Renewable Energy Global Innovations features: Analysis of rain-induced erosion in wind turbine blades

Significance Statement

In conjunction with the increasing interest in renewable energy as an alternative to fossil fuels, researchers have continually focused on wind energy industry in a bid to increase the power output of wind turbines. This has prompted production of more wind turbines with higher power output. Increasing the blade size is a primary method for enhancing the turbine’s power output which has resulted in blade tip velocities of up to 120m/s.

With the high blade tip velocities, high susceptibility to erosion comes in, particularly in harsh environments such as regions with heavy rain and hail. Rain erosion of the blades initiates with a consistent rise in the blade’s surface roughness until small pits form close to the leading edge. With time, the density of the resulting pits increase until gouges form. An increase in surface roughness of the blades translates to a rise in aerodynamic drag coefficient that consequently leads to low performance as well as energy loss.

University of Massachusetts Dartmouth researchers, led by Dr. Mazdak Tootkaboni from the department of civil engineering,  have recently published a two-part research paper on predicting rain erosion  in wind turbine blades. The aim of the research was to integrate well-established theories as well as computational models to come up with a framework that could approximate the expected erosion lifetime of a selected blade, given rainfall history at a particular region, blade shell attributes, and operational conditions of the wind turbine. These papers are published in the Journal of Wind Engineering and Industrial Aerodynamics.

As a first step, the research team developed a stochastic model of rain texture that was capable of relating the integral attributes of rain, for instance, rain intensity and average volume of water per unit volume of air to its micro-structural attributes including raindrop sizes as well as their spatial distribution. The model allowed for the reproduction of three-dimensional fields of raindrops.

Temporal and spatial variations of the impact pressure developed in  droplet-surface collision were then computed using a GPU accelerated CFD model of free surface flows. The authors proposed a multiresolution method in a bid to minimize computational cost and an interpolation scheme to compute the impact pressure profile for any drop size efficiently and accurately.

The final component of the proposed framework  entailed the computation of fatigue damage for every raindrop by undertaking a stress analysis of its collision with the coating surface and probabilistically integrating these fatigue damages to estimate the “expected” erosion life time of the coating. The authors computed the stresses through a finite element modeling of the drop impact, where the droplet impact pressure, already calculated from CFD analysis of rain drop impact on the coating surface, was applied on the surface as a spatially varying time dependent external load.

Ingredients of Computational Framework

About The Author

Dr. Mazdak Tootkaboni is an associate professor in the in the Department of Civil and Environmental Engineering at the University of Massachusetts Dartmouth. He holds a Ph.D. and a M.Sc. in Engineering Mechanics from the Johns Hopkins University. Dr Tootkaboni’s research interests include uncertainty quantification, stochastic computational mechanics, topology optimization, design under uncertainty, and design of multifunctional architected materials. Dr. Tootkaboni is also interested in the application of stochastic analysis, data Analytics, and machine learning techniques in predictive modeling in solid and structural mechanics.

About The Author

Behrooz Amirzadeh holds a M.Sc. degree in Mechanical Engineering from University of Massachusetts Dartmouth and a B.Sc. degree in Materials Science and Engineering from Sharif University of Technology in Tehran. During his time at UMass Dartmouth, his research was primarily focused on stochastic modeling and high performance computational simulation of fluid-structure interaction. He is currently working at RAID Inc in Andover, MA as a Senior HPC Solutions Architect helping scientists in national labs and universities design and deploy HPC clusters for next generation simulations research.

About The Author

Dr. Arghavan Louhghalam is an assistant professor in the Department of Civil and Environmental Engineering at the University of Massachusetts Dartmouth. Dr. Louhghalam holds a Ph.D. and a M.Sc. in Engineering Mechanics from the Johns Hopkins University and  prior to joining  University of Massachusetts, she was a postdoctoral research associate at Massachusetts Institute of Technology’s Concrete Sustainability Hub (CSHub@MIT). Dr. Louhghalam’s research interests are mainly focused on interconnected areas of solid mechanics, material modeling and applied statistics with applications to sustainability, durability and resilience of civil infrastructure as well as high-performance structures such as light weight high speed trains and wind-turbine blades.

About The Author

Dr. Mehdi Raessi is an associate professor in the Mechanical Engineering Department at the University of Massachusetts Dartmouth. His research interests include advanced computational simulations of multiphase flows with applications in energy systems (renewable and conventional), material processing, and microscale transport phenomena. Raessi has a PhD in mechanical engineering from the University of Toronto and was a Postdoctoral Fellow at NASA-Stanford University’s Center for Turbulence Research before joining UMASS-Dartmouth.

Reference

Amirzadeh, A. Louhghalam, M. Raessi, M. Tootkaboni. A computational framework for the analysis of rain-induced erosion in wind turbine blades, part I: Stochastic rain texture model and drop impact simulations. Journal of Wind Engineering & Industrial Aerodynamics, volume 163 (2017), pages 33–43.

Go To Journal of Wind Engineering & Industrial Aerodynamics

 

Amirzadeh, A. Louhghalam, M. Raessi, M. Tootkaboni. A computational framework for the analysis of rain-induced erosion in wind turbine blades, part II: Drop impact-induced stresses and blade coating fatigue life. Journal of Wind Engineering and Industrial Aerodynamics, Volume 163, (2017), Pages 44–54.

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