Cotter, Emma; Scott, Mitchell; Gibbs, Paul; Bassett, Christopher; Stewart, Andrew
Integrated instrumentation packages are an attractive option for environmental and ecological monitoring at marine energy sites, as they can support a range of sensors in a form factor compact enough for the operational constraints posed by energetic waves and currents. Here we present details of the architecture and performance for one such system—the Adaptable Monitoring Package—which supports active acoustic, passive acoustic, and optical sensing to quantify the physical environment and animal presence at marine energy sites. We describe cabled and autonomous deployments and contrast the relatively limited system capabilities in an autonomous operating mode with more expansive capabilities, including real-time data processing, afforded by shore power or in situ power harvesting from waves. Across these deployments, we describe sensor performance, outcomes for biological target classification algorithms using data from multibeam sonars and optical cameras, and the effectiveness of measures to limit biofouling and corrosion. On the basis of these experiences, we discuss the demonstrated requirements for integrated instrumentation, possible operational concepts for monitoring the environmental and ecological effects of marine energy converters using such systems, and the engineering trade-offs inherent in their development. Overall, we find that integrated instrumentation can provide powerful capabilities for observing rare events, managing the volume of data collected, and mitigating potential bias to marine animal behavior. These capabilities may be as relevant to the broader oceanographic community as they are to the emerging marine energy sector.
Supplementary material for "An experimental evaluation of blockage effects on the wake of a cross-flow current turbine"
(2020) Ross, Hannah; Polagye, Brian
These files accompany the manuscript "An experimental evaluation of blockage effects on the wake of a cross-flow current turbine". The files include turbine wake data collected in recirculating water flumes at the Bamfield Marine Sciences Centre's Fluid Dynamics Laboratory and the University of Washington's Harris Hydraulics Laboratory. The data contain time-average, three-dimensional velocity measurements collected in the wake of the turbine, in addition to several derived quantities used to compare the wake at different blockage ratios. The processing codes used to produce the results in the manuscript are included as well. The data are described in detail in the README file.
An experimental assessment of analytical blockage corrections for turbines
(2019) Ross, Hannah; Polagye, Brian
In laboratory experiments involving wind or water turbines, it is often desirable to correct measured performance for the eﬀects of model blockage. However, there has been limited experimental validation of the analytical blockage corrections presented in the literature. Therefore, the objective of this study is to evaluate corrections against experimental data and recommend one or more for future use. For this investigation, we tested a cross-ﬂow turbine and an axial-ﬂow turbine under conditions of varying blockage with other non-dimensional parameters, such as the free-stream Reynolds and Froude numbers, held approximately constant. We used the resulting experimental data to assess the eﬀectiveness of multiple analytical blockage corrections for both turbine types. Of the corrections evaluated, two are recommended. However, as these methods are based on axial momentum theory, we observe that corrections are more eﬀective for thrust than power. We also ﬁnd that increasing blockage changes the local Reynolds number, which can aﬀect turbine performance but is not reﬂected in axial momentum theory.
Comparison of cross-flow turbine performance under torque-regulated and speed-regulated control
(AIP, 2019) Polagye, Brian; Strom, Ben; Ross, Hannah; Forbush, Dominic; Cavagnaro, Robert
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, though torque-regulated control is restricted to a narrower range of rotational speeds and the two strategies result in slightly different blade kinematics.
Supplementary MATLAB toolbox and data for "Comparative evaluation of volumetric current measurements in a tidally-dominated, coastal setting with an emphasis on float swarms"
(2019) Harrison, Trevor William; Thyng, Kristen M.; Polagye, Brian
These files comprise the MATLAB code used to generate the results presented in "Comparative evaluation of volumetric current measurements in a tidally-dominated, coastal setting with an emphasis on float swarms," written by Trevor Harrison (University of Washington), Kristen M. Thyng (Texas A&M University), and Brian Polagye (Univeristy of Washington). The code was based on the outputs of a previous hydrodynamic simulation of Admiralty Inlet, Puget Sound, WA. Those outputs are separately available at http://pong.tamu.edu/~kthyng/froude/ai65/OUT/ and managed by Kristen Thyng (kthyng [at] tamu.edu). Further information regarding implementation of the toolbox can be found in the README.txt tile, as well as comments embedded in scripts and functions. The code was last known to be stable on MATLAB2018b.
Towards a General Method for Constructing Manufacturability Design Rules for an Additive Manufacturing Process
(2019-07) Weiss, Benjamin M; Hamel, Joshua M; Storti, Duane W; Ganter, Mark A
Additive manufacturing (AM) presents a unique set of manufacturability constraints, among the most important of which are the smallest producible feature size and the maximum overhang angle before support structures are required. In this work, an approach is presented which includes both a parameterization strategy for small features, and a subsequent iterative experiment for realizing minimum feature size design rules as functions of feature shape and orientation. This approach was designed to be applicable to a wide variety of AM processes, and was applied to an example machine in the material extrusion AM process category for demonstration purposes. This case study involved a thorough experimental evaluation to explore the tradeoffs between the number of oriented shapes evaluated and the predictive quality of the resulting design rules, and the results produced found that minimum feature size can vary by as much as 10x over the set of considered oriented shapes for the AM system studied. Compared to existing design rules in the literature, using the proposed approach made it possible to increase the design space for the AM system considered by providing lower minimum feature sizes when possible, by incorporating more accurate overhang angle constraints into the minimum feature size definition, and by detecting un-manufacturable features that existing design rules would have incorrectly allowed.
Data-Driven Additive Manufacturing Constraints for Topology Optimization
(2019-07-05) Weiss, Benjamin M; Hamel, Joshua M; Ganter, Mark A; Storti, Duane W
The topology optimization (TO) of structures to be produced using additive manufacturing (AM) is explored using a data-driven constraint function that predicts the minimum producible size of small features in different shapes and orientations. This shape- and orientation-dependent manufacturing constraint, derived from experimental data, is implemented within a TO framework using a modified version of the Moving Morphable Components (MMC) approach. Because the analytic constraint function is fully differentiable, gradient-based optimization can be used. The MMC approach is extended in this work to include a “bootstrapping” step, which provides initial component layouts to the MMC algorithm based on intermediate Solid Isotropic Material with Penalization (SIMP) topology optimization results. This “bootstrapping” approach improves convergence compared to reference MMC implementations. Results from two compliance design optimization example problems demonstrate the successful integration of the manufacturability constraint in the MMC approach, and the optimal designs produced show minor changes in topology and shape compared to designs produced using fixed-radius filters in the traditional SIMP approach. The use of this data-driven manufacturability constraint makes it possible to take better advantage of the achievable complexity in additive manufacturing processes, while resulting in typical penalties to the design objective function of around only 2% when compared to the unconstrained case.

Browse

Recent Submissions