Wake effects on the aerodynamic performance of horizontal axis wind turbines

Technical Report · Wed Aug 01 04:00:00 EDT 1984

OSTI ID:5549341

Afjeh, A A

Success of vortex theories in the performance analysis of horizontal axis wind turbines depends greatly upon accurate specification of the geometry of the vortex wake. In this study, two methods of analysis are developed: a new simplified free wake method (SFW) and a prescribed wake method. In addition, an earlier wake model of helicopter rotors is extended for wind turbine applications. This method is referred to as the fast free wake method (FFW). The FFW was accomplished by partitioning the flow field downstream of the rotor into three regions: the near wake, modeled as a series of straight vortex lines; the intermediate wake, modeled as a number of vortex rings; and the far wake, taken to be a semi-infinite cylindrical wake. In the SFW, a new wake model is proposed. The model assumes that the wake is composed of an intense tip vortex and a diffused inboard wake, consistent with the experimentally observed wake of hovering helicopters. However, due to the complexity of the tip vortex formation and due to the lack of such experimental data for wind turbines, it was assumed that the vortex formation was almost immediate as opposed to the actual gradual rolling-up of the tip vortex. For the prescribed wake analysis the expansion of the wake must be known. Unfortunately, detailed wake measurements for wind turbines are sparse in number; hence, the method was demonstrated by assuming the wake expansion could be represented by an analytical expression.

• Research Organization: Toledo Univ., OH (USA)
• DOE Contract Number: AI01-76ET20320
• OSTI ID: 5549341
• Report Number(s): DOE/NASA-0005-1-84; NASA-CR-174920; ON: DE85014516
• Country of Publication: United States
• Language: English

Related Subjects

17 WIND ENERGY
170602* -- Wind Energy Engineering-- Turbine Design & Operation
AERODYNAMICS
FLUID FLOW
FLUID MECHANICS
HORIZONTAL AXIS TURBINES
MACHINERY
MECHANICS
PERFORMANCE
ROTORS
TURBINES
TURBOMACHINERY
VORTEX FLOW
WIND TURBINES