Roughness Sensitivity Considerations for Thick Rotor Blade Airfoils

2003 ◽  
Author(s):  
R. P. J. O. M. van Rooij ◽  
W. A. Timmer
Keyword(s):  
Rotor Blade ◽  
Turbine Blades ◽  
Leading Edge ◽  
Lower Surface ◽  
Wind Turbine Blades ◽  
Strong Reduction ◽  
High Lift ◽  
Edge Roughness ◽  
Drag Ratio ◽  
Lift To Drag Ratio

In modern wind turbine blades airfoils of more than 25% thickness can be found at mid-span and inboard locations. In particular at mid-span aerodynamic requirements dominate, demanding a high lift-to-drag ratio, moderate to high lift and low roughness sensitivity. Towards the root srtuctural requirements become more important. In this paper the performance for the airfoil series DU, FFA, S8xx, AH, Riso̸ and NACA are reviewed. For the 25% and 30% thick airfoils the best performing airfoils can be recognized by a restricted upper surface thickness and a S-shaped lower surface for aft-loading. Differences in performance of the DU 91-W2-250 (25%), S814 (24%) and Riso̸-A1-24 (24%) airfoil are small. For a 30% thickness the DU 97-W-300 meets the requirements best. At inboard locations the influence of rotation can be significant and 2d wind tunnel tests do not represent the characteristics well. The RFOIL code is believed to be capable of approximating the rotational effect. In particular the change in lift characteristics in the case of leading edge roughness for the 35% and 40% thick DU airfoils, respectively DU 00-W-350 and DU 00-W–401, is remarkable. Due to the strong reduction of roughness sensitivity the design for inboard airfoils could primarily focus on high lift and structural demands.

Roughness Sensitivity Considerations for Thick Rotor Blade Airfoils

2003 ◽  
Vol 125 (4) ◽  
pp. 468-478 ◽  
Author(s):  
R. P. J. O. M. van Rooij ◽  
W. A. Timmer
Keyword(s):  
Turbine Blades ◽  
Leading Edge ◽  
Lower Surface ◽  
Vortex Generators ◽  
Wind Turbine Blades ◽  
High Lift ◽  
Edge Roughness ◽  
Proper Design ◽  
Drag Ratio ◽  
Lift To Drag Ratio

In modern wind turbine blades, airfoils of more than 25% thickness can be found at mid-span and inboard locations. At mid-span, aerodynamic requirements dominate, demanding a high lift-to-drag ratio, moderate to high lift and low roughness sensitivity. Towards the root, structural requirements become more important. In this paper, the performance for the airfoil series DU FFA, S8xx, AH, Risø and NACA are reviewed. For the 25% and 30% thick airfoils, the best performing airfoils can be recognized by a restricted upper-surface thickness and an S-shaped lower surface for aft-loading. Differences in performance of the DU 91-W2-250 (25%), S814 (24%) and Risø-A1-24 (24%) airfoils are small. For a 30% thickness, the DU 97-W-300 meets the requirements best. Reduction of roughness sensitivity can be achieved both by proper design and by application of vortex generators on the upper surface of the airfoil. Maximum lift and lift-to-drag ratio are, in general, enhanced for the rough configuration when vortex generators are used. At inboard locations, 2-D wind tunnel tests do not represent the performance characteristics well because the influence of rotation is not included. The RFOIL code is believed to be capable of approximating the rotational effect. Results from this code indicate that rotational effects dramatically reduce roughness sensitivity effects at inboard locations. In particular, the change in lift characteristics in the case of leading edge roughness for the 35% and 40% thick DU airfoils, DU 00-W-350 and DU 00-W-401, respectively, is remarkable. As a result of the strong reduction of roughness sensitivity, the design for inboard airfoils can primarily focus on high lift and structural demands.

scholarly journals High-Resolution Structure-from-Motion for Quantitative Measurement of Leading-Edge Roughness

Energies ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3916 ◽  
Author(s):  
Mikkel Schou Nielsen ◽  
Ivan Nikolov ◽  
Emil Krog Kruse ◽  
Jørgen Garnæs ◽  
Claus Brøndgaard Madsen
Keyword(s):  
High Resolution ◽  
Wind Turbine ◽  
Structure From Motion ◽  
Turbine Blades ◽  
Leading Edge ◽  
Cost Effective ◽  
Wind Turbine Blades ◽  
Edge Roughness ◽  
High Resolution Structure ◽  
Resolution Structure

Over time, erosion of the leading edge of wind turbine blades increases the leading-edge roughness (LER). This may reduce the aerodynamic performance of the blade and hence the annual energy production of the wind turbine. As early detection is key for cost-effective maintenance, inspection methods are needed to quantify the LER of the blade. The aim of this proof-of-principle study is to determine whether high-resolution Structure-from-Motion (SfM) has the sufficient resolution and accuracy for quantitative inspection of LER. SfM provides 3D reconstruction of an object geometry using overlapping images of the object acquired with an RGB camera. Using information of the camera positions and orientations, absolute scale of the reconstruction can be achieved. Combined with a UAV platform, SfM has the potential for remote blade inspections with a reduced downtime. The tip of a decommissioned blade with an artificially enhanced erosion was used for the measurements. For validation, replica molding was used to transfer areas-of-interest to the lab for reference measurements using confocal microscopy. The SfM reconstruction resulted in a spatial resolution of 1 mm as well as a sub-mm accuracy in both the RMS surface roughness and the size of topographic features. In conclusion, high-resolution SfM demonstrated a successful quantitative reconstruction of LER.

Modification impact on aerodynamic performance of hypersonic waverider

2011 ◽  
Vol 115 (1168) ◽  
pp. 325-334 ◽  
Author(s):  
C. Xiao-Qing ◽  
H. Zhong-Xi ◽  
L. Jian-Xia ◽  
G. Xian-Zhong
Keyword(s):  
Leading Edge ◽  
Aerodynamic Performance ◽  
Hypersonic Vehicles ◽  
Flow Conditions ◽  
Aerodynamic Coefficient ◽  
High Lift ◽  
Computational Fluid Dynamics Cfd ◽  
Drag Ratio ◽  
Lift To Drag Ratio ◽  
Sharp Leading Edge

Abstract Waverider serves as a good candidate for hypersonic vehicles. The typical waverider has sharp leading edge and no control face, which is inappropriate for practical use. This paper puts forward a method modifying the waverider, and the modification impact on the performance of waverider at hypersonic flow conditions is studied. The modification is based on blunted waverider, includes cutting the tip and introducing two control wings. The modification’s effect on aerodynamic performance is obtained and analysed through Computational Fluid Dynamics (CFD) techniques. When blunted with 2cm radius, the waverider retains its good aerodynamic performance and the heat flux at the stagnation point can be managed. Three factors of the introduced wing are argued, the fixed angle, aspect ratio and wing area. Results show that influence on the aerodynamic coefficient is slight and the vehicle retains its high lift-to-drag ratio. The main influences of the modification are the control ability and trim efficiency, which is the motivation of this work and can be adapted when designing a practical waverider.

Development of a new aerofoil profile with a high lift-to-drag ratio for wind turbines using a low fidelity accurate optimization flow solver

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Moutaz Elgammi ◽  
Aljonid Aokaly ◽  
Yasser Aldali
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Turbine Blades ◽  
Operating Conditions ◽  
High Lift ◽  
Operational Conditions ◽  
2D Simulation ◽  
Free Environment ◽  
Drag Ratio ◽  
Lift To Drag Ratio

Abstract A significant amount of work is performed on various aerofoil profiles to improve their characteristics for wind turbine applications. The main purpose is to increase the power output of wind turbines by increasing the lift-to-drag ratio of the aerofoil blade sections. However, most of the developed aerofoil profiles work well only at their design angles of attack and for low Reynolds numbers with a very dramatic stall that could significantly influence the characteristics of the aerofoil profiles and the performance of wind turbines. The present paper is conducted to develop a new aerofoil profile with more gradual stall characteristics that works efficiently for different operational conditions (clean and rough working conditions) similar to those encountered by wind turbines in the free environment. The new aerofoil profile was developed based on a combination between experimental Box–Behnken design and XFOIL code, measurements, and 2D simulation conducted by computational fluid dynamics (CFD) method. The established aerofoil can be used for wind turbine blades because it gives high lift-to-drag-ratios with very smooth and gradual stall characteristics even under very rough operating conditions.

scholarly journals New Airfoils for Small Horizontal Axis Wind Turbines

1998 ◽  
Vol 120 (2) ◽  
pp. 108-114 ◽  
Author(s):  
P. Gigue`re ◽  
M. S. Selig
Keyword(s):  
Wind Turbines ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Horizontal Axis ◽  
Variable Speed ◽  
Edge Roughness ◽  
Horizontal Axis Wind Turbines ◽  
Wind Energy Systems ◽  
Drag Ratio ◽  
Lift To Drag Ratio

In a continuing effort to enhance the performance of small wind energy systems, one root airfoil and three primary airfoils were specifically designed for small horizontal axis wind turbines. These airfoils are intended primarily for 1–5 kW variable-speed wind turbines for both conventional (tapered/twisted) or pultruded blades. The four airfoils were wind-tunnel tested at Reynolds numbers between 100,000 and 500,000. Tests with simulated leading-edge roughness were also conducted. The results indicate that small variable-speed wind turbines should benefit from the use of the new airfoils which provide enhanced lift-to-drag ratio performance as compared with previously existing airfoils.

Multivariable Analysis of Aerodynamic Forces on Slotted Airfoils for Wind Turbine Blades

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Saman Beyhaghi ◽  
Ryoichi S. Amano
Keyword(s):  
Reynolds Number ◽  
Turbine Blades ◽  
Multivariable Analysis ◽  
Leading Edge ◽  
Operating Conditions ◽  
Vertical Position ◽  
Wind Turbine Blades ◽  
Design Variables ◽  
Inlet Angle ◽  
Drag Ratio

Improvement of the aerodynamic performance for cambered airfoils with leading-edge slots is investigated in this work. This concept is proven both computationally and experimentally in recent years. Five design variables of interest are slot's length, slot's width or thickness, inlet angle, exit angle, and the vertical position. The objective is to perform design of experiment and optimization studies on these variables and evaluate the behavior of the objective functions, namely lift and lift over drag ratio (LoD), within the appropriate ranges of the independent variables. Simulations are mainly carried out at the Reynolds number of 1.6 × 106 and the angles of attack (AoA) of 6 deg for NACA 4412 airfoil. However, some of the analyses are repeated at Reynolds number of 3.2 × 106 and AoA of 0 and 8 deg to show the scalability of the results. Results indicate that the proper selection of three of the design variables, i.e., length, inlet angle, and vertical position, can have a significant impact on both lift and LoD, while the other two variables seem less influential. For the combination of the operating conditions and the values of the design variables considered in this investigation, a LoD improvement as large as 11% is observed.

Optimization of Flatback Airfoils for Wind Turbine Blades Using a Multi-Objective Genetic Algorithm

2012 ◽  
Author(s):  
Xiaomin Chen ◽  
Ramesh Agarwal
Keyword(s):  
Genetic Algorithm ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Navier Stokes ◽  
Wind Turbine Blades ◽  
Multi Objective ◽  
Artificial Neural Network Ann ◽  
Drag Ratio ◽  
Lift To Drag Ratio ◽  
Single Objective

In recent years, the airfoil sections with blunt trailing edge (called flatback airfoils) have been proposed for the inboard regions of large wind-turbine blades because they provide several structural and aerodynamic performance advantages. In a previous paper, ASME ES2010-90373, we employed a single objective genetic algorithm (GA) for shape optimization of flatback airfoils for generating maximum lift to drag ratio. The computational efficiency of GA was significantly enhanced with an artificial neural network (ANN). The commercially available software FLUENT was employed for calculation of the flow field using the Reynolds-Averaged Navier-Stokes (RANS) equations in conjunction with a turbulence model. In this paper, we employ a multi-objective GA to optimize the flatback airfoils to achieve two objectives, namely the generation of maximum lift as well as the maximum lift to drag ratio. It is shown that the multi-objective GA optimization can generate superior flatback airfoils compared to those obtained by using single objective GA algorithm.

scholarly journals Shape Optimization of NREL S809 Airfoil for Wind Turbine Blades Using a Multiobjective Genetic Algorithm

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Yilei He ◽  
Ramesh K. Agarwal
Keyword(s):  
Genetic Algorithm ◽  
Wind Turbine ◽  
Lift Coefficient ◽  
Optimization Technique ◽  
Turbine Blades ◽  
Wind Turbine Blades ◽  
Multiobjective Genetic Algorithm ◽  
Lift And Drag ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The goal of this paper is to employ a multiobjective genetic algorithm (MOGA) to optimize the shape of a well-known wind turbine airfoil S809 to improve its lift and drag characteristics, in particular to achieve two objectives, that is, to increase its lift and its lift to drag ratio. The commercially available software FLUENT is employed to calculate the flow field on an adaptive structured mesh using the Reynolds-Averaged Navier-Stokes (RANS) equations in conjunction with a two-equationk-ωSST turbulence model. The results show significant improvement in both lift coefficient and lift to drag ratio of the optimized airfoil compared to the original S809 airfoil. In addition, MOGA results are in close agreement with those obtained by the adjoint-based optimization technique.

Effects of Leading-Edge Protection Tape on Wind Turbine Blade Performance

2012 ◽  
Vol 36 (5) ◽  
pp. 525-534 ◽  
Author(s):  
Agrim Sareen ◽  
Chinmay A. Sapre ◽  
Michael S. Selig
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Lower Surface ◽  
Wind Turbine Blades ◽  
Potential Benefits ◽  
Wind Turbine Airfoil ◽  
Turbine Airfoils ◽  
The Impact

This paper presents results of a study to investigate the impact of using wind protection tape (WPT) to protect the leading edge of wind turbine airfoils from erosion. The tests were conducted on the DU 96-W-180 wind turbine airfoil at three Reynolds numbers between 1 and 1.85 million and angles of attack spanning the low drag range of the airfoil. Tests were run by varying the chordwise extent of the wind protection tape on the upper and lower surface in order to determine the relative impact of each configuration on the aerodynamics of the airfoil. The objective was to assess the performance losses due to the wind protection tape and compare them with losses due to leading-edge erosion in order to determine the potential benefits of using such tape to protect wind turbine blades. Results showed that the application of wind protection tape caused a drag increase of 5–15% for the various configurations tested and was significantly less detrimental to airfoil performance than leading edge erosion that could otherwise occur.

Optimization of Flatback Airfoils for Wind Turbine Blades

2010 ◽  
Author(s):  
Xiaomin Chen ◽  
Ramesh Agarwal
Keyword(s):  
Wind Turbine ◽  
Optimization Technique ◽  
Turbine Blades ◽  
Navier Stokes ◽  
Wind Turbine Blades ◽  
Blunt Trailing Edge ◽  
Artificial Neural Network Ann ◽  
Drag Ratio ◽  
Large Wind ◽  
Lift To Drag Ratio

In recent years, the airfoil sections with blunt trailing edge (called flatback airfoils) have been proposed for the inboard regions of large wind-turbine blades because they provide several structural and aerodynamic performance advantages. In this paper, we employ a genetic algorithm (GA) for shape optimization of flatback airfoils for generating maximum lift to drag ratio. The computational efficiency of GA is significantly enhanced with an artificial neural network (ANN). The commercially available software FLUENT is used for calculation of the flow field using the Reynolds-Averaged Navier-Stokes (RANS) equations in conjunction with a turbulence model. It is shown that the combined GA/ANN optimization technique is capable of accurately and efficiently finding globally optimal flatback airfoils.

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