Off-campus UMass Amherst users: To download dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.

Non-UMass Amherst users, please click the view more button below to purchase a copy of this dissertation from Proquest.

(Some titles may also be available free of charge in our Open Access Dissertation Collection, so please check there first.)

The analysis of horizontal axis wind turbine aerodynamics using wavelet theory, spectral and time series methods

Jonathon Edward Slepski, University of Massachusetts Amherst


The study of wind turbine blade aerodynamics during full operation has only recently received attention, due to the high cost of conducting such experiments. Data used in this dissertation was received from the National Renewable Energy Laboratory. Such unsteady aerodynamic processes as dynamic stall, boundary layer separation, and turbulent inflow will contribute to increased blade loadings and reduced machine life. The research presented in this dissertation utilizes time series, spectral, and wavelet techniques to analyse wind turbine aerodynamics. In particular, the tower shadow event at 30, 47, and 63% span is linked to rapid reattachment, followed by detachment of the boundary layer. It is also shown that the intensity of these events may be reduced by operating at a slight yaw error, between $-$4 and $-$10 degrees. Furthermore, a unique wavelet analysis technique has been developed to study a 2p effect seen in pressure and lift coefficient data. This wavelet technique is used to show that 2p results from the splitting of the signal time series into two halves by intense tower shadow spikes. Through careful analysis of C$\rm\sb{p}$ plots, the blade section boundary at 30, 47, and 63% span was seen to be detached in 90% of the revolutions studied. Boundary layer transition to separated conditions occurs when the attack angle surpasses 18 degrees, indicating a stall delay of about 8 degrees. Dynamic stall vortex shedding rarely occurs for the conditions seen in the data set analysed in this dissertation. Slight yaw error, as well as the three dimensional effect of rotation, appears to be beneficial for maintaining a slight favorable pressure gradient at inboard blade section during deep stall operation, thereby reducing the potential for vortex growth.

Subject Area

Mechanical engineering|Aerospace materials

Recommended Citation

Slepski, Jonathon Edward, "The analysis of horizontal axis wind turbine aerodynamics using wavelet theory, spectral and time series methods" (1996). Doctoral Dissertations Available from Proquest. AAI9619439.