Integrated Rotor Performance Improvement and Vibration Reduction Using Active Camber Morphing

2019 ◽  
Author(s):  
Sumeet Kumar ◽  
Dominik Komp ◽  
Manfred Hajek ◽  
Jürgen Rauleder
Keyword(s):  
Active Control ◽  
Closed Loop ◽  
Vibration Reduction ◽  
Fish Bone ◽  
Open Loop ◽  
Beam Elements ◽  
Line Theory ◽  
Wake Model ◽  
Lifting Line ◽  
Lifting Line Theory

Abstract This paper discusses open-loop and closed-loop active control investigations of a full-scale Bo 105 helicopter rotor with active camber morphing. The potential of an active camber morphing concept to reduce non-rotating vibratory hub loads and rotor power using active control was investigated. The mechanism employed was a dynamically actuated airfoil camber morphing concept known as Fish Bone Active Camber (FishBAC) that smoothly deforms the camber over the aft section of the airfoil. A comprehensive rotorcraft aeromechanics analysis was used that modeled the blade elastic motion using one-dimensional finite beam elements combined with multibody dynamics. Aerodynamic forces were calculated with a free-vortex wake model together with lifting line theory for the blade aerodynamics. The open-loop investigation comprised of a parametric study of relevant control parameters that govern the active camber deflection cyclic actuation profile and their effects on rotor performance and hub vibration. It was found that active camber morphing using superimposed once-per-revolution (1P) and 2P control inputs was able to simultaneously reduce rotor power by 4.3% and overall vibratory hub loads by 27%. Additionally, a closed-loop adaptive multicyclic controller was used to identify the potential of this morphing concept for hub vibration reduction using multicyclic active control inputs. Active camber actuation using a sum of four control harmonic inputs, i.e. 1-4P, resulted in a maximum hub vibration reduction of 50%.

scholarly journals Modelling yawed wind turbine wakes: a lifting line approach

2018 ◽  
Vol 841 ◽  
Author(s):  
Carl R. Shapiro ◽  
Dennice F. Gayme ◽  
Charles Meneveau
Keyword(s):  
Initial Conditions ◽  
Transverse Velocity ◽  
Vortex Pair ◽  
Streamwise Velocity ◽  
Wake Flow ◽  
Wind Tunnel Experiments ◽  
Line Theory ◽  
Wake Model ◽  
Lifting Line ◽  
Lifting Line Theory

Yawing wind turbines has emerged as an appealing method for wake deflection. However, the associated flow properties, including the magnitude of the transverse velocity associated with yawed turbines, are not fully understood. In this paper, we view a yawed turbine as a lifting surface with an elliptic distribution of transverse lift. Prandtl’s lifting line theory provides predictions for the transverse velocity and magnitude of the shed counter-rotating vortex pair known to form downstream of the yawed turbine. The streamwise velocity deficit behind the turbine can then be obtained using classical momentum theory. This new model for the near-disk inviscid region of the flow is compared to numerical simulations and found to yield more accurate predictions of the initial transverse velocity and wake skewness angle than existing models. We use these predictions as initial conditions in a wake model of the downstream evolution of the turbulent wake flow and compare predicted wake deflection with measurements from wind tunnel experiments.

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.

An improved nonlinear lifting-line theory.

AIAA Journal ◽  
1973 ◽  
Vol 11 (5) ◽  
pp. 739-742 ◽  
Author(s):  
CHUAN-TAU LAN
Keyword(s):  
Line Theory ◽  
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.

scholarly journals Three-Dimensional Aerodynamic Analysis of a Darrieus Wind Turbine Blade Using Computational Fluid Dynamics and Lifting Line Theory

2017 ◽  
Author(s):  
Francesco Balduzzi ◽  
Alessandro Bianchini ◽  
Giovanni Ferrara ◽  
David Marten ◽  
George Pechlivanoglou ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Performance ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Cost Effective ◽  
Navier Stokes ◽  
Line Theory ◽  
Wake Model ◽  
Lifting Line

Due to the rapid progress in high-performance computing and the availability of increasingly large computational resources, Navier-Stokes computational fluid dynamics (CFD) now offers a cost-effective, versatile and accurate means to improve the understanding of the unsteady aerodynamics of Darrieus wind turbines and deliver more efficient designs. In particular, the possibility of determining a fully resolved flow field past the blades by means of CFD offers the opportunity to both further understand the physics underlying the turbine fluid dynamics and to use this knowledge to validate lower-order models, which can have a wider diffusion in the wind energy sector, particularly for industrial use, in the light of their lower computational burden. In this context, highly spatially and temporally refined time-dependent three-dimensional Navier-Stokes simulations were carried out using more than 16,000 processor cores per simulation on an IBM BG/Q cluster in order to investigate thoroughly the three-dimensional unsteady aerodynamics of a single blade in Darrieus-like motion. Particular attention was payed to tip losses, dynamic stall, and blade/wake interaction. CFD results are compared with those obtained with an open-source code based on the Lifting Line Free Vortex Wake Model (LLFVW). At present, this approach is the most refined method among the “lower-fidelity” models and, as the wake is explicitly resolved in contrast to BEM-based methods, LLFVW analyses provide three-dimensional flow solutions. Extended comparisons between the two approaches are presented and a critical analysis is carried out to identify the benefits and drawbacks of the two approaches.

scholarly journals Three-Dimensional Aerodynamic Analysis of a Darrieus Wind Turbine Blade Using Computational Fluid Dynamics and Lifting Line Theory

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Francesco Balduzzi ◽  
David Marten ◽  
Alessandro Bianchini ◽  
Jernej Drofelnik ◽  
Lorenzo Ferrari ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Performance ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Cost Effective ◽  
Navier Stokes ◽  
Line Theory ◽  
Wake Model ◽  
Lifting Line

Due to the rapid progress in high-performance computing and the availability of increasingly large computational resources, Navier–Stokes (NS) computational fluid dynamics (CFD) now offers a cost-effective, versatile, and accurate means to improve the understanding of the unsteady aerodynamics of Darrieus wind turbines and deliver more efficient designs. In particular, the possibility of determining a fully resolved flow field past the blades by means of CFD offers the opportunity to both further understand the physics underlying the turbine fluid dynamics and to use this knowledge to validate lower-order models, which can have a wider diffusion in the wind energy sector, particularly for industrial use, in the light of their lower computational burden. In this context, highly spatially and temporally refined time-dependent three-dimensional (3D) NS simulations were carried out using more than 16,000 processor cores per simulation on an IBM BG/Q cluster in order to investigate thoroughly the 3D unsteady aerodynamics of a single blade in Darrieus-like motion. Particular attention was paid to tip losses, dynamic stall, and blade/wake interaction. CFD results are compared with those obtained with an open-source code based on the lifting line free vortex wake model (LLFVW). At present, this approach is the most refined method among the “lower-fidelity” models, and as the wake is explicitly resolved in contrast to blade element momentum (BEM)-based methods, LLFVW analyses provide 3D flow solutions. Extended comparisons between the two approaches are presented and a critical analysis is carried out to identify the benefits and drawbacks of the two approaches.

Modern Adaptation of Prandtl's Classic Lifting-Line Theory

2000 ◽  
Vol 37 (4) ◽  
pp. 662-670 ◽  
Author(s):  
W. F. Phillips ◽  
D. O. Snyder
Keyword(s):  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory
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