Influence analysis of wind shear and tower shadow on load and power based on blade element theory

Auto-rotation or autogyro is a well-known phenomenon where a rotor in a wind field generates significant lift while the wind induces considerable aerodynamic torque on the rotor. The principle has been studied extensively for applications in aviation. However, with recent works indicating immense, persistent, and pervasive, available wind energy at high altitudes, the principle of autogyro could potentially be exploited for energy harvesting. In this paper, we carry out a preliminary investigation on the viability of using autogyros for energy extraction. We mainly focus on one of the earliest documented works on modeling of autogyro and extend its use to explore energy harvesting. The model is based on blade element theory. We provide simulation results of the concept. Although the results are encouraging, there are various practical aspects that need to be investigated to build confidence on this approach of energy harvesting. This work aims to build a framework upon which more comprehensive research can be conducted.

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A Theoretical and Experimental Comparison of Optimizing Angle of Twist Using BET and BEMT

Volume 6: Oil and Gas Applications; Concentrating Solar Power Plants; Steam Turbines; Wind Energy ◽

10.1115/gt2012-68350 ◽

2012 ◽

Author(s):

Timothy A. Burdett ◽

Kenneth W. Van Treuren

Keyword(s):

Experimental Testing ◽

Element Model ◽

Experimental Comparison ◽

Speed Ratio ◽

Small Scale ◽

Blade Element Theory ◽

Wind Speeds ◽

Subsonic Wind Tunnel ◽

Element Theory ◽

Blade Element

Wind turbines are often designed using some form of Blade Element Model (BEM). However, different models can produce significantly different results when optimizing the angle of twist for power production. This paper compares the theoretical result of optimizing the angle of twist using Blade Element Theory (BET) and Blade Element Momentum Theory (BEMT) with a tip-loss correction for a 3-bladed, 1.15-m diameter wind turbine with a design tip speed ratio (TSR) of 5. These two theories have been chosen because they are readily available to small-scale designers. Additionally, the turbine was scaled for experimental testing in the Baylor Subsonic Wind Tunnel. Angle of twist distributions differed by as much as 15 degrees near the hub, and the coefficient of power differed as much as 0.08 for the wind speeds tested.

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Helical vortices and wind turbine aerodynamics

International Journal of Mathematics for Industry ◽

10.1142/s2661335220500021 ◽

2020 ◽

pp. 2050002

Author(s):

David H. Wood

Keyword(s):

Fundamental Interest ◽

Blade Element Theory ◽

Wind Turbine Aerodynamics ◽

Vortex Theory ◽

Helical Vortices ◽

Constant Pitch ◽

Induced Motion ◽

The Relationship ◽

Element Theory ◽

Blade Element

All rotating blades shed helical vortices which have a significant effect on the velocity over the blades and the forces acting on them. Nevertheless, knowledge of vortex behavior is not used in blade element theory (BET), the most common method to calculate the thrust produced by propellers and the power by wind turbines. Helical vortices of constant pitch and radius are also of fundamental interest as one of only three geometries that do not deform under their “self-induced” motion. This aspect of vortex theory is reviewed historically and the relationship with the forces acting on submerged bodies briefly reviewed. The development of helical vortex theory (HVT) in the 20th century is then described. It is shown that HVT allows BET to be used for a number of important problems that cannot be analyzed by current versions of the theory.

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Multi-Fidelity Aerodynamic Modeling of a Floating Offshore Wind Turbine Rotor

Volume 10: Fluids Engineering ◽

10.1115/imece2020-24608 ◽

2020 ◽

Author(s):

Kai Zhang ◽

Onur Bilgen

Keyword(s):

Wind Turbine ◽

Turbine Rotor ◽

Modeling Method ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Blade Element Theory ◽

Momentum Theory ◽

Element Theory ◽

Wind Turbine Rotor ◽

Blade Element

Abstract This paper presents a comparison of low- and mid-fidelity aerodynamic modelling of floating offshore wind turbine rotors. The low-fidelity approach employs the conventional Blade Element Momentum theory implemented in AeroDyn of OpenFAST. This model ignores the aerodynamic interactions between different blade elements, and the forces on the blade are determined from the balance between momentum theory and blade element theory. With this method, it is possible to calculate the aerodynamic performance for different settings with low computational cost. For the mid-fidelity approach, the Actuator Line Modeling method implemented in turbinesFoam (an OpenFOAM library) is used. This method is built upon a combination of the blade element theory for modeling the blades, and a Navier-Stokes description of the wake flow field. Thus, it can capture the wake dynamics without resolving the detailed flows near the blades. The aerodynamic performance of the DTU 10 MW reference wind turbine rotor is studied using the two methods. The effects of wind speed, tip speed ratio, and blade pitch angles are assessed. Good agreement is observed between the two methods at low tip speed ratios, while the Actuator Line Modeling method predicts slightly higher power coefficients at high tip speed ratios. In addition, the ability of the Actuator Line Modeling Method to capture the wake dynamics of the rotor in an unsteady inflow is demonstrated. In the future, the multi-fidelity aerodynamic modules developed in this paper will be integrated with the hydro-kinematics and hydro-dynamics of a floating platform and a mooring system, to achieve a fully coupled framework for the analysis and design optimization of floating offshore wind turbines.

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The wing beat of Drosophila Melanogaster . II. Dynamics

Philosophical Transactions of the Royal Society of London Series B Biological Sciences ◽

10.1098/rstb.1990.0041 ◽

1990 ◽

Vol 327 (1238) ◽

pp. 19-44 ◽

Cited By ~ 43

Keyword(s):

Drosophila Melanogaster ◽

Three Dimensional ◽

Laser Interferometry ◽

Longitudinal Axis ◽

Wing Beat ◽

Average Force ◽

Kinematic Data ◽

Blade Element Theory ◽

Element Theory ◽

Blade Element

The wing beat of tiny insects has attracted considerable interest because conventional aerodynamics predicts a reduction of flight efficiency when aerofoils are comparatively small and slow. Here, two approaches are reported by which we investigated the dynamics of the wing beat of tethered flying Drosophila melanogaster . First, the forces acting on the moving wing were calculated from three-dimensional kinematic data, following the blade-element theory which assumes quasi-steady aerodynamics. Under these conditions, the flight force is directed upwards, relative to the longitudinal body axis, during the second half of the downstroke; it is oriented forwards and downwards during the upstroke. The time average of the force generated according to this theory does not correspond to the direction and magnitude of the actual average force of flight. The expected force is directed forwards, along the body’s longitudinal axis, and is too small to keep the fly airborne. Secondly, an attempt is made to measure the timecourse of flight forces by attaching the fly to along the body’s longitudinal axis, and is too small to keep the fly airborne. Secondly, an attempt is made to measure the timecourse of flight forces by attaching the fly to a string, the displacement of which is monitored by means of laser interferometry. A sharp lift-pulse is observed when the wing is rapidly rotated during the ventral reversal of the wing-beat cycle. A second lift maximum of variable strength seems to be associated with the squeeze-peel events during the dorsal reversal. These results support the notion that flight in small insects might be dominated by unsteady mechanisms.

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