Impacts of atmospheric turbulence on wind turbine rotor aerodynamics and drivetrain main bearing function
University of Colorado Boulder
Abstract
This discussion will integrate three series of research studies into the nonsteady forces and moments that are generated at the rotor hub of utility scale wind turbines by the continual passage through the wind turbine rotor of the energy-dominant turbulence eddies that are embedded within the daytime atmospheric boundary layer (ABL). One series, developed at Penn State, applied large-eddy simulation (LES) of a wind turbine within the ABL to identify three characteristic time scales in the aerodynamic response to the passage of atmospheric turbulence eddies through the wind turbine rotor at the minute, second and sub-second time scales. These temporal scales are confirmed with analysis at Penn State of data from a GE field study. The third study was developed by comparing LES results with analysis at the University of Colorado Boulder (UCB) of field data obtained from the NREL/GE 1.5 MW wind turbine at the National Wind Technology Center, a site to the east of the Front Range of the Rocky Mountains. The NREL wind turbine responds to mountain-generated turbulence eddies embedded within westerly winds and confirms a key result from the LES-based study—that the continual passage of the energy-containing atmospheric eddies creates time-variations in the axial moment on the main shaft (torque and power) that are fundamentally different from the non-axial moment components that directly force the main bearing. The LES explains the turbulence-rotor interactions underlying these undamentally different responses. The implication is that that methods to suppress the potentially deleterious impacts of atmospheric turbulence on main bearing failure (the numerator in the levelized cost of energy (LCOE)) must differ fundamentally from methods designed to suppress turbulence-induced time variations in power (the denominator in LCOE). Current research at UCB integrates aerodynamics-based models with models of the main bearing to determine the extent to which atmospheric turbulence increases main bearing failure and LCOE.
About the speaker
Dr. James Brasseur is currently Research Professor of Aerospace Engineering Sciences at the University of Colorado Boulder after 27 years as Professor of Mechanical Engineering, Biomedical Engineering and Mathematics at the Pennsylvania State University, where he retains Emeritus Professor status. Dr. Brasseur is a fluid dynamist with extensive expertise in turbulence physics, turbulent flows, and large-eddy simulation, including atmospheric and reacting turbulent flows. Dr. Brasseur has separate expertise in the mechanics and physiology of the gastro-intestinal tract, including pharmaceutical release, transport and absorption. Dr. Brasseur completed his Ph.D. in 1979 from the Department of Aeronautics and Astronautics at Stanford University and completed postdoctoral positions at NASA-Ames (CFD), University of Southampton (aerodynamics) and Johns Hopkins University (turbulence). He has been visiting professor/scientist at a number of institutions and has served on governing boards of the American Physical Society (APS) and the APS Division of Fluid Dynamics, was past president of a medical society, and was founding Chair of the APS Topical Group on the Physics of Climate. Dr. Brasseur is a member of the Johns Hopkins Society of Scholars and is Fellow of the American Physical Society.
