A numerical wake alignment method for horizontal axis wind turbines with the lifting line theory

2018 ◽  
Vol 174 ◽  
pp. 382-390 ◽  
Author(s):  
D.B. Melo ◽  
J. Baltazar ◽  
J.A.C. Falcão de Campos
Keyword(s):  
Wind Turbines ◽  
Horizontal Axis ◽  
Alignment Method ◽  
Horizontal Axis Wind Turbines ◽  
Line Theory ◽  
Wake Alignment ◽  
Lifting Line ◽  
Lifting Line Theory

A comprehensive comparative investigation of the Lifting Line Theory and Blade Element Momentum Theory applied to small wind turbines

2021 ◽  
pp. 1-25
Author(s):  
K.A.R. Ismail ◽  
Willian Okita
Keyword(s):  
Wind Turbines ◽  
Power Coefficient ◽  
Computational Time ◽  
Local Flow ◽  
Small Wind Turbines ◽  
Wake Effects ◽  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Blade Element

Abstract Small wind turbines are adequate for electricity generation in isolated areas to promote local expansion of commercial activities and social inclusion. Blade element momentum (BEM) method is usually used for performance prediction, but generally produces overestimated predictions since the wake effects are not precisely accounted for. Lifting line theory (LLT) can represent the blade and wake effects more precisely. In the present investigation the two methods are analyzed and their predictions of the aerodynamic performance of small wind turbines are compared. Conducted simulations showed a computational time of about 149.32 s for the Gottingen GO 398 based rotor simulated by the BEM and 1007.7 s for simulation by the LLT. The analysis of the power coefficient showed a maximum difference between the predictions of the two methods of about 4.4% in the case of Gottingen GO 398 airfoil based rotor and 6.3% for simulations of the Joukowski J 0021 airfoil. In the case of the annual energy production a difference of 2.35% is found between the predictions of the two methods. The effects of the blade geometrical variants such as twist angle and chord distributions increase the numerical deviations between the two methods due to the big number of iterations in the case of LLT. The cases analyzed showed deviations between 3.4% and 4.1%. As a whole, the results showed good performance of both methods; however the lifting line theory provides more precise results and more information on the local flow over the rotor blades.

A Vortex Lifting Line Method for the Analysis of Horizontal Axis Wind Turbines

1986 ◽  
Vol 108 (4) ◽  
pp. 303-309 ◽  
Author(s):  
A. A. Afjeh ◽  
T. G. Keith
Keyword(s):  
Wind Turbines ◽  
Operating Conditions ◽  
Horizontal Axis ◽  
Horizontal Axis Wind Turbines ◽  
Bladed Rotor ◽  
Load Analysis ◽  
Wake Model ◽  
Free Wake ◽  
Lifting Line ◽  
Lifting Line Method

The present paper utilizes an earlier analytical wake model, which essentially applies to helicopter load analysis, to determine the performance of horizontal axis wind turbines. The advantage of this method is that it makes use of an integrated version of the Biot-Savart law for each part of the wake and thereby avoids some of the numerical difficulties present in the Biot-Savart law. Numerical computations were performed for a number of two-bladed rotor geometries and operating conditions. Results were compared with experimental data as well as with predictions of a full free wake method. Good overall agreement with both was observed.

On the Rotor Lifting Line Wake Model

2017 ◽  
Vol 33 (01) ◽  
pp. 31-45
Author(s):  
Brenden Epps
Keyword(s):  
Horizontal Axis ◽  
Preliminary Design ◽  
Trailing Vortices ◽  
Line Theory ◽  
Wake Model ◽  
Model Versus ◽  
Line Design ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Horizontal Axis Turbine

This article comments on the wake model used in moderately loaded rotor lifting line theory for the preliminary design of propellers and horizontal-axis turbines. Mathematical analysis of the classic wake model reveals an inconsistency between the induced velocities numerically computed by the model versus those theoretically predicted by the model. An improved wake model is presented, which better agrees with theory than previous models and thus improves the numerical consistency and robustness of rotor lifting line design algorithms. The present wake model analytically relates the pitch of the trailing vortices to the pitch of the total inflow computed at the lifting line control points. For conciseness, the article focuses on the propeller case, although both propeller and horizontal-axis turbine examples are presented.

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