Composite Structural Analysis of Flat-Back Shaped Blade for Multi-MW Class Wind Turbine

Science.gov (United States)

Kim, Soo-Hyun; Bang, Hyung-Joon; Shin, Hyung-Ki; Jang, Moon-Seok

2014-06-01

This paper provides an overview of failure mode estimation based on 3D structural finite element (FE) analysis of the flat-back shaped wind turbine blade. Buckling stability, fiber failure (FF), and inter-fiber failure (IFF) analyses were performed to account for delamination or matrix failure of composite materials and to predict the realistic behavior of the entire blade region. Puck's fracture criteria were used for IFF evaluation. Blade design loads applicable to multi-megawatt (MW) wind turbine systems were calculated according to the Germanischer Lloyd (GL) guideline and the International Electrotechnical Commission (IEC) 61400-1 standard, under Class IIA wind conditions. After the post-processing of final load results, a number of principal load cases were selected and converted into applied forces at the each section along the blade's radius of the FE model. Nonlinear static analyses were performed for laminate failure, FF, and IFF check. For buckling stability, linear eigenvalue analysis was performed. As a result, we were able to estimate the failure mode and locate the major weak point.

Wind turbine airfoil catalogue

Energy Technology Data Exchange (ETDEWEB)

Bertagnolio, F.; Soerensen, N.; Johansen, J.; Fuglsang, P.

2001-08-01

The aim of this work is two-sided. Firstly, experimental results obtained for numerous sets of airfoil measurements (mainly intended for wind turbine applications) are collected and compared with computational results from the 2D Navier-Stokes solver EllipSys2D, as well as results from the panel method code XFOIL. Secondly, we are interested in validating the code EllipSys2D and finding out for which air-foils it does not perform well compared to the experiments, as well as why, when it does so. The airfoils are classified according to the agreement between the numerical results and experimental data. A study correlating the available data and this classification is performed. It is found that transition modelling is to a large extent responsible for the poor quality of the computational results for most of the considered airfoils. The transition model mechanism that leads to these discrepancies is identified. Some advices are given for elaborating future airfoil design processes that would involve the numerical code EllipSys2D in particular, and transition modelling in general. (au)

Wind turbine airfoil catalogue

OpenAIRE

Bertagnolio, F.; Sørensen, Niels N.; Johansen, Jeppe; Fuglsang, P.

2001-01-01

The aim of this work is two-sided. Firstly, experimental results obtained for numerous sets of airfoil measurements (mainly intended for wind turbine applications) are collected and compared with computational results from the 2D Navier-Stokes solverEllipSys2D, as well as results from the panel method code XFOIL. Secondly, we are interested in validating the code EllipSys2D and finding out for which airfoils it does not perform well compared to the experiments, as well as why, when it does so...

Design analysis of vertical wind turbine with airfoil variation

Science.gov (United States)

Maulana, Muhammad Ilham; Qaedy, T. Masykur Al; Nawawi, Muhammad

2016-03-01

With an ever increasing electrical energy crisis occurring in the Banda Aceh City, it will be important to investigate alternative methods of generating power in ways different than fossil fuels. In fact, one of the biggest sources of energy in Aceh is wind energy. It can be harnessed not only by big corporations but also by individuals using Vertical Axis Wind Turbines (VAWT). This paper presents a three-dimensional CFD analysis of the influence of airfoil design on performance of a Darrieus-type vertical-axis wind turbine (VAWT). The main objective of this paper is to develop an airfoil design for NACA 63-series vertical axis wind turbine, for average wind velocity 2,5 m/s. To utilize both lift and drag force, some of designs of airfoil are analyzed using a commercial computational fluid dynamics solver such us Fluent. Simulation is performed for this airfoil at different angles of attach rearranging from -12°, -8°, -4°, 0°, 4°, 8°, and 12°. The analysis showed that the significant enhancement in value of lift coefficient for airfoil NACA 63-series is occurred for NACA 63-412.

Genetic Algorithms in Wind Turbine Airfoil Design

Energy Technology Data Exchange (ETDEWEB)

Grasso, F. [ECN Wind Energy, Petten (Netherlands); Bizzarrini, N.; Coiro, D.P. [Department of Aerospace Engineering, University of Napoli ' Federico II' , Napoli (Italy)

2011-03-15

One key element in the aerodynamic design of wind turbines is the use of specially tailored airfoils to increase the ratio of energy capture to the loading and thereby to reduce cost of energy. This work is focused on the design of a wind turbine airfoil by using numerical optimization. Firstly, the optimization approach is presented; a genetic algorithm is used, coupled with RFOIL solver and a composite Bezier geometrical parameterization. A particularly sensitive point is the choice and implementation of constraints; in order to formalize in the most complete and effective way the design requirements, the effects of activating specific constraints are discussed. A numerical example regarding the design of a high efficiency airfoil for the outer part of a blade by using genetic algorithms is illustrated and the results are compared with existing wind turbine airfoils. Finally a new hybrid design strategy is illustrated and discussed, in which the genetic algorithms are used at the beginning of the design process to explore a wide domain. Then, the gradient based algorithms are used in order to improve the first stage optimum.

Simulation of flow over double-element airfoil and wind tunnel test for use in vertical axis wind turbine

DEFF Research Database (Denmark)

Chougule, Prasad; Nielsen, Søren R.K.

2014-01-01

been made to utilize high lift technology for vertical axis wind turbines in order to improve power efficiency. High lift is obtained by double-element airfoil mainly used in aeroplane wing design. In this current work a low Reynolds number airfoil is selected to design a double-element airfoil blade...... for use in vertical axis wind turbine to improve the power efficiency. Double-element airfoil blade design consists of a main airfoil and a slat airfoil. Orientation of slat airfoil is a parameter of investigation in this paper and air flow simulation over double-element airfoil. With primary wind tunnel...... that there is an increase in the lift coefficient by 26% for single-element airfoil at analysed conditions. The CFD simulation results were validated with wind tunnel tests. It is also observe that by selecting proper airfoil configuration and blade sizes an increase in lift coefficient can further be achieved....

Experimental study of wind-turbine airfoil aerodynamics in high turbulence

Energy Technology Data Exchange (ETDEWEB)

Devinant, Ph.; Laverne, T.; Hureau, J. [Laboratoire de Mecanique et d' Energetique Ecole Superieure de l' Energie et des Materiaux Universite d' Orleans, rue Leonard de Vinci F-45072 , Cedex 2 Orleans (France)

2002-06-01

Wind turbines very often have to operate in high turbulence related, for example, with lower layers atmospheric turbulence or wakes of other wind turbines. Most available data on airfoil aerodynamics concerns mainly aeronautical applications, which are characterized by a low level of turbulence (generally less than 1%) and low angles of attack. This paper presents wind tunnel test data for the aerodynamic properties-lift, drag, pitching moment, pressure distributions-of an airfoil used on a wind turbine when subjected to incident flow turbulence levels of 0.5-16% and placed at angles of attack up to 90. The results show that the aerodynamic behavior of the airfoil can be strongly affected by the turbulence level both qualitatively and quantitatively. This effect is especially evidenced in the angle of attack range corresponding to airfoil stall, as the boundary layer separation point advances along the leeward surface of the airfoil.

Load alleviation on wind turbine blades using variable airfoil geometry

Energy Technology Data Exchange (ETDEWEB)

Basualdo, S.

2005-03-01

A two-dimensional theoretical study of the aeroelastic behaviour of an airfoil has been performed, whose geometry can be altered using a rear-mounted flap. This device is governed by a controller, whose objective is to reduce the airfoil displacements and, therefore, the stresses present in a real blade. The aerodynamic problem was solved numerically by a panel method using the potential theory, suitable for modelling attached flows. It is therefore mostly applicable for Pitch Regulated Variable Speed (PRVS) wind turbines, which mainly operate under this flow condition. The results show evident reductions in the airfoil displacements by using simple control strategies having the airfoil position and its first and second derivatives as input, especially at the system's eigenfrequency. The use of variable airfoil geometry is an effective means of reducing the vibration magnitudes of an airfoil that represents a section of a wind turbine blade, when subject to stochastic wind signals. The results of this investigation encourage further investigations with 3D aeroelastic models to predict the reduction in loads in real wind turbines. (author)

Simulation of flow over double-element airfoil and wind tunnel test for use in vertical axis wind turbine

International Nuclear Information System (INIS)

Chougule, Prasad; Nielsen, Søren R K

2014-01-01

Nowadays, small vertical axis wind turbines are receiving more attention due to their suitability in micro-electricity generation. There are few vertical axis wind turbine designs with good power curve. However, the efficiency of power extraction has not been improved. Therefore, an attempt has been made to utilize high lift technology for vertical axis wind turbines in order to improve power efficiency. High lift is obtained by double-element airfoil mainly used in aeroplane wing design. In this current work a low Reynolds number airfoil is selected to design a double-element airfoil blade for use in vertical axis wind turbine to improve the power efficiency. Double-element airfoil blade design consists of a main airfoil and a slat airfoil. Orientation of slat airfoil is a parameter of investigation in this paper and air flow simulation over double-element airfoil. With primary wind tunnel test an orientation parameter for the slat airfoil is initially obtained. Further a computational fluid dynamics (CFD) has been used to obtain the aerodynamic characteristics of double-element airfoil. The CFD simulations were carried out using ANSYS CFX software. It is observed that there is an increase in the lift coefficient by 26% for single-element airfoil at analysed conditions. The CFD simulation results were validated with wind tunnel tests. It is also observe that by selecting proper airfoil configuration and blade sizes an increase in lift coefficient can further be achieved

CFD aerodynamic analysis of non-conventional airfoil sections for very large rotor blades

International Nuclear Information System (INIS)

Papadakis, G; Voutsinas, S; Sieros, G; Chaviaropoulos, T

2014-01-01

The aerodynamic performance of flat-back and elliptically shaped airfoils is analyzed on the basis of CFD simulations. Incompressible and low-Mach preconditioned compressible unsteady simulations have been carried out using the k-w SST and the Spalart Allmaras turbulence models. Time averaged lift and drag coefficients are compared to wind tunnel data for the FB 3500-1750 flat back airfoil while amplitudes and frequencies are also recorded. Prior to separation averaged lift is well predicted while drag is overestimated keeping however the trend in the tests. The CFD models considered, predict separation with a 5° delay which is reflected on the load results. Similar results are provided for a modified NACA0035 with a rounded (elliptically shaped) trailing edge. Finally as regards the dynamic characteristics in the load signals, there is fair agreement in terms of Str number but significant differences in terms of lift and drag amplitudes

Wind turbine airfoil design method with low noise and experimental analysis

DEFF Research Database (Denmark)

Wang, Quan; Chen, Jin; Cheng, Jiangtao

2015-01-01

In order to study the noise characteristic of wind turbine airfoils, the airfoil optimal design mathematic model was built based on airfoil functional integrated theory and noise calculated model. The new optimized objective function of maximizing lift/drag to noise was developed on the design......, though there is a certain difference between the theory results and experiment data. Compared with NACA-64-618 airfoil, the CQU-DTU-B18 airfoil exhibits lower noise, which validates the feasibility of this design method. It is a guide to design wind turbine airfoil with lower noise and to reduce airfoil...

Usage of Numerical Optimization in Wind Turbine Airfoil Design

Energy Technology Data Exchange (ETDEWEB)

Grasso, F. [ECN Wind Energy, Petten (Netherlands)

2011-01-15

One important key element in the aerodynamic design of wind turbines is the use of specially tailored airfoils to increase the ratio of energy capture to the loading and thereby to reduce the cost of energy. This work is focused on the design of a wind turbine airfoil by using numerical optimization. First, the requirements for this class of airfoils are illustrated and discussed in order to have an exhaustive outline of the complexity of the problem. Then the optimization approach is presented; a gradient-based algorithm is used, coupled with RFOIL solver and a composite Bezier geometrical parameterization. A particularly sensitive point is the choice and implementation of constraints; to formalize the design requirements in the most complete and effective way, the effects of activating specific constraints are discussed. Finally, a numerical example regarding the design of a high-efficiency airfoil for the outer part of a blade is illustrated, and the results are compared with existing wind turbine airfoils.

Wind turbine airfoil catalogue

DEFF Research Database (Denmark)

Bertagnolio, F.; Sørensen, Niels N.; Johansen, Jeppe

2001-01-01

The aim of this work is two-sided. Firstly, experimental results obtained for numerous sets of airfoil measurements (mainly intended for wind turbine applications) are collected and compared with computational results from the 2D Navier-Stokes solverEllipSys2D, as well as results from the panel...... method code XFOIL. Secondly, we are interested in validating the code EllipSys2D and finding out for which airfoils it does not perform well compared to the experiments, as well as why, when it does so. Theairfoils are classified according to the agreement between the numerical results and experimental...... data. A study correlating the available data and this classification is performed. It is found that transition modelling is to a large extent responsible forthe poor quality of the computational results for most of the considered airfoils. The transition model mechanism that leads...

Design of a 3 kW wind turbine generator with thin airfoil blades

Energy Technology Data Exchange (ETDEWEB)

Ameku, Kazumasa; Nagai, Baku M.; Roy, Jitendro Nath [Faculty of Mechanical Engineering, University of the Ryukyus, 1 Senbaru, Nishihara-cho, Okinawa 903-0213 (Japan)

2008-09-15

Three blades of a 3 kW prototype wind turbine generator were designed with thin airfoil and a tip speed ratio of 3. The wind turbine has been controlled via two control methods: the variable pitch angle and by regulation of the field current of the generator and examined under real wind conditions. The characteristics of the thin airfoil, called ''Seven arcs thin airfoil'' named so because the airfoil is composed of seven circular arcs, are analyzed with the airfoil design and analysis program XFOIL. The thin airfoil blade is designed and calculated by blade element and momentum theory. The performance characteristics of the machine such as rotational speed, generator output as well as stability for wind speed changes are described. In the case of average wind speeds of 10 m/s and a maximum of 19 m/s, the automatically controlled wind turbine ran safely through rough wind conditions and showed an average generator output of 1105 W and a power coefficient 0.14. (author)

Design of the new Risoe-A1 airfoil family for wind turbines

Energy Technology Data Exchange (ETDEWEB)

Fuglsang, P; Dahl, K S [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark)

1999-03-01

A new airfoil family for wind turbines was developed by use of a design method using numerical optimization and the flow solver, XFOIL. The results were evaluated with the Navier-Stokes solver EllipSys2D. The airfoil family constitutes 6 airfoils ranging in thickness from 15% to 30%. The airfoils were designed to have a maximum lift coefficient around 1.5 in natural conditions and high lift-drag ratios below maximum lift. Insensitivity to leading edge roughness was obtained by securing that transition from laminar to turbulent flow on the suction side occurred close to the leading edge just before stall. The airfoil family was designed for a 600 kW wind turbine and provides a basis for further enhancing the characteristics of airfoils for wind turbines and to tailor airfoils for specific rotor sizes and power regulation principles. (au) EFP-95; EFP-98. 16 refs.

Design of advanced airfoil for stall-regulated wind turbines

Directory of Open Access Journals (Sweden)

F. Grasso

2017-07-01

Full Text Available Nowadays, all the modern megawatt-class wind turbines make use of pitch control to optimise the rotor performance and control the turbine. However, for kilowatt-range machines, stall-regulated solutions are still attractive and largely used for their simplicity and robustness. In the design phase, the aerodynamics plays a crucial role, especially concerning the selection/design of the necessary airfoils. This is because the airfoil performance is supposed to guarantee high wind turbine performance but also the necessary machine control capabilities. In the present work, the design of a new airfoil dedicated to stall machines is discussed. The design strategy makes use of a numerical optimisation scheme, where a gradient-based algorithm is coupled with the RFOIL code and an original Bezier-curves-based parameterisation to describe the airfoil shape. The performances of the new airfoil are compared in free- and fixed-transition conditions. In addition, the performance of the rotor is analysed, comparing the impact of the new geometry with alternative candidates. The results show that the new airfoil offers better performance and control than existing candidates do.

Optimization design of airfoil profiles based on the noise of wind turbines

DEFF Research Database (Denmark)

Cheng, Jiangtao; Chen, Jin; Cheng, Jiangtao

2012-01-01

Based on design theory of airfoil profiles and airfoil self-noise prediction model, a new method with the target of the airfoil average efficiency-noise ratio of design ranges for angle of attack had been developed for designing wind turbine airfoils. The airfoil design method was optimized for a...

Effects of finite aspect ratio on wind turbine airfoil measurements

DEFF Research Database (Denmark)

Kiefer, Janik; Miller, Mark A.; Hultmark, Marcus

2016-01-01

Wind turbines partly operate in stalled conditions within their operational cycle. To simulate these conditions, it is also necessary to obtain 2-D airfoil data in terms of lift and drag coefficients at high angles of attack. Such data has been obtained previously, but often at low aspect ratios...... and only barely past the stall point, where strong wall boundary layer influence is expected. In this study, the influence of the wall boundary layer on 2D airfoil data, especially in the post stall domain, is investigated. Here, a wind turbine airfoil is tested at different angles of attack and with two...

Design and verification of the Risø-B1 airfoil family for wind turbines

DEFF Research Database (Denmark)

Fuglsang, P.; Bak, C.; Gaunaa, M.

2004-01-01

This paper presents the design and experimental verification of the Risø-B1 airfoil family for MW-size wind turbines with variable speed and pitch control. Seven airfoils were designed with thickness-to-chord ratios between 15% and 53% to cover the entire span of a wind turbine blade. The airfoils...

Research on improved design of airfoil profiles based on the continuity of airfoil surface curvature of wind turbines

DEFF Research Database (Denmark)

Chen, Jin; Cheng, Jiangtao; Shen, Wenzhong

2013-01-01

Aerodynamic of airfoil performance is closely related to the continuity of its surface curvature, and airfoil profiles with a better aerodynamic performance plays an important role in the design of wind turbine. The surface curvature distribution along the chord direction and pressure distributio...

Integrated airfoil and blade design method for large wind turbines

DEFF Research Database (Denmark)

Zhu, Wei Jun; Shen, Wen Zhong

2013-01-01

This paper presents an integrated method for designing airfoil families of large wind turbine blades. For a given rotor diameter and tip speed ratio, the optimal airfoils are designed based on the local speed ratios. To achieve high power performance at low cost, the airfoils are designed...... with an objective of high Cp and small chord length. When the airfoils are obtained, the optimum flow angle and rotor solidity are calculated which forms the basic input to the blade design. The new airfoils are designed based on the previous in-house airfoil family which were optimized at a Reynolds number of 3...... million. A novel shape perturbation function is introduced to optimize the geometry on the existing airfoils and thus simplify the design procedure. The viscos/inviscid code Xfoil is used as the aerodynamic tool for airfoil optimization where the Reynolds number is set at 16 million with a free...

Integrated airfoil and blade design method for large wind turbines

DEFF Research Database (Denmark)

Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær

2014-01-01

This paper presents an integrated method for designing airfoil families of large wind turbine blades. For a given rotor diameter and a tip speed ratio, optimal airfoils are designed based on the local speed ratios. To achieve a high power performance at low cost, the airfoils are designed...... with the objectives of high Cp and small chord length. When the airfoils are obtained, the optimum flow angle and rotor solidity are calculated which forms the basic input to the blade design. The new airfoils are designed based on a previous in-house designed airfoil family which was optimized at a Reynolds number...... of 3 million. A novel shape perturbation function is introduced to optimize the geometry based on the existing airfoils which simplifies the design procedure. The viscous/inviscid interactive code XFOIL is used as the aerodynamic tool for airfoil optimization at a Reynolds number of 16 million...

Bionic Design of Wind Turbine Blade Based on Long-Eared Owl's Airfoil.

Science.gov (United States)

Tian, Weijun; Yang, Zhen; Zhang, Qi; Wang, Jiyue; Li, Ming; Ma, Yi; Cong, Qian

2017-01-01

The main purpose of this paper is to demonstrate a bionic design for the airfoil of wind turbines inspired by the morphology of Long-eared Owl's wings. Glauert Model was adopted to design the standard blade and the bionic blade, respectively. Numerical analysis method was utilized to study the aerodynamic characteristics of the airfoils as well as the blades. Results show that the bionic airfoil inspired by the airfoil at the 50% aspect ratio of the Long-eared Owl's wing gives rise to a superior lift coefficient and stalling performance and thus can be beneficial to improving the performance of the wind turbine blade. Also, the efficiency of the bionic blade in wind turbine blades tests increases by 12% or above (up to 44%) compared to that of the standard blade. The reason lies in the bigger pressure difference between the upper and lower surface which can provide stronger lift.

Steady and Unsteady Analysis of NACA 0018 Airfoil in Vertical-Axis Wind Turbine

DEFF Research Database (Denmark)

Rogowski, Krzysztof; Hansen, Martin Otto Laver; Maronski, Ryszard

2018-01-01

Numerical results are presented for aerodynamic unsteady and steady airfoil characteristtcs of the NACA 0018 airfoil of a two-dimensional vertical-axis wind turbine. A geometrical model of the Darrieus-type wind turbine and the rotor operating parameters used for nurnerieal simulation are taken...

Adjoint Airfoil Optimization of Darrieus-Type Vertical Axis Wind Turbine

Science.gov (United States)

Fuchs, Roman; Nordborg, Henrik

2012-11-01

We present the feasibility of using an adjoint solver to optimize the torque of a Darrieus-type vertical axis wind turbine (VAWT). We start with a 2D cross section of a symmetrical airfoil and restrict us to low solidity ratios to minimize blade vortex interactions. The adjoint solver of the ANSYS FLUENT software package computes the sensitivities of airfoil surface forces based on a steady flow field. Hence, we find the torque of a full revolution using a weighted average of the sensitivities at different wind speeds and angles of attack. The weights are computed analytically, and the range of angles of attack is given by the tip speed ratio. Then the airfoil geometry is evolved, and the proposed methodology is evaluated by transient simulations.

Evolving aerodynamic airfoils for wind turbines through a genetic algorithm

Science.gov (United States)

Hernández, J. J.; Gómez, E.; Grageda, J. I.; Couder, C.; Solís, A.; Hanotel, C. L.; Ledesma, JI

2017-01-01

Nowadays, genetic algorithms stand out for airfoil optimisation, due to the virtues of mutation and crossing-over techniques. In this work we propose a genetic algorithm with arithmetic crossover rules. The optimisation criteria are taken to be the maximisation of both aerodynamic efficiency and lift coefficient, while minimising drag coefficient. Such algorithm shows greatly improvements in computational costs, as well as a high performance by obtaining optimised airfoils for Mexico City's specific wind conditions from generic wind turbines designed for higher Reynolds numbers, in few iterations.

Aerodynamic analysis of S series wind turbine airfoils by using X foil technique

International Nuclear Information System (INIS)

Zaheer, M.A.; Munir, M.A.; Zahid, I.; Rizwan, M.

2015-01-01

In order to attain supreme energy from wind turbine economically, blade profile enactment must be acquired. For extracting extreme power from wind, it is necessary to develop rotor models of wind turbine which have high rotation rates and power coefficients. Maximum power can also be haul out by using suitable airfoils at root and tip sections of wind turbine blades. In this research four different S-series airfoils have been selected to study their behavior for maximum power extraction from wind. The wind conditions during the research were scertained from the wind speeds over Kallar Kahar Pakistan. In order to study the wind turbine operation, the extremely important parameters are lift and drag forces. Therefore an endeavor to study lift force and drag force at various sections of wind turbine blade is shown in current research. In order to acquire the utmost power from wind turbine, highest value of sliding ratio is prerequisite. At various wind speeds, performance of several blade profiles was analyzed and for every wind speed, the appropriate blade profile is ascertained grounded on the utmost sliding ratio. For every airfoil, prime angle of attack is resolute at numerous wind speeds. (author)

Design of a family of new advanced airfoils for low wind class turbines

International Nuclear Information System (INIS)

Grasso, Francesco

2014-01-01

In order to maximize the ratio of energy capture and reduce the cost of energy, the selection of the airfoils to be used along the blade plays a crucial role. Despite the general usage of existing airfoils, more and more, families of airfoils specially tailored for specific applications are developed. The present research is focused on the design of a new family of airfoils to be used for the blade of one megawatt wind turbine working in low wind conditions. A hybrid optimization scheme has been implemented, combining together genetic and gradient based algorithms. Large part of the work is dedicated to present and discuss the requirements that needed to be satisfied in order to have a consistent family of geometries with high efficiency, high lift and good structural characteristics. For each airfoil, these characteristics are presented and compared to the ones of existing airfoils. Finally, the aerodynamic design of a new blade for low wind class turbine is illustrated and compared to a reference shape developed by using existing geometries. Due to higher lift performance, the results show a sensitive saving in chords, wetted area and so in loads in idling position

Performance assessment of Darrieus wind turbine with symmetric and cambered airfoils

Energy Technology Data Exchange (ETDEWEB)

Cisse, H.; Trifu, O.; Paraschivoiu, I. [Ecole Polytechnique, Montreal, PQ (Canada). Dept. de Genie Mecanique

2007-07-01

This paper outlined the wind turbine and design software used to predict the flow conditions and performance of a straight-bladed Darrieus wind turbine. Three different blade sections were considered, notably the NACA 0018; the SNLA NLF 18/50 symmetrical airfoil; and the FX63-137 cambered airfoil. The numerical predictions of the flow conditions during the operation of the rotors were also presented. Torque yield for each blade section under a variety of operating conditions was presented. The numerical software program used in the study was based on a double-multiple streamtube model which considered a partition of the rotor in streamtubes and considered each of the 2 blade elements as an actuator disk. The actuator disk theory was based on a theory of momentum conservation. Wind velocities were determined in order to calculate forces acting on the actuator disks. A second set of equations was used to determine the forces acting on the upwind and downwind blade elements. Equations were also derived for the downwind interference factor. The following 3 main sets of data were used: (1) a geometry definition of the wind turbine; (2) operational conditions; and (3) main control parameters. Results of the study showed that the cambered airfoil blade section produced 10 times more torque in turbine starting conditions than the NACA 0018. Laminar airfoil lift to drag ratio at low angles of attack, and the use of appropriate Reynolds numbers resulted in higher efficiency. The large static stall angle of the cambered airfoil allowed higher power outputs than symmetrical airfoils. It was concluded that the starting torque of a Darrieus turbine can be increased by using a cambered blade section. 13 refs., 19 figs.

Experimental verification of the new RISOe-A1 airfoil family for wind turbines

Energy Technology Data Exchange (ETDEWEB)

Dahl, K S; Fuglsang, P; Antoniou, I [Risoe National Lab., Roskilde (Denmark)

1999-03-01

This paper concerns the experimental verification of a new airfoil family for wind turbines. The family consist of airfoils in the relative thickness range from 15% to 30%. Three airfoils, Risoe-A1-18, Risoe-A1-21, and Risoe-A1-24 were tested in a wind tunnel. The verification consisted of both static and dynamic measurements. Here, the static results are presented for a Reynolds number of 1.6x10{sup 6} for the following airfoil configurations: smooth surface (all three airfoils) and Risoe-A1-24 mounted with leading edge roughness, vortex generators, and Gurney-flaps, respectively. All three airfoils have constant lift curve slope and almost constant drag coefficient until the maximum lift coefficient of about 1.4 is reached. The experimental results are compared with corresponding computational from the general purpose flow solver, EllipSys2D, showing good agreement. (au)

Turbulence intensity measurement in the wind tunnel used for airfoil flutter investigation

Directory of Open Access Journals (Sweden)

Šidlof Petr

2017-01-01

Full Text Available The paper reports on hot wire turbulence intensity measurements performed in the entry of a suction-type wind tunnel, used for investigation of flow-induced vibration of airfoils and slender structures. The airfoil is elastically supported with two degrees of freedom (pitch and plunge in the test section of the wind tunnel with lateral optical access for interferometric measurements, and free to oscillate. The turbulence intensity was measured for velocities up to M = 0.3 i with the airfoil blocked, ii with the airfoil self-oscillating. Measurements were performed for a free inlet and further with two different turbulence grids generating increased turbulence intensity levels. For the free inlet and static airfoil, the turbulence intensity lies below 0.4%. The turbulence grids G1 and G2 increase the turbulence level up to 1.8% and 2.6%, respectively. When the airfoil is free to oscillate due to fluid-structure interaction, its motion disturbs the surrounding flow field and increases the measured turbulence intensity levels up to 5%.

Wind Tunnel and Numerical Analysis of Thick Blunt Trailing Edge Airfoils

Science.gov (United States)

McLennan, Anthony William

Two-dimensional aerodynamic characteristics of several thick blunt trailing edge airfoils are presented. These airfoils are not only directly applicable to the root section of wind turbine blades, where they provide the required structural strength at a fraction of the material and weight of an equivalent sharp trailing edge airfoil, but are also applicable to the root sections of UAVs having high aspect ratios, that also encounter heavy root bending forces. The Reynolds averaged Navier-Stokes code, ARC2D, was the primary numerical tool used to analyze each airfoil. The UCD-38-095, referred to as the Pareto B airfoil in this thesis, was also tested in the University of California, Davis Aeronautical Wind Tunnel. The Pareto B has an experimentally determined maximum lift coefficient of 1.64 at 14 degrees incidence, minimum drag coefficient of 0.0385, and maximum lift over drag ratio of 35.9 at a lift coefficient of 1.38, 10 degrees incidence at a Reynolds number of 666,000. Zig-zag tape at 2% and 5% of the chord was placed on the leading edge pressure and suction side of the Pareto B model in order to determine the aerodynamic performance characteristics at turbulent flow conditions. Experimental Pareto B wind tunnel data and previous FB-3500-0875 data is also presented and used to validate the ARC2D results obtained in this study. Additionally MBFLO, a detached eddy simulation Navier-Stokes code, was used to analyze the Pareto B airfoil for comparison and validation purposes.

Bionic Design of Wind Turbine Blade Based on Long-Eared Owl’s Airfoil

Directory of Open Access Journals (Sweden)

Weijun Tian

2017-01-01

Full Text Available The main purpose of this paper is to demonstrate a bionic design for the airfoil of wind turbines inspired by the morphology of Long-eared Owl’s wings. Glauert Model was adopted to design the standard blade and the bionic blade, respectively. Numerical analysis method was utilized to study the aerodynamic characteristics of the airfoils as well as the blades. Results show that the bionic airfoil inspired by the airfoil at the 50% aspect ratio of the Long-eared Owl’s wing gives rise to a superior lift coefficient and stalling performance and thus can be beneficial to improving the performance of the wind turbine blade. Also, the efficiency of the bionic blade in wind turbine blades tests increases by 12% or above (up to 44% compared to that of the standard blade. The reason lies in the bigger pressure difference between the upper and lower surface which can provide stronger lift.

Predicting the Extreme Loads on a Wind Turbine Considering Uncertainty in Airfoil Data

DEFF Research Database (Denmark)

Abdallah, Imad; Natarajan, Anand; Sørensen, John Dalsgaard

2014-01-01

The sources contributing to uncertainty in a wind turbine blade static airfoil data include wind tunnel testing, CFD calculations, 3D rotational corrections based on CFD or emprircal models, surface roughness corrections, Reynolds number corrections, expansion to the full 360-degree angle of attack...... range, validation by full scale measurements, and geometric distortions of the blade during manufacturing and under loading. In this paper a stochastic model of the static airfoil data is proposed to supplement the prediction of extreme loads effects for large wind turbines. It is shown...... that the uncertainty in airfoil data can have e significant impact on the prediction of extreme loads effects depending on the component, and the correlation along the span of the blade....

Numerical investigation of airfoils for small wind turbine applications

Directory of Open Access Journals (Sweden)

Natarajan Karthikeyan

2016-01-01

Full Text Available A detailed numerical investigation of the aerodynamic performance on the five airfoils namely Mid321a, Mid321b, Mid321c, Mid321d, and Mid321e were carried out at Reynolds numbers ranging from 0.5×105 to 2.5×105. The airfoils used for small wind turbines are designed for Reynolds number ranges between 3×105 and 5×105 and the blades are tend to work on off-design conditions. The blade element moment method was applied to predict the aerodynamic loads, power coefficient, and blade parameters for the airfoils. Based on the evaluate data, it was found that Mid321c airfoil has better lift to drag ratio over the range of Reynolds numbers and attained maximum power coefficient of 0.4487 at Re = 2×105.

Design and Wind Tunnel Testing of a Thick, Multi-Element High-Lift Airfoil

DEFF Research Database (Denmark)

Zahle, Frederik; Gaunaa, Mac; Sørensen, Niels N.

2012-01-01

In this work a 2D CFD solver has been used to optimize the shape of a leading edge slat with a chord length of 30% of the main airfoil which was 40% thick. The airfoil configuration was subsequently tested in a wind tunnel and compared to numerical predictions. The multi-element airfoil was predi...

Experimental study of the effect of a slat angle on double-element airfoil and application in vertical axis wind turbine

DEFF Research Database (Denmark)

Chougule, Prasad; Rosendahl, Lasse; Nielsen, Søren R.K.

2015-01-01

A design of double-element airfoil is proposed for its use in the vertical axis wind turbine. The double-element airfoil system consists of a main airfoil and a slat airfoil. The design parameters of the double-element airfoil system are given by the position and orientation of the trailing edge......-element airfoil system designed in this paper. Further, the performance of new design of a vertical axis wind turbine shows considerable increase in the power coefficient and the total power output as compared to the reference wind turbine...

Design of low noise airfoil with high aerodynamic performance for use on small wind turbines

Institute of Scientific and Technical Information of China (English)

Taehyung; KIM; Seungmin; LEE; Hogeon; KIM; Soogab; LEE

2010-01-01

Wind power is one of the most reliable renewable energy sources and internationally installed capacity is increasing radically every year.Although wind power has been favored by the public in general,the problem with the impact of wind turbine noise on people living in the vicinity of the turbines has been increased.Low noise wind turbine design is becoming more and more important as noise is spreading more adverse effect of wind turbine to public.This paper demonstrates the design of 10 kW class wind turbines,each of three blades,a rotor diameter 6.4 m,a rated rotating speed 200 r/min and a rated wind speed 10 m/s.The optimized airfoil is dedicated for the 75% spanwise position because the dominant source of a wind turbine blade is trailing edge noise from the outer 25% of the blade.Numerical computations are performed for incompressible flow and for Mach number at 0.145 and for Reynolds numbers at 1.02×106 with a lift performance,which is resistant to surface contamination and turbulence intensity.The objectives in the design process are to reduce noise emission,while sustaining high aerodynamic efficiency.Dominant broadband noise sources are predicted by semi-empirical formulas composed of the groundwork by Brooks et al.and Lowson associated with typical wind turbine operation conditions.During the airfoil redesign process,the aerodynamic performance is analyzed to reduce the wind turbine power loss.The results obtained from the design process show that the design method is capable of designing airfoils with reduced noise using a commercial 10 kW class wind turbine blade airfoil as a basis.Therefore,the new optimized airfoil showing 2.9 dB reductions of total sound pressure level(SPL) and higher aerodynamic performance are achieved.

WIND TUNNEL RESEARCH ON THE INFLUENCE OF ACTIVE AIRFLOW ON THE LIFT FORCE GENERATED BY THE AIRFOIL

Directory of Open Access Journals (Sweden)

Paweł Magryta

2013-09-01

Full Text Available The paper discusses the results of wind tunnel tests of airfoils with additional active airflow applied to their upper surfaces. These studies were carried out for a range of velocities up to 28 m/s in an open wind tunnel. Several types of airfoils selected for the examination feature different geometries and are widely applied in today’s aviation industry. The changes in the lift and drag force generated by these airfoils were recorded during the study. The test bench for the tests was equipped with a compressor and a vacuum pump to enable airflow through some holes on the airfoil upper surface. A rapid prototyping method and a 3D printer based on a powder printing technique were applied to print the airfoils. All of their surfaces were subject to surface grinding to smooth their external surfaces. The wind tunnel tests with and without active airflow applied to airfoils are summarised in the paper.

On the influence of airfoil deviations on the aerodynamic performance of wind turbine rotors

International Nuclear Information System (INIS)

Winstroth, J; Seume, J R

2016-01-01

The manufacture of large wind turbine rotor blades is a difficult task that still involves a certain degree of manual labor. Due to the complexity, airfoil deviations between the design airfoils and the manufactured blade are certain to arise. Presently, the understanding of the impact of manufacturing uncertainties on the aerodynamic performance is still incomplete. The present work analyzes the influence of a series of airfoil deviations likely to occur during manufacturing by means of Computational Fluid Dynamics and the aeroelastic code FAST. The average power production of the NREL 5MW wind turbine is used to evaluate the different airfoil deviations. Analyzed deviations include: Mold tilt towards the leading and trailing edge, thick bond lines, thick bond lines with cantilever correction, backward facing steps and airfoil waviness. The most severe influences are observed for mold tilt towards the leading and thick bond lines. By applying the cantilever correction, the influence of thick bond lines is almost compensated. Airfoil waviness is very dependent on amplitude height and the location along the surface of the airfoil. Increased influence is observed for backward facing steps, once they are high enough to trigger boundary layer transition close to the leading edge. (paper)

Trailing edge noise model applied to wind turbine airfoils

Energy Technology Data Exchange (ETDEWEB)

Bertagnolio, F.

2008-01-15

The aim of this work is firstly to provide a quick introduction to the theory of noise generation that are relevant to wind turbine technology with focus on trailing edge noise. Secondly, the socalled TNO trailing edge noise model developed by Parchen [1] is described in more details. The model is tested and validated by comparing with other results from the literature. Finally, this model is used in the optimization process of two reference airfoils in order to reduce their noise signature: the RISOE-B1-18 and the S809 airfoils. (au)

Prediction of the wind turbine performance by using BEM with airfoil data extracted from CFD

DEFF Research Database (Denmark)

Yang, Hua; Shen, Wen Zhong; Xu, Haoran

2014-01-01

Blade element momentum (BEM) theory with airfoil data is a widely used technique for prediction of wind turbine aerodynamic performance, but the reliability of the airfoil data is an important factor for the prediction accuracy of aerodynamic loads and power. The airfoil characteristics used in BEM...

Virtual incidence effect on rotating airfoils in Darrieus wind turbines

International Nuclear Information System (INIS)

Bianchini, Alessandro; Balduzzi, Francesco; Ferrara, Giovanni; Ferrari, Lorenzo

2016-01-01

Highlights: • Novel methods to reduce CFD results into 1D aerodynamic parameters. • Assessment of the virtual incidence (VI) effect on Darrieus VAWT blades. • It is shown that blades experience a virtual AoA variation with respect to theoretical expectations. • Real AoAs are calculated for different airfoils in motion and compared to BEM predictions. - Abstract: Small Darrieus wind turbines are one of the most interesting emerging technologies in the renewable energies scenario, even if they still are characterized by lower efficiencies than those of conventional horizontal-axis wind turbines due to the more complex aerodynamics involved in their functioning. In case of small rotors, in which the chord-to-radius ratios are generally high not to limit the blade Reynolds number, the performance of turbine blades has been suggested to be moreover influenced by the so-called “flow curvature effects”. Recent works have indeed shown that the curved flowpath encountered by the blades makes them work like virtually cambered airfoils in a rectilinear flow. In the present study, focus is instead given to a further effect that is generated in reason of the curved streamline incoming on the blades, i.e. an extra-incidence seen by the airfoil, generally referred to as “virtual incidence”. In detail, a novel computational method to define the incidence angle has been applied to unsteady CFD simulations of three airfoils in a Darrieus-like motion and their effective angles of attack have been compared to theoretical expectations. The analysis confirmed the presence of an additional virtual incidence on the airfoils and quantified it for different airfoils, chord-to-radius ratios and tip-speed ratios. A comparative discussion on BEM prediction capabilities is finally reported in the study.

Airfoil data sensitivity analysis for actuator disc simulations used in wind turbine applications

DEFF Research Database (Denmark)

Nilsson, Karl; Breton, Simon-Philippe; Sørensen, Jens Nørkær

2014-01-01

To analyse the sensitivity of blade geometry and airfoil characteristics on the prediction of performance characteristics of wind farms, large-eddy simulations using an actuator disc (ACD) method are performed for three different blade/airfoil configurations. The aim of the study is to determine ...

Numerical simulation of transitional flow on a wind turbine airfoil with RANS-based transition model

Science.gov (United States)

Zhang, Ye; Sun, Zhengzhong; van Zuijlen, Alexander; van Bussel, Gerard

2017-09-01

This paper presents a numerical investigation of transitional flow on the wind turbine airfoil DU91-W2-250 with chord-based Reynolds number Rec = 1.0 × 106. The Reynolds-averaged Navier-Stokes based transition model using laminar kinetic energy concept, namely the k - kL - ω model, is employed to resolve the boundary layer transition. Some ambiguities for this model are discussed and it is further implemented into OpenFOAM-2.1.1. The k - kL - ω model is first validated through the chosen wind turbine airfoil at the angle of attack (AoA) of 6.24° against wind tunnel measurement, where lift and drag coefficients, surface pressure distribution and transition location are compared. In order to reveal the transitional flow on the airfoil, the mean boundary layer profiles in three zones, namely the laminar, transitional and fully turbulent regimes, are investigated. Observation of flow at the transition location identifies the laminar separation bubble. The AoA effect on boundary layer transition over wind turbine airfoil is also studied. Increasing the AoA from -3° to 10°, the laminar separation bubble moves upstream and reduces in size, which is in close agreement with wind tunnel measurement.

Computer investigations of the turbulent flow around a NACA2415 airfoil wind turbine

Science.gov (United States)

Driss, Zied; Chelbi, Tarek; Abid, Mohamed Salah

2015-12-01

In this work, computer investigations are carried out to study the flow field developing around a NACA2415 airfoil wind turbine. The Navier-Stokes equations in conjunction with the standard k-ɛ turbulence model are considered. These equations are solved numerically to determine the local characteristics of the flow. The models tested are implemented in the software "SolidWorks Flow Simulation" which uses a finite volume scheme. The numerical results are compared with experiments conducted on an open wind tunnel to validate the numerical results. This will help improving the aerodynamic efficiency in the design of packaged installations of the NACA2415 airfoil type wind turbine.

Finding optimum airfoil shape to get maximum aerodynamic efficiency for a wind turbine

Science.gov (United States)

Sogukpinar, Haci; Bozkurt, Ismail

2017-02-01

In this study, aerodynamic performances of S-series wind turbine airfoil of S 825 are investigated to find optimum angle of attack. Aerodynamic performances calculations are carried out by utilization of a Computational Fluid Dynamics (CFD) method withstand finite capacity approximation by using Reynolds-Averaged-Navier Stokes (RANS) theorem. The lift and pressure coefficients, lift to drag ratio of airfoil S 825 are analyzed with SST turbulence model then obtained results crosscheck with wind tunnel data to verify the precision of computational Fluid Dynamics (CFD) approximation. The comparison indicates that SST turbulence model used in this study can predict aerodynamics properties of wind blade.

Comparison of NACA 6-series and 4-digit airfoils for Darrieus wind turbines

Science.gov (United States)

Migliore, P. G.

1983-08-01

The aerodynamic efficiency of Darrieus wind turbines as effected by blade airfoil geometry was investigated. Analysis was limited to curved-bladed machines having rotor solidities of 7-21 percent and operating at a Reynolds number of 3 x 10 to the 6th. Ten different airfoils, having thickness-to-chord ratios of 12, 15, and 18 percent, were studied. Performance estimates were made using a blade element/momentum theory approach. Results indicated that NACA 6-series airfoils yield peak power coefficients as great as NACA 4-digit airfoils and have broader and flatter power coefficient-tip speed ratio curves. Sample calculations for an NACA 63(2)-015 airfoil showed an annual energy output increase of 17-27 percent, depending on rotor solidity, compared to an NACA 0015 airfoil.

Design of a new urban wind turbine airfoil using a pressure-load inverse method

Energy Technology Data Exchange (ETDEWEB)

Henriques, J.C.C.; Gato, L.M.C. [IDMEC, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Marques da Silva, F. [LNEC - Laboratorio Nacional de Engenharia Civil, Av. Brasil, 101, 1700-066 Lisboa (Portugal); Estanqueiro, A.I. [INETI - Instituto Nacional de Engenharia, Tecnologia e Inovacao Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal)

2009-12-15

This paper presents the design methodology of a new wind turbine airfoil that achieves high performance in urban environment by increasing the maximum lift. For this purpose, an inverse method was applied to obtain a new wind turbine blade section with constant pressure-load along the chord, at the design inlet angle. In comparison with conventional blade section designs, the new airfoil has increased maximum lift, reduced leading edge suction peak and controlled soft-stall behaviour, due to a reduction of the adverse pressure gradient on the suction side. Wind tunnel experimental results confirmed the computational results. (author)

Airfoils and method for designing airfoils

DEFF Research Database (Denmark)

2010-01-01

The present invention relates to airfoils and design and design optimization of airfoils, in particular airfoils of rotor blades for wind turbines. One aspect of the invention relates to an airfoil with an external shape provided by an airfoil profile defined by a limited number of parameters......, such as a set of parameters. Another aspect of the invention relates to a method for designing an airfoil by means of an analytical airfoil profile, said method comprising the step of applying a conformal mapping to a near circle in a near circle plane, wherein the near circle is at least partly expressed...... by means of an analytical function, said conformal mapping transforming the near circle in the near circle plane to the airfoil profile in an airfoil plane. L...

Numerical simulation of the divergence of a wind turbine airfoil : part 2

Energy Technology Data Exchange (ETDEWEB)

Ramdenee, D.; Minea, I.S.; Tardiff d' Hamonville, T.; Illinca, A. [Quebec Univ., Rimouski, PQ (Canada). Laboratoire de Recherche en Energie Eolienne

2010-07-01

The development of larger, more flexible wind turbine blades is creating the need for an improved understanding of the mechanisms surrounding unsteady flow-structure interactions. This 2-part study used computational fluid dynamics (CFD) to identify and model the aerodynamic and aeroelastic phenomena around wind turbine blades. Aeroelastic divergence was modelled using coupled aerodynamic and elastic models with an ANSYS software program. The fluid-structure interactions of an NACA0012 airfoil were simulated in order to determine the divergence phenomenon created by aerodynamic loads and transient fluid flow. The airfoil profile was fixed and exempted from all rotational degrees of liberty while being subjected to a constant flow of velocity. The fixing was then removed and the constant flow was compared with a shock wave on the airfoil profile. The profile then oscillated with damped amplitude due to the aerodynamic damping imposed. Results of the analysis will be compared with results obtained in future studies. 7 refs., 2 tabs., 6 figs.

Airfoil data sensitivity analysis for actuator disc simulations used in wind turbine applications

International Nuclear Information System (INIS)

Nilsson, Karl; Breton, Simon-Philippe; Ivanell, Stefan; Sørensen, Jens N

2014-01-01

To analyse the sensitivity of blade geometry and airfoil characteristics on the prediction of performance characteristics of wind farms, large-eddy simulations using an actuator disc (ACD) method are performed for three different blade/airfoil configurations. The aim of the study is to determine how the mean characteristics of wake flow, mean power production and thrust depend on the choice of airfoil data and blade geometry. In order to simulate realistic conditions, pre-generated turbulence and wind shear are imposed in the computational domain. Using three different turbulence intensities and varying the spacing between the turbines, the flow around 4-8 aligned turbines is simulated. The analysis is based on normalized mean streamwise velocity, turbulence intensity, relative mean power production and thrust. From the computations it can be concluded that the actual airfoil characteristics and blade geometry only are of importance at very low inflow turbulence. At realistic turbulence conditions for an atmospheric boundary layer the specific blade characteristics play an minor role on power performance and the resulting wake characteristics. The results therefore give a hint that the choice of airfoil data in ACD simulations is not crucial if the intention of the simulations is to compute mean wake characteristics using a turbulent inflow

Wind tunnel tests of the NACA 63-415 and a modified NACA 63-415 airfoil

DEFF Research Database (Denmark)

Bak, C.; Fuglsang, P.; Johansen, J.

2000-01-01

This report contains 2D measurements of the NACA 63-415 and a NACA 63-415 airfoil with modified leading edge called NACA 63-415-Risø-D. The aerodynamic properties were derived from pressure measurements on the airfoil surface and in the wake. The VELUXopen jet wind tunnel was used having a backgr......This report contains 2D measurements of the NACA 63-415 and a NACA 63-415 airfoil with modified leading edge called NACA 63-415-Risø-D. The aerodynamic properties were derived from pressure measurements on the airfoil surface and in the wake. The VELUXopen jet wind tunnel was used having...... a background turbulence intensity of 1%, an inlet flow velocity of 40 m/s which resulted in a Reynolds number of 1.6×106. The airfoil sections had a chord of 0.600 m and 0.606 m for NACA 63-415 and NACA 63-415-Risø-D,respectively. The span was 1.9 m and end plates were used to minimise 3D flow effects...

Aerodynamic characteristics of an oscillating airfoil. [For Vertical Axis Wind Turbine

Energy Technology Data Exchange (ETDEWEB)

Wickens, R H

1986-03-01

Results are reported from wind tunnel tests to study the effects of dynamic aerodynamics on the efficiency of a NACA 0018 airfoil used on a Darreius vertical axis wind turbine (VAWT). The topic is of interest because of uncontrolled pitching which occurs during operation and which produces stall, turbulence and separation effects that reduce efficiency. Present stream-tube theory and axial momentum models are not applicable in the unstable regimes. The wind tunnel tests were conducted with a 45 m/sec flow with an Re of 1.5 million. The situation mimicked typical wind turbine operational conditions. The airfoil was mounted on a hydraulic actuator to allow it to rotate about its quarter-chord location and to control the extent and frequency of oscillations. Data were also gathered on the performance in a steady flow for comparative purposes. Summary data are provided on the static and total pressures over a complete cycle of oscillation, and related to the angles of attack, time of onset of stall, and the lift and drag coefficients. The limitations of the study with regard to the absence of consideration of the flow acceleration experienced by an advancing blade are noted. 13 references.

Wind tunnel test on airfoil Riso-B1-18 with an Active Trailing Edge Flap

DEFF Research Database (Denmark)

Bak, Christian; Gaunaa, Mac; Andersen, Peter Bjørn

2010-01-01

A wind tunnel test of the wind turbine airfoil Risø-B1-18 equipped with an Active Trailing Edge Flap (ATEF) was carried out. The ATEF was 9% of the total chord, made of piezo electric actuators attached to the trailing edge of a non-deformable airfoil and actuated using an (electric) amplifier....... The airfoil was tested at Re = 1.66 × 106. Steady state and dynamic tests were carried out with prescribed deflections of the ATEF. The steady state tests showed that deflecting the ATEF towards the pressure side (positive ) translated the lift curve to higher lift values and deflecting the ATEF towards...... the suction side (negative ) translated the lift curve to lower lift values. Testing the airfoil for a step change of the ATEF from = -3.0 to +1.8 showed that the obtainable cl was 0.10 to 0.13 in the linear part of the lift curve. Modeling the step response with an indicial function formulation showed...

Propagation of Shock on NREL Phase VI Wind Turbine Airfoil under Compressible Flow

Directory of Open Access Journals (Sweden)

Mohammad A. Hossain

2013-01-01

Full Text Available The work is focused on numeric analysis of compressible flow around National Renewable Energy Laboratory (NREL phase VI wind turbine blade airfoil S809. Although wind turbine airfoils are low Reynolds number airfoils, a reasonable investigation of compressible flow under extreme condition might be helpful. A subsonic flow (mach no. M=0.8 has been considered for this analysis and the impacts of this flow under seven different angles of attack have been determined. The results show that shock takes place just after the mid span at the top surface and just before the mid span at the bottom surface at zero angle of attack. Slowly the shock waves translate their positions as angle of attack increases. A relative translation of the shock waves in upper and lower face of the airfoil are presented. Variation of Turbulent viscosity ratio and surface Y+ have also been determined. A k-ω SST turbulent model is considered and the commercial CFD code ANSYS FLUENT is used to find the pressure coefficient (Cp as well as the lift (CL and drag coefficients (CD. A graphical comparison of shock propagation has been shown with different angle of attack. Flow separation and stream function are also determined.

Design of wind turbine airfoils based on maximum power coefficient

DEFF Research Database (Denmark)

Cheng, Jiangtao; Chen, Jin; Cheng, Jiangtao

2010-01-01

Based on the blade element momentum (BEM) theory, the power coefficient of a wind turbine can be expressed in function of local tip speed ratio and lift-drag ratio. By taking the power coefficient in a predefined range of angle of attack as the final design objective and combining with an airfoil...

Innovative Design of a Darrieus Straight Bladed Vertical Axis Wind Turbine by using Multi Element Airfoil

DEFF Research Database (Denmark)

Chougle, Prasad Devendra

. Mainly, there is the horizontal axis wind turbine (HAWT) and vertical axis wind turbine (VAWT). HAWTs are more popular than VAWTs due to failure of VAWT commercialization during the late of 1980s on a large scale. However, in recent research work it has been documented that VAWTs are more economical......, and the wind tunnel testing of double-element airfoil is performed. It is found that the aerodynamic characteristics of the airfoil increased considerably by delaying the angle of stall. These two facts are very suitable for vertical axis wind turbine since they operate in a larger range of angle of attack......, ±40_, compared to the horizontal axis wind turbines which operate in the range of attack, ±15_. A new design of vertical axis wind turbine is then proposed, and aerodynamic performance is evaluated based on double multiple stream tube methods. The performance parameters are almost doubled compared...

Pressure distribution over an NACA 23012 airfoil with an NACA 23012 external-airfoil flap

Science.gov (United States)

Wenzinger, Carl J

1938-01-01

Report presents the results of pressure-distribution tests of an NACA 23012 airfoil with an NACA 23012 external airfoil flap made in the 7 by 10-foot wind tunnel. The pressures were measured on the upper and lower surfaces at one chord section on both the main airfoil and on the flap for several different flap deflections and at several angles of attack. A test installation was used in which the airfoil was mounted horizontally in the wind tunnel between vertical end planes so that two-dimensional flow was approximated. The data are presented in the form of pressure-distribution diagrams and as graphs of calculated coefficients for the airfoil-and-flap combination and for the flap alone.

Thick airfoil designs for the root of the 10MW INNWIND.EU wind turbine

Science.gov (United States)

Mu≁oz, A.; Méndez, B.; Munduate, X.

2016-09-01

The main objective of the “INNWIND.EU” project is to investigate and demonstrate innovative designs for 10-20MW offshore wind turbines and their key components, such as lightweight rotors. In this context, the present paper describes the development of two new airfoils for the blade root region. From the structural point of view, the root is the region in charge of transmitting all the loads of the blade to the hub. Thus, it is very important to include airfoils with adequate structural properties in this region. The present article makes use of high-thickness and blunt trailing edge airfoils to improve the structural characteristics of the airfoils used to build this blade region. CENER's (National Renewable Energy Center of Spain) airfoil design tool uses the airfoil software XFOIL to compute the aerodynamic characteristics of the designed airfoils. That software is based on panel methods which show some problems with the calculation of airfoils with thickness bigger than 35% and with blunt trailing edge. This drawback has been overcome with the development of an empirical correction for XFOIL lift and drag prediction based on airfoil experiments. From the aerodynamic point of view, thick airfoils are known to be very sensitive to surface contamination or turbulent inflow conditions. Consequently, the design optimization takes into account the aerodynamic torque in both clean and contaminated conditions. Two airfoils have been designed aiming to improve the structural and the aerodynamic behaviour of the blade in clean and contaminated conditions. This improvement has been corroborated with Blade Element Momentum (BEM) computations.

Thick airfoil designs for the root of the 10MW INNWIND.EU wind turbine

International Nuclear Information System (INIS)

Muñoz, A; Méndez, B; Munduate, X

2016-01-01

The main objective of the “INNWIND.EU” project is to investigate and demonstrate innovative designs for 10-20MW offshore wind turbines and their key components, such as lightweight rotors. In this context, the present paper describes the development of two new airfoils for the blade root region. From the structural point of view, the root is the region in charge of transmitting all the loads of the blade to the hub. Thus, it is very important to include airfoils with adequate structural properties in this region. The present article makes use of high-thickness and blunt trailing edge airfoils to improve the structural characteristics of the airfoils used to build this blade region. CENER's (National Renewable Energy Center of Spain) airfoil design tool uses the airfoil software XFOIL to compute the aerodynamic characteristics of the designed airfoils. That software is based on panel methods which show some problems with the calculation of airfoils with thickness bigger than 35% and with blunt trailing edge. This drawback has been overcome with the development of an empirical correction for XFOIL lift and drag prediction based on airfoil experiments. From the aerodynamic point of view, thick airfoils are known to be very sensitive to surface contamination or turbulent inflow conditions. Consequently, the design optimization takes into account the aerodynamic torque in both clean and contaminated conditions. Two airfoils have been designed aiming to improve the structural and the aerodynamic behaviour of the blade in clean and contaminated conditions. This improvement has been corroborated with Blade Element Momentum (BEM) computations. (paper)

Features of vertical axis wind turbine and development of airfoils sections; Chokusen yokugata suichoku jiku fusha no tokucho to yokugata ni kansuru kenkyu

Energy Technology Data Exchange (ETDEWEB)

Seki, K; Shimizu, Y; Yasui, T [Tokai University, Tokyo (Japan); Nakayama, H [Oriental Kiden Company, Osaka (Japan)

1996-10-27

Features of a straight wing type vertical axis wind turbine (VAW) and its airfoil sections were studied. The wind turbine in which various aerodynamic work components are mounted on the rotation axis normal to the ground surface is named VAW. Like the airfoil section of aircraft, in lift type VAW, wind turbines were driven by lift 70-90 times as large as drag in some cases. Features of the VAW airfoil section which is a straight wing in plan and a fixed pitch wing (with a fixed angle to a blade support arm) in cross section, and those of wind turbines were studied. Some factors affecting the features, work principle and performance of VAW were clarified. On airfoil sections, products of each weight function and each corresponding aerodynamic factor (lift, drag and pitching moment factors) were plotted on an attack angle ({alpha}) axis. From the conditions for increasing the total sum of areas drawn by the products on the {alpha} axis, various characteristics required for airfoil sections were clarified. Such characteristics nearly agreed between an airfoil section for favorable starting characteristics and that for high efficiency. 3 refs., 7 figs.

Design and preliminary testing of a MEMS microphone phased array for aeroacoustic testing of a small-scale wind turbine airfoil

Energy Technology Data Exchange (ETDEWEB)

Bale, A.; Orlando, S.; Johnson, D. [Waterloo Univ., ON (Canada). Wind Energy Group

2010-07-01

One of the barriers preventing the widespread utilization of wind turbines is the audible sound that they produce. Developing quieter wind turbines will increase the amount of available land onto which wind farms can be built. Noise emissions from wind turbines can be attributed to the aerodynamic effects between the turbine blades and the air surrounding them. A dominant source of these aeroacoustic emissions from wind turbines is known to originate at the trailing edges of the airfoils. This study investigated the flow physics of noise generation in an effort to reduce noise from small-scale wind turbine airfoils. The trailing edge noise was studied on scale-models in wind tunnels and applied to full scale conditions. Microphone phased arrays are popular research tools in wind tunnel aeroacoustic studies because they can measure and locate noise sources. However, large arrays of microphones can be prohibitively expensive. This paper presented preliminary testing of micro-electrical mechanical system (MEMS) microphones in phased arrays for aeroacoustic testing on a small wind turbine airfoil. Preliminary results showed that MEMS microphones are an acceptable low-cost alternative to costly condenser microphones. 19 refs., 1 tab., 11 figs.

Study on optimal design of wind turbine blade airfoil and its application

International Nuclear Information System (INIS)

Sun, Min Young; Kim, Dong Yong; Lim, Jae Kyoo

2012-01-01

This study was carried out with two goals. One was the development of a model of a wind turbine blade airfoil and the other was the application of the folding blade. In general, in large sized (MW) wind turbines, damage is prevented in small wind turbines since equipment costs and maintenance costs are high, and therefore, the blade will cause serious damage. The wind turbine proposed in this study does not require maintenance, and the blades do not break during high winds because they are folded in accordance with changes in the wind speed. But generators are not cut out, while maintaining a constant angle will continue to produce. The focus of this study, the wind turbine is continued by folding blade system in strong winds and gusts without stopping production

Study on optimal design of wind turbine blade airfoil and its application

Energy Technology Data Exchange (ETDEWEB)

Sun, Min Young; Kim, Dong Yong; Lim, Jae Kyoo [Chonbuk Nat' l Univ., Jeonju (Korea, Republic of)

2012-05-15

This study was carried out with two goals. One was the development of a model of a wind turbine blade airfoil and the other was the application of the folding blade. In general, in large sized (MW) wind turbines, damage is prevented in small wind turbines since equipment costs and maintenance costs are high, and therefore, the blade will cause serious damage. The wind turbine proposed in this study does not require maintenance, and the blades do not break during high winds because they are folded in accordance with changes in the wind speed. But generators are not cut out, while maintaining a constant angle will continue to produce. The focus of this study, the wind turbine is continued by folding blade system in strong winds and gusts without stopping production.

Numerical simulation of a wind turbine airfoil : part 1

Energy Technology Data Exchange (ETDEWEB)

Ramdenee, D.; Minea, I.S.; Tardiff d' Hamonville, T.; Illinca, A. [Quebec Univ., Rimouski, PQ (Canada). Laboratoire de Recherche en Energie Eolienne

2010-07-01

This 2-part study used computational fluid dynamics (CFD) to identify and model the aerodynamic and aeroelastic phenomena around wind turbine blades. The aim of the study was to better understand the mechanisms surrounding unsteady flow-structure interactions. Aerodynamic and elastic models were coupled using an ANSYS multi-domain program to simulate the aeroelastic divergence of a typical section airfoil with a single rotational structural degree of freedom. Solvers were used to realize a sequence of multi-domain time steps and coupling iterations between time steps. Each element of the airfoil was divided into interpolation faces which were then transformed into 2-D polygons. An intersection process was used to create a large number of control surfaces that were used to study interactions between the structural and fluid domains. The calculations were used to determine the divergence speed and Eigen modes of vibration. A literature review was also included. 19 refs., 7 figs.

Aerodynamic behavior of an airfoil with morphing trailing edge for wind turbine applications

Science.gov (United States)

Wolff, T.; Ernst, B.; Seume, J. R.

2014-06-01

The length of wind turbine rotor blades has been increased during the last decades. Higher stresses arise especially at the blade root because of the longer lever arm. One way to reduce unsteady blade-root stresses caused by turbulence, gusts, or wind shear is to actively control the lift in the blade tip region. One promising method involves airfoils with morphing trailing edges to control the lift and consequently the loads acting on the blade. In the present study, the steady and unsteady behavior of an airfoil with a morphing trailing edge is investigated. Two-dimensional Reynolds-Averaged Navier-Stokes (RANS) simulations are performed for a typical thin wind turbine airfoil with a morphing trailing edge. Steady-state simulations are used to design optimal geometry, size, and deflection angles of the morphing trailing edge. The resulting steady aerodynamic coefficients are then analyzed at different angles of attack in order to determine the effectiveness of the morphing trailing edge. In order to investigate the unsteady aerodynamic behavior of the optimal morphing trailing edge, time- resolved RANS-simulations are performed using a deformable grid. In order to analyze the phase shift between the variable trailing edge deflection and the dynamic lift coefficient, the trailing edge is deflected at four different reduced frequencies for each different angle of attack. As expected, a phase shift between the deflection and the lift occurs. While deflecting the trailing edge at angles of attack near stall, additionally an overshoot above and beyond the steady lift coefficient is observed and evaluated.

Aerodynamic behavior of an airfoil with morphing trailing edge for wind turbine applications

International Nuclear Information System (INIS)

Wolff, T; Ernst, B; Seume, J R

2014-01-01

The length of wind turbine rotor blades has been increased during the last decades. Higher stresses arise especially at the blade root because of the longer lever arm. One way to reduce unsteady blade-root stresses caused by turbulence, gusts, or wind shear is to actively control the lift in the blade tip region. One promising method involves airfoils with morphing trailing edges to control the lift and consequently the loads acting on the blade. In the present study, the steady and unsteady behavior of an airfoil with a morphing trailing edge is investigated. Two-dimensional Reynolds-Averaged Navier-Stokes (RANS) simulations are performed for a typical thin wind turbine airfoil with a morphing trailing edge. Steady-state simulations are used to design optimal geometry, size, and deflection angles of the morphing trailing edge. The resulting steady aerodynamic coefficients are then analyzed at different angles of attack in order to determine the effectiveness of the morphing trailing edge. In order to investigate the unsteady aerodynamic behavior of the optimal morphing trailing edge, time- resolved RANS-simulations are performed using a deformable grid. In order to analyze the phase shift between the variable trailing edge deflection and the dynamic lift coefficient, the trailing edge is deflected at four different reduced frequencies for each different angle of attack. As expected, a phase shift between the deflection and the lift occurs. While deflecting the trailing edge at angles of attack near stall, additionally an overshoot above and beyond the steady lift coefficient is observed and evaluated

Influence of transition on steady and unsteady wind-turbine airfoil aerodynamics

Science.gov (United States)

Paterson, Eric; Lavely, Adam; Vijayakumar, Ganesh; Brasseur, James

2011-11-01

Laminar-flow airfoils for large stall-regulated horizontal-axis wind turbines are designed to achieve a restrained maximum lift coefficient and a broad laminar low- drag bucket under steady flow conditions and at specific Reynolds numbers. Blind- comparisons of the 2000 NREL Unsteady Aerodynamics Experiment showed large discrepancies and illustrated the need for improved physics modeling. We have studied the S809 airfoil under static and dynamic (ramp-up, ramp-down, and oscillatory) conditions, using the four-equation transition model of Langtry and Menter (2009), which has been implemented as a library accessible by an OpenFOAM RANS solver. Model validation is performed using surface-pressure and lift/drag data from U. Glasgow (2009) and OSU (1995) wind tunnel experiments. Performance of the transition model is assessed by analyzing integrated performance metrics, as well as detailed surface pressure and pressure gradient, wall-shear stress, and boundary-layer profiles and separation points. Demonstration of model performance in the light- and deep-stall regimes of dynamic stall is an important step in reducing uncertainties in full 3D simulations of turbines operating in the atmospheric boundary layer. Supported by NSF Grant 0933647.

High Humidity Aerodynamic Effects Study on Offshore Wind Turbine Airfoil/Blade Performance through CFD Analysis

Directory of Open Access Journals (Sweden)

Weipeng Yue

2017-01-01

Full Text Available Damp air with high humidity combined with foggy, rainy weather, and icing in winter weather often is found to cause turbine performance degradation, and it is more concerned with offshore wind farm development. To address and understand the high humidity effects on wind turbine performance, our study has been conducted with spread sheet analysis on damp air properties investigation for air density and viscosity; then CFD modeling study using Fluent was carried out on airfoil and blade aerodynamic performance effects due to water vapor partial pressure of mixing flow and water condensation around leading edge and trailing edge of airfoil. It is found that the high humidity effects with water vapor mixing flow and water condensation thin film around airfoil may have insignificant effect directly on airfoil/blade performance; however, the indirect effects such as blade contamination and icing due to the water condensation may have significant effects on turbine performance degradation. Also it is that found the foggy weather with microwater droplet (including rainy weather may cause higher drag that lead to turbine performance degradation. It is found that, at high temperature, the high humidity effect on air density cannot be ignored for annual energy production calculation. The blade contamination and icing phenomenon need to be further investigated in the next study.

Experimental demonstration of wind turbine noise reduction through optimized airfoil shape and trailing-edge serrations

Energy Technology Data Exchange (ETDEWEB)

Oerlemans, S. [National Aerospace Laboratory NLR, Emmeloord (Netherlands); Schepers, J.G. [Unit Wind Energy, Energy research Centre of the Netherlands ECN, Petten (Netherlands); Guidati, G.; Wagner, S. [Institut fuer Aerodynamik und Gasdynamik IAG, Universitaet Stuttgart (Germany)

2001-07-15

The objective of the European project DATA (Design and Testing of Acoustically Optimized Airfoils for Wind Turbines) is a reduction of trailing-edge (TE) noise by modifying the airfoil shape and/or the application of trailing-edge serrations. This paper describes validation measurements that were performed in the DNW-LLF wind tunnel, on a model scale wind turbine with a two-bladed 4.5 m diameter rotor which was designed in the project. Measurements were done for one reference- and two acoustically optimized rotors, for varying flow conditions. The aerodynamic performance of the rotors was measured using a torque meter in the hub, and further aerodynamic information was obtained from flow visualization on the blades. The acoustic measurements were done with a 136 microphone out-of-flow acoustic array. Besides the location of the noise sources in the (stationary) rotor plane, a new acoustic processing method enabled identification of dominant noise source regions on the rotating blades. The results show dominant noise sources at the trailing-edge of the blade, close to the tip. The optimized airfoil shapes result in a significant reduction of TE noise levels with respect to the reference rotor, without loss in power production. A further reduction can be achieved by the application of trailing-edge serrations. The aerodynamic measurements are generally in good agreement with the aerodynamic predictions made during the design of the model turbine.

Viscous-inviscid method for the simulation of turbulent unsteady wind turbine airfoil flow

Energy Technology Data Exchange (ETDEWEB)

Bermudez, L.; Velazquez, A.; Matesanz, A. [Thermal Engineering Area, Carlos III University of Madrid, Avd. Universidad 30, 28911 Leganes, Madrid (Spain)

2002-06-01

A Viscous-inviscid interaction method is presented that allows for the simulation of unsteady airfoil flow in the context of wind turbine applications. The method couples a 2-D external unsteady potential flow to a 2-D unsteady turbulent boundary layer. The separation point on the airfoil leeward side is determined in a self-consistent way from the boundary-layer equations, and the separated flow region is modelled independently. Wake shape and motion are also determined in a self-consistent way, while an unsteady Kutta condition is implemented. The method is able to deal with attached flow and light stall situations characterised by unsteady turbulent boundary-layer separation size up to 50% of the airfoil chord length. The results of the validation campaign show that the method could be used for industrial design purposes because of its numerical robustness, reasonable accuracy, and limited computational time demands.

Design of a 21 m blade with Risø-A1 airfoils for active stall controlled wind turbines

DEFF Research Database (Denmark)

Fuglsang, Peter; Sangill, O.; Hansen, P.

2002-01-01

This is the final report, from the project, "Design of a Rotor/Airfoil Family for Active Stall-regulated Wind Turbines by Use of Multi-point Optimization". It describes the full scale testing of a 21 m wind turbine blade specially designed for active stallregulation. Design objectives were...... increased ratio of produced energy to turbine loads and more stable power control characteristics. Both were taken directly into account during the design of the blade using numerical optimization. The blade used theRisø-A1 airfoil family, which was specially designed for operation on wind turbine blades....... The new blade was designed to replace the LM 21.0P blade. A measurement campaign was carried out simultaneously on two identical adjacent wind turbines where onehad the new blades and the other had LM 21.0P blades. Power and loads including blade section moments for the new blades were measured to assess...

Vortex-Induced Vibration of an Airfoil Used in Vertical-Axis Wind Turbines

Science.gov (United States)

Benner, Bridget; Carlson, Daniel; Seyed-Aghazadeh, Banafsheh; Modarres-Sadeghi, Yahya

2017-11-01

In Vertical-axis wind turbines (VAWTs), when the blades are placed at high angles of attack with respect to the incoming flow, they could experience flow-induced oscillations. A series of experiments in a re-circulating water tunnel was conducted to study the possible Vortex-Induced Vibration (VIV) of a fully-submerged, flexibly-mounted NACA 0021 airfoil, which is used in some designs of VAWTs. The airfoil was free to oscillate in the crossflow direction, and the tests were conducted in a Reynolds number range of 600airfoil were measured at various angles of attack, α, in the range of 0< α<90. The airfoil was observed to oscillate in the range of 60< α<90, where α = 90 exhibited the widest lock-in range (1.67< U * <11.74) and the largest peak amplitude (A * = 1.93 at U * = 5.7). For all cases where oscillations were observed, the oscillation frequency remained close to the structure's natural frequency, defining a lock-in range. Flow visualization tests were also conducted to study the changes in the vortex shedding patterns. This research is supported in part by the National Science Foundation under NSF Award Numbers 1460461 and CBET-1437988.

BOUNDARY LAYER AND AMPLIFIED GRID EFFECTS ON AERODYNAMIC PERFORMANCES OF S809 AIRFOIL FOR HORIZONTAL AXIS WIND TURBINE (HAWT

Directory of Open Access Journals (Sweden)

YOUNES EL KHCHINE

2017-11-01

Full Text Available The design of rotor blades has a great effect on the aerodynamics performances of horizontal axis wind turbine and its efficiency. This work presents the effects of mesh refinement and boundary layer on aerodynamic performances of wind turbine S809 rotor. Furthermore, the simulation of fluid flow is taken for S809 airfoil wind turbine blade using ANSYS/FLUENT software. The problem is solved by the conservation of mass and momentum equations for unsteady and incompressible flow using advanced SST k-ω turbulence model, in order to predict the effects of mesh refinement and boundary layer on aerodynamics performances. Lift and drag coefficients are the most important parameters in studying the wind turbine performance, these coefficients are calculated for four meshes refinement and different angles of attacks with Reynolds number is 106. The study is applied to S809 airfoil which has 21% thickness, specially designed by NREL for horizontal axis wind turbines.

EUDP Project: Low Noise Airfoil - Final Report

DEFF Research Database (Denmark)

This document summarizes the scientific results achieved during the EUDP-funded project `Low-Noise Airfoil'. The goals of this project are, on one side to develop a measurement technique that permits the evaluation of trailing edge noise in a classical aerodynamic wind tunnel, and on the other side...... to develop and implement a design procedure to manufacture airfoil profiles with low noise emission. The project involved two experimental campaigns: one in the LM Wind Power wind tunnel, a classical aerodynamic wind tunnel, in Lunderskov (DK), the second one in the Virginia Tech Stability Wind Tunnel....... In particular, the so-called TNO trailing edge noise model could be significantly improved by introducing turbulence anisotropy in its formulation, as well as the influence of the boundary layer mean pressure gradient. This two characteristics are inherent to airfoil flows but were neglected in the original...

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

Directory of Open Access Journals (Sweden)

Yilei He

2014-01-01

Full Text Available 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-equation k-ω SST 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.

Discontinuous Galerkin methodology for Large-Eddy Simulations of wind turbine airfoils

DEFF Research Database (Denmark)

Frére, A.; Sørensen, Niels N.; Hillewaert, K.

2016-01-01

This paper aims at evaluating the potential of the Discontinuous Galerkin (DG) methodology for Large-Eddy Simulation (LES) of wind turbine airfoils. The DG method has shown high accuracy, excellent scalability and capacity to handle unstructured meshes. It is however not used in the wind energy...... sector yet. The present study aims at evaluating this methodology on an application which is relevant for that sector and focuses on blade section aerodynamics characterization. To be pertinent for large wind turbines, the simulations would need to be at low Mach numbers (M ≤ 0.3) where compressible...... at low and high Reynolds numbers and compares the results to state-of-the-art models used in industry, namely the panel method (XFOIL with boundary layer modeling) and Reynolds Averaged Navier-Stokes (RANS). At low Reynolds number (Re = 6 × 104), involving laminar boundary layer separation and transition...

Research on design methods and aerodynamics performance of CQUDTU-B21 airfoil

DEFF Research Database (Denmark)

Chen, Jin; Cheng, Jiangtao; Wen, Zhong Shen

2012-01-01

This paper presents the design methods of CQU-DTU-B21 airfoil for wind turbine. Compared with the traditional method of inverse design, the new method is described directly by a compound objective function to balance several conflicting requirements for design wind turbine airfoils, which based...... on design theory of airfoil profiles, blade element momentum (BEM) theory and airfoil Self-Noise prediction model. And then an optimization model with the target of maximum power performance on a 2D airfoil and low noise emission of design ranges for angle of attack has been developed for designing CQU......-DTU-B21 airfoil. To validate the optimization results, the comparison of the aerodynamics performance by XFOIL and wind tunnels test respectively at Re=3×106 is made between the CQU-DTU-B21 and DU93-W-210 which is widely used in wind turbines. © (2012) Trans Tech Publications, Switzerland....

Design of the LRP airfoil series using 2D CFD

DEFF Research Database (Denmark)

Zahle, Frederik; Bak, Christian; Sørensen, Niels N.

2014-01-01

This paper describes the design and wind tunnel testing of a high-Reynolds number, high lift airfoil series designed for wind turbines. The airfoils were designed using direct gradient- based numerical multi-point optimization based on a Bezier parameterization of the shape, coupled to the 2D...... Navier-Stokes flow solver EllipSys2D. The resulting airfoils, the LRP2-30 and LRP2-36, achieve both higher operational lift coefficients and higher lift to drag ratios compared to the equivalent FFA-W3 airfoils....

Design of the LRP airfoil series using 2D CFD

International Nuclear Information System (INIS)

Zahle, Frederik; Bak, Christian; Sørensen, Niels N; Vronsky, Tomas; Gaudern, Nicholas

2014-01-01

This paper describes the design and wind tunnel testing of a high-Reynolds number, high lift airfoil series designed for wind turbines. The airfoils were designed using direct gradient- based numerical multi-point optimization based on a Bezier parameterization of the shape, coupled to the 2D Navier-Stokes flow solver EllipSys2D. The resulting airfoils, the LRP2-30 and LRP2-36, achieve both higher operational lift coefficients and higher lift to drag ratios compared to the equivalent FFA-W3 airfoils

Profile catalogue for airfoil sections based on 3D computations

DEFF Research Database (Denmark)

Bertagnolio, F.; Sørensen, Niels N.; Johansen, Jeppe

2006-01-01

This report is a continuation of the Wind Turbine Airfoil Catalogue [1] which objective was, firstly to provide a database of aerodynamic characteristics for a wide range of airfoil profiles aimed at wind turbine applications, and secondly to test thetwo-dimensional Navier-Stokes solver EllipSys2D...... and the actual fluid flow, and thereby the incorrect prediction of airfoil characteristics. In addition, other features of the flow solver, such astransition and turbulence modelling, and their influence onto the numerical results are investigated. Conclusions are drawn regarding the evaluation of airfoil...

Wind Tunnel Aeroacoustic Tests of Six Airfoils for Use on Small Wind Turbines; Period of Performance: August 23, 2002 through March 31, 2004

Energy Technology Data Exchange (ETDEWEB)

Oerlemans, S.

2004-08-01

The U.S. Department of Energy, working through the National Renewable Energy Laboratory, is engaged in a comprehensive research effort to improve our understanding of wind turbine aeroacoustics. Quiet wind turbines are an inducement to widespread deployment, so the goal of NREL's aeroacoustic research is to develop tools that the U.S. wind industry can use in developing and deploying highly efficient, quiet wind turbines at low wind speed sites. NREL's National Wind Technology Center is implementing a multifaceted approach that includes wind tunnel tests, field tests, and theoretical analyses in direct support of low wind speed turbine development by its industry partners. To that end, wind tunnel aerodynamic tests and aeroacoustic tests have been performed on six airfoils that are candidates for use on small wind turbines. Results are documented in this report.

On the influence of virtual camber effect on airfoil polars for use in simulations of Darrieus wind turbines

International Nuclear Information System (INIS)

Rainbird, John M.; Bianchini, Alessandro; Balduzzi, Francesco; Peiró, Joaquim; Graham, J. Michael R.; Ferrara, Giovanni; Ferrari, Lorenzo

2015-01-01

Highlights: • Darrieus wind turbine blades are affected by virtual camber. • A NACA 0018 and two transforms of it shaped after virtual camber theory are tested. • A blockage tolerant wind tunnel test section is used for experiments. • Turbine numerical simulations for the same airfoils are compared to experiments. • Virtual camber corrections for low order simulation models are recommended. - Abstract: Darrieus vertical-axis wind turbines are experiencing renewed interest from researchers and manufacturers, though their efficiencies still lag those of horizontal-axis wind turbines. A better understanding of their aerodynamics is required to improve on designs, for example through the development of more accurate low-order (e.g. blade element momentum) models. Many of these models neglect the impact of the curved paths that are followed by blades on their performance. It has been theorized that the curved streamlines of the flow impart a virtual camber and incidence on them, giving a performance analogous to a cambered blade in a rectilinear flow. To test the extent of this effect, wind tunnel experiments have been conducted in a rectilinear flow to obtain lift and drag for three airfoils: a NACA 0018 and two conformal transforms of the profile. The transformed airfoils exhibit the virtual camber that the theory predicts is imparted to a NACA 0018 when used in a Darrieus turbine with blade chord-to-turbine radius ratios, c/R, of 0.114 and 0.25. A parallel computational fluid dynamics campaign has been conducted to study the aerodynamic behavior of the same blades in curvilinear flow in Darrieus-like motion with c/R = 0.114 and 0.25, at tip–speed ratios of 2.1 and 3.1, using novel techniques to obtain blade effective angles of attack. The analysis confirms that the theory holds, with the wind tunnel results for the NACA 0018 being analogous to numerical results for the relevant cambered airfoils. In addition, turbine performance is calculated using

Nonlinear aeroelastic behavior of compliant airfoils

International Nuclear Information System (INIS)

Thwapiah, G; Campanile, L F

2010-01-01

Since the beginning of aviation and up to the present time, airfoils have always been built as rigid structures. They are designed to fly under their divergence speed in order to avoid static aeroelastic instabilities and the resulting large deformations, which are not compatible with the typically low compliance of such airfoils. In recent years, research on airfoil morphing has generated interest in innovative ideas like the use of compliant systems, i.e. systems built to allow for large deformations without failure, in airfoil construction. Such systems can operate in the neighborhood of divergence and take advantage of large aeroelastic servo-effects. This, in turn, allows compact, advanced actuators to control the airfoil's deformation and loads, and hence complement or even replace conventional flaps. In order to analyze and design such compliant, active aeroelastic structures a nonlinear approach to static aeroelasticity is needed, which takes into account the effect of large deformations on aerodynamics and structure. Such an analytical approach is presented in this paper and applied to a compliant passive airfoil as the preliminary step in the realization of a piezoelectrically driven, active aeroelastic airfoil. Wind tunnel test results are also presented and compared with the analytic prediction. The good agreement and the observed behavior in the wind tunnel give confidence in the potential of this innovative idea

Nonlinear aeroelastic behavior of compliant airfoils

Science.gov (United States)

Thwapiah, G.; Campanile, L. F.

2010-03-01

Since the beginning of aviation and up to the present time, airfoils have always been built as rigid structures. They are designed to fly under their divergence speed in order to avoid static aeroelastic instabilities and the resulting large deformations, which are not compatible with the typically low compliance of such airfoils. In recent years, research on airfoil morphing has generated interest in innovative ideas like the use of compliant systems, i.e. systems built to allow for large deformations without failure, in airfoil construction. Such systems can operate in the neighborhood of divergence and take advantage of large aeroelastic servo-effects. This, in turn, allows compact, advanced actuators to control the airfoil's deformation and loads, and hence complement or even replace conventional flaps. In order to analyze and design such compliant, active aeroelastic structures a nonlinear approach to static aeroelasticity is needed, which takes into account the effect of large deformations on aerodynamics and structure. Such an analytical approach is presented in this paper and applied to a compliant passive airfoil as the preliminary step in the realization of a piezoelectrically driven, active aeroelastic airfoil. Wind tunnel test results are also presented and compared with the analytic prediction. The good agreement and the observed behavior in the wind tunnel give confidence in the potential of this innovative idea.

Inviscid double wake model for stalled airfoils

International Nuclear Information System (INIS)

Marion, L; Ramos-García, N; Sørensen, J N

2014-01-01

An inviscid double wake model based on a steady two-dimensional panel method has been developed to predict aerodynamic loads of wind turbine airfoils in the deep stall region. The separated flow is modelled using two constant vorticity sheets which are released at the trailing edge and at the separation point. A calibration of the code through comparison with experiments has been performed using one set of airfoils. A second set of airfoils has been used for the validation of the calibrated model. Predicted aerodynamic forces for a wide range of angles of attack (0 to 90 deg) are in overall good agreement with wind tunnel measurements

EUDP project 'Low noise airfoil' - Final report

Energy Technology Data Exchange (ETDEWEB)

Bertagnolio, F. (ed.)

2012-06-15

This document summarizes the scientific results achieved during the EUDP-funded project 'Low-Noise Airfoil'. The goals of this project are, on one side to develop a measurement technique that permits the evaluation of trailing edge noise in a classical aerodynamic wind tunnel, and on the other side to develop and implement a design procedure to manufacture airfoil profiles with low noise emission. The project involved two experimental campaigns: one in the LM Wind Power wind tunnel, a classical aerodynamic wind tunnel, in Lunderskov (Denmark), the second one in the Virginia Tech Stability Wind Tunnel at the Aerospace and Ocean Engineering Department of Virginia Tech (Blacksburg, VA, USA), also a classical aerodynamic wind tunnel but equipped with an anechoic chamber that allow to perform acoustic measurements. On the theoretical side, the above experiments yield a series of model validations and improvements. In particular, the so-called TNO trailing edge noise model could be significantly improved by introducing turbulence anisotropy in its formulation, as well as the influence of the boundary layer mean pressure gradient. This two characteristics are inherent to airfoil flows but were neglected in the original approach. In addition, the experimental results are confronted to detailed Large Eddy Simulations of the airfoil flow giving more insight into the flow turbulence characteristics. The methodology which consists in measuring surface pressure spectra directly on the airfoil surface using flush-mounted microphones in order to evaluate far-field noise emission using additional theoretical results has been validated. This technique presents the advantage that it can easily be used in a classical aerodynamic wind tunnel and does not require the use of an anechoic facility. It was developed as a substitute to the original plan that consisted in measuring acoustic waves using hot-wire velocimetry. This last technique proved ineffective in the LM Wind

Presentations from the Aeroelastic Workshop - latest results from AeroOpt

Energy Technology Data Exchange (ETDEWEB)

Hartvig Hansen, M. (ed.)

2011-10-15

This report contains the slides of the presentations at the Aeroelastic Workshop held at Risoe-DTU for the wind energy industry in Denmark on October 27, 2011. The scientific part of the agenda at this workshop was 1) Detailed and reduced models of dynamic mooring system (Anders M. Hansen). 2) Bend-twist coupling investigation in HAWC2 (Taeseong Kim). 3) Q3UIC - A new aerodynamic airfoil tool including rotational effects (Nestor R. Garcia). 4) Influence of up-scaling on loads, control and aerodynamic modeling (Helge Aa. Madsen). 5) Aerodynamic damping of lateral tower vibrations (Bjarne S. Kallesoee). 6) Open- and closed-loop aeroservoelastic analysis with HAWCStab2 (Morten H. Hansen). 7) Design and test of a thick, flatback, high-lift multielement airfoil (Frederik Zahle). The presented results are mainly obtained in the EUDP project ''Aeroelastic Optimization of MW Wind Turbines (AeroOpt)''. (Author)

Desirable airfoil features for smaller-capacity straight-bladed VAWT

Energy Technology Data Exchange (ETDEWEB)

Islam, Mazharul; Ting, D.S.-K.; Fartaj, Amir

2007-05-15

In the small scale wind turbine market, the simple straight-bladed Darrieus type vertical axis wind turbine (SB-VAWT) is very attractive for its simple blade design. A detailed aerodynamic performance analysis was conducted on a smaller capacity fixed-pitch SB-VAWT. Brief analyses of the main aerodynamic challenges of this type of wind turbine were first discussed and subsequently the authors conducted further literature survey and computational analysis to shortlist aerodynamic characteristics of a desirable airfoil for a self-starting and better performing SB-VAWT. The required geometric features of the desirable airfoil to achieve the short listed characteristics were also discussed. It has been found out that conventionally used NACA symmetric airfoils are not suitable for smaller capacity SB-VAWT. Rather, it is advantageous to utilize a high-lift and low-drag asymmetric thick airfoil suitable for low speed operation typically encountered by SB-VAWT. (author)

Investigation of the two-element airfoil with flap structure for the vertical axis wind turbine

International Nuclear Information System (INIS)

Wei, Y; Li, C

2013-01-01

The aerodynamic performance of Vertical axis wind turbine (VAWT) is not as simple as its structure because of the large changing range of angle of attack. We have designed a new kind of two-element airfoil for VAWT on the basis of NACA0012. CFD calculation has been confirmed to have high accuracy by comparison with the experiment data and Xfoil result. The aerodynamic parameter of two-element airfoil has been acquired by CFD calculation in using the Spalart-Allmaras (S-A) turbulence model and the Simple scheme. The relationship between changings of angle of attack and flap's tilt angle has been found and quantified. The analysis will lay the foundation for further research on the control method for VAWT

Numerical modeling of a pitch oscillating S809 airfoil dynamic stall in 2D with application to a horizontal axis wind turbine

Energy Technology Data Exchange (ETDEWEB)

Gharali, K.; Johnson, D.A. [Waterloo Univ., ON (Canada). Dept. of Mechanical and Mechatronics Engineering, Wind Energy Group

2010-07-01

Natural wind can sometimes have a strong wind shear that causes the Dynamic Stall (DS) phenomena which may result in dynamic loads and varying lift coefficients. The DS phenomena cannot be prevented in horizontal axis wind turbines (HAWTs). Therefore, it is necessary to study the unsteady aerodynamics in order to modify common wind turbine rotor designs. This paper reported on a study that investigated the dynamic flow fields around an oscillating 2D S809 airfoil, representing the aerodynamic characteristics of HAWT airfoils for dynamic stall conditions. A computational fluid dynamic (CFD) flow solver package with Fluent was used with different turbulence models, notably the Spalart-Allmaras and Detached Eddy Simulation (DES) methods. A sliding mesh is commonly used in numerical methods for simulating an oscillating foil, but sliding meshes suffer from mesh generation complexity and increased computational time. In this study, instead of a sinusoidally pitching airfoil, the direction of the far-field flow was changed according to a user-defined function in the software to simulate a proper angle of attack for the boundary conditions in each time step. This strategy helped to decrease processing time. The simulation results were in good agreement with experimental data and the Beddoes-Leishman model results. The DES method for unsteady 2D flow was not recommended. It was concluded that the Fluent package is time efficient, reliable and economic for the wind turbine industry. 17 refs., 3 figs.

Vertical axis wind turbines

Science.gov (United States)

Krivcov, Vladimir [Miass, RU; Krivospitski, Vladimir [Miass, RU; Maksimov, Vasili [Miass, RU; Halstead, Richard [Rohnert Park, CA; Grahov, Jurij [Miass, RU

2011-03-08

A vertical axis wind turbine is described. The wind turbine can include a top ring, a middle ring and a lower ring, wherein a plurality of vertical airfoils are disposed between the rings. For example, three vertical airfoils can be attached between the upper ring and the middle ring. In addition, three more vertical airfoils can be attached between the lower ring and the middle ring. When wind contacts the vertically arranged airfoils the rings begin to spin. By connecting the rings to a center pole which spins an alternator, electricity can be generated from wind.

Predicting the aerodynamic characteristics of 2D airfoil and the performance of 3D wind turbine using a CFD code

Energy Technology Data Exchange (ETDEWEB)

Kim, Bum Suk; Kim, Mann Eung [Korean Register of Shipping, Daejeon (Korea, Republic of); Lee, Young Ho [Korea Maritime Univ., Busan (Korea, Republic of)

2008-07-15

Despite of the laminar-turbulent transition region co-exist with fully turbulence region around the leading edge of an airfoil, still lots of researchers apply to fully turbulence models to predict aerodynamic characteristics. It is well known that fully turbulent model such as standard k-model couldn't predict the complex stall and the separation behavior on an airfoil accurately, it usually leads to over prediction of the aerodynamic characteristics such as lift and drag forces. So, we apply correlation based transition model to predict aerodynamic performance of the NREL (National Renewable Energy Laboratory) Phase IV wind turbine. And also, compare the computed results from transition model with experimental measurement and fully turbulence results. Results are presented for a range of wind speed, for a NREL Phase IV wind turbine rotor. Low speed shaft torque, power, root bending moment, aerodynamic coefficients of 2D airfoil and several flow field figures results included in this study. As a result, the low speed shaft torque predicted by transitional turbulence model is very good agree with the experimental measurement in whole operating conditions but fully turbulent model(K- {epsilon}) over predict the shaft torque after 7m/s. Root bending moment is also good agreement between the prediction and experiments for most of the operating conditions, especially with the transition model.

Predicting the aerodynamic characteristics of 2D airfoil and the performance of 3D wind turbine using a CFD code

International Nuclear Information System (INIS)

Kim, Bum Suk; Kim, Mann Eung; Lee, Young Ho

2008-01-01

Despite of the laminar-turbulent transition region co-exist with fully turbulence region around the leading edge of an airfoil, still lots of researchers apply to fully turbulence models to predict aerodynamic characteristics. It is well known that fully turbulent model such as standard k-model couldn't predict the complex stall and the separation behavior on an airfoil accurately, it usually leads to over prediction of the aerodynamic characteristics such as lift and drag forces. So, we apply correlation based transition model to predict aerodynamic performance of the NREL (National Renewable Energy Laboratory) Phase IV wind turbine. And also, compare the computed results from transition model with experimental measurement and fully turbulence results. Results are presented for a range of wind speed, for a NREL Phase IV wind turbine rotor. Low speed shaft torque, power, root bending moment, aerodynamic coefficients of 2D airfoil and several flow field figures results included in this study. As a result, the low speed shaft torque predicted by transitional turbulence model is very good agree with the experimental measurement in whole operating conditions but fully turbulent model(K- ε) over predict the shaft torque after 7m/s. Root bending moment is also good agreement between the prediction and experiments for most of the operating conditions, especially with the transition model

Numerical simulation of airfoil trailing edge serration noise

DEFF Research Database (Denmark)

Zhu, Wei Jun; Shen, Wen Zhong

In the present work, numerical simulations are carried out for a low noise airfoil with and without serrated Trailing Edge. The Ffowcs Williams-Hawkings acoustic analogy is implemented into the in-house incompressible flow solver EllipSys3D. The instantaneous hydrodynamic pressure and velocity...... field are obtained using Large Eddy Simulation. To obtain the time history data of sound pressure, the flow quantities are integrated around the airfoil surface through the FW-H approach. The extended length of the serration is about 16.7% of the airfoil chord and the geometric angle of the serration...... is 28 degrees. The chord based Reynolds number is around 1.5x106. Simulations are compared with existing wind tunnel experiments at various angles of attack. Even though the airfoil under investigation is already optimized for low noise emission, numerical simulations and wind tunnel experiments show...

基于海鸥翼型的小型风力机叶片仿生设计与试验%Bionic design and test of small-sized wind turbine blade based on seagull airfoil

Institute of Scientific and Technical Information of China (English)

王骥月; 丛茜; 梁宁; 毛士佳; 关欢欢; 刘林鹏; 陈创发

2015-01-01

针对现有小型风力发电机效率远低于理论值问题，对100 W水平轴风力机叶片进行仿生改进。采用Spalart-Allmaras模型分析不同攻角下海鸥翼型与标准翼型的气动特性；以标准100 W水平轴风力机叶片为原型，结合海鸥翼型、标准弦长和计算得出的安装角，设计得到仿海鸥翼型叶片；利用SST k-ω模型进行仿海鸥翼型叶片与标准叶片气动特性数值模拟；搭建室内风力机效率测试平台，进行仿海鸥翼型风力机与标准风力机效率对比试验。结果表明：海鸥翼型气动性能优良，最大升力系数是标准翼型的2.19倍，最大升阻比是标准翼型的1.34倍；仿海鸥翼型叶片与标准叶片相比，输出功率提高25.77%。该研究可为小型风力发电机的改进设计提供参考。%Power of the existing small-sized wind turbine blades is much less than the theoretical value. This study improved 100 W wind turbine blades to increase the power of wind turbine. First of all, Spalart-Allmaras model which was suitable for airfoil stalling characteristics research was used to analyze the aerodynamic characteristics of seagull airfoil and standard airfoil with different angles of attack (AOA). Seagull airfoil and standard airfoil were got from seagull wing and standard blade by portable three-dimension scanner, Imageware software and Geomagic Studio software through standard blade scan, seagull wing scan, point cloud processing, reverse engineering modeling and cross section capture. Lift coefficients and lift-drag ratios of seagull airfoil and standard airfoil were calculated by Fluent software. Secondly, bionic blade was designed based on standard 100 W blades and Glauert theory. Thirdly, numerical simulations of bionic blade and standard blade were performed by using SST(shear stress transport) k-ω model which was suitable for blade performance research to analyze the aerodynamic characteristics of bionic blade and standard

Effects of Inclined Treadmill Walking on Pelvic Anterior Tilt Angle, Hamstring Muscle Length, and Trunk Muscle Endurance of Seated Workers with Flat-back Syndrome.

Science.gov (United States)

Kim, Min-Hee; Yoo, Won-Gyu

2014-06-01

[Purpose] This study investigated the effects of inclined treadmill walking on pelvic anterior tilt angle, hamstring muscle length, and back muscle endurance of seated workers with flat-back syndrome. [Subjects] Eight seated workers with flat-back syndrome who complained of low-back pain in the L3-5 region participated in this study. [Methods] The subjects performed a walking exercise on a 30° inclined treadmill. We measured the pelvic anterior tilt angle, hamstring muscle length, and back muscle endurance before and after inclined treadmill walking. [Results] Anterior pelvic tilt angle and active knee extension angle significantly increased after inclined treadmill walking. Trunk extensor and flexor muscle endurance times were also significantly increased compared to the baseline. [Conclusion] Inclined treadmill walking may be an effective approach for the prevention or treatment of low-back pain in flat-back syndrome.

Overview of results from 2D airfoil testing at Risoe

Energy Technology Data Exchange (ETDEWEB)

Fuglsang, P. [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark)

1997-12-31

This paper gives an overview of the results from two dimensional airfoil testing at Risoe. A two dimensional testing method was recently developed where a test rig is inserted into an open jet flow in a wind tunnel of the close return loop type with an open test section. Pressure measurements provide the lift and drag forces. Both stationary flow and dynamic inflow from pitch motion are possible. The wind tunnel static pressure and total dynamic pressures were calibrated and wind tunnel boundary corrections were found. So far, the testing method was verified by comparison of NACA 63-215 airfoil measurements to numerical predictions and to measurements. Furthermore, the Risoe-1, FFA-W3-241, FFA-W3-301 and NACA 63-430 airfoils were measured. Different types of leading edge roughness and vortex generators were investigated. For all airfoils, good agreements with predictions were obtained on both pressure distribution and on lift coefficient. The drag coefficients were slightly higher than predicted. (eg) 10 refs.

Airfoil optimization for noise emission problem on small scale turbines

Energy Technology Data Exchange (ETDEWEB)

Gocmen, Tuhfe; Ozerdem, Baris [Mechanical Engineering Department, Yzmir Institute of Technology (Turkey)

2011-07-01

Wind power is a preferred natural resource and has had benefits for the energy industry and for the environment all over the world. However, noise emission from wind turbines is becoming a major concern today. This study paid close attention to small scale wind turbines close to urban areas and proposes an optimum number of six airfoils to address noise emission concerns and performance criteria. The optimization process aimed to decrease the noise emission levels and enhance the aerodynamic performance of a small scale wind turbine. This study determined the sources and the operating conditions of broadband noise emissions. A new design is presented which enhances aerodynamic performance and at the same time reduces airfoil self noise. It used popular aerodynamic functions and codes based on aero-acoustic empirical models. Through numerical computations and analyses, it is possible to derive useful improvements that can be made to commercial airfoils for small scale wind turbines.

Numerical calculation of aerodynamics wind turbine blade S809 airfoil and comparison of theoretical calculations with experimental measurements and confirming with NREL data

Science.gov (United States)

Sogukpinar, Haci; Bozkurt, Ismail

2018-02-01

Aerodynamic performance of the airfoil plays the most important role to obtain economically maximum efficiency from a wind turbine. Therefore airfoil should have an ideal aerodynamic shape. In this study, aerodynamic simulation of S809 airfoil is conducted and obtained result compared with previously made NASA experimental result and NREL theoretical data. At first, Lift coefficient, lift to drag ratio and pressure coefficient around S809 airfoil are calculated with SST turbulence model, and are compared with experimental and other theoretical data to correlate simulation correctness of the computational approaches. And result indicates good correlation with both experimental and theoretical data. This calculation point out that as the increasing relative velocity, lift to drag ratio increases. Lift to drag ratio attain maximum at the angle around 6 degree and after that starts to decrease again. Comparison shows that CFD code used in this calculation can predict aerodynamic properties of airfoil.

An overview of NACA 6-digit airfoil series characteristics with reference to airfoils for large wind turbine blades

NARCIS (Netherlands)

Timmer, W.A.

2009-01-01

This paper investigates the NACA 63 and 64 6-digit series of airfoils tested in the NACA LTPT in view to verify the RFOIL calculated airfoil characteristics for high Reynolds numbers. Some anomalies in the zero-lift angles of 15% and 18% thick airfoils from these series are identified, both in the

Pitching Airfoil Boundary Layer Investigations

OpenAIRE

Raffel, Markus; Richard, Hugues; Richter, Kai; Bosbach, Johannes; Geißler, Wolfgang

2006-01-01

The present paper describes an experiment performed in a transonic wind tunnel facility where a new test section has been developed especially for the investigation of the unsteady flow above oscillating airfoils under dynamic stall conditions. Dynamic stall is characterized by the development, movement and shedding of one or more concentrated vortices on the airfoils upper surface. The hysteresis loops of lift-, drag- and pitching moment are highly influenced by these vortices. To understand...

Artificial intelligence metamodel comparison and application to wind turbine airfoil uncertainty analysis

Directory of Open Access Journals (Sweden)

Yaping Ju

2016-05-01

Full Text Available The Monte Carlo simulation method for turbomachinery uncertainty analysis often requires performing a huge number of simulations, the computational cost of which can be greatly alleviated with the help of metamodeling techniques. An intensive comparative study was performed on the approximation performance of three prospective artificial intelligence metamodels, that is, artificial neural network, radial basis function, and support vector regression. The genetic algorithm was used to optimize the predetermined parameters of each metamodel for the sake of a fair comparison. Through testing on 10 nonlinear functions with different problem scales and sample sizes, the genetic algorithm–support vector regression metamodel was found more accurate and robust than the other two counterparts. Accordingly, the genetic algorithm–support vector regression metamodel was selected and combined with the Monte Carlo simulation method for the uncertainty analysis of a wind turbine airfoil under two types of surface roughness uncertainties. The results show that the genetic algorithm–support vector regression metamodel can capture well the uncertainty propagation from the surface roughness to the airfoil aerodynamic performance. This work is useful to the application of metamodeling techniques in the robust design optimization of turbomachinery.

Cross-Validation of Numerical and Experimental Studies of Transitional Airfoil Performance

DEFF Research Database (Denmark)

Frere, Ariane; Hillewaert, Koen; Sarlak, Hamid

2015-01-01

The aerodynamic performance characteristic of airfoils are the main input for estimating wind turbine blade loading as well as annual energy production of wind farms. For transitional flow regimes these data are difficult to obtain, both experimentally as well as numerically, due to the very high...... sensitivity of the flow to perturbations, large scale separation and performance hysteresis. The objective of this work is to improve the understanding of the transitional airfoil flow performance by studying the S826 NREL airfoil at low Reynolds numbers (Re = 4:104 and 1:105) with two inherently different...

Comparison of measured and predicted airfoil self-noise with application to wind turbine noise reduction

International Nuclear Information System (INIS)

Dassen, T.; Parchen, R.; Guidati, G.; Wagner, S.; Kang, S.; Khodak, A.E.

1998-01-01

In the ongoing JOULE-III project 'Development of Design Tools for Reduced Aerodynamic Noise Wind Turbines (DRAW)', prediction codes for inflow-turbulence (IT) noise and turbulent boundary layer trailing-edge (TE) noise, are developed and validated. It is shown that the differences in IT noise radiation between airfoils having a different shape, are correctly predicted. The first, preliminary comparison made between predicted and measured TE noise spectra yields satisfactory results. 17 refs

Aerodynamic Analysis of Trailing Edge Enlarged Wind Turbine Airfoils

DEFF Research Database (Denmark)

Xu, Haoran; Shen, Wen Zhong; Zhu, Wei Jun

2014-01-01

characteristics of blunt trailing edge airfoils are caused by blunt body vortices at low angles of attack, and by the combined effect of separation and blunt body vortices at large angles of attack. With the increase of thickness of blunt trailing edge, the vibration amplitudes of lift and drag curves increase......The aerodynamic performance of blunt trailing edge airfoils generated from the DU- 91-W2-250, DU-97-W-300 and DU-96-W-350 airfoils by enlarging the thickness of trailing edge symmetrically from the location of maximum thickness to chord to the trailing edge were analyzed by using CFD and RFOIL...... methods at a chord Reynolds number of 3 × 106. The goal of this study is to analyze the aerodynamic performance of blunt trailing edge airfoils with different thicknesses of trailing edge and maximum thicknesses to chord. The steady results calculated by the fully turbulent k-ω SST, transitional k-ω SST...

Airfoils in Turbulent Inflow

DEFF Research Database (Denmark)

Gilling, Lasse

of resolved inflow turbulence on airfoil simulations in CFD. The detached-eddy simulation technique is used because it can resolve the inflow turbulence without becoming too computationally expensive due to its limited requirements for mesh resolution in the boundary layer. It cannot resolve the turbulence......Wind turbines operate in inflow turbulence whether it originates from the shear in the atmospheric boundary layer or from the wake of other wind turbines. Consequently, the airfoils of the wings experience turbulence in the inflow. The main topic of this thesis is to investigate the effect...... that is formed in attached boundary layers, but the freestream turbulence can penetrate the boundary layer. The idea is that the resolved turbulence from the freestream should mix high momentum flow into the boundary layer and thereby increase the resistance against separation and increase the maximum lift...

Aerodynamic Optimization of Airfoil Profiles for Small Horizontal Axis Wind Turbines

Directory of Open Access Journals (Sweden)

Ali Cemal Benim

2018-04-01

Full Text Available The purpose of this study is the development of an automated two-dimensional airfoil shape optimization procedure for small horizontal axis wind turbines (HAWT, with an emphasis on high thrust and aerodynamically stable performance. The procedure combines the Computational Fluid Dynamics (CFD analysis with the Response Surface Methodology (RSM, the Biobjective Mesh Adaptive Direct Search (BiMADS optimization algorithm and an automatic geometry and mesh generation tool. In CFD analysis, a Reynolds Averaged Numerical Simulation (RANS is applied in combination with a two-equation turbulence model. For describing the system behaviour under alternating wind conditions, a number of CFD 2D-RANS-Simulations with varying Reynolds numbers and wind angles are performed. The number of cases is reduced by the use of RSM. In the analysis, an emphasis is placed upon the role of the blade-to-blade interaction. The average and the standard deviation of the thrust are optimized by a derivative-free optimization algorithm to define a Pareto optimal set, using the BiMADS algorithm. The results show that improvements in the performance can be achieved by modifications of the blade shape and the present procedure can be used as an effective tool for blade shape optimization.

Effects of Inclined Treadmill Walking on Pelvic Anterior Tilt Angle, Hamstring Muscle Length, and Trunk Muscle Endurance of Seated Workers with Flat-back Syndrome

OpenAIRE

Kim, Min-hee; Yoo, Won-gyu

2014-01-01

[Purpose] This study investigated the effects of inclined treadmill walking on pelvic anterior tilt angle, hamstring muscle length, and back muscle endurance of seated workers with flat-back syndrome. [Subjects] Eight seated workers with flat-back syndrome who complained of low-back pain in the L3–5 region participated in this study. [Methods] The subjects performed a walking exercise on a 30° inclined treadmill. We measured the pelvic anterior tilt angle, hamstring muscle length, and back mu...

Aero-elastic stability of airfoil flow using 2-D CFD

Energy Technology Data Exchange (ETDEWEB)

Johansen, J [Risoe National Lab., Roskilde (Denmark)

1999-03-01

A three degrees-of-freedom structural dynamics model has been coupled to a two-dimensional incompressible CFD code. The numerical investigation considers aero-elastic stability for two different airfoils; the NACA0012 and the LM 2 18 % airfoils. Stable and unstable configurations and limit cycle oscillations are predicted in accordance with literature for the first airfoil. An attempt to predict stall induced edge-wise vibrations on a wind turbine airfoil fails using this two-dimensional approach. (au)

Aerodynamic Analysis of Trailing Edge Enlarged Wind Turbine Airfoils

International Nuclear Information System (INIS)

Xu, Haoran; Yang, Hua; Liu, Chao; Shen, Wenzhong; Zhu, Weijun

2014-01-01

The aerodynamic performance of blunt trailing edge airfoils generated from the DU- 91-W2-250, DU-97-W-300 and DU-96-W-350 airfoils by enlarging the thickness of trailing edge symmetrically from the location of maximum thickness to chord to the trailing edge were analyzed by using CFD and RFOIL methods at a chord Reynolds number of 3 × 10 6 . The goal of this study is to analyze the aerodynamic performance of blunt trailing edge airfoils with different thicknesses of trailing edge and maximum thicknesses to chord. The steady results calculated by the fully turbulent k-ω SST, transitional k-ω SST model and RFOIL all show that with the increase of thickness of trailing edge, the linear region of lift is extended and the maximum lift also increases, the increase rate and amount of lift become limited gradually at low angles of attack, while the drag increases dramatically. For thicker airfoils with larger maximum thickness to chord length, the increment of lift is larger than that of relatively thinner airfoils when the thickness of blunt trailing edge is increased from 5% to 10% chord length. But too large lift can cause abrupt stall which is profitless for power output. The transient characteristics of blunt trailing edge airfoils are caused by blunt body vortices at low angles of attack, and by the combined effect of separation and blunt body vortices at large angles of attack. With the increase of thickness of blunt trailing edge, the vibration amplitudes of lift and drag curves increase. The transient calculations over-predict the lift at large angles of attack and drag at all angles of attack than the steady calculations which is likely to be caused by the artificial restriction of the flow in two dimensions

An Experimental Comparison Between Flexible and Rigid Airfoils at Low Reynolds Numbers

Science.gov (United States)

Uzodinma, Jaylon; Macphee, David

2017-11-01

This study uses experimental and computational research methods to compare the aerodynamic performance of rigid and flexible airfoils at a low Reynolds number throughout varying angles of attack. This research can be used to improve the design of small wind turbines, micro-aerial vehicles, and any other devices that operate at low Reynolds numbers. Experimental testing was conducted in the University of Alabama's low-speed wind tunnel, and computational testing was conducted using the open-source CFD code OpenFOAM. For experimental testing, polyurethane-based (rigid) airfoils and silicone-based (flexible) airfoils were constructed using acrylic molds for NACA 0012 and NACA 2412 airfoil profiles. Computer models of the previously-specified airfoils were also created for a computational analysis. Both experimental and computational data were analyzed to examine the critical angles of attack, the lift and drag coefficients, and the occurrence of laminar boundary separation for each airfoil. Moreover, the computational simulations were used to examine the resulting flow fields, in order to provide possible explanations for the aerodynamic performances of each airfoil type. EEC 1659710.

Design and optimization of tidal turbine airfoil

Energy Technology Data Exchange (ETDEWEB)

Grasso, F. [ECN Wind Energy, Petten (Netherlands)

2012-03-15

To increase the ratio of energy capture to the loading and, thereby, to reduce cost of energy, the use of specially tailored airfoils is needed. This work is focused on the design of an airfoil for marine application. Firstly, the requirements for this class of airfoils are illustrated and discussed with reference to the requirements for wind turbine airfoils. Then, the design approach is presented. This is a numerical optimization scheme in which a gradient-based algorithm is used, coupled with the RFOIL solver and a composite Bezier geometrical parameterization. A particularly sensitive point is the choice and implementation of constraints .A section of the present work is dedicated to address this point; particular importance is given to the cavitation phenomenon. Finally, a numerical example regarding the design of a high-efficiency hydrofoil is illustrated, and the results are compared with existing turbine airfoils, considering also the effect on turbine performance due to different airfoils.

Design and optimization of tidal turbine airfoil

Energy Technology Data Exchange (ETDEWEB)

Grasso, F. [ECN Wind Energy, Petten (Netherlands)

2011-07-15

In order to increase the ratio of energy capture to the loading and thereby to reduce cost of energy, the use of specially tailored airfoils is needed. This work is focused on the design of an airfoil for marine application. Firstly, the requirements for this class of airfoils are illustrated and discussed with reference to the requirements for wind turbine airfoils. Then, the design approach is presented. This is a numerical optimization scheme in which a gradient based algorithm is used, coupled with RFOIL solver and a composite Bezier geometrical parameterization. A particularly sensitive point is the choice and implementation of constraints; in order to formalize in the most complete and effective way the design requirements, the effects of activating specific constraints are discussed. Particularly importance is given to the cavitation phenomenon. Finally, a numerical example regarding the design of a high efficiency, tidal turbine airfoil is illustrated and the results are compared with existing turbine airfoils.

Profile catalogue for airfoil sections based on 3D

Energy Technology Data Exchange (ETDEWEB)

Bertagnolio, F.; Soerensen, Niels N.; Johansen, Jeppe

2006-12-15

This report is a continuation of the Wind Turbine Airfoil Catalogue which objective was, firstly to provide a database of aerodynamic characteristics for a wide range of airfoil profiles aimed at wind turbine applications, and secondly to test the two-dimensional Navier-Stokes solver EllipSys2D by comparing its results with experimental data. In the present work, the original two-dimensional results are compared with three-dimensional calculations as it was surmised that the two-dimensional assumption might be in some cases responsible for discrepancies between the numerical flow solution and the actual fluid flow, and thereby the incorrect prediction of airfoil characteristics. In addition, other features of the flow solver, such as transition and turbulence modelling, and their influence onto the numerical results are investigated. Conclusions are drawn regarding the evaluation of airfoil aerodynamic characteristics, as well as the use of the Navier-Stokes solver for fluid flow calculations in general. (au)

Aerodynamic Response of a Pitching Airfoil with Pulsed Circulation Control for Vertical Axis Wind Turbine Applications

Science.gov (United States)

Panther, Chad C.

Vertical Axis Wind Turbines (VAWTs) have experienced a renewed interest in development for urban, remote, and offshore applications. Past research has shown that VAWTs cannot compete with Horizontals Axis Wind Turbines (HAWTs) in terms of energy capture efficiency. VAWT performance is plagued by dynamic stall (DS) effects at low tip-speed ratios (lambda), where each blade pitches beyond static stall multiple times per revolution. Furthermore, for lambdaoperate outside of stall during over 70% of rotation. However, VAWTs offer many advantages such as omnidirectional operation, ground proximity of generator, lower sound emission, and non-cantilevered blades with longer life. Thus, mitigating dynamic stall and improving VAWT blade aerodynamics for competitive power efficiency has been a popular research topic in recent years and the directive of this study. Past research at WVU focused on the addition of circulation control (CC) technology to improve VAWT aerodynamics and expand the operational envelope. A novel blade design was generated from the augmentation of a NACA0018 airfoil to include CC capabilities. Static wind tunnel data was collected for a range of steady jet momentum coefficients (0.01≤ Cmu≤0.10) for analytical vortex model performance projections. Control strategies were developed to optimize CC jet conditions throughout rotation, resulting in improved power output for 2≤lambda≤5. However, the pumping power required to produce steady CC jets reduced net power gains of the augmented turbine by approximately 15%. The goal of this work was to investigate pulsed CC jet actuation to match steady jet performance with reduced mass flow requirements. To date, no experimental studies have been completed to analyze pulsed CC performance on a pitching airfoil. The research described herein details the first study on the impact of steady and pulsed jet CC on pitching VAWT blade aerodynamics. Both numerical and experimental studies were implemented, varying

Boundary layer development on turbine airfoil suction surfaces

Science.gov (United States)

Sharma, O. P.; Wells, R. A.; Schlinker, R. H.; Bailey, D. A.

1981-01-01

The results of a study supported by NASA under the Energy Efficient Engine Program, conducted to investigate the development of boundary layers under the influence of velocity distributions that simulate the suction sides of two state-of-the-art turbine airfoils, are presented. One velocity distribution represented a forward loaded airfoil ('squared-off' design), while the other represented an aft loaded airfoil ('aft loaded' design). These velocity distributions were simulated in a low-speed, high-aspect-ratio wind tunnel specifically designed for boundary layer investigations. It is intended that the detailed data presented in this paper be used to develop improved turbulence model suitable for application to turbine airfoil design.

Visualization of boundary layer separation and passive flow control on airfoils and bodies in wind-tunnel and in-flight experiments

Directory of Open Access Journals (Sweden)

Matejka Milan

2012-04-01

Full Text Available Infrared camera, Particle Image Velocimetry, smoke-wire, tuft filaments and oil-flow visualization techniques were used for wind-tunnel and in-flight investigation of boundary layer separation, both stall and separation bubbles, related to the low-Reynolds numbers transition mechanism. Airfoils of Wortmann FX66 series and FX66 series wing-fuselage interaction, as well as modern airfoils and their wing-fuselage geometry were subject to study. The presence of previously identified structures in the CFD modelling, such as horse-shoe vortices, was confirmed in the flow. Wind-tunnels and in-flight measurements on sailplanes were carried out and effect of passive flow control devices - vortex generators - was surveyed; namely counter-rotating vortex generators and Zig-zag type turbulators were applied. Separation suppression and consequent drag coefficient reduction of test aircrafts was reached. PIV investigation was further extended by Time-Resolved techniques. An important study on structure of the turbulent flow in the lower atmosphere, creating an environment of the soaring flight, was presented.

Visualization of boundary layer separation and passive flow control on airfoils and bodies in wind-tunnel and in-flight experiments

Science.gov (United States)

Popelka, Lukas; Kuklova, Jana; Simurda, David; Souckova, Natalie; Matejka, Milan; Uruba, Vaclav

2012-04-01

Infrared camera, Particle Image Velocimetry, smoke-wire, tuft filaments and oil-flow visualization techniques were used for wind-tunnel and in-flight investigation of boundary layer separation, both stall and separation bubbles, related to the low-Reynolds numbers transition mechanism. Airfoils of Wortmann FX66 series and FX66 series wing-fuselage interaction, as well as modern airfoils and their wing-fuselage geometry were subject to study. The presence of previously identified structures in the CFD modelling, such as horse-shoe vortices, was confirmed in the flow. Wind-tunnels and in-flight measurements on sailplanes were carried out and effect of passive flow control devices - vortex generators - was surveyed; namely counter-rotating vortex generators and Zig-zag type turbulators were applied. Separation suppression and consequent drag coefficient reduction of test aircrafts was reached. PIV investigation was further extended by Time-Resolved techniques. An important study on structure of the turbulent flow in the lower atmosphere, creating an environment of the soaring flight, was presented.

Prediction of the Effect of Vortex Generators on Airfoil Performance

DEFF Research Database (Denmark)

Sørensen, Niels N.; Zahle, Frederik; Bak, Christian

2014-01-01

Vortex Generators (VGs) are widely used by the wind turbine industry, to control the flow over blade sections. The present work describes a computational fluid dynamic procedure that can handle a geometrical resolved VG on an airfoil section. After describing the method, it is applied to two...... different airfoils at a Reynolds number of 3 million, the FFA- W3-301 and FFA-W3-360, respectively. The computations are compared with wind tunnel measurements from the Stuttgart Laminar Wind Tunnel with respect to lift and drag variation as function of angle of attack. Even though the method does...

Derivation of airfoil characteristics for the LM 19.1 blade based on 3D CFD rotor calculations

Energy Technology Data Exchange (ETDEWEB)

Bak, C; Soerensen, N N; Madsen, H A [Risoe National Lab., Roskilde (Denmark)

1999-03-01

Airfoil characteristics for the LM 19.1 blade are derived from 3D CFD computations on a full-scale 41-m rotor. Based on 3D CFD the force distributions on the blades are determined, from which airfoil characteristics are derived using the momentum theory. The final airfoil characteristics are constructed using both wind tunnel measurements and 3D CFD. Compared to 2D wind tunnel measurements they show a low lift in stall for the airfoil sections at the tip. At the airfoil sections at the inner part of the blade, they show a high lift in stall. At about 60% radius the lift agrees well to 2D wind tunnel measurements. Aero-elastic calculations using the final airfoil characteristics show good agreement to measured power and flap moments. Furthermore, a fatigue load analysis shows a reduction of up to 15% of the load compared to commonly used data. (au)

Aerodynamics of S809 Airfoil at Low and Transitional Reynolds Numbers

Science.gov (United States)

Carreras, Jaime J.; Laal-Dehghani, Nader; Gorumlu, Serdar; Mehdi, Faraz; Castillo, Luciano; Aksak, Burak; Sheng, Jian

2013-11-01

The S809 is a thick airfoil extensively used in wind turbine design applications and model studies in wind tunnel. With increased interests in reducing energy production cost and understanding turbulence and turbine interactions, scaled down models (Re ~103) are often used as an alternative to full scale field experimentation (Re >106). This Reynolds number discrepancy raises the issue of scaling for the airfoil performance from laboratory studies to field scale applications. To the best of our knowledge, there are no studies existing in literature to characterize the lift- and drag-coefficients of S809 airfoil at Re less than 3 ×105 . This study is to fill the deficit in the current state of knowledge by performing high resolution force measurements. The lift and drag measurements are carried out in Texas Tech Wind Tunnel Facility using an in-house developed dual-cell force balance. The configuration eliminates the large torque and torsion often accompanied by conventional mounts. This unique design allows us to reach a measurement accuracy of 0.02N (0.1%). Comparative studies are performed on a two-dimensional airfoil with a smooth- as well as a well-engineered surface covered by micro-pillar array to simulate the surface conditions of a real life airfoil.

Monitoring pressure profiles across an airfoil with a fiber Bragg grating sensor array

Science.gov (United States)

Papageorgiou, Anthony W.; Parkinson, Luke A.; Karas, Andrew R.; Hansen, Kristy L.; Arkwright, John W.

2018-02-01

Fluid flow over an airfoil section creates a pressure difference across the upper and lower surfaces, thus generating lift. Successful wing design is a combination of engineering design and experience in the field, with subtleties in design and manufacture having significant impact on the amount of lift produced. Current methods of airfoil optimization and validation typically involve computational fluid dynamics (CFD) and extensive wind tunnel testing with pressure sensors embedded into the airfoil to measure the pressure over the wing. Monitoring pressure along an airfoil in a wind tunnel is typically achieved using surface pressure taps that consist of hollow tubes running from the surface of the airfoil to individual pressure sensors external to the tunnel. These pressure taps are complex to configure and not ideal for in-flight testing. Fiber Bragg grating (FBG) pressure sensing arrays provide a highly viable option for both wind tunnel and inflight pressure measurement. We present a fiber optic sensor array that can detect positive and negative pressure suitable for validating CFD models of airfoil profile sections. The sensing array presented here consists of 6 independent sensing elements, each capable of a pressure resolution of less than 10 Pa over the range of 70 kPa to 120 kPa. The device has been tested with the sensor array attached to a 90mm chord length airfoil section subjected to low velocity flow. Results show that the arrays are capable of accurately detecting variations of the pressure profile along the airfoil as the angle of attack is varied from zero to the point at which stall occurs.

Aerodynamic characteristics of wind turbine blade airfoils at high angles-of-attack

NARCIS (Netherlands)

Timmer, W.A.

2010-01-01

Airfoil characteristics at deep stall angles were investigated. It appeared that the maximum drag coefficient as a function of the airfoil upwind y/c ordinate at x/c=0.0125 can be approximated by a straight line. The lift-drag ratios in deep stall of a number of airfoils with moderate lower surface

Design Of An Aerodynamic Measurement System For Unmanned Aerial Vehicle Airfoils

Directory of Open Access Journals (Sweden)

L. Velázquez-Araque

2012-10-01

Full Text Available This paper presents the design and validation of a measurement system for aerodynamic characteristics of unmanned aerial vehicles. An aerodynamic balance was designed in order to measure the lift, drag forces and pitching moment for different airfoils. During the design process, several aspects were analyzed in order to produce an efficient design, for instance the range of changes of the angle of attack with and a small increment and the versatility of being adapted to different type of airfoils, since it is a wire balance it was aligned and calibrated as well. Wind tunnel tests of a two dimensional NACA four digits family airfoil and four different modifications of this airfoil were performed to validate the aerodynamic measurement system. The modification of this airfoil was made in order to create a blowing outlet with the shape of a step on the suction surface. Therefore, four different locations along the cord line for this blowing outlet were analyzed. This analysis involved the aerodynamic performance which meant obtaining lift, drag and pitching moment coefficients curves as a function of the angle of attack experimentally for the situation where the engine of the aerial vehicle is turned off, called the no blowing condition, by means of wind tunnel tests. The experiments were performed in a closed circuit wind tunnel with an open test section. Finally, results of the wind tunnel tests were compared with numerical results obtained by means of computational fluid dynamics as well as with other experimental references and found to be in good agreement.

Prediction of unsteady separated flows on oscillating airfoils

Science.gov (United States)

Mccroskey, W. J.

1978-01-01

Techniques for calculating high Reynolds number flow around an airfoil undergoing dynamic stall are reviewed. Emphasis is placed on predicting the values of lift, drag, and pitching moments. Methods discussed include: the discrete potential vortex method; thin boundary layer method; strong interaction between inviscid and viscous flows; and solutions to the Navier-Stokes equations. Empirical methods for estimating unsteady airloads on oscillating airfoils are also described. These methods correlate force and moment data from wind tunnel tests to indicate the effects of various parameters, such as airfoil shape, Mach number, amplitude and frequency of sinosoidal oscillations, mean angle, and type of motion.

Interaction of an Artificially Thickened Boundary Layer with a Vertically Mounted Pitching Airfoil

Science.gov (United States)

Hohman, Tristen; Smits, Alexander; Martinelli, Luigi

2011-11-01

Wind energy represents a large portion of the growing market in alternative energy technologies and the current landscape has been dominated by the more prevalent horizontal axis wind turbine. However, there are several advantages to the vertical axis wind turbine (VAWT) or Darrieus type design and yet there is much to be understood about how the atmospheric boundary layer (ABL) affects their performance. In this study the ABL was simulated in a wind tunnel through the use of elliptical shaped vortex generators, a castellated wall, and floor roughness elements as described in the method of Counihan (1967) and then verified its validity by hot wire measurement of the mean velocity profile as well as the turbulence intensity. The motion of an blade element around a vertical axis is approximated through the use of a pitching airfoil. The wake of the airfoil is investigated through hot wire anemometry in both uniform flow and in the simulated boundary layer both at Re = 1 . 37 ×105 based on the chord of the airfoil. Sponsored by Hopewell Wind Power (Hong Kong) Limited.

Design and Experimental Validation of Thick Airfoils for Large Wind Turbines

DEFF Research Database (Denmark)

Hrgovan, Iva; Shen, Wen Zhong; Zhu, Wei Jun

2015-01-01

In this chapter, two new airfoils with thickness to chord ratios of 30 and 36 % are presented, which were designed with an objective of good aerodynamic and structural features. Airfoil design is based on a direct method using shape perturbation function. The optimization algorithm is coupled wit...

Experimental benchmark and code validation for airfoils equipped with passive vortex generators

DEFF Research Database (Denmark)

Baldacchino, D.; Manolesos, M.; Ferreira, Célia Maria Dias

2016-01-01

Experimental results and complimentary computations for airfoils with vortex generators are compared in this paper, as part of an effort within the AVATAR project to develop tools for wind turbine blade control devices. Measurements from two airfoils equipped with passive vortex generators, a 30...

New airfoil sections for straight bladed turbine

Science.gov (United States)

Boumaza, B.

1987-07-01

A theoretical investigation of aerodynamic performance for vertical axis Darrieus wind turbine with new airfoils sections is carried out. The blade section aerodynamics characteristics are determined from turbomachines cascade model. The model is also adapted to the vertical Darrieus turbine for the performance prediction of the machine. In order to choose appropriate value of zero-lift-drag coefficient in calculation, an analytical expression is introduced as function of chord-radius ratio and Reynolds numbers. New airfoils sections are proposed and analyzed for straight-bladed turbine.

New airfoil sections for straight bladed turbine

International Nuclear Information System (INIS)

Boumaza, B.

1987-07-01

A theoretical investigation of aerodynamic performance for vertical axis Darrieus wind turbine with new airfoils sections is carried out. The blade section aerodynamics characteristics are determined from turbomachines cascade model. The model is also adapted to the vertical Darrieus turbine for the performance prediction of the machine. In order to choose appropriate value of zero-lift-drag coefficient in calculation, an analytical expression is introduced as function of chord-radius ratio and Reynolds numbers. New airfoils sections are proposed and analyzed for straight-bladed turbine

Drop "impact" on an airfoil surface.

Science.gov (United States)

Wu, Zhenlong

2018-05-17

Drop impact on an airfoil surface takes place in drop-laden two-phase flow conditions such as rain and icing, which are encountered by wind turbines or airplanes. This phenomenon is characterized by complex nonlinear interactions that manifest rich flow physics and pose unique modeling challenges. In this article, the state of the art of the research about drop impact on airfoil surface in the natural drop-laden two-phase flow environment is presented. The potential flow physics, hazards, characteristic parameters, droplet trajectory calculation, drop impact dynamics and effects are discussed. The most key points in establishing the governing equations for a drop-laden flow lie in the modeling of raindrop splash and water film. The various factors affecting the drop impact dynamics and the effects of drop impact on airfoil aerodynamic performance are summarized. Finally, the principle challenges and future research directions in the field as well as some promising measures to deal with the adverse effects of drop-laden flows on airfoil performance are proposed. Copyright © 2017 Elsevier B.V. All rights reserved.

S833, S834, and S835 Airfoils: November 2001--November 2002

Energy Technology Data Exchange (ETDEWEB)

Somers, D. M.

2005-08-01

A family of quiet, thick, natural-laminar-flow airfoils, the S833, S834, and S835, for 1 - 3-meter-diameter, variable-speed/variable-pitch, horizontal-axis wind turbines has been designed and analyzed theoretically. The two primary objectives of high maximum lift, relatively insensitive to roughness, and low profile drag have been achieved. The airfoils should exhibit docile stalls, which meet the design goal. The constraints on the pitching moment and the airfoils thicknesses have been satisfied.

S830, S831, and S832 Airfoils: November 2001-November 2002

Energy Technology Data Exchange (ETDEWEB)

Somers, D. M.

2005-08-01

A family of quiet, thick, natural-laminar-flow airfoils, the S830, S831, and S832, for 40 - 50-meter-diameter, variable-speed/variable-pitch, horizontal-axis wind turbines has been designed and analyzed theoretically. The two primary objectives of high maximum lift, relatively insensitive to roughness, and low profile drag have been achieved. The airfoils should exhibit docile stalls, which meet the design goal. The constraints on the pitching moment and the airfoils thicknesses have been satisfied.

Prediction of the Effect of Vortex Generators on Airfoil Performance

International Nuclear Information System (INIS)

Sørensen, Niels N; Zahle, F; Bak, C; Vronsky, T

2014-01-01

Vortex Generators (VGs) are widely used by the wind turbine industry, to control the flow over blade sections. The present work describes a computational fluid dynamic procedure that can handle a geometrical resolved VG on an airfoil section. After describing the method, it is applied to two different airfoils at a Reynolds number of 3 million, the FFA- W3-301 and FFA-W3-360, respectively. The computations are compared with wind tunnel measurements from the Stuttgart Laminar Wind Tunnel with respect to lift and drag variation as function of angle of attack. Even though the method does not exactly capture the measured performance, it can be used to compare different VG setups qualitatively with respect to chord- wise position, inter and intra-spacing and inclination of the VGs already in the design phase

Validation of DYSTOOL for unsteady aerodynamic modeling of 2D airfoils

Science.gov (United States)

González, A.; Gomez-Iradi, S.; Munduate, X.

2014-06-01

From the point of view of wind turbine modeling, an important group of tools is based on blade element momentum (BEM) theory using 2D aerodynamic calculations on the blade elements. Due to the importance of this sectional computation of the blades, the National Renewable Wind Energy Center of Spain (CENER) developed DYSTOOL, an aerodynamic code for 2D airfoil modeling based on the Beddoes-Leishman model. The main focus here is related to the model parameters, whose values depend on the airfoil or the operating conditions. In this work, the values of the parameters are adjusted using available experimental or CFD data. The present document is mainly related to the validation of the results of DYSTOOL for 2D airfoils. The results of the computations have been compared with unsteady experimental data of the S809 and NACA0015 profiles. Some of the cases have also been modeled using the CFD code WMB (Wind Multi Block), within the framework of a collaboration with ACCIONA Windpower. The validation has been performed using pitch oscillations with different reduced frequencies, Reynolds numbers, amplitudes and mean angles of attack. The results have shown a good agreement using the methodology of adjustment for the value of the parameters. DYSTOOL have demonstrated to be a promising tool for 2D airfoil unsteady aerodynamic modeling.

Validation of DYSTOOL for unsteady aerodynamic modeling of 2D airfoils

International Nuclear Information System (INIS)

González, A; Gomez-Iradi, S; Munduate, X

2014-01-01

From the point of view of wind turbine modeling, an important group of tools is based on blade element momentum (BEM) theory using 2D aerodynamic calculations on the blade elements. Due to the importance of this sectional computation of the blades, the National Renewable Wind Energy Center of Spain (CENER) developed DYSTOOL, an aerodynamic code for 2D airfoil modeling based on the Beddoes-Leishman model. The main focus here is related to the model parameters, whose values depend on the airfoil or the operating conditions. In this work, the values of the parameters are adjusted using available experimental or CFD data. The present document is mainly related to the validation of the results of DYSTOOL for 2D airfoils. The results of the computations have been compared with unsteady experimental data of the S809 and NACA0015 profiles. Some of the cases have also been modeled using the CFD code WMB (Wind Multi Block), within the framework of a collaboration with ACCIONA Windpower. The validation has been performed using pitch oscillations with different reduced frequencies, Reynolds numbers, amplitudes and mean angles of attack. The results have shown a good agreement using the methodology of adjustment for the value of the parameters. DYSTOOL have demonstrated to be a promising tool for 2D airfoil unsteady aerodynamic modeling

Usage of advanced thick airfoils for the outer part of very large offshore turbines

International Nuclear Information System (INIS)

Grasso, F; Ceyhan, O

2014-01-01

Nowadays one of the big challenges in wind energy is connected to the development of very large wind turbines with 100 m blades and 8-10MW power production. The European project INNWIND.EU plays an important role in this challenge because it is focused on exploring and exploiting technical innovations to make these machines not only feasible but also cost effective. In this context, the present work investigates the benefits of adopting thick airfoils also at the outer part of the blade. In fact, if these airfoils are comparable to the existing thinner ones in terms of aerodynamics, the extra thickness would lead to a save in weight. Lightweight blades would visibly contribute to reduce the cost of energy of the turbines and make them cost effective. The reference turbine defined in INNWIND.EU project has been adjusted to use the new airfoils. The results show that the rotor performance is not sacrificed when the 24% airfoils are replaced by the ECN 30% thick airfoils, while 24% extra thickness can be obtained

Extraction of airfoil data using PIV and pressure measurements

DEFF Research Database (Denmark)

Yang, Hua; Shen, Wen Zhong; Sørensen, Jens Nørkær

2011-01-01

of the rotor. The extraction technique is verified by employing the derived airfoil characteristics as input to computations using the BEM technique and comparing the calculated axial and tangential forces to the measured data. The comparison also demonstrates that the used technique of determining the AOA...... airfoil data are compared to 2D data from wind tunnel experiments and XFOIL computations. The comparison suggests that the rotor is subject to severe 3D effects originating from the geometry of the rotor, and explains why the Blade Element Momentum technique with 2D airfoil data over‐predicts the loading......A newly developed technique for determining the angle of attack (AOA) on a rotating blade is used to extract AOAs and airfoil data from measurements obtained during the MEXICO (Model rotor EXperiments in COntrolled conditions) rotor experiment. Detailed surface pressure and Particle Image...

Development and testing of airfoils for high-altitude aircraft

Science.gov (United States)

Drela, Mark (Principal Investigator)

1996-01-01

Specific tasks included airfoil design; study of airfoil constraints on pullout maneuver; selection of tail airfoils; examination of wing twist; test section instrumentation and layout; and integrated airfoil/heat-exchanger tests. In the course of designing the airfoil, specifically for the APEX test vehicle, extensive studies were made over the Mach and Reynolds number ranges of interest. It is intended to be representative of airfoils required for lightweight aircraft operating at extreme altitudes, which is the primary research objective of the APEX program. Also considered were thickness, pitching moment, and off-design behavior. The maximum ceiling parameter M(exp 2)C(sub L) value achievable by the Apex-16 airfoil was found to be a strong constraint on the pullout maneuver. The NACA 1410 and 2410 airfoils (inverted) were identified as good candidates for the tail, with predictable behavior at low Reynolds numbers and good tolerance to flap deflections. With regards to wing twist, it was decided that a simple flat wing was a reasonable compromise. The test section instrumentation consisted of surface pressure taps, wake rakes, surface-mounted microphones, and skin-friction gauges. Also, a modest wind tunnel test was performed for an integrated airfoil/heat-exchanger configuration, which is currently on Aurora's 'Theseus' aircraft. Although not directly related to the APEX tests, the aerodynamics or heat exchangers has been identified as a crucial aspect of designing high-altitude aircraft and hence is relevant to the ERAST program.

Parallel numerical simulation of oscillating airfoil NACA0015 in the channel due to flutter instability

Directory of Open Access Journals (Sweden)

Řidký Václav

2014-03-01

Full Text Available The work is devoted to 3D and 2D parallel numerical computation of pressure and velocity fields around an elastically supported airfoil self-oscillating due to interaction with the airflow. Numerical solution is computed in the OpenFOAM package, an open-source software package based on finite volume method. Movement of airfoil is described by translation and rotation, identified from experimental data. A new boundary condition for the 2DOF motion of the airfoil was implemented. The results of numerical simulations (velocity are compared with data measured in a wind tunnel, where a physical model of NACA0015 airfoil was mounted and tuned to exhibit the flutter instability. The experimental results were obtained previously in the Institute of Thermomechanics by interferographic measurements in a subsonic wind tunnel in Nový Knín.

Indicial lift response function: an empirical relation for finite‐thickness airfoils, and effects on aeroelastic simulations

DEFF Research Database (Denmark)

Bergami, Leonardo; Gaunaa, Mac; Heinz, Joachim Christian

2013-01-01

The aeroelastic response of wind turbines is often simulated in the time domain by using indicial response techniques. Unsteady aerodynamics in attached flow are usually based on Jones's approximation of the flat plate indicial response, although the response for finite‐thickness airfoils differs...... from the flat plate one. The indicial lift response of finite‐thickness airfoils is simulated with a panel code, and an empirical relation is outlined connecting the airfoil indicial response to its geometric characteristics. The effects of different indicial approximations are evaluated on a 2D...... of equivalent fatigue loads, ultimate loads, and stability limits. The agreement with CFD computations of a 2D profile in harmonic motion is improved by the indicial function accounting for the finite‐thickness of the airfoil. Concerning the full wind turbine aeroelastic behavior, the differences between...

Aerodynamic behaviour of NREL S826 airfoil at Re=100,000

International Nuclear Information System (INIS)

Sarlak, H; Mikkelsen, R; Sarmast, S; Sørensen, J N

2014-01-01

This paper presents wind tunnel measurements of the NREL S826 airfoil at Reynolds number Re = 100,000 for angles of attack in a range of -10° to 25° the corresponding Large Eddy Simulation (LES) for selected angles of attack. The measurements have been performed at the low speed wind tunnel located at Fluid Mechanics laboratory of the Technical University of Denmark (DTU). Lift coefficient is obtained from the forge gauge measurements while the drag is measured according to the integration of the wake profiles downstream of the airfoil. The pressure distribution is measured by a set of pressure taps on the airfoil surface. The lift and drag polars are obtained from the LES computations using DTU's inhouse CFD solver, EllipSys3D, and good agreement is found between the measurement and the simulations. At high angles of attack, the numerical computations tend to over-predict the lift coefficients, however, there is a better agreement between the drag measurements and computations. It is concluded that LES computations are able to capture the lift and drag polars as well as the pressure distribution around the airfoil with an acceptable accuracy

Design and validation of the high performance and low noise CQU-DTU-LN1 airfoils

DEFF Research Database (Denmark)

Cheng, Jiangtao; Zhu, Wei Jun; Fischer, Andreas

2014-01-01

with the blade element momentum theory, the viscous-inviscid XFOIL code and an airfoil self-noise prediction model, an optimization algorithm has been developed for designing the high performance and low noise CQU-DTU-LN1 series of airfoils with targets of maximum power coefficient and low noise emission...... emission between the CQU-DTU-LN118 airfoil and the National Advisory Committee for Aeronautics (NACA) 64618 airfoil, which is used in modern wind turbine blades, are carried out. Copyright © 2013 John Wiley & Sons, Ltd....

Aerodynamic behaviour of NREL S826 airfoil at Re=100,000

DEFF Research Database (Denmark)

Chivaee, Hamid Sarlak; Mikkelsen, Robert Flemming; Sarmast, Sasan

2014-01-01

This paper presents wind tunnel measurements of the NREL S826 airfoil at Reynolds number Re = 100,000 for angles of attack in a range of -10° to 25° the corresponding Large Eddy Simulation (LES) for selected angles of attack. The measurements have been performed at the low speed wind tunnel located...... at Fluid Mechanics laboratory of the Technical University of Denmark (DTU). Lift coefficient is obtained from the forge gauge measurements while the drag is measured according to the integration of the wake profiles downstream of the airfoil. The pressure distribution is measured by a set of pressure taps...... on the airfoil surface. The lift and drag polars are obtained from the LES computations using DTU's inhouse CFD solver, EllipSys3D, and good agreement is found between the measurement and the simulations. At high angles of attack, the numerical computations tend to over-predict the lift coefficients, however...

Experimental Study of Tip Vortex Flow from a Periodically Pitched Airfoil Section

Science.gov (United States)

Zaman, Khairul; Fagan, Amy; Mankbadi, Mina

2016-01-01

An experimental investigation of tip vortex flow from a NACA0012 airfoil, pitched periodically at various frequencies, is conducted in a low-speed wind tunnel. Initially, data for stationary airfoil held fixed at various angles-of-attack are gathered. Flow visualization pictures as well as detailed cross-sectional properties areobtained at various streamwise locations using hot-wire anemometry. Data include mean velocity, streamwise vorticity as well as various turbulent stresses. Preliminary data are also acquired for periodically pitched airfoil. These results are briefly presented in this extended abstract.

An Experimental Investigation of an Airfoil Traversing Across a Shear Flow

Science.gov (United States)

Hamedani, Borhan A.; Naguib, Ahmed; Koochesfahani, Manoochehr

2017-11-01

While the aerodynamics of an airfoil in a uniform approach flow is well understood, less attention has been paid to airfoils in non-uniform flows. An aircraft encounters such flow, for example, during landing through the air wake of an aircraft carrier. The present work is focused on investigating the fundamental aerodynamics of airfoils in such an environment using canonical flow experiments. To generate a shear approach flow, a shaped honeycomb block is employed in a wind tunnel setup. Direct force measurements are performed on a NACA 0012 airfoil, with an aspect ratio of 1.8, as the airfoil traverses steadily across the shear region. Measurements are conducted at a chord Reynolds number Rec 75k, based on the mean approach stream velocity at the center of the shear zone, for a range of airfoil traverse velocities and angles of attack (0 - 12 degree). The results are compared to those obtained for the same airfoil when placed statically at different points along the traverse path inside the shear zone. The comparison enables examination of the applicability of quasi-steady analysis in computing the forces on the moving airfoil. This work is supported by ONR Grant Number N00014-16-1-2760.

Wind tunnel testing of scaled models of a newly developed Darrieus-style vertical axis wind turbine with auxiliary straight blades

International Nuclear Information System (INIS)

Scungio, M.; Arpino, F.; Focanti, V.; Profili, M.; Rotondi, M.

2016-01-01

Highlights: • Wind tunnel investigations of Darrieus-style VAWT with auxiliary blades have been made. • Results have been compared with those from standard Darrieus VAWT. • Static and dynamic power and torque coefficients were measured and evaluated. • The auxiliary airfoils have demonstrated to give more torque at the lower wind speeds. • The proposed VAWT configuration is able to work in a wide range of wind speeds. - Abstract: Renewable sources of energy, needed because of the increasing price of fossil derivatives, global warming and energy market instabilities, have led to an increasing interest in wind energy. Among the different typologies, small scale Vertical Axis Wind Turbines (VAWT) present the greatest potential for off grid power generation at low wind speeds. In the present work, wind tunnel investigations about the performance of an innovative configuration of straight-blades Darrieus-style vertical axis micro wind turbine, specifically developed for small scale energy conversion at low wind speeds, has been made on scaled models. The micro turbine under investigation consists of three pairs of airfoils. Each pair consists of a main and auxiliary airfoil with different chord lengths. A standard Darrieus configuration, consisting of three single airfoils, was also tested for comparison. The experiments were conducted in a closed circuit open chamber wind tunnel facility available at the Laboratory of Industrial Measurements (LaMI) of the University of Cassino and Lazio Meridionale (UNICLAM). Measured data were reported in terms of dimensionless power and torque coefficients for dynamic performance analysis and static torque coefficient for static performance analysis. The adoption of auxiliary airfoils has demonstrated to give more dynamic torque at the lower wind speeds with respect to a standard Darrieus rotor, resulting in better performance for all the wind speeds considered. In terms of dynamic power coefficient, the standard Darrieus

Numerical study of the static and pitching RISØ-B1-18 airfoil

DEFF Research Database (Denmark)

Bertagnolio, Franck

2004-01-01

The objective of this report is the better understanding of the physics of the aeroelastic motion of wind turbine blades in order to improve the numerical models used for their design. In this study, the case of the RISØ-B1-18 airfoil which was equippedand measured in an open jet wind tunnel...... that are available both for the static airfoil and in the case of pitching motions. It is shown that the Navier-Stokes simulations can reproduced the maincharacteristic features of the flow. The DES model seems also to be able to reproduce some details of the unsteady aerodynamics. The Navier-Stokes computations can...

Investigation of a Novel Turbulence Model and Using Leading-Edge Slots for Improving the Aerodynamic Performance of Airfoils and Wind Turbines

Science.gov (United States)

Beyhaghi, Saman

as compared to the baseline DES. In the second part of this study, the focus is on improving the aerodynamic performance of airfoils and wind turbines in terms of lift and drag coefficients and power generation. One special type of add-on feature for wind turbines and airfoils, i.e., leading-edge slots are investigated through numerical simulation and laboratory experiments. Although similar slots are designed and employed for aircrafts, a special slot with a reversed flow direction is drilled in the leading edge of a sample wind turbine airfoil to study its influence on the aerodynamic performance. The objective is to vary the five main geometrical parameters of slot and characterize the performance improvement of the new design under different operating conditions. A number of Design of Experiment and optimization studies are conducted to determine the most suitable slot configuration to maximize the lift or lift-over-drag ratio. Results indicate that proper sizing and placement of slot can improve the lift coefficient, while it has negligible negative impact on the drag. Some recommendations for future investigation on slot are proposed at the end. The performance of a horizontal axis wind turbine blade equipped with leading-edge slot is also studied, and it is concluded that slotted blades can generate about 10% more power than solid blades, for the two operating conditions investigated. The good agreement between the CFD predictions and experimental data confirms the validity of the model and results.

Prediction of the aerodynamic performance of the Mexico rotor by using airfoil data extracted from CFD

DEFF Research Database (Denmark)

Yang, Hua; Shen, Wen Zhong; Xu, Haoran

2013-01-01

Blade Element Momentum (BEM) theory is a widely used technique for prediction of wind turbine aerodynamics performance, but the reliability of airfoil data is an important factor to improve the prediction accuracy of aerodynamic loads and power using a BEM code. The airfoil characteristics used...

Wind turbine blade vibration at standstill conditions — the effect of imposing lag on the aerodynamic response of an elastically mounted airfoil

DEFF Research Database (Denmark)

Skrzypinski, Witold Robert; Gaunaa, Mac

2015-01-01

The present study investigated physical phenomena related to stall-induced vibrations potentially existing on wind turbine blades at standstill conditions. The study considered two-dimensional airfoil sections while it omitted three-dimensional effects. In the study, a new engineering-type...... computational model for the aeroelastic response of an elastically mounted airfoil was used to investigate the influence of temporal lag in the aerodynamic response on the aeroelastic stability in deep stall. The study indicated that even a relatively low lag significantly increases the damping of the model....... A comparison between the results from a model with lag imposed on all force components with the results from a model with lag imposed exclusively on the lift showed only marginal difference between the damping in the two cases. A parameter study involving positions of the elastic hinge point and the center...

A Two Element Laminar Flow Airfoil Optimized for Cruise. M.S. Thesis

Science.gov (United States)

Steen, Gregory Glen

1994-01-01

Numerical and experimental results are presented for a new two-element, fixed-geometry natural laminar flow airfoil optimized for cruise Reynolds numbers on the order of three million. The airfoil design consists of a primary element and an independent secondary element with a primary to secondary chord ratio of three to one. The airfoil was designed to improve the cruise lift-to-drag ratio while maintaining an appropriate landing capability when compared to conventional airfoils. The airfoil was numerically developed utilizing the NASA Langley Multi-Component Airfoil Analysis computer code running on a personal computer. Numerical results show a nearly 11.75 percent decrease in overall wing drag with no increase in stall speed at sailplane cruise conditions when compared to a wing based on an efficient single element airfoil. Section surface pressure, wake survey, transition location, and flow visualization results were obtained in the Texas A&M University Low Speed Wind Tunnel. Comparisons between the numerical and experimental data, the effects of the relative position and angle of the two elements, and Reynolds number variations from 8 x 10(exp 5) to 3 x 10(exp 6) for the optimum geometry case are presented.

Denmark Wind Energy Programme

DEFF Research Database (Denmark)

Shen, Wen Zhong

2015-01-01

In this chapter, a summary of some ongoing wind energy projects in Denmark is given. The research topics comprise computational model development, wind turbine (WT) design, low-noise airfoil and blade design, control device development, wake modelling and wind farm layout optimization....

Self-induced vibrations of a DU96-W-180 airfoil in stall

DEFF Research Database (Denmark)

Skrzypinski, Witold Robert; Gaunaa, Mac; Sørensen, Niels N.

2014-01-01

This work presents an analysis of two-dimensional (2D) and three-dimensional (3D) non-moving, prescribed motion and elastically mounted airfoil computational fluid dynamics (CFD) computations. The elastically mounted airfoil computations were performed by means of a 2D structural model with two...... degrees of freedom. The computations aimed at investigating the mechanisms of both vortex-induced and stall-induced vibrations related to a wind turbine blade at standstill conditions. In this work, a DU96-W-180 airfoil was used in the angle-of-attack region potentially corresponding to stallinduced...... vibrations. The analysis showed significant differences between the aerodynamic stability limits predicted by 2D and 3D CFD computations. A general agreement was reached between the prescribed motion and elastically mounted airfoil computations. 3D computations indicated that vortex-induced vibrations...

Airfoil structure

Science.gov (United States)

Frey, G.A.; Twardochleb, C.Z.

1998-01-13

Past airfoil configurations have been used to improve aerodynamic performance and engine efficiencies. The present airfoil configuration further increases component life and reduces maintenance by reducing internal stress within the airfoil itself. The airfoil includes a chord and a span. Each of the chord and the span has a bow being summed to form a generally ``C`` configuration of the airfoil. The generally ``C`` configuration includes a compound bow in which internal stresses resulting from a thermal temperature gradient are reduced. The structural configuration reduces internal stresses resulting from thermal expansion. 6 figs.

Mechanism of unconventional aerodynamic characteristics of an elliptic airfoil

Directory of Open Access Journals (Sweden)

Sun Wei

2015-06-01

Full Text Available The aerodynamic characteristics of elliptic airfoil are quite different from the case of conventional airfoil for Reynolds number varying from about 104 to 106. In order to reveal the fundamental mechanism, the unsteady flow around a stationary two-dimensional elliptic airfoil with 16% relative thickness has been simulated using unsteady Reynolds-averaged Navier–Stokes equations and the γ-Reθt‾ transition turbulence model at different angles of attack for flow Reynolds number of 5 × 105. The aerodynamic coefficients and the pressure distribution obtained by computation are in good agreement with experimental data, which indicates that the numerical method works well. Through this study, the mechanism of the unconventional aerodynamic characteristics of airfoil is analyzed and discussed based on the computational predictions coupled with the wind tunnel results. It is considered that the boundary layer transition at the leading edge and the unsteady flow separation vortices at the trailing edge are the causes of the case. Furthermore, a valuable insight into the physics of how the flow behavior affects the elliptic airfoil’s aerodynamics is provided.

Free-stream turbulence effects on the flow around an S809 wind turbine airfoil

Energy Technology Data Exchange (ETDEWEB)

Torres-Nieves, Sheilla; Maldonado, Victor; Lebron, Jose [Rensselaer Polytechnic Institute, Troy, NY (United States); Kang, Hyung-Suk [United States Naval Academy, Annapolis, MD (United States); Meneveau, Charles [Johns Hopkins Univ., Baltimore, MD (United States); Castillo, Luciano [Texas Tech Univ., Lubbock, TX (United States)

2012-07-01

Two-dimensional Particle Image Velocimetry (2-D PIV) measurements were performed to study the effect of free-stream turbulence on the flow around a smooth and rough surface airfoil, specifically under stall conditions. A 0.25-m chord model with an S809 profile, common for horizontal-axis wind turbine applications, was tested at a wind tunnel speed of 10 m/s, resulting in Reynolds numbers based on the chord of Re{sub c} {approx} 182,000 and turbulence intensity levels of up to 6.14%. Results indicate that when the flow is fully attached, turbulence significantly decreases aerodynamic efficiency (from L/D {approx} 4.894 to L/D {approx} 0.908). On the contrary, when the flow is mostly stalled, the effect is reversed and aerodynamic performance is slightly improved (from L/D {approx} 1.696 to L/D {approx} 1.787). Analysis of the mean flow over the suction surface shows that, contrary to what is expected, free-stream turbulence is actually advancing separation, particularly when the turbulent scales in the free-stream are of the same order as the chord. This is a result of the complex dynamics between the boundary layer scales and the free-stream turbulence length scales when relatively high levels of active-grid generated turbulence are present. (orig.)

Experimental Investigation of a Passively Deforming Airfoil Under Dynamic Flow Conditions

OpenAIRE

Cordes, Ulrike

2016-01-01

A rigid and a passively deforming airfoil, designed to alleviate fatigue causing load fluctuations that appear during normal operation of wind turbines, is investigated under unsteady conditions in two dimensional wind tunnel experiments. In a first series of experiments, a vertical gust encounter is generated by means of an active grid. This approximates the wind turbine blade’s passage through the atmospheric boundary layer and corresponds to the theoretical formulation of the Sears problem...

Composite airfoil assembly

Science.gov (United States)

Garcia-Crespo, Andres Jose

2015-03-03

A composite blade assembly for mounting on a turbine wheel includes a ceramic airfoil and an airfoil platform. The ceramic airfoil is formed with an airfoil portion, a blade shank portion and a blade dovetail tang. The metal platform includes a platform shank and a radially inner platform dovetail. The ceramic airfoil is captured within the metal platform, such that in use, the ceramic airfoil is held within the turbine wheel independent of the metal platform.

Reduction of airfoil trailing edge noise by trailing edge blowing

International Nuclear Information System (INIS)

Gerhard, T; Carolus, T; Erbslöh, S

2014-01-01

The paper deals with airfoil trailing edge noise and its reduction by trailing edge blowing. A Somers S834 airfoil section which originally was designed for small wind turbines is investigated. To mimic realistic Reynolds numbers the boundary layer is tripped on pressure and suction side. The chordwise position of the blowing slot is varied. The acoustic sources, i.e. the unsteady flow quantities in the turbulent boundary layer in the vicinity of the trailing edge, are quantified for the airfoil without and with trailing edge blowing by means of a large eddy simulation and complementary measurements. Eventually the far field airfoil noise is measured by a two-microphone filtering and correlation and a 40 microphone array technique. Both, LES-prediction and measurements showed that a suitable blowing jet on the airfoil suction side is able to reduce significantly the turbulence intensity and the induced surface pressure fluctuations in the trailing edge region. As a consequence, trailing edge noise associated with a spectral hump around 500 Hz could be reduced by 3 dB. For that a jet velocity of 50% of the free field velocity was sufficient. The most favourable slot position was at 90% chord length

Airfoil shape optimization using non-traditional optimization technique and its validation

Directory of Open Access Journals (Sweden)

R. Mukesh

2014-07-01

Full Text Available Computational fluid dynamics (CFD is one of the computer-based solution methods which is more widely employed in aerospace engineering. The computational power and time required to carry out the analysis increase as the fidelity of the analysis increases. Aerodynamic shape optimization has become a vital part of aircraft design in the recent years. Generally if we want to optimize an airfoil we have to describe the airfoil and for that, we need to have at least hundred points of x and y co-ordinates. It is really difficult to optimize airfoils with this large number of co-ordinates. Nowadays many different schemes of parameter sets are used to describe general airfoil such as B-spline, and PARSEC. The main goal of these parameterization schemes is to reduce the number of needed parameters as few as possible while controlling the important aerodynamic features effectively. Here the work has been done on the PARSEC geometry representation method. The objective of this work is to introduce the knowledge of describing general airfoil using twelve parameters by representing its shape as a polynomial function. And also we have introduced the concept of Genetic Algorithm to optimize the aerodynamic characteristics of a general airfoil for specific conditions. A MATLAB program has been developed to implement PARSEC, Panel Technique, and Genetic Algorithm. This program has been tested for a standard NACA 2411 airfoil and optimized to improve its coefficient of lift. Pressure distribution and co-efficient of lift for airfoil geometries have been calculated using the Panel method. The optimized airfoil has improved co-efficient of lift compared to the original one. The optimized airfoil is validated using wind tunnel data.

Macro-Fiber Composite actuated simply supported thin airfoils

International Nuclear Information System (INIS)

Bilgen, Onur; Kochersberger, Kevin B; Inman, Daniel J; Ohanian, Osgar J III

2010-01-01

A piezoceramic composite actuator known as Macro-Fiber Composite (MFC) is used for actuation in the design of a variable camber airfoil intended for a ducted fan aircraft. The study focuses on response characterization under aerodynamic loads for circular arc airfoils with variable pinned boundary conditions. A parametric study of fluid–structure interaction is employed to find pin locations along the chordwise direction that result in high lift generation. Wind tunnel experiments are conducted on a 1.0% thick, 127 mm chord MFC actuated bimorph airfoil that is simply supported at 5% and 50% of the chord. Aerodynamic and structural performance results are presented for a flow rate of 15 m s −1 and a Reynolds number of 127 000. Non-linear effects due to aerodynamic and piezoceramic hysteresis are identified and discussed. A lift coefficient change of 1.46 is observed, purely due to voltage actuation. A maximum 2D L/D ratio of 17.8 is recorded through voltage excitation

Dynamic lift measurements on a FX79W151A airfoil via pressure distribution on the wind tunnel walls

Energy Technology Data Exchange (ETDEWEB)

Wolken-Moehlmann, Gerrit [ForWind - Center for Wind Energy Research, University of Oldenburg (Germany); Knebel, Pascal [ForWind - Center for Wind Energy Research, University of Oldenburg (Germany); Barth, Stephan [ECN Wind Energy, Energy research Centre of the (Netherlands); Peinke, Joachim [ForWind - Center for Wind Energy Research, University of Oldenburg (Germany)

2007-07-15

We report on an experimental setup for measurements of dynamic stall for airfoils via the pressure distribution over wind tunnel walls. This measuring technique, hitherto used for lift measurements under static conditions, is also an adequate method for dynamic conditions until stall occurs. A step motor is used, allowing for sinusoidal as well as non-sinusoidal and stochastic pitching to simulate fast fluctuating flow conditions. Measurements with sinusoidal pitching and constant angular velocities were done and show dynamic stall characteristics. Under dynamic stall conditions, maximum lift coefficients were up to 80% higher than the maximum for static lift.

LES tests on airfoil trailing edge serration

International Nuclear Information System (INIS)

Zhu, Wei Jun; Shen, Wen Zhong

2016-01-01

In the present study, a large number of acoustic simulations are carried out for a low noise airfoil with different Trailing Edge Serrations (TES). The Ffowcs Williams-Hawkings (FWH) acoustic analogy is used for noise prediction at trailing edge. The acoustic solver is running on the platform of our in-house incompressible flow solver EllipSys3D. The flow solution is first obtained from the Large Eddy Simulation (LES), the acoustic part is then carried out based on the instantaneous hydrodynamic pressure and velocity field. To obtain the time history data of sound pressure, the flow quantities are integrated around the airfoil surface through the FWH approach. For all the simulations, the chord based Reynolds number is around 1.5x10 6 . In the test matrix, the effects from angle of attack, the TE flap angle, the length/width of the TES are investigated. Even though the airfoil under investigation is already optimized for low noise emission, most numerical simulations and wind tunnel experiments show that the noise level is further decreased by adding the TES device. (paper)

Comprehensive performance comparison of airfoil fin PCHEs with NACA 00XX series airfoil

Energy Technology Data Exchange (ETDEWEB)

Chen, Fei, E-mail: chenfei@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190 (China); Heating Technology Research and Development Center, Beijing District Heating Group, Beijing 100028 (China); Zhang, Lishen, E-mail: lishenzhang@sina.com [Heating Technology Research and Development Center, Beijing District Heating Group, Beijing 100028 (China); Huai, Xiulan, E-mail: hxl@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190 (China); Li, Jufeng, E-mail: lijufeng.net@163.com [Nuclear and Radiation Safety Center, Ministry of Environmental Protection, Beijing 100082 (China); Zhang, Hang, E-mail: zhanghang@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190 (China); Liu, Zhigang, E-mail: zgliu9322@163.com [Energy Research Institute of Shandong Academy of Sciences, Jinan, Shandong 250014 (China)

2017-04-15

Highlights: • Pressure drop of NACA 0020 airfoil fin PCHE reduces strikingly in comparison with the zigzag PCHE. • Pressure drop of NACA 00XX airfoil fin PCHE decreases as airfoil thickness increases. • Heat transfer performance of NACA 00XX airfoil fin PCHE increases as airfoil thickness rises. • Comprehensive performance of NACA 00XX airfoil fin PCHE degrades as airfoil thickness increases. - Abstract: Printed circuit heat exchanger (PCHE) can be used in supercritical carbon dioxide (S-CO{sub 2}) Brayton cycle. The present study compares NACA 0020 airfoil fin PCHE with conventional zigzag PCHE by numerical analysis. Pressure drop of the former has a striking reduction while maintaining excellent heat transfer performance. Comparison on four NACA 00XX series airfoil fin PCHEs is performed to investigate the influence of airfoil profile on flow and heat transfer performance. With a fixed vertical pitch, heat transfer performance of NACA series airfoil fin PCHE increases as airfoil thickness increases. However, comprehensive performance, in which both flow and heat transfer are taken into account, degrades with increasing airfoil thickness. Among four NACA airfoil fin PCHEs presented in this paper, NACA 0010 airfoil fin PCHE demonstrates the best comprehensive performance.

Comprehensive performance comparison of airfoil fin PCHEs with NACA 00XX series airfoil

International Nuclear Information System (INIS)

Chen, Fei; Zhang, Lishen; Huai, Xiulan; Li, Jufeng; Zhang, Hang; Liu, Zhigang

2017-01-01

Highlights: • Pressure drop of NACA 0020 airfoil fin PCHE reduces strikingly in comparison with the zigzag PCHE. • Pressure drop of NACA 00XX airfoil fin PCHE decreases as airfoil thickness increases. • Heat transfer performance of NACA 00XX airfoil fin PCHE increases as airfoil thickness rises. • Comprehensive performance of NACA 00XX airfoil fin PCHE degrades as airfoil thickness increases. - Abstract: Printed circuit heat exchanger (PCHE) can be used in supercritical carbon dioxide (S-CO_2) Brayton cycle. The present study compares NACA 0020 airfoil fin PCHE with conventional zigzag PCHE by numerical analysis. Pressure drop of the former has a striking reduction while maintaining excellent heat transfer performance. Comparison on four NACA 00XX series airfoil fin PCHEs is performed to investigate the influence of airfoil profile on flow and heat transfer performance. With a fixed vertical pitch, heat transfer performance of NACA series airfoil fin PCHE increases as airfoil thickness increases. However, comprehensive performance, in which both flow and heat transfer are taken into account, degrades with increasing airfoil thickness. Among four NACA airfoil fin PCHEs presented in this paper, NACA 0010 airfoil fin PCHE demonstrates the best comprehensive performance.

Large eddy simulations of an airfoil in turbulent inflow

DEFF Research Database (Denmark)

Gilling, Lasse; Sørensen, Niels N.

2008-01-01

Wind turbines operate in the turbulent boundary layer of the atmosphere and due to the rotational sampling effect the blades experience a high level of turbulence [1]. In this project the effect of turbulence is investigated by large eddy simulations of the turbulent flow past a NACA 0015 airfoil...

Flapping wing applied to wind generators

Science.gov (United States)

Colidiuc, Alexandra; Galetuse, Stelian; Suatean, Bogdan

2012-11-01

The new conditions at the international level for energy source distributions and the continuous increasing of energy consumption must lead to a new alternative resource with the condition of keeping the environment clean. This paper offers a new approach for a wind generator and is based on the theoretical aerodynamic model. This new model of wind generator helped me to test what influences would be if there will be a bird airfoil instead of a normal wind generator airfoil. The aim is to calculate the efficiency for the new model of wind generator. A representative direction for using the renewable energy is referred to the transformation of wind energy into electrical energy, with the help of wind turbines; the development of such systems lead to new solutions based on high efficiency, reduced costs and suitable to the implementation conditions.

Self streamlining wind tunnel: Further low speed testing and final design studies for the transonic facility

Science.gov (United States)

Wolf, S. W. D.

1978-01-01

Work was continued with the low speed self streamlining wind tunnel (SSWT) using the NACA 0012-64 airfoil in an effort to explain the discrepancies between the NASA Langley low turbulence pressure tunnel (LTPT) and SSWT results obtained with the airfoil stalled. Conventional wind tunnel corrections were applied to straight wall SSWT airfoil data, to illustrate the inadequacy of standard correction techniques in circumstances of high blockage. Also one SSWT test was re-run at different air speeds to investigate the effects of such changes (perhaps through changes in Reynold's number and freestream turbulence levels) on airfoil data and wall contours. Mechanical design analyses for the transonic self-streamlining wind tunnel (TSWT) were completed by the application of theoretical airfoil flow field data to the elastic beam and streamline analysis. The control system for the transonic facility, which will eventually allow on-line computer operation of the wind tunnel, was outlined.

Dynamic Stall Characteristics of Drooped Leading Edge Airfoils

Science.gov (United States)

Sankar, Lakshmi N.; Sahin, Mehmet; Gopal, Naveen

2000-01-01

Helicopters in high-speed forward flight usually experience large regions of dynamic stall over the retreating side of the rotor disk. The rapid variations in the lift and pitching moments associated with the stall process can result in vibratory loads, and can cause fatigue and failure of pitch links. In some instances, the large time lag between the aerodynamic forces and the blade motion can trigger stall flutter. A number of techniques for the alleviation of dynamic stall have been proposed and studied by researchers. Passive and active control techniques have both been explored. Passive techniques include the use of high solidity rotors that reduce the lift coefficients of individual blades, leading edge slots and leading edge slats. Active control techniques include steady and unsteady blowing, and dynamically deformable leading edge (DDLE) airfoils. Considerable amount of experimental and numerical data has been collected on the effectiveness of these concepts. One concept that has not received as much attention is the drooped-leading edge airfoil idea. It has been observed in wind tunnel studies and flight tests that drooped leading edge airfoils can have a milder dynamic stall, with a significantly milder load hysteresis. Drooped leading edge airfoils may not, however, be suitable at other conditions, e.g. in hover, or in transonic flow. Work needs to be done on the analysis and design of drooped leading edge airfoils for efficient operation in a variety of flight regimes (hover, dynamic stall, and transonic flow). One concept that is worthy of investigation is the dynamically drooping airfoil, where the leading edge shape is changed roughly once-per-rev to mitigate the dynamic stall.

Numerical study of unsteady viscous flow past oscillating airfoil

Energy Technology Data Exchange (ETDEWEB)

Jin Yan; Yuan Xin [Tsinghua Univ., Dept. of Thermal Engineering, Beijing (China)

2001-07-01

Accurate simulation of the dynamic stall of an oscillating airfoil is of major importance to wing and wind turbine blade design. However, dynamic stall is complicated and influenced by many factors, such as geometry shape of the airfoil, reduced frequency, etc. The difficulties of simulation are both mathematical (numerical method) and physical (turbulence model). The present paper has introduced a new numerical method (new LU-type scheme and fourth-order higher resolution MUSCL TVD scheme) and q-{omega} turbulence modelling to calculate the unsteady flowfields of an oscillating NACA0015 airfoil. The test targets include attached flow, light-stall and deep-stall of the airfoil. The calculated results for attached flow and light-stall are in good agreement with those of experiments. The calculated results for deep-stall also show improvement, especially during the downstroke of the oscillation. However, there is still a significant difference between the results of calculation and experiment in the hysteresis curves of the drag coefficient. One reason is that the q-{omega} turbulence model still has limitations. Another is that the drag coefficient is difficult to measure and the experiments are not reliable. (Author)

CFD simulation of flow-induced vibration of an elastically supported airfoil

Directory of Open Access Journals (Sweden)

Šidlof Petr

2016-01-01

Full Text Available Flow-induced vibration of lifting or control surfaces in aircraft may lead to catastrophic consequences. Under certain circumstances, the interaction between the airflow and the elastic structure may lead to instability with energy transferred from the airflow to the structure and with exponentially increasing amplitudes of the structure. In the current work, a CFD simulation of an elastically supported NACA0015 airfoil with two degrees of freedom (pitch and plunge coupled with 2D incompressible airflow is presented. The geometry of the airfoil, mass, moment of inertia, location of the centroid, linear and torsional stiffness was matched to properties of a physical airfoil model used for wind-tunnel measurements. The simulations were run within the OpenFOAM computational package. The results of the CFD simulations were compared with the experimental data.

Tenth ASME wind energy symposium

International Nuclear Information System (INIS)

Berg, D.E.; Veers, P.S.

1991-01-01

This book contains papers presented at the Fourteenth Annual Energy-Sources Technology Conference and Exhibition. Included are the following papers: Wind Power Farm Site Selection, Turbulence characterization for wind energy development, Effects of insect configuration on wind turbine airfoils, Power fluctuations from horizontal and vertical axis wind turbines, Power regulation by active yaw control for a teetered wind rotor, and economic aspects of wind energy

An experimental investigation of the low Reynolds number performance of the Lissaman 7769 airfoil

Science.gov (United States)

Conigliaro, P. E.

1983-01-01

A Lissaman 7769 airfoil, used on the Gossamer Condor and Gossamer Albatross human-powered aircraft, was tested in a low turbulence subsonic wind tunnel. Lift and drag data were collected at chord Reynolds numbers of 100,000, 150,000, 200,000, 250,000, and 300,000; at angles of attack from -10 to +20 deg by using an external strain gage force balance. Lift curves, drag curves, and drag polars were generated from both uncorrected data and data corrected for wind tunnel blockage effects. A flow visualization study was performed to correlate with the force data. The results of the investigation have shown that the airfoil exhibits a significant degradation in performance for chord Reynolds numbers below 150,000.

Effects of grit roughness and pitch oscillations on the S801 airfoil

Energy Technology Data Exchange (ETDEWEB)

Ramsay, R.R.; Hoffman, M.J.; Gregorek, G.M. [Ohio State Univ., Columbus, OH (United States)

1996-01-01

Horizontal axis wind turbine rotors experience unsteady aerodynamics due to wind shear when the rotor is yawed, when rotor blades pass through the support tower wake, and when the wind is gusting. An understanding of this unsteady behavior is necessary to assist in the calculation of rotor performance and loads. The rotors also experience performance degradation due to surface roughness. These surface irregularities are due to the accumulation of insect debris, ice, and the aging process. Wind tunnel studies that examine both the steady and unsteady behavior of airfoils can help define pertinent flow phenomena, and the resultant data can be used to validate analytical computer codes. A S801 airfoil model was tested in The Ohio State University Aeronautical and Astronautical Research Laboratory (OSU/AARL) 3x5 subsonic wind tunnel (3x5) under steady flow and stationary model conditions, as well as with the model undergoing pitch oscillations. To study the possible extent of performance loss due to surface roughness, a standard grit pattern (LEGR) was used to simulate leading edge contamination. After baseline cases were completed, the LEGR was applied for both steady state and model pitch oscillation cases. The Reynolds numbers used for steady state conditions were 0.75, 1, 1.25, and 1.5 million, while the angle of attack ranged from -20{degrees} to +40{degrees}. With the model undergoing pitch oscillations, data were acquired at Reynolds numbers of 0.75, 1, 1.25, and 1.4 million, at frequencies of 0.6, 1.2, and 1.8 Hz. Two sine wave forcing functions were used, {plus_minus} 5.5 {degrees}and {plus_minus} 10{degrees}, at mean angles of attack of 8{degrees} 14{degrees} and 20{degrees} For purposes herein, any reference to unsteady conditions means that the airfoil model was in pitch oscillation about the quarter chord.

Schlieren visualization of flow-field modification over an airfoil by near-surface gas-density perturbations generated by a nanosecond-pulse-driven plasma actuator

International Nuclear Information System (INIS)

Komuro, Atsushi; Konno, Kaiki; Ando, Akira; Takashima, Keisuke; Kaneko, Toshiro; Tanaka, Naoki; Nonomura, Taku; Asai, Keisuke

2017-01-01

Gas-density perturbations near an airfoil surface generated by a nanosecond dielectric-barrier-discharge plasma actuator (ns-DBDPA) are visualized using a high-speed Schlieren imaging method. Wind-tunnel experiments are conducted for a wind speed of 20 m s −1 with an NACA0015 airfoil whose chord length is 100 mm. The results show that the ns-DBDPA first generates a pressure wave and then stochastic perturbations of the gas density near the leading edge of the airfoil. Two structures with different characteristics are observed in the stochastic perturbations. One structure propagates along the boundary between the shear layer and the main flow at a speed close to that of the main flow. The other propagates more slowly on the surface of the airfoil and causes mixing between the main and shear flows. It is observed that these two heated structures interact with each other, resulting in a recovery in the negative pressure coefficient at the leading edge of the airfoil. (paper)

A New Method for Horizontal Axis Wind Turbine (HAWT Blade Optimization

Directory of Open Access Journals (Sweden)

Mohammadreza Mohammadi

2016-02-01

Full Text Available Iran has a great potential for wind energy. This paper introduces optimization of 7 wind turbine blades for small and medium scales in a determined wind condition of Zabol site, Iran, where the average wind speed is considered 7 m /s. Considered wind turbines are 3 bladed and radius of 7 case study turbine blades are 4.5 m, 6.5 m, 8 m, 9 m, 10 m, 15.5 m and 20 m. As the first step, an initial design is performed using one airfoil (NACA 63-215 across the blade. In the next step, every blade is divided into three sections, while the 20 % of first part of the blade is considered as root, the 5% of last the part is considered as tip and the rest of the blade as mid part. Providing necessary input data, suitable airfoils for wind turbines including 43 airfoils are extracted and their experimental data are entered in optimization process. Three variables in this optimization problem would be airfoil type, attack angle and chord, where the objective function is maximum output torque. A MATLAB code was written for design and optimization of the blade, which was validated with a previous experimental work. In addition, a comparison was made to show the effect of optimization with two variables (airfoil type and attack angle versus optimization with three variables (airfoil type, attack angle and chord on output torque increase. Results of this research shows a dramatic increase in comparison to initial designed blade with one airfoil where two variable optimization causes 7.7% to 22.27 % enhancement and three variable optimization causes 17.91% up to 24.48% rise in output torque .Article History: Received Oct 15, 2015; Received in revised form January 2, 2016; Accepted January 14, 2016; Available online How to Cite This Article: Mohammadi, M., Mohammadi, A. and Farahat, S. (2016 A New Method for Horizontal Axis Wind Turbine (HAWT Blade Optimization. Int. Journal of Renewable Energy Development, 5(1,1-8. http://dx.doi.org/10.14710/ijred.5.1.1-8

Unsteady Double Wake Model for the Simulation of Stalled Airfoils

DEFF Research Database (Denmark)

Ramos García, Néstor; Cayron, Antoine; Sørensen, Jens Nørkær

2015-01-01

In the present work, the recent developed Unsteady Double Wake Model, USDWM, is used to simulate separated flows past a wind turbine airfoil at high angles of attack. The solver is basically an unsteady two-dimensional panel method which uses the unsteady double wake technique to model flow separ...

Investigation of flow past a translatoric oscillating airfoil using detached eddy simulation

DEFF Research Database (Denmark)

Reck, Mads; Hansen, Martin Otto Laver; Sørensen, Jens Nørkær

2003-01-01

Wind turbine rotor blades in operation have been observed to undergo stall-induced lead-lag instabilities resulting in dramatic reduction of blade life, due to structural fatigue. Previous attempts to numerically simulate the flow past a translatoric oscillating airfoil have been few and feeble...... at the high angle of attacks often experienced by the individual rotor blade. The present paper covers simulation of a translatoric oscillating NACA 0015 airfoil at a Reynolds number of 555,000, corresponding to avialable experimental data, using the newly adopted Detached Eddy Simulation (DES) approach...

Airfoil design: Finding the balance between design lift and structural stiffness

DEFF Research Database (Denmark)

Bak, Christian; Gaudern, Nicholas; Zahle, Frederik

2014-01-01

When upscaling wind turbine blades there is an increasing need for high levels of structural efficiency. In this paper the relationships between the aerodynamic characteristics; design lift and lift-drag ratio; and the structural characteristics were investigated. Using a unified optimization setup......, the design lift coefficient increases if the box length reduces and at the same time the relative thickness increases. Even though the conclusions are specific to the airfoil design approach used, the study indicated that an increased design lift required slightly higher relative thickness compared...... to airfoils with lower design lift to maintain the flapwise stiffness. Also, the study indicated that the lift-drag ratio as a function of flapwise stiffness was relatively independent of the airfoil design with a tendency that the lift-drag ratio decreased for large box lengths. The above conclusions were...

Ice Accretion on Wind Turbine Blades

DEFF Research Database (Denmark)

Hudecz, Adriána; Koss, Holger; Hansen, Martin Otto Laver

2013-01-01

In this paper, both experimental and numerical simulations of the effects of ice accretion on a NACA 64-618 airfoil section with 7° angle of attack are presented. The wind tunnel tests were conducted in a closed-circuit climatic wind tunnel at Force Technology in Denmark. The changes of aerodynamic...... forces were monitored as ice was building up on the airfoil for glaze, rime and mixed ice. In the first part of the numerical analysis, the resulted ice profiles of the wind tunnel tests were compared to profiles estimated by using the 2D ice accretion code TURBICE. In the second part, Ansys Fluent...... of the rime iced ice profile follows the streamlines quite well, disturbing the flow the least. The TURBICE analysis agrees fairly with the profiles produced during the wind tunnel testing....

Airfoil design: Finding the balance between design lift and structural stiffness

International Nuclear Information System (INIS)

Bak, Christian; Gaudern, Nicholas; Zahle, Frederik; Vronsky, Tomas

2014-01-01

When upscaling wind turbine blades there is an increasing need for high levels of structural efficiency. In this paper the relationships between the aerodynamic characteristics; design lift and lift-drag ratio; and the structural characteristics were investigated. Using a unified optimization setup, airfoils were designed with relative thicknesses between 18% and 36%, a structural box height of 85% of the relative thickness, and varying box widths in chordwise direction between 20% and 40% of the chord length. The results from these airfoil designs showed that for a given flapwise stiffness, the design lift coefficient increases if the box length reduces and at the same time the relative thickness increases. Even though the conclusions are specific to the airfoil design approach used, the study indicated that an increased design lift required slightly higher relative thickness compared to airfoils with lower design lift to maintain the flapwise stiffness. Also, the study indicated that the lift-drag ratio as a function of flapwise stiffness was relatively independent of the airfoil design with a tendency that the lift-drag ratio decreased for large box lengths. The above conclusions were supported by an analysis of the three airfoil families Riso-C2, DU and FFA, where the lift-drag ratio as a function of flapwise stiffness was decreasing, but relatively independent of the airfoil design, and the design lift coefficient was varying depending on the design philosophy. To make the analysis complete also design lift and lift- drag ratio as a function of edgewise and torsional stiffness were shown

Computation of aerodynamic interference effects on oscillating airfoils with controls in ventilated subsonic wind tunnels

Science.gov (United States)

Fromme, J. A.; Golberg, M. A.

1979-01-01

Lift interference effects are discussed based on Bland's (1968) integral equation. A mathematical existence theory is utilized for which convergence of the numerical method has been proved for general (square-integrable) downwashes. Airloads are computed using orthogonal airfoil polynomial pairs in conjunction with a collocation method which is numerically equivalent to Galerkin's method and complex least squares. Convergence exhibits exponentially decreasing error with the number n of collocation points for smooth downwashes, whereas errors are proportional to 1/n for discontinuous downwashes. The latter can be reduced to 1/n to the m+1 power with mth-order Richardson extrapolation (by using m = 2, hundredfold error reductions were obtained with only a 13% increase of computer time). Numerical results are presented showing acoustic resonance, as well as the effect of Mach number, ventilation, height-to-chord ratio, and mode shape on wind-tunnel interference. Excellent agreement with experiment is obtained in steady flow, and good agreement is obtained for unsteady flow.

Separated Flow over Wind Turbines

Science.gov (United States)

Brown, David; Lewalle, Jacques

2015-11-01

The motion of the separation point on an airfoil under unsteady flow can affect its performance and longevity. Of interest is to understand and control the performance decrease in wind turbines subject to turbulent flow. We examine flow separation on an airfoil at a 19 degree angle of attack under unsteady flow conditions. We are using a DU-96-W180 airfoil of chord length 242 mm. The unsteadiness is generated by a cylinder with diameter 203 mm located 7 diameters upstream of the airfoil's leading edge. The data comes from twenty surface pressure sensors located on the top and bottom of the airfoil as well as on the upstream cylinder. Methods of analysis include Mexican hat transforms, Morlet wavelet transforms, power spectra, and various cross correlations. With this study I will explore how the differences of signals on the pressure and suction sides of an airfoil are related to the motion of the separation point.

Experimental parameter study for passive vortex generators on a 30% thick airfoil

NARCIS (Netherlands)

Baldacchino, D.; Simao Ferreira, C.; De Tavernier, D.A.M.; Timmer, W.A.; van Bussel, G.J.W.

2018-01-01

Passive vane-type vortex generators (VGs) are commonly used on wind turbine blades to mitigate the effects of flow separation. However, significant uncertainty surrounds VG design guidelines. Understanding the influence of VG parameters on airfoil performance requires a systematic approach

CFD modelling of laminar-turbulent transition for airfoils and rotors using the gamma-(Re)over-tilde (theta) model

DEFF Research Database (Denmark)

Sørensen, Niels N.

2009-01-01

When predicting the flow over airfoils and rotors, the laminar-turbulent transition process can be important for the aerodynamic performance. Today, the most widespread approach is to use fully turbulent computations, where the transitional process is ignored and the entire boundary layer...... to flow over a flat plate, flow over the S809 and the NACA63-415 airfoils, flow over a prolate spheroid at zero and thirty degrees angle of attack, and finally to the NREL Phase VI wind turbine rotor for the zero yaw upwind cases from the NREL/NASA Ames wind tunnel test. Copyright © 2009 John Wiley & Sons...

Reinforced Airfoil Shaped Body

DEFF Research Database (Denmark)

2011-01-01

The present invention relates to an airfoil shaped body with a leading edge and a trailing edge extending along the longitudinal extension of the body and defining a profile chord, the airfoil shaped body comprising an airfoil shaped facing that forms the outer surface of the airfoil shaped body...

Boundary Layer Separation and Reattachment Detection on Airfoils by Thermal Flow Sensors

Directory of Open Access Journals (Sweden)

Peter Busche

2012-10-01

Full Text Available A sensor concept for detection of boundary layer separation (flow separation, stall and reattachment on airfoils is introduced in this paper. Boundary layer separation and reattachment are phenomena of fluid mechanics showing characteristics of extinction and even inversion of the flow velocity on an overflowed surface. The flow sensor used in this work is able to measure the flow velocity in terms of direction and quantity at the sensor’s position and expected to determine those specific flow conditions. Therefore, an array of thermal flow sensors has been integrated (flush-mounted on an airfoil and placed in a wind tunnel for measurement. Sensor signals have been recorded at different wind speeds and angles of attack for different positions on the airfoil. The sensors used here are based on the change of temperature distribution on a membrane (calorimetric principle. Thermopiles are used as temperature sensors in this approach offering a baseline free sensor signal, which is favorable for measurements at zero flow. Measurement results show clear separation points (zero flow and even negative flow values (back flow for all sensor positions. In addition to standard silicon-based flow sensors, a polymer-based flexible approach has been tested showing similar results.

Low-Reynolds number compressible flow around a triangular airfoil

Science.gov (United States)

Munday, Phillip; Taira, Kunihiko; Suwa, Tetsuya; Numata, Daiju; Asai, Keisuke

2013-11-01

We report on the combined numerical and experimental effort to analyze the nonlinear aerodynamics of a triangular airfoil in low-Reynolds number compressible flow that is representative of wings on future Martian air vehicles. The flow field around this airfoil is examined for a wide range of angles of attack and Mach numbers with three-dimensional direct numerical simulations at Re = 3000 . Companion experiments are conducted in a unique Martian wind tunnel that is placed in a vacuum chamber to simulate the Martian atmosphere. Computational findings are compared with pressure sensitive paint and direct force measurements and are found to be in agreement. The separated flow from the leading edge is found to form a large leading-edge vortex that sits directly above the apex of the airfoil and provides enhanced lift at post stall angles of attack. For higher subsonic flows, the vortical structures elongate in the streamwise direction resulting in reduced lift enhancement. We also observe that the onset of spanwise instability for higher angles of attack is delayed at lower Mach numbers. Currently at Mitsubishi Heavy Industries, Ltd., Nagasaki.

A new method for measuring lift forces acting on an airfoil under dynamic conditions

Energy Technology Data Exchange (ETDEWEB)

Wolken-Moehlmann, Gerrit; Peinke, Joachim [Institute of Physics, University of Oldenburg (Germany)

2008-07-01

Wind turbines operate in a turbulent atmospheric boundary layer and are exposed to strong wind fluctuations in time and space. This can induce the dynamic stall, a phenomenon that causes extra loads. Dynamic stall occurs under fast changes in the angle of attack (AoA) and was determined in detail in helicopter research. But in contrast to helicopter aerodynamics, the changes in the AoA of wind turbine airfoils are in general non-sinusoidal, and thus it seems to be difficult to use these measurements and models. Our goal is to acquire lift data under conditions more comparable to real wind turbines, including non-periodic changes in the AoA. For this purpose a closed test section for our wind tunnel was built. An airfoil with a chord length of 0.2m will be rotated by a stepping motor with angular velocities of up to 300 {sup circle} /s. With a maximum wind velocity of 50m/s, Reynolds numbers of Re=700 000 can be realized. The lift force is determined by the counter forces acting on the wind tunnel walls. These are measured by two lines of 40 pressure sensors with sampling rates up to 2kHz. The results show distinct dynamic stall characteristics. Further experiments with different parameters and foils will give a better insight in dynamic stall and a verification and improvement of existing models.

Closed loop steam cooled airfoil

Science.gov (United States)

Widrig, Scott M.; Rudolph, Ronald J.; Wagner, Gregg P.

2006-04-18

An airfoil, a method of manufacturing an airfoil, and a system for cooling an airfoil is provided. The cooling system can be used with an airfoil located in the first stages of a combustion turbine within a combined cycle power generation plant and involves flowing closed loop steam through a pin array set within an airfoil. The airfoil can comprise a cavity having a cooling chamber bounded by an interior wall and an exterior wall so that steam can enter the cavity, pass through the pin array, and then return to the cavity to thereby cool the airfoil. The method of manufacturing an airfoil can include a type of lost wax investment casting process in which a pin array is cast into an airfoil to form a cooling chamber.

Icing Problems of Wind Turbine Blades in Cold Climates

DEFF Research Database (Denmark)

Hudecz, Adriána

Climatic Wind Tunnel located at FORCE Technology. The aerodynamic forces acting on the blade during ice accretion for different angles of attack at various air temperatures were measured along with the mass of ice and the final ice shape. For all three types of ice accretion, glaze, mixed and rime ice...... and on the aerodynamic characteristics of the airfoil. The trend of the reduction of lift coefficients agrees quite well with the wind tunnel test results, although based on the measured and the numerical lift coefficients of the clean airfoil, the presence of the wind tunnel walls had significant influence...

Investigation of a bio-inspired lift-enhancing effector on a 2D airfoil.

Science.gov (United States)

Johnston, Joe; Gopalarathnam, Ashok

2012-09-01

A flap mounted on the upper surface of an airfoil, called a 'lift-enhancing effector', has been shown in wind tunnel tests to have a similar function to a bird's covert feathers, which rise off the wing's surface in response to separated flows. The effector, fabricated from a thin Mylar sheet, is allowed to rotate freely about its leading edge. The tests were performed in the NCSU subsonic wind tunnel at a chord Reynolds number of 4 × 10(5). The maximum lift coefficient with the effector was the same as that for the clean airfoil, but was maintained over an angle-of-attack range from 12° to almost 20°, resulting in a very gentle stall behavior. To better understand the aerodynamics and to estimate the deployment angle of the free-moving effector, fixed-angle effectors fabricated out of stiff wood were also tested. A progressive increase in the stall angle of attack with increasing effector angle was observed, with diminishing returns beyond the effector angle of 60°. Drag tests on both the free-moving and fixed effectors showed a marked improvement in drag at high angles of attack. Oil flow visualization on the airfoil with and without the fixed-angle effectors proved that the effector causes the separation point to move aft on the airfoil, as compared to the clean airfoil. This is thought to be the main mechanism by which an effector improves both lift and drag. A comparison of the fixed-effector results with those from the free-effector tests shows that the free effector's deployment angle is between 30° and 45°. When operating at and beyond the clean airfoil's stall angle, the free effector automatically deploys to progressively higher angles with increasing angles of attack. This slows down the rapid upstream movement of the separation point and avoids the severe reduction in the lift coefficient and an increase in the drag coefficient that are seen on the clean airfoil at the onset of stall. Thus, the effector postpones the stall by 4-8° and makes the

Effects of grit roughness and pitch oscillations on the S814 airfoil

Energy Technology Data Exchange (ETDEWEB)

Janiszewska, J.M.; Ramsay, R.R.; Hoffmann, M.J.; Gregorek, G.M. [Ohio State Univ., Columbus, OH (United States)

1996-07-01

Horizontal-axis wind turbine rotors experience unsteady aerodynamics when the rotor is yawed, when rotor blades pass through the support tower wake, and when the wind is gusting. An understanding of this unsteady behavior is necessary to assist in the design of new rotor airfoils. The rotors also experience performance degradation due to surface roughness. These surface irregularities are due to the accumulation of insect debris, ice, and/or the aging process. Wind tunnel studies that examine both the steady and unsteady behavior of airfoils can help define pertinent flow phenomena, and the resultant data can also be used to validate analytical computer codes. An S814 airfoil model was tested in The Ohio State University Aeronautical and Astronautical Research Laboratory (OSU/AARL) 3 X 5 subsonic wind tunnel (3 X 5) under steady flow with both stationary model conditions and pitch oscillations. To study the extent of performance loss due to surface roughness, a leading edge grit roughness pattern (LEGR) was used to simulate leading edge contamination. After baseline cases were completed, the LEGR was applied for both steady state and model pitch oscillation cases. The Reynolds numbers for steady state conditions were 0.75, 1, 1.25 and 1.5 million, while the angle of attack ranged from -20{degrees} to +40{degrees}. While the model underwent pitch oscillations, data were acquired at Reynolds numbers of 0.75, 1, 1.25, and 1.5 million, at frequencies of 0.6, 1.2, and 1.8 Hz. Two sine wave forcing functions {+-}5.5{degrees} and {+-}10{degrees}, were used; at mean angles of attack of 8{degrees}, 14{degrees}, and 20{degrees}. For purposes herein, any reference to unsteady conditions means the model was in pitch oscillation.

High-Altitude Wind Power Generation

NARCIS (Netherlands)

Fagiano, L.; Milanese, M.; Piga, D.

2010-01-01

Abstract—The paper presents the innovative technology of highaltitude wind power generation, indicated as Kitenergy, which exploits the automatic flight of tethered airfoils (e.g., power kites) to extract energy from wind blowing between 200 and 800 m above the ground. The key points of this

Airfoil System for Cruising Flight

Science.gov (United States)

Shams, Qamar A. (Inventor); Liu, Tianshu (Inventor)

2014-01-01

An airfoil system includes an airfoil body and at least one flexible strip. The airfoil body has a top surface and a bottom surface, a chord length, a span, and a maximum thickness. Each flexible strip is attached along at least one edge thereof to either the top or bottom surface of the airfoil body. The flexible strip has a spanwise length that is a function of the airfoil body's span, a chordwise width that is a function of the airfoil body's chord length, and a thickness that is a function of the airfoil body's maximum thickness.

Summary of the Blind Test Campaign to predict the High Reynolds number performance of DU00-W-210 airfoil

DEFF Research Database (Denmark)

Yilmaz, Özlem Ceyhan; Pires, Oscar; Munduate, Xabier

2017-01-01

This paper summarizes the results of a blind test campaign organized in the AVATAR project to predict the high Reynolds number performance of a wind turbine airfoil for wind turbine applications. The DU00-W-210 airfoil was tested in the DNW-HDG pressurized wind tunnel in order to investigate...... the flow at high Reynolds number range from 3 to 15 million which is the operating condition of the future large 10MW+ offshore wind turbine rotors. The results of the experiment was used in a blind test campaign to test the prediction capability of the CFD tools used in the wind turbine rotor simulations....... As a result of the blind test campaign it was found that although the codes are in general capable of predicting increased max lift and decreased minimum drag with Re number, the Re trend predictions in particular the glide ratio (lift over drag) need further improvement. In addition to that, the significant...

Wind Tunnel Measurements at LM Wind Power

DEFF Research Database (Denmark)

Bertagnolio, Franck

2012-01-01

This section presents the results obtained during the experimental campaign that was conducted in the wind tunnel at LM Wind Power in Lunderskov from August 16th to 26th, 2010. The goal of this study is to validate the so-called TNO trailing edge noise model through measurements of the boundary...... layer turbulence characteristics and the far-field noise generated by the acoustic scattering of the turbulent boundary layer vorticies as they convect past the trailing edge. This campaign was conducted with a NACA0015 airfoil section that was placed in the wind tunnel section. It is equipped with high...

Airfoil design and optimization

Energy Technology Data Exchange (ETDEWEB)

Lutz, T. [Stuttgart Univ. (Germany). Inst. fuer Aerodynamik und Gasdynamik

2001-07-01

The aerodynamic efficiency of mildly swept wings is mainly influenced by the characteristics of the airfoil sections. The specific design of airfoils is therefore one of the classical tasks of aerodynamics. Since the airfoil characteristics are directly dependent on the inviscid pressure distribution the application of inverse calculation methods is obvious. The direct numerical airfoil optimization offers an alternative to the manual design and attracts increasing interest. (orig.)

URANS simulations of separated flow with stall cells over an NREL S826 airfoil

DEFF Research Database (Denmark)

Sarlak Chivaee, Hamid; Nishino, T.; Sørensen, Jens Nørkær

2016-01-01

airfoil using unsteady Reynolds-averaged Navier-Stokes (URANS) approach. Results of the simulations are demonstrated in terms of mean flow velocity, lift and drag, as well as pressure distribution, and validated against available experimental data. The simulations are carried out with a wide computational......A series of wind tunnel measurements and oil flow visualization was recently carried out at the Technical University of Denmark in order to investigate flow characteristics over a 14% thick NREL S826 airfoil at low Reynolds numbers. This paper aims at presenting numerical simulations of the same...

Flow past a self-oscillating airfoil with two degrees of freedom: measurements and simulations

Directory of Open Access Journals (Sweden)

Šidlof Petr

2014-03-01

Full Text Available The paper focuses on investigation of the unsteady subsonic airflow past an elastically supported airfoil for subcritical flow velocities and during the onset of the flutter instability. A physical model of the NACA0015 airfoil has been designed and manufactured, allowing motion with two degrees of freedom: pitching (rotation about the elastic axis and plunging (vertical motion. The structural mass and stiffness matrix can be tuned to certain extent, so that the natural frequencies of the two modes approach as needed. The model was placed in the measuring section of the wind tunnel in the aerodynamic laboratory of the Institute of Thermomechanics in Nový Knín, and subjected to low Mach number airflow up to the flow velocities when self-oscillation reach amplitudes dangerous for the structural integrity of the model. The motion of the airfoil was registered by a high-speed camera, with synchronous measurement of the mechanic vibration and discrete pressure sensors on the surface of the airfoil. The results of the measurements are presented together with numerical simulation results, based on a finite volume CFD model of airflow past a vibrating airfoil.

Dynamic Stall Control on the Wind Turbine Airfoil via a Co-Flow Jet

Directory of Open Access Journals (Sweden)

He-Yong Xu

2016-06-01

Full Text Available Dynamic stall control of a S809 airfoil is numerically investigated by implementing a co-flow jet (CFJ. The numerical methods of the solver are validated by comparing results with the baseline experiment as well as a NACA 6415-based CFJ experiment, showing good agreement in both static and dynamic characteristics. The CFJ airfoil with inactive jet is simulated to study the impact that the jet channel imposes upon the dynamic characteristics. It is shown that the presence of a long jet channel could cause a negative effect of decreasing lift and increasing drag, leading to fluctuating extreme loads in terms of drag and moment. The main focus of the present research is the investigation of the dynamic characteristics of the CFJ airfoil with three different jet momentum coefficients, which are compared with the baseline, giving encouraging results. Dynamic stall can be greatly suppressed, showing a very good control performance of significantly increased lift and reduced drag and moment. Analysis of the amplitude of variation in the aerodynamic coefficients indicates that the fluctuating extreme aerodynamic loads are significantly alleviated, which is conducive to structural reliability and improved life cycle. The energy consumption analysis shows that the CFJ concept is applicable and economical in controlling dynamic stall.

Application of a Beamforming Technique to the Measurement of Airfoil Leading Edge Noise

Directory of Open Access Journals (Sweden)

Thomas Geyer

2012-01-01

Full Text Available The present paper describes the use of microphone array technology and beamforming algorithms for the measurement and analysis of noise generated by the interaction of a turbulent flow with the leading edge of an airfoil. Experiments were performed using a setup in an aeroacoustic wind tunnel, where the turbulent inflow is provided by different grids. In order to exactly localize the aeroacoustic noise sources and, moreover, to separate airfoil leading edge noise from grid-generated noise, the selected deconvolution beamforming algorithm is extended to be used on a fully three-dimensional source region. The result of this extended beamforming are three-dimensional mappings of noise source locations. Besides acoustic measurements, the investigation of airfoil leading edge noise requires the measurement of parameters describing the incident turbulence, such as the intensity and a characteristic length scale or time scale. The method used for the determination of these parameters in the present study is explained in detail. To demonstrate the applicability of the extended beamforming algorithm and the experimental setup as a whole, the noise generated at the leading edge of airfoils made of porous materials was measured and compared to that generated at the leading edge of a common nonporous airfoil.

High frequency microphone measurements for transition detection on airfoils. NACA-0015 appendix report

DEFF Research Database (Denmark)

Døssing, Mads

Time series of pressure fluctuations has been obtained using high frequency microphones distributed over the surface of airfoils undergoing wind tunnel tests in the LM Windtunnel, owned by ’LM Glasfiber’, Denmark. The present report describes the dataanalysis, with special attention given to tran...

CFD Study of NACA 0018 Airfoil with Flow Control

Science.gov (United States)

Eggert, Christopher A.; Rumsey, Christopher L.

2017-01-01

The abilities of two different Reynolds-Averaged Navier-Stokes codes to predict the effects of an active flow control device are evaluated. The flow control device consists of a blowing slot located on the upper surface of an NACA 0018 airfoil, near the leading edge. A second blowing slot present on the airfoil near mid-chord is not evaluated here. Experimental results from a wind tunnel test show that a slot blowing with high momentum coefficient will increase the lift of the airfoil (compared to no blowing) and delay flow separation. A slot with low momentum coefficient will decrease the lift and induce separation even at low angles of attack. Two codes, CFL3D and FUN3D, are used in two-dimensional computations along with several different turbulence models. Two of these produced reasonable results for this flow, when run fully turbulent. A more advanced transition model failed to predict reasonable results, but warrants further study using different inputs. Including inviscid upper and lower tunnel walls in the simulations was found to be important in obtaining pressure distributions and lift coefficients that best matched experimental data. A limited number of three-dimensional computations were also performed.

Airfoil Drag Reduction using Controlled Trapped Vorticity Concentrations

Science.gov (United States)

Desalvo, Michael; Glezer, Ari

2017-11-01

The aerodynamic performance of a lifting surface at low angles of attack (when the base flow is fully attached) is improved through fluidic modification of its ``apparent'' shape by superposition of near-surface trapped vorticity concentrations. In the present wind tunnel investigations, a controlled trapped vorticity concentration is formed on the pressure surface of an airfoil (NACA 4415) using a hybrid actuator comprising a passive obstruction of scale O(0.01c) and an integral synthetic jet actuator. The jet actuation frequency [Stact O(10)] is selected to be at least an order of magnitude higher than the characteristic unstable frequency of the airfoil wake, thereby decoupling the actuation from the global instabilities of the base flow. Regulation of vorticity accumulation in the vicinity of the actuator by the jet effects changes in the local pressure, leading in turn to changes in the airfoil's drag and lift. Trapped vorticity can lead to a significant reduction in drag and reduced lift (owing to the sense of the vorticity), e.g. at α =4° and Re = 6.7 .105 the drag and lift reductions are 14% and 2%, respectively. PIV measurements show the spatial variation in the distribution of vorticity concentrations and yield estimates of the corresponding changes in circulation.

Development of an experimental setup for analyzing the influence of Magnus effect on the performance of airfoil

Science.gov (United States)

Aktharuzzaman, Md; Sarker, Md. Samad; Safa, Wasiul; Sharah, Nahreen; Salam, Md. Abdus

2017-12-01

Magnus effect is a phenomenon where pressure difference is created according to Bernoulli's effect due to induced velocity changes caused by a rotating object in a fluid. Using this concept, the idea of delaying boundary layer separation on airfoil by providing moving surface boundary layer control has been developed. In order to analyze the influence of Magnus effect on the aerodynamic performance of an airfoil, there is no alternative of developing an experimental setup. This paper aims to develop such an experimental setup which will be capable of analyzing the influence of Magnus effect on both symmetric and asymmetric airfoils by placing a cylinder at the leading edge. To provide arrangements for a rotating cylinder at the leading edge of airfoil, necessary modifications and additions have been done in the test section of an AF100 subsonic wind tunnel.

Progress in wind tunnel experimental techniques for wind turbine?

Institute of Scientific and Technical Information of China (English)

Jingping XIAO; Li CHEN; Qiang WANG; Qiao WANG

2016-01-01

Based on the unsteady aerodynamics experiment (UAE) phase VI and the model experiment in controlled conditions (MEXICO) projects and the related research carried out in China Aerodynamic Research and Development Center (CARDC), the recent progress in the wind tunnel experimental techniques for the wind turbine is sum-marized. Measurement techniques commonly used for di?erent types of wind tunnel ex-periments for wind turbine are reviewed. Important research achievements are discussed, such as the wind tunnel disturbance, the equivalence of the airfoil in?ow condition, the three-dimensional (3D) e?ect, the dynamic in?ow in?uence, the ?ow ?eld structure, and the vortex induction. The corresponding research at CARDC and some ideas on the large wind turbine are also introduced.

Nozzle airfoil having movable nozzle ribs

Science.gov (United States)

Yu, Yufeng Phillip; Itzel, Gary Michael

2002-01-01

A nozzle vane or airfoil structure is provided in which the nozzle ribs are connected to the side walls of the vane or airfoil in such a way that the ribs provide the requisite mechanical support between the concave side and convex side of the airfoil but are not locked in the radial direction of the assembly, longitudinally of the airfoil. The ribs may be bi-cast onto a preformed airfoil side wall structure or fastened to the airfoil by an interlocking slide connection and/or welding. By attaching the nozzle ribs to the nozzle airfoil metal in such a way that allows play longitudinally of the airfoil, the temperature difference induced radial thermal stresses at the nozzle airfoil/rib joint area are reduced while maintaining proper mechanical support of the nozzle side walls.

Performance prediction of asymmetrical bladed H-Darrieus VAWT rotors in low wind speed condition using CFD

Science.gov (United States)

Mazarbhuiya, Hussain Mahamed Sahed Mostafa; Biswas, Agnimitra; Sharma, Kaushal Kumar

2018-04-01

Wind energy is an essential and carbon free form of renewable energy resources. Energy can be easily extracted from wind with the use of Horizontal axis and Vertical axis wind turbine(VAWT). The performance of turbine depends on airfoil shape. The present work emphasizes the aerodynamics of different asymmetrical airfoils used in VAWT rotors. This investigation is conducted for the selection of efficient asymmetrical bladed H-Darrieus VAWT rotor. Five numbers of thick and cambered asymmetrical airfoil is considered for this investigation. A free stream velocity of 6.0 m/s is considered to simulate 2D CFD analysis using k-ɛ turbulence model. The power coefficient (Cp) of all H-Darrieus VAWT rotor increase with increase in TSR value to a certain limit and after it starts decrease with further increase of TSR. In the present investigation the Cp and TSR of NACA 63415 (RT-30%) are found to be higher among all considered asymmetrical airfoils. Moreover, Ct values of NACA 63415 (RT-30%) are also high corresponding to all TSR values. This is due to the long duration of attachment of flow with blade surroundings. Hence, NACA 63415 (RT- 30%) airfoil may be considered as an efficient airfoil among S818, GOE 561, GU25-5(11)8, and KENNEDY AND MARSDEN (kenmar) asymmetrical airfoils.

Experimental benchmark and code validation for airfoils equipped with passive vortex generators

International Nuclear Information System (INIS)

Baldacchino, D; Ferreira, C; Florentie, L; Timmer, N; Van Zuijlen, A; Manolesos, M; Chaviaropoulos, T; Diakakis, K; Papadakis, G; Voutsinas, S; González Salcedo, Á; Aparicio, M; García, N R.; Sørensen, N N.; Troldborg, N

2016-01-01

Experimental results and complimentary computations for airfoils with vortex generators are compared in this paper, as part of an effort within the AVATAR project to develop tools for wind turbine blade control devices. Measurements from two airfoils equipped with passive vortex generators, a 30% thick DU97W300 and an 18% thick NTUA T18 have been used for benchmarking several simulation tools. These tools span low-to-high complexity, ranging from engineering-level integral boundary layer tools to fully-resolved computational fluid dynamics codes. Results indicate that with appropriate calibration, engineering-type tools can capture the effects of vortex generators and outperform more complex tools. Fully resolved CFD comes at a much higher computational cost and does not necessarily capture the increased lift due to the VGs. However, in lieu of the limited experimental data available for calibration, high fidelity tools are still required for assessing the effect of vortex generators on airfoil performance. (paper)

Optimization of Wind Turbine Airfoil Using Nondominated Sorting Genetic Algorithm and Pareto Optimal Front

Directory of Open Access Journals (Sweden)

Ziaul Huque

2012-01-01

Full Text Available A Computational Fluid Dynamics (CFD and response surface-based multiobjective design optimization were performed for six different 2D airfoil profiles, and the Pareto optimal front of each airfoil is presented. FLUENT, which is a commercial CFD simulation code, was used to determine the relevant aerodynamic loads. The Lift Coefficient (CL and Drag Coefficient (CD data at a range of 0° to 12° angles of attack (α and at three different Reynolds numbers (Re=68,459, 479, 210, and 958, 422 for all the six airfoils were obtained. Realizable k-ε turbulence model with a second-order upwind solution method was used in the simulations. The standard least square method was used to generate response surface by the statistical code JMP. Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II was used to determine the Pareto optimal set based on the response surfaces. Each Pareto optimal solution represents a different compromise between design objectives. This gives the designer a choice to select a design compromise that best suits the requirements from a set of optimal solutions. The Pareto solution set is presented in the form of a Pareto optimal front.

Numerical study of the static and pitching RISOe-B1-18 airfoil[STALL

Energy Technology Data Exchange (ETDEWEB)

Bertagnolio, F.

2004-01-01

The objective of this report is the better understanding of the physics of the aeroelastic motion of wind turbine blades in order to improve the numerical models used for their design. In this study, the case of the RISOe-B1-18 airfoil which was equipped and measured in an open jet wind tunnel is studied. Two and three dimensional Navier-Stokes calculations using the k-w SST and Detached Eddy Simulation turbulence models are conducted. An engineering semi-empirical dynamic stall model is also used for performing calculations. Computational results are compared to the experimental results that are available both for the static airfoil and in the case of pitching motions. It is shown that the Navier-Stokes simulations can reproduced the main characteristic features of the flow. The DES model seems also to be able to reproduce some details of the unsteady aerodynamics. The Navier-Stokes computations can then be used to improve the performance of the engineering model. (au)

Numerical study on effect of boundary layer trips on aerodynamic performance of E216 airfoil

Directory of Open Access Journals (Sweden)

B.K. Sreejith

2018-02-01

Full Text Available Simulation is carried out to find the performance of airfoil E216 using Transition γ-Reθ model at Reynolds number of 100,000. Flow behaviour and effect of angle of attack (AOA on laminar separation bubble (LSB formation are examined. The results are validated with wind tunnel experimental results. LSB formation is clearly spotted in the velocity vector plot and coefficient of pressure distribution over airfoil. LSB moved upstream towards the leading edge with increase in AOA. Effect of boundary layer trip on LSB formation over the airfoil and performance of airfoil are studied. Two different trip locations, 17% of chord and 10% of chord from leading edge, and different trip heights (0.3 mm, 0.5 mm, 0.7 mm, 1 mm are investigated in this study. Results showed that boundary layer trip could eliminate LSB partially or completely and improve aerodynamic performance of the airfoil. Maximum improvement in drag by 15.48% and lift to drag ratio by 21.62% are obtained at angle of attack of 60. In all the cases, improvement in performance is observed only up to trip height of 0.5 mm.

Energy and exergy efficiency comparison of horizontal and vertical axis wind turbines

Energy Technology Data Exchange (ETDEWEB)

Pope, K.; Dincer, I.; Naterer, G.F. [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, Ontario (Canada)

2010-09-15

In this paper, an energy and exergy analysis is performed on four different wind power systems, including both horizontal and vertical axis wind turbines. Significant variability in turbine designs and operating parameters are encompassed through the selection of systems. In particular, two airfoils (NACA 63(2)-215 and FX 63-137) commonly used in horizontal axis wind turbines are compared with two vertical axis wind turbines (VAWTs). A Savonius design and Zephyr VAWT benefit from operational attributes in wind conditions that are unsuitable for airfoil type designs. This paper analyzes each system with respect to both the first and second laws of thermodynamics. The aerodynamic performance of each system is numerically analyzed by computational fluid dynamics software, FLUENT. A difference in first and second law efficiencies of between 50 and 53% is predicted for the airfoil systems, whereas 44-55% differences are predicted for the VAWT systems. Key design variables are analyzed and the predicted results are discussed. The exergetic efficiency of each wind turbine is studied for different geometries, design parameters and operating conditions. It is shown that the second law provides unique insight beyond a first law analysis, thereby providing a useful design tool for wind power development. (author)

Conference on Low Reynolds Number Airfoil Aerodynamics, Notre Dame, IN, June 16-18, 1985, Proceedings

Science.gov (United States)

Mueller, T. J. (Editor)

1985-01-01

Topics of interest in the design, flow modeling and visualization, and turbulence and flow separation effects for low Reynolds number (Re) airfoils are discussed. Design methods are presented for Re from 50,000-500,000, including a viscous-inviscid coupling method and by using a constrained pitching moment. The effects of pressure gradients, unsteady viscous aerodynamics and separation bubbles are investigated, with particular note made of factors which most influence the size and location of separation bubbles and control their effects. Attention is also given to experimentation with low Re airfoils and to numerical models of symmetry breaking and lift hysteresis from separation. Both steady and unsteady flow experiments are reviewed, with the trials having been held in wind tunnels and the free atmosphere. The topics discussed are of interest to designers of RPVs, high altitude aircraft, sailplanes, ultralights and wind turbines.

Inverse airfoil design method for low-speed straight-bladed Darrieus-type VAWT applications

Energy Technology Data Exchange (ETDEWEB)

Saeed, F. [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia); Paraschivoiu, I.; Trifu, O. [Ecole Polytechnique, Montreal, PQ (Canada); Hess, M.; Gabrys, C. [Mariah Power Inc., Reno, NV (United States)

2008-07-01

Inverse airfoil design of a low-speed straight-bladed Darrieus-type vertical axis wind turbine (VAWT) can help improve aerodynamic performance and power output by eliminating undesirable flow field characteristics at very low Reynolds number. This study used an interactive inverse airfoil design method (PROFOIL) that allows specification of velocity and boundary-layer characteristics over different segments of the airfoil subject to constraints on the geometry (closure) and the flow field (far field boundary). Additional constraints were also considered to address pitching moment coefficient, thickness and the power output for a given tip-speed ratio. Performance analyses of the airfoil and the VAWT were carried out using state-of-the-art analyses codes XFOIL and CARDAAV, respectively. XFOIL is a panel method with a coupled boundary-layer scheme and is used to obtain the aerodynamic characteristics of resulting airfoil shapes. The final airfoil geometry is obtained through a multi-dimensional Newton iteration. The study showed that the strength of the method lies in the inverse design methodology whereas its weaknesses is in reliably predicting aerodynamic characteristics of airfoils at low Reynolds numbers and high angles of attack. A 10-15 per cent increase in the relative performance of the VAWT was achieved with this method. Although the results of the study showed that the method has great application potential for VAWTs in general, there is much room for improvement in flow analysis capabilities for low Re flows in reliably predicting post-stall aerodynamic characteristics. In the absence of such analysis capabilities, the authors suggested that the results should be viewed qualitatively and not quantitatively. 36 refs., 1 tab., 4 figs.

A Dynamic Stall Model for Airfoils with Deformable Trailing Edges

International Nuclear Information System (INIS)

Andersen, Peter Bjoern; Gaunaa, Mac; Bak, Christian; Hansen, Morten Hartvig

2007-01-01

The present work contains an extension of the Beddoes-Leishman (B-L) type dynamic stall model, as described by Hansen et al. In this work a Deformable Trailing Edge Geometry (DTEG) has been added to the dynamic stall model. The model predicts the unsteady aerodynamic forces and moments on an airfoil section undergoing arbitrary motion in heave, lead-lag, pitch, Trailing Edge (TE) flapping. In the linear region, the model reduces to the inviscid model of Gaunaa, which includes the aerodynamic effect of a thin airfoil with a deformable camberline in inviscid flow. Therefore, the proposed model can be considered a crossover between the work of Gaunaa for the attached flow region and Hansen et al. The model will be compared to wind tunnel measurements from Velux described by Bak et al

Aerodynamic Performance of a NREL S809 Airfoil in an Air-Sand Particle Two-Phase Flow

Directory of Open Access Journals (Sweden)

Dimitra C. Douvi

2017-02-01

Full Text Available This paper opens up a new perspective on the aerodynamic performance of a wind turbine airfoil. More specifically, the paper deals with a steady, incompressible two-phase flow, consisting of air and two different concentrations of sand particles, over an airfoil from the National Renewable Energy Laboratory, NREL S809. The numerical simulations were performed on turbulence models for aerodynamic operations using commercial computational fluid dynamics (CFD code. The computational results obtained for the aerodynamic performance of an S809 airfoil at various angles of attack operating at Reynolds numbers of Re = 1 × 106 and Re = 2 × 106 in a dry, dusty environment were compared with existing experimental data on air flow over an S809 airfoil from reliable sources. Notably, a structured mesh consisting of 80,000 cells had already been identified as the most appropriate for numerical simulations. Finally, it was concluded that sand concentration significantly affected the aerodynamic performance of the airfoil; there was an increase in the values of the predicted drag coefficients, as well as a decrease in the values of the predicted lift coefficients caused by increasing concentrations of sand particles. The region around the airfoil was studied by using contours of static pressure and discrete phase model (DPM concentration.

Computational study of the Risø-B1-18 airfoil with a hinged flap providing variable trailing edge geometry

DEFF Research Database (Denmark)

Troldborg, Niels

2005-01-01

A comprehensive computational study, in both steady and unsteady flow conditions, has been carried out to investigate the aerodynamic characteristics of the Risø-B1.18 airfoil equipped with variable trailing edge geometry as produced by a hinged flap. The function of such flaps should...... on the baseline airfoil showed excellent agreement with measurements on the same airfoil with the same specified conditions. Furthermore, a more widespread comparison with an advanced potential theory code is presented. The influence of various key parameters, such as flap shape, flap size and oscillating...... frequencies, was investigated so that an optimum design can be suggested for application with wind turbine blades. It is concluded that a moderately curved flap with flap chord to airfoil curve ratio between 0.05 and 0.10 would be an optimum choice....

A Comparative Study Using CFD to Predict Iced Airfoil Aerodynamics

Science.gov (United States)

Chi, x.; Li, Y.; Chen, H.; Addy, H. E.; Choo, Y. K.; Shih, T. I-P.

2005-01-01

WIND, Fluent, and PowerFLOW were used to predict the lift, drag, and moment coefficients of a business-jet airfoil with a rime ice (rough and jagged, but no protruding horns) and with a glaze ice (rough and jagged end has two or more protruding horns) for angles of attack from zero to and after stall. The performance of the following turbulence models were examined by comparing predictions with available experimental data. Spalart-Allmaras (S-A), RNG k-epsilon, shear-stress transport, v(sup 2)-f, and a differential Reynolds stress model with and without non-equilibrium wall functions. For steady RANS simulations, WIND and FLUENT were found to give nearly identical results if the grid about the iced airfoil, the turbulence model, and the order of accuracy of the numerical schemes used are the same. The use of wall functions was found to be acceptable for the rime ice configuration and the flow conditions examined. For rime ice, the S-A model was found to predict accurately until near the stall angle. For glaze ice, the CFD predictions were much less satisfactory for all turbulence models and codes investigated because of the large separated region produced by the horns. For unsteady RANS, WIND and FLUENT did not provide better results. PowerFLOW, based on the Lattice Boltzmann method, gave excellent results for the lift coefficient at and near stall for the rime ice, where the flow is inherently unsteady.

A strong viscous–inviscid interaction model for rotating airfoils

DEFF Research Database (Denmark)

Ramos García, Néstor; Sørensen, Jens Nørkær; Shen, Wen Zhong

2014-01-01

Two-dimensional (2D) and quasi-three dimensional (3D), steady and unsteady, viscous–inviscid interactive codes capable of predicting the aerodynamic behavior of wind turbine airfoils are presented. The model is based on a viscous–inviscid interaction technique using strong coupling between...... a boundary-layer trip or computed using an en envelope transition method. Validation of the incompressible 2D version of the code is carried out against measurements and other numerical codes for different airfoil geometries at various Reynolds numbers, ranging from 0.9 ⋅ 106 to 8.2 ⋅ 106. In the quasi-3D...... version, a parametric study on rotational effects induced by the Coriolis and centrifugal forces in the boundary-layer equations shows that the effects of rotation are to decrease the growth of the boundary-layer and delay the onset of separation, hence increasing the lift coefficient slightly while...

Modal Parameter Identification of New Design of Vertical Axis Wind Turbine

DEFF Research Database (Denmark)

Chougule, Prasad; Nielsen, Søren R.K.

2013-01-01

Vertical axis wind turbines have lower power efficiency than the horizontal axis wind turbines. However vertical axis wind turbines are proven to be economical and noise free on smaller scale. A new design of three bladed vertical axis wind turbine by using two airfoils in construction of each...... blade has been proposed to improve power efficiency. The purpose of two airfoils in blade design of vertical axis wind turbine is to create high lift which in turns gives higher power output. In such case the structural parameter identification is important to understand the system behavior due to its...... first kind of design before experimental analysis. Therefore a study is carried out to determine the natural frequency to avoid unstable state of the system due to rotational frequency of rotor. The present paper outlines a conceptual design of vertical axis wind turbine and a modal analysis by using...

On the acoustic signature of tandem airfoils: The sound of an elastic airfoil in the wake of a vortex generator

International Nuclear Information System (INIS)

Manela, A.

2016-01-01

The acoustic signature of an acoustically compact tandem airfoil setup in uniform high-Reynolds number flow is investigated. The upstream airfoil is considered rigid and is actuated at its leading edge with small-amplitude harmonic pitching motion. The downstream airfoil is taken passive and elastic, with its motion forced by the vortex-street excitation of the upstream airfoil. The non-linear near-field description is obtained via potential thin-airfoil theory. It is then applied as a source term into the Powell-Howe acoustic analogy to yield the far-field dipole radiation of the system. To assess the effect of downstream-airfoil elasticity, results are compared with counterpart calculations for a non-elastic setup, where the downstream airfoil is rigid and stationary. Depending on the separation distance between airfoils, airfoil-motion and airfoil-wake dynamics shift between in-phase (synchronized) and counter-phase behaviors. Consequently, downstream airfoil elasticity may act to amplify or suppress sound through the direct contribution of elastic-airfoil motion to the total signal. Resonance-type motion of the elastic airfoil is found when the upstream airfoil is actuated at the least stable eigenfrequency of the downstream structure. This, again, results in system sound amplification or suppression, depending on the separation distance between airfoils. With increasing actuation frequency, the acoustic signal becomes dominated by the direct contribution of the upstream airfoil motion, whereas the relative contribution of the elastic airfoil to the total signature turns negligible.

On the acoustic signature of tandem airfoils: The sound of an elastic airfoil in the wake of a vortex generator

Energy Technology Data Exchange (ETDEWEB)

Manela, A. [Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, Haifa 32000 (Israel)

2016-07-15

The acoustic signature of an acoustically compact tandem airfoil setup in uniform high-Reynolds number flow is investigated. The upstream airfoil is considered rigid and is actuated at its leading edge with small-amplitude harmonic pitching motion. The downstream airfoil is taken passive and elastic, with its motion forced by the vortex-street excitation of the upstream airfoil. The non-linear near-field description is obtained via potential thin-airfoil theory. It is then applied as a source term into the Powell-Howe acoustic analogy to yield the far-field dipole radiation of the system. To assess the effect of downstream-airfoil elasticity, results are compared with counterpart calculations for a non-elastic setup, where the downstream airfoil is rigid and stationary. Depending on the separation distance between airfoils, airfoil-motion and airfoil-wake dynamics shift between in-phase (synchronized) and counter-phase behaviors. Consequently, downstream airfoil elasticity may act to amplify or suppress sound through the direct contribution of elastic-airfoil motion to the total signal. Resonance-type motion of the elastic airfoil is found when the upstream airfoil is actuated at the least stable eigenfrequency of the downstream structure. This, again, results in system sound amplification or suppression, depending on the separation distance between airfoils. With increasing actuation frequency, the acoustic signal becomes dominated by the direct contribution of the upstream airfoil motion, whereas the relative contribution of the elastic airfoil to the total signature turns negligible.

A dynamic stall model for airfoils with deformable trailing edges

DEFF Research Database (Denmark)

Andersen, Peter Bjørn; Gaunaa, Mac; Bak, Christian

2009-01-01

, lead-lag, pitch, trailing-edge flapping. In the linear region, the model reduces to the inviscid model, which includes the aerodynamic effect of a thin airfoil with a deformable camberline in inviscid flow. Therefore, the proposed model can be considered a crossover between the work of Gaunaa......The present work contains an extension of the Beddoes-Leishman-type dynamic stall model. In this work, a deformable trailing-edge flap has been added to the dynamic stall model. The model predicts the unsteady aerodynamic forces and moments on an airfoil section undergoing arbitrary motion in heave...... for the attached flow region and Hansen et al. The model is compared qualitatively to wind tunnel measurements of a Riso/ B1-18 blade section equipped with deformable trailing-edge flap devices in the form of piezoelectric devices. Copyright © 2009 John Wiley & Sons, Ltd....

Wake structure and similar behavior of wake profiles downstream of a plunging airfoil

Directory of Open Access Journals (Sweden)

Ali R. DAVARI

2017-08-01

Full Text Available Very limited attention has already been paid to the velocity behavior in the wake region in unsteady aerodynamic problems. A series of tests has been performed on a flapping airfoil in a subsonic wind tunnel to study the wake structure for different sets of mean angle of attack, plunging amplitude and reduced frequency. In this study, the velocity profiles in the wake for various oscillation parameters have been measured using a wide shoulder rake, especially designed for the present experiments. The airfoil under consideration was a critical section of a 660 kW wind turbine. The results show that for a flapping airfoil the wake structure can be of drag producing type, thrust producing or neutral, depending on the mean angle of attack, oscillation amplitude and reduced frequency. In a thrust producing wake, a high-momentum high-velocity jet flow is formed in the core region of the wake instead of the conventional low-momentum flow. As a result, the drag force normally experienced by the body due to the momentum deficit would be replaced by a thrust force. According to the results, the momentum loss in the wake decreases as the reduced frequency increases. The thrust producing wake pattern for the flapping airfoil has been observed for sufficiently low angles of attack in the absence of the viscous effects. This phenomenon has also been observed for either high oscillation amplitudes or high reduced frequencies. According to the results, for different reduced frequencies and plunging amplitudes, such that the product of them be a constant, the velocity profiles exhibit similar behavior and coalesce on each other. This similarity parameter works excellently at small angles of attack. However, at near stall boundaries, the similarity is not as evident as before.

VISUALISASI DISTRIBUSI TEKANAN PADA AIRFOIL JOUKOWSKY

Directory of Open Access Journals (Sweden)

Eddy Maryonoto

2009-02-01

Full Text Available The goal of this research is to develop a computer based system that can beused to visualize pressure distribution on the Joukowsky's airfoil and streamlinespattern around the airfoil. The pressure on the airfoil is calculdted usingformulasderived from potensial theory. Visualization of pressure distribution implementedby using color gradation technique and coded b.v using Borland Delphi 6programming language. The result of the test shotus lhat lhe system has performedperfectly. Pressure dislribution on some kinds of JoukowslE's airfoil shapes andstresmlines pattern around the airfoils can be presenled and seen clearly byusing this visualization system, where the paltern of the pressure distribution onthe airfoil marked by color gradation.

Numerical and experimental study of blowing jet on a high lift airfoil

Science.gov (United States)

Bobonea, A.; Pricop, M. V.

2013-10-01

Active manipulation of separated flows over airfoils at moderate and high angles of attack in order to improve efficiency or performance has been the focus of a number of numerical and experimental investigations for many years. One of the main methods used in active flow control is the usage of blowing devices with constant and pulsed blowing. Through CFD simulation over a 2D high-lift airfoil, this study is trying to highlight the impact of pulsed blowing over its aerodynamic characteristics. The available wind tunnel data from INCAS low speed facility are also beneficial for the validation of the numerical analysis. This study intends to analyze the impact of the blowing jet velocity and slot geometry on the efficiency of an active flow control.

Aspects of the influence of an oscillating mini-flap upon the near wake of an airfoil NACA 4412

Energy Technology Data Exchange (ETDEWEB)

Delnero, J S; Di Leo, J Maranon; Colman, J; Garcia Sainz, M; Munoz, F; Herouard, N; Camocardi, M E, E-mail: delnero@ing.unlp.edu.ar [LaCLyFA, Departamento Aeronautica, Facultad de Ingenieria, Universidad Nacional de La Plata, calle 116 entre 47 y 48, CP 1900, La Plata (Argentina)

2011-05-01

A NACA 4412 airfoil was tested, in a boundary layer wind tunnel, with the aim to study the effect of a Gurney mini-flap, as an active and passive flow control device submitted to a turbulent flow field. The main objective was the experimental determination of flow pattern characteristics downstream the airfoil in the near wake. The untwisted wing model used for the experiments had 80 cm wingspan and 50 cm chord, with airfoil NACA 4412. The mini-flap was located on the lower surface at a distance, from the trailing edge, of 8%c (c airfoil chord). The Reynolds number, based upon the wing chord and the mean free stream velocity was 326,000 and 489,000. The turbulence intensity was 1.8%. The model was located into the wind tunnel between two panels, in order to assure a close approximation to two-dimensional flow over the model. As an active control device a rotating mini-flaps, geared by an electromechanical system (which rotate to a 30{sup 0}) was constructed. The wake pattern and pressure values near the trailing edge were measured. The results obtained, for this mechanism, show us that the oscillating mini-flap change the wake flow pattern, alleviating the near wake turbulence and enhancing the vortex pair near the trailing edge at the mini-flap level and below that level, magnifying the effect described first by Liebeck. That effect grows with the oscillating frequency. Additionally, the wake alleviation probably affects also the far wake. All of these facts suggest us to continue with the experiments, trying to measure the pressure distribution around the airfoil in all the cases, obtaining the lift and drag characteristics.

Virtual Shaping of a Two-dimensional NACA 0015 Airfoil Using Synthetic Jet Actuator

Science.gov (United States)

Chen, Fang-Jenq; Beeler, George B.

2002-01-01

The Aircraft Morphing Program at NASA Langley envisions an aircraft without conventional control surfaces. Instead of moving control surfaces, the vehicle control systems may be implemented with a combination of propulsive forces, micro surface effectors, and fluidic devices dynamically operated by an intelligent flight control system to provide aircraft maneuverability over each mission segment. As a part of this program, a two-dimensional NACA 0015 airfoil model was designed to test mild maneuvering capability of synthetic jets in a subsonic wind tunnel. The objective of the experiments is to assess the applicability of using unsteady suction and blowing to alter the aerodynamic shape of an airfoil with a purpose to enhance lift and/or to reduce drag. Synthetic jet actuation at different chordwise locations, different forcing frequencies and amplitudes, under different freestream velocities are investigated. The effect of virtual shape change is indicated by a localized increase of surface pressure in the neighborhood of synthetic jet actuation. That causes a negative lift to the airfoil with an upper surface actuation. When actuation is applied near the airfoil leading edge, it appears that the stagnation line is shifted inducing an effect similar to that caused by a small angle of attack to produce an overall lift change.

A rod-airfoil experiment as a benchmark for broadband noise modeling

Energy Technology Data Exchange (ETDEWEB)

Jacob, M.C. [Ecole Centrale de Lyon, Laboratoire de Mecanique des Fluides et d' Acoustique, Ecully Cedex (France); Universite Claude Bernard/Lyon I, Villeurbanne Cedex (France); Boudet, J.; Michard, M. [Ecole Centrale de Lyon, Laboratoire de Mecanique des Fluides et d' Acoustique, Ecully Cedex (France); Casalino, D. [Ecole Centrale de Lyon, Laboratoire de Mecanique des Fluides et d' Acoustique, Ecully Cedex (France); Fluorem SAS, Ecully Cedex (France)

2005-07-01

A low Mach number rod-airfoil experiment is shown to be a good benchmark for numerical and theoretical broadband noise modeling. The benchmarking approach is applied to a sound computation from a 2D unsteady-Reynolds-averaged Navier-Stokes (U-RANS) flow field, where 3D effects are partially compensated for by a spanwise statistical model and by a 3D large eddy simulation. The experiment was conducted in the large anechoic wind tunnel of the Ecole Centrale de Lyon. Measurements taken included particle image velocity (PIV) around the airfoil, single hot wire, wall pressure coherence, and far field pressure. These measurements highlight the strong 3D effects responsible for spectral broadening around the rod vortex shedding frequency in the subcritical regime, and the dominance of the noise generated around the airfoil leading edge. The benchmarking approach is illustrated by two examples: the validation of a stochastical noise generation model applied to a 2D U-RANS computation; the assessment of a 3D LES computation using a new subgrid scale (SGS) model coupled to an advanced-time Ffowcs-Williams and Hawkings sound computation. (orig.)

Airfoil shape for a turbine nozzle

Science.gov (United States)

Burdgick, Steven Sebastian; Patik, Joseph Francis; Itzel, Gary Michael

2002-01-01

A first-stage nozzle vane includes an airfoil having a profile according to Table I. The annulus profile of the hot gas path is defined in conjunction with the airfoil profile and the profile of the inner and outer walls by the Cartesian coordinate values given in Tables I and II, respectively. The airfoil is a three-dimensional bowed design, both in the airfoil body and in the trailing edge. The airfoil is steam and air-cooled by flowing cooling mediums through cavities extending in the vane between inner and outer walls.

2-D and 3-D CFD Investigation of NREL S826 Airfoil at Low Reynolds Numbers

International Nuclear Information System (INIS)

Cakmakcioglu, S C; Sert, I O; Tugluk, O; Sezer-Uzol, N

2014-01-01

In this study CFD investigation of flow over the NREL S826 airfoil is performed. NREL S826 airfoil was designed for HAWTs of 10-15 meter diameters. However, it is used in the NTNU wind turbine rotor model and low Reynolds number flow characteristics become important in the validations with the test cases of this rotor model. The airfoil CFD simulations are carried out in 2-D and 3-D computational domains. The k-rn SST turbulence model with Langtry-Menter (γ-Re θ ) transition prediction model for turbulence closure is used in the calculations. The Delayed DES is also performed in the stall region for comparisons. The results are compared with the available METUWIND experimental data, and are shown to be in fair agreement. It is observed that 3-D CFD analysis provides increased accuracy at increased computational cost

CFD analysis for H-rotor Darrieus turbine as a low speed wind energy converter

Directory of Open Access Journals (Sweden)

M.H. Mohamed

2015-03-01

Full Text Available Vertical axis wind turbines like the Darrieus turbine appear to be promising for the conditions of low wind speed, but suffer from a low efficiency compared to horizontal axis turbines. A fully detailed numerical analysis is introduced in this work to improve the global performance of this wind turbine. A comparison between ANSYS Workbench and Gambit meshing tools for the numerical modeling is performed to summarize a final numerical sequence for the Darrieus rotor performance. Then, this model sequence is applied for different blade airfoils to obtain the best performance. Unsteady simulations performed for different speed ratios and based on URANS turbulent calculations using sliding mesh approach. Results show that the accuracy of ANSYS Workbench meshing is improved by using SST K-omega model but it is not recommended for other turbulence models. Moreover, this CFD procedure is used in this paper to assess the turbine performance with different airfoil shapes (25 airfoils. The results introduced new shapes for this turbine with higher efficiency than the regular airfoils by 10%. In addition, blade pitch angle has been studied and the results indicated that the zero pitch angle gives best performance.

Airfoil shape for a turbine bucket

Science.gov (United States)

Hyde, Susan Marie; By, Robert Romany; Tressler, Judd Dodge; Schaeffer, Jon Conrad; Sims, Calvin Levy

2005-06-28

Third stage turbine buckets have airfoil profiles substantially in accordance with Cartesian coordinate values of X, Y and Z set forth Table I wherein X and Y values are in inches and the Z values are non-dimensional values from 0 to 0.938 convertible to Z distances in inches by multiplying the Z values by the height of the airfoil in inches. The X and Y values are distances which, when connected by smooth continuing arcs, define airfoil profile sections at each distance Z. The profile sections at each distance Z are joined smoothly to one another to form a complete airfoil shape. The X and Y distances may be scalable as a function of the same constant or number to provide a scaled up or scaled down airfoil section for the bucket. The nominal airfoil given by the X, Y and Z distances lies within an envelop of .+-.0.150 inches in directions normal to the surface of the airfoil.

High frequency microphone measurements for transition detection on airfoils. Risø C2-18 appendix report

DEFF Research Database (Denmark)

Døssing, Mads

Time series of pressure fluctuations has been obtained using high frequency microphones distributed over the surface of airfoils undergoing wind tunnel tests in the LM Windtunnel, owned by ’LM Glasfiber’, Denmark. The present report describes the dataanalysis, with special attention given to tran...

High frequency microphone measurements for transition detection on airfoils. Risø B1-18 appendix report

DEFF Research Database (Denmark)

Døssing, Mads

Time series of pressure fluctuations has been obtained using high frequency microphones distributed over the surface of airfoils undergoing wind tunnel tests in the LM Windtunnel, owned by ’LM Glasfiber’, Denmark. The present report describes the dataanalysis, with special attention given to tran...

A computational procedure to define the incidence angle on airfoils rotating around an axis orthogonal to flow direction

International Nuclear Information System (INIS)

Bianchini, Alessandro; Balduzzi, Francesco; Ferrara, Giovanni; Ferrari, Lorenzo

2016-01-01

Highlights: • New method to calculate the incidence angle from a computed CFD flow field. • Applicable to each airfoil rotating around an axis orthogonal to flow direction. • Composed by four, easily automatable steps explained in details. • Robustness of the model assessed on two Darrieus turbine study cases. - Abstract: Numerical simulations provided in the last few years a significant contribution for a better understanding of many phenomena connected to the flow past rotating blades. In case of airfoils rotating around an axis orthogonal to flow direction, one of the most critical issues is represented by the definition of the incidence angle on the airfoil from the computed flow field. Incidence indeed changes continuously as a function of the azimuthal position of the blade and a distribution of peripheral speed is experienced along the airfoil’s thickness due to radius variation. The possibility of reducing the flow to lumped parameters (relative speed modulus and direction), however, would be of capital relevance to transpose accurate CFD numerical results into effective inputs to low-order models that are often exploited for preliminary design analyses. If several techniques are available for this scope in the case of blades rotating around an axis parallel to flow direction (e.g., horizontal-axis wind turbines), the definition of a robust procedure in case the revolution axis is orthogonal to the flow is still missing. In the study, a novel technique has been developed using data from Darrieus-like rotating airfoils. The method makes use of the virtual camber theory to define a virtual airfoil whose pressure coefficient distributions in straight flow are used to match those of the real airfoil in curved flow. Even if developed originally for vertical-axis wind turbines, the method is of general validity and is thought to represent in the near future a valuable tool for researchers to get a new insight on many complex phenomena connected to flow

Wind power engine

Energy Technology Data Exchange (ETDEWEB)

Musgrove, P J

1977-02-10

The device is a wind-power engine with vertical axis and with one or several wings with airfoil profile fixed on a frame which is pivoted at the vertical axis. Each wing forms at least on one part of its length an angle of inclination with the vertical. The angle increases under the influence of the centrifugal force when the r.p.m. exceed a normal operation range. This method helps to reduce mechanical loads occurring with high wind speeds without requiring a complicated construction.

Effects of grit roughness and pitch oscillations on the S815 airfoil

Energy Technology Data Exchange (ETDEWEB)

Reuss Ramsay, R.; Hoffman, M.J.; Gregorek, G.M. [Ohio State Univ., Columbus, OH (United States)

1996-07-01

Horizontal axis wind turbine rotors experience unsteady aerodynamics due to wind shear when the rotor is yawed, when rotor blades pass through the support tower wake, and when the wind is gusting. An understanding of this unsteady behavior is necessary to assist in the calculation of rotor performance and loads. The rotors also experience performance degradation due to surface roughness. These surface irregularities are cause by the accumulation of insect debris, ice, and the aging process. Wind tunnel studies that examine both the steady and unsteady behavior of airfoils can help define pertinent flow phenomena, and the resultant data can be used to validate analytical computer codes. A S815 airfoil model was tested in The Ohio State University Aeronautical and Astronautical Research Laboratory (OSU/AARL) 3 x 5 subsonic wind tunnel (3 x 5) under steady flow and stationary model conditions, as well as with the model undergoing pitch oscillations. To study the possible extent of performance loss due to surface roughness, a standard grit pattern (LEGR) was used to simulate leading edge contamination. After baseline cases were completed, the LEGR was applied for both steady state and model pitch oscillation cases. The Reynolds numbers used for steady state conditions were 0.75, 1, 1.25, and 1.4 million, while the angle of attack ranged from {minus}20{degree} to +40{degree}. With the model undergoing pitch oscillations, data were acquired at Reynolds numbers of 0.75, 1, 1.25, and 1.4 million, at frequencies of 0.6, 1.2, and 1.8 Hz. Two sine wave forcing functions were used; {+-}5.5{degree} and {+-}10{degree}, at mean angles of attack of 8{degree}, 14{degree}, and 20{degree}. For purposes herein, any reference to unsteady conditions means that the model was in pitch oscillation about the quarter chord.

Research in aeroelasticity[Wind turbines

Energy Technology Data Exchange (ETDEWEB)

Bak, C.

2006-05-15

In the Energy Research Project 'Program for Research in Applied Aeroelasticity' (EFP2005), Risoe National Laboratory (Risoe) and the Technical University of Denmark (DTU) have applied and further developed the tools in the aeroelastic design complex. The main results from the project are: 1) Adding a winglet to a wind turbine blade for minimizing the induced drag of the blade led to the biggest increase in power of 1.4%. 2) Transient wind loads during pitch motion are determined using CFD. Compared to the NREL/NASA Ames test, reasonably good agreement is seen. 3) A general method was developed for the determination of 3D angle of attack for rotating blades from either measurements or numerical computations using CFD. 4) A model of the far wake behind wind turbines was developed for stability studies of the tip vortices in the far wake. 5) Investigating the blade root region showed that the power efficiency, CP, locally can be increased significantly beyond the Betz limit, but that the global CP for the rotor cannot exceed the Betz limit. When including tip losses and a minimum blade drag coefficient, a maximum rotor CP in the range of 0.51-0.52 was obtained. 6) A new airfoil family was designed and a 3D airfoil design tool was developed. Compared to the Risoe-B1 family, the new airfoil family showed similar or improved aerodynamic and structural characteristics. 7) Four different airfoils were analyzed to reveal the differences between 2D and 3D CFD. The major conclusions are the dependency of computational results to transition modelling, and the ability of 3D DES calculations to realistically simulate the turbulent wake of an airfoil in stall. 8) The capability of a theory for simulation of Gaussian turbulence driven gust events was demonstrated by emulating a violent shear gust event from a complex site. An asymptotic model for the PDF of the largest excursion from the mean level, during an arbitrary recurrence period, has been derived for a stochastic

Turbine airfoil to shround attachment

Science.gov (United States)

Campbell, Christian X; Morrison, Jay A; James, Allister W; Snider, Raymond G; Eshak, Daniel M; Marra, John J; Wessell, Brian J

2014-05-06

A turbine airfoil (31) with an end portion (42) that tapers (44) toward the end (43) of the airfoil. A ridge (46) extends around the end portion. It has proximal (66) and distal (67) sides. A shroud platform (50) is bi-cast onto the end portion around the ridge without bonding. Cooling shrinks the platform into compression (62) on the end portion (42) of the airfoil. Gaps between the airfoil and platform are formed using a fugitive material (56) in the bi-casting stage. These gaps are designed in combination with the taper angle (44) to accommodate differential thermal expansion while maintaining a gas seal along the contact surfaces. The taper angle (44) may vary from lesser on the pressure side (36) to greater on the suction side (38) of the airfoil. A collar portion (52) of the platform provides sufficient contact area for connection stability.

Multiple piece turbine airfoil

Science.gov (United States)

Kimmel, Keith D; Wilson, Jr., Jack W.

2010-11-02

A turbine airfoil, such as a rotor blade or a stator vane, for a gas turbine engine, the airfoil formed as a shell and spar construction with a plurality of dog bone struts each mounted within openings formed within the shell and spar to allow for relative motion between the spar and shell in the airfoil chordwise direction while also forming a seal between adjacent cooling channels. The struts provide the seal as well as prevent bulging of the shell from the spar due to the cooling air pressure.

Investigation of piezoelectric flaps for load alleviation using CFD; Wind turbines

Energy Technology Data Exchange (ETDEWEB)

Heinz, J.C.

2010-03-15

Cost efficient wind power generation demands for large wind turbines with a long lifetime. These demands place high interests on sophisticated load control techniques such as deformable trailing edge flaps. In this work a previously tested prototype airfoil was investigated by using the 2D incompressible RANS solver EllipSys2D. The prototype was built with a Risoe-B1-18 airfoil where piezoelectric actuators THUNDER TH-6R were attached at the trailing edge to realize a movable flap. The results of the simulation were compared to measurements of the previous wind tunnel test and comprehensive steady state computations were conducted to gain information about the general airfoil properties. The model was subsequently used to investigate aero-servo-elastic effects on the 2D airfoil section exposed to a fluctuating inflow. It is explained how a fluctuating inflow was simulated with EllipSys2D and how the CFD solver was coupled with a 3 DOF structural model and with two different control algorithms. Control 1 used the measured AOA in front of the LE as input, Control 2 used the pressure difference between suction and pressure side as input. The model showed a substantial load reduction potential for the present prototype airfoil. For a wind step from 10 m/s to 10.5 m/s the standard deviation of the structural deflection normal to the rotor plane could be reduced with up to 98 % (Control 1) and 96 % (Control 2). A 4 s turbulent inflow with TI=2.2 % could be reduced with up to 81 % (Control 1) and 82 % (Control 2). For a 12 s inflow with TI=2.4 % the standard deviation could be reduced with up to 68 % (Control 1) and 67 % (Control 2). The influence of possible time lags inside the control loop on the reduction potential of the prototype was also investigated. For a 12 s inflow with a tripled turbulence intensity of TI=7.7 % the prototype airfoil could still reach a reduction of up to 54 %. For an extended flap range of -6 to +6 degrees the reduction could be returned to 66

Influences of some parameters on the performance of a small vertical axis wind turbine

Directory of Open Access Journals (Sweden)

Dumitrache Alexandru

2016-01-01

Full Text Available The effects of various parameters on the performance of a straight bladed vertical axis wind turbine, using the vortex model, have been numerically investigated. A vortex model has been used to evaluate the performance of a vertical axis wind turbine, by means of aerodynamic characteristics of different airfoils for Reynolds numbers between 105 and 106. Parameters such as the thickness and the camber of the blade airfoil, the solidity, the type of blade profile, the number of blades and the pitch angle, which influence the power coefficient, CP, and the start-up regime. This study can be used in the designing an optimal vertical axis wind turbine in a specific location, when the prevailed wind regime is known.

Roughness Sensitivity Comparisons of Wind Turbine Blade Sections

Energy Technology Data Exchange (ETDEWEB)

Wilcox, Benjamin J. [Texas A & M Univ., College Station, TX (United States). Dept. of Aerospace Engineering; White, Edward B. [Texas A & M Univ., College Station, TX (United States). Dept. of Aerospace Engineering; Maniaci, David Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Wind Energy Technologies Dept.

2017-10-01

One explanation for wind turbine power degradation is insect roughness. Historical studies on insect-induced power degradation have used simulation methods which are either un- representative of actual insect roughness or too costly or time-consuming to be applied to wide-scale testing. Furthermore, the role of airfoil geometry in determining the relations between insect impingement locations and roughness sensitivity has not been studied. To link the effects of airfoil geometry, insect impingement locations, and roughness sensitivity, a simulation code was written to determine representative insect collection patterns for different airfoil shapes. Insect collection pattern data was then used to simulate roughness on an NREL S814 airfoil that was tested in a wind tunnel at Reynolds numbers between 1.6 x 10⁶ and 4.0 x 10⁶. Results are compared to previous tests of a NACA 63₃ -418 airfoil. Increasing roughness height and density results in decreased maximum lift, lift curve slope, and lift-to-drag ratio. Increasing roughness height, density, or Reynolds number results in earlier bypass transition, with critical roughness Reynolds numbers lying within the historical range. Increased roughness sensitivity on the 25% thick NREL S814 is observed compared to the 18% thick NACA 63 3 -418. Blade-element-momentum analysis was used to calculate annual energy production losses of 4.9% and 6.8% for a NACA 63₃ -418 turbine and an NREL S814 turbine, respectively, operating with 200 μm roughness. These compare well to historical field measurements.

Detection of aeroacoustic sound sources on aircraft and wind turbines

International Nuclear Information System (INIS)

Oerlemans, S.

2009-01-01

This thesis deals with the detection of aeroacoustic sound sources on aircraft and wind turbines using phased microphone arrays. First, the reliability of the array technique is assessed using airframe noise measurements in open and closed wind tunnels. It is demonstrated that quantitative acoustic measurements are possible in both wind tunnels. Then, the array technique is applied to characterize the noise sources on two modern large wind turbines. It is shown that practically all noise emitted to the ground is produced by the outer part of the blades during their downward movement. This asymmetric source pattern, which causes the typical swishing noise during the passage of the blades, can be explained by trailing edge noise directivity and convective amplification. Next, a semi-empirical prediction method is developed for the noise from large wind turbines. The prediction code is successfully validated against the experimental results, not only with regard to sound levels, spectra, and directivity, but also with regard to the noise source distribution in the rotor plane and the temporal variation in sound level (swish). The validated prediction method is then applied to calculate wind turbine noise footprints, which show that large swish amplitudes can occur even at large distance. The influence of airfoil shape on blade noise is investigated through acoustic wind tunnel tests on a series of wind turbine airfoils. Measurements are carried out at various wind speeds and angles of attack, with and without upstream turbulence and boundary layer tripping. The speed dependence, directivity, and tonal behaviour are determined for both trailing edge noise and inflow turbulence noise. Finally, two noise reduction concepts are tested on a large wind turbine: acoustically optimized airfoils and trailing edge serrations. Both blade modifications yield a significant trailing edge noise reduction at low frequencies, but also cause increased tip noise at high frequencies

Second Stage Turbine Bucket Airfoil.

Science.gov (United States)

Xu, Liming; Ahmadi, Majid; Humanchuk, David John; Moretto, Nicholas; Delehanty, Richard Edward

2003-05-06

The second-stage buckets have airfoil profiles substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in inches in Table I wherein Z is a perpendicular distance from a plane normal to a radius of the turbine centerline and containing the X and Y values with the Z value commencing at zero in the X, Y plane at the radially innermost aerodynamic section of the airfoil and X and Y are coordinate values defining the airfoil profile at each distance Z. The X, Y and Z values may be scaled as a function of the same constant or number to provide a scaled-up or scaled-down airfoil section for the bucket.

Third-stage turbine bucket airfoil

Science.gov (United States)

Pirolla, Peter Paul; Siden, Gunnar Leif; Humanchuk, David John; Brassfield, Steven Robert; Wilson, Paul Stuart

2002-01-01

The third-stage buckets have airfoil profiles substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in inches in Table I wherein Z is a perpendicular distance from a plane normal to a radius of the turbine centerline and containing the X and Y values with the Z value commencing at zero in the X, Y plane at the radially innermost aerodynamic section of the airfoil and X and Y are coordinates defining the airfoil profile at each distance Z. The X, Y and Z values may be scaled as a function of the same constant or number to provide a scaled-up or scaled-down airfoil section for the bucket.

Airfoil Shape Optimization in Transonic Flow

International Nuclear Information System (INIS)

Islam, Z.

2004-01-01

A computationally efficient and adaptable design tool is constructed by coupling a flow analysis code based on Euler equations, with the well established numerical optimization algorithms. Optimization technique involving two analysis methods of Simplex and Rosenbrock have been used. The optimization study involves the minimization of wave drag for two different airfoils with geometric constraints on the airfoil maximum thickness or the cross sectional area along with aerodynamic constraint on lift coefficient. The method is applied to these airfoils transonic flow design points, and the results are compared with the original values. This study shows that the conventional low speed airfoils can be optimized to become supercritical for transonic flight speeds, while existing supercritical airfoils can still be improved further at particular design condition. (author)

Aerodynamics and Optimal Design of Biplane Wind Turbine Blades

Science.gov (United States)

Chiu, Phillip

In order to improve energy capture and reduce the cost of wind energy, in the past few decades wind turbines have grown significantly larger. As their blades get longer, the design of the inboard region (near the blade root) becomes a trade-off between competing structural and aerodynamic requirements. State-of-the-art blades require thick airfoils near the root to efficiently support large loads inboard, but those thick airfoils have inherently poor aerodynamic performance. New designs are required to circumvent this design compromise. One such design is the "biplane blade", in which the thick airfoils in the inboard region are replaced with thinner airfoils in a biplane configuration. This design was shown previously to have significantly increased structural performance over conventional blades. In addition, the biplane airfoils can provide increased lift and aerodynamic efficiency compared to thick monoplane inboard airfoils, indicating a potential for increased power extraction. This work investigates the fundamental aerodynamic aspects, aerodynamic design and performance, and optimal structural design of the biplane blade. First, the two-dimensional aerodynamics of biplanes with relatively thick airfoils are investigated, showing unique phenomena which arise as a result of airfoil thickness. Next, the aerodynamic design of the full biplane blade is considered. Two biplane blades are designed for optimal aerodynamic loading, and their aerodynamic performance quantified. Considering blades with practical chord distributions and including the drag of the mid-blade joint, it is shown that biplane blades have comparable power output to conventional monoplane designs. The results of this analysis also show that the biplane blades can be designed with significantly less chord than conventional designs, a characteristic which enables larger blade designs. The aerodynamic loads on the biplane blades are shown to be increased in gust conditions and decreased under

METHOD FOR NUMERICAL MODELING OF UNSTEADY SEPARATED FLOW AROUND AIRFOILS MOVING CLOSE TO FLAT SCREEN

Directory of Open Access Journals (Sweden)

V. Pogrebnaya Tamara

2017-01-01

Full Text Available In this article an attempt is made to explain the nature of differences in measurements of forces and moments, which influence an aircraft at take-off and landing when testing on different types of stands. An algorithm for numerical simulation of unsteady separated flow around airfoil is given. The algorithm is based on the combination of discrete vortex method and turbulent boundary layer equations. An unsteady flow separation modeling has been used. At each interval vortex method was used to calculate the potential flow around airfoils located near a screen. Calculated pressures and velocities were then used in boundary layer calculations to determine flow separation points and separated vortex in- tensities. After that calculation were made to determine free vortex positions to next time step and the process was fulfilled for next time step. The proposed algorithm allows using numeric visualization to understand physical picture of flow around airfoil moving close to screen. Three different ways of flow modeling (mirror method, fixed or movable screens were tested. In each case the flow separation process, which determines pressure distribution over airfoil surface and influ- ences aerodynamic performance, was viewed. The results of the calculations showed that at low atitudes of airfoil over screen mirror method over predicts lift force compared with movable screen, while fixed screen under predicts it. The data obtained can be used when designing equipment for testing in wind tunnels.

Second-stage turbine bucket airfoil

Science.gov (United States)

Wang, John Zhiqiang; By, Robert Romany; Sims, Calvin L.; Hyde, Susan Marie

2002-01-01

The second-stage buckets have airfoil profiles substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in inches in Table I wherein Z is a perpendicular distance from a plane normal to a radius of the turbine centerline and containing the X and Y values with the Z value commencing at zero in the X, Y plane at the radially innermost aerodynamic section of the airfoil and X and Y are coordinate values defining the airfoil profile at each distance Z. The X and Y values may be scaled as a function of the same constant or number to provide a scaled-up or scaled-down airfoil section for the bucket. The second-stage wheel has sixty buckets.

Wind Tunnel Tests of Ailerons at Various Speeds I : Ailerons of 0.20 Airfoil Chord and True Contour with 0.35 Aileron-chord Extreme Blunt Nose Balance on the NACA 66,2-216 Airfoil

Science.gov (United States)

Letko, W; Denaci, H. G.; Freed, C

1943-01-01

Hinge-moment, lift, and pressure-distribution measurements were made in the two-dimensional test section of the NACA stability tunnel on a blunt-nose balance-type aileron on an NACA 66,2-216 airfoil at speeds up to 360 miles per hour corresponding to a Mach number of 0.475. The tests were made primarily to determine the effect of speed on the action of this type of aileron. The balance-nose radii of the aileron were varied from 0 to 0.02 of the airfoil chord and the gap width was varied from 0.0005 to 0.0107 of the airfoil chord. Tests were also made with the gap sealed.

Numerical study on small scale vertical axis wind turbine

Directory of Open Access Journals (Sweden)

Parra-Santos Teresa

2016-01-01

Full Text Available The performance of a Vertical Axis Wind Turbine (VAWT is numerically analyzed. The set-up is Hdarrieus with three straight blades airfoils NACA attached to a rotating vertical shaft. The wind turbine has solidity equals to the unity operating with wind velocity of 7 m/s. Influence of pitch angle is tested to get design tendencies. 2D, transient, Navier Stokes equations are solved using the code Ansys-Fluent. Conservation equations were solved with a Third-Order MUSCL scheme using SIMPLE to couple pressure and velocity. More than six revolutions must be simulated to get the periodic behavior. Two models of turbulence have been contrasted Realizable k-epsilon and Transition SST concluding the last one show more realistic flow features. Pitch angles of 0º, -6º and -10º have been tested with Tip Speed Ratios ranging from 0.7 and 1.6. The no null pitch angles improve the performance of the wind turbine. Instantaneous and averaged power coefficients as well as detailed flow field around the airfoils are showed.

An experimental study of airfoil-spoiler aerodynamics

Science.gov (United States)

Mclachlan, B. G.; Karamcheti, K.

1985-01-01

The steady/unsteady flow field generated by a typical two dimensional airfoil with a statically deflected flap type spoiler was investigated. Subsonic wind tunnel tests were made over a range of parameters: spoiler deflection, angle of attack, and two Reynolds numbers; and comprehensive measurements of the mean and fluctuating surface pressures, velocities in the boundary layer, and velocities in the wake. Schlieren flow visualization of the near wake structure was performed. The mean lift, moment, and surface pressure characteristics are in agreement with previous investigations of spoiler aerodynamics. At large spoiler deflections, boundary layer character affects the static pressure distribution in the spoiler hingeline region; and, the wake mean velocity fields reveals a closed region of reversed flow aft of the spoiler. It is shown that the unsteady flow field characteristics are as follows: (1) the unsteady nature of the wake is characterized by vortex shedding; (2) the character of the vortex shedding changes with spoiler deflection; (3) the vortex shedding characteristics are in agreement with other bluff body investigations; and (4) the vortex shedding frequency component of the fluctuating surface pressure field is of appreciable magnitude at large spoiler deflections. The flow past an airfoil with deflected spoiler is a particular problem in bluff body aerodynamics is considered.

Review paper on wind turbine aerodynamics

DEFF Research Database (Denmark)

Hansen, Martin Otto Laver; Aagaard Madsen, Helge

2011-01-01

The paper describes the development and description of the aerodynamic models used to estimate the aerodynamic loads on wind turbine constructions. This includes a status of the capabilities of computation fluid dynamics and the need for reliable airfoil data for the simpler engineering models...

Prediction of ice accretion and anti-icing heating power on wind turbine blades using standard commercial software

International Nuclear Information System (INIS)

Villalpando, Fernando; Reggio, Marcelo; Ilinca, Adrian

2016-01-01

An approach to numerically simulate ice accretion on 2D sections of a wind turbine blade is presented. The method uses standard commercial ANSYS-Fluent and Matlab tools. The Euler-Euler formulation is used to calculate the water impingement on the airfoil, and a UDF (Used Defined Function) has been devised to turn the airfoil's solid wall into a permeable boundary. Mayer's thermodynamic model is implemented in Matlab for computing ice thickness and for updating the airfoil contour. A journal file is executed to systematize the procedure: meshing, droplet trajectory calculation, thermodynamic model application for computing ice accretion, and the updating of airfoil contours. The proposed ice prediction strategy has been validated using iced airfoil contours obtained experimentally in the AMIL refrigerated wind tunnel (Anti-icing Materials International Laboratory). Finally, a numerical prediction method has been generated for anti-icing assessment, and its results compared with data obtained in this laboratory. - Highlights: • A methodology for ice accretion prediction using commercial software is proposed. • Euler model gives better prediction of airfoil water collection with detached flow. • A source term is used to change from a solid wall to a permeable wall in Fluent. • Energy needed for ice-accretion mitigation system is predicted.

The aerodynamic design of an advanced rotor airfoil

Science.gov (United States)

Blackwell, J. A., Jr.; Hinson, B. L.

1978-01-01

An advanced rotor airfoil, designed utilizing supercritical airfoil technology and advanced design and analysis methodology is described. The airfoil was designed subject to stringent aerodynamic design criteria for improving the performance over the entire rotor operating regime. The design criteria are discussed. The design was accomplished using a physical plane, viscous, transonic inverse design procedure, and a constrained function minimization technique for optimizing the airfoil leading edge shape. The aerodynamic performance objectives of the airfoil are discussed.

Wind tunnel tests of Risø-B1-18 and Risø-B1-24

DEFF Research Database (Denmark)

Fuglsang, P.; Bak, Christian; Gaunaa, Mac

2003-01-01

This report contains 2D measurements of the Risø-B1-18 and Risø-B1-24 airfoils. The aerodynamic properties were derived from pressure measurements on the airfoil surface and in the wake. The measurements were conducted in the VELUX open jet wind tunnel,which has a background turbulence intensity...

Airfoil computations using the gamma-Retheta model; Wind turbines

Energy Technology Data Exchange (ETDEWEB)

Soerensen, Niels N.

2009-05-15

The present work addresses the validation of the implementation of the Menter, Langtry et al. gamma-theta correlation based transition model [1, 2, 3] in the EllipSys2D code. Firstly the 2. order of accuracy of the code is verified using a grid refinement study for laminar, turbulent and transitional computations. Based on this, an estimate of the error in the computations is determined to be approximately one percent in the attached region. Following the verification of the implemented model, the model is applied to four airfoils, NACA64-018, NACA64-218, NACA64-418 and NACA64-618 and the results are compared to measurements [4] and computations using the Xfoil code by Drela et al. [5]. In the linear pre stall region good agreement is observed both for lift and drag, while differences to both measurements and Xfoil computations are observed in stalled conditions. (au)

Reynolds number effect on airfoil wake structures under pitching and heaving motion

Science.gov (United States)

Kim, Kyung Chun; Karbasian, Hamidreza; ExpTENsys Team

2017-11-01

Detached Eddy Simulation (DES) and particle image velocimetry (PIV) measurements were performed to investigate the wake flow characteristics of an airfoil under pitching and heaving motion. A NACA0012 airfoil was selected for the numerical simulation and experiments were carried out in a wind tunnel and a water tunnel at Reynolds number of 15,000 and 90,000, respectively. The airfoil oscillated around an axis located 1/4 distance from the leading edge chord. Two different angles of attack, 20° and 30°, were selected with +/-10° maximum amplitude of oscillation. In order to extract the coherent flow structures from time-resolved PIV data, proper orthogonal decomposition (POD) analysis was performed on 1,000 instantaneous realisations for each condition using the method of snapshots. Vorticity contour and velocity profiles for both PIV and DES results are in good agreement for pitching and heaving motion. At high Reynolds number, 3D stream-wise vortices appeared after generating span-wise vortices. The higher maximum angle of attack allows the leading edge vortex to grow stronger and that the angle of attack appears to be more important in influencing the growth of the leading edge vortex structure than the reduced frequency. National Research Foundation of Korea (No. 2011-0030013).

Study of airfoil trailing edge bluntness noise

DEFF Research Database (Denmark)

Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær

2010-01-01

This paper deals with airfoil trailing edge noise with special focus on airfoils with blunt trailing edges. Two methods are employed to calculate airfoil noise: The flow/acoustic splitting method and the semi-empirical method. The flow/acoustic splitting method is derived from compressible Navier...... design or optimization. Calculations from both methods are compared with exist experiments. The airfoil blunt noise is found as a function of trailing edge bluntness, Reynolds number, angle of attack, etc....

Characterization of Oscillatory Lift in MFC Airfoils

OpenAIRE

Lang Jr, Joseph Reagle

2014-01-01

The purpose of this research is to characterize the response of an airfoil with an oscillatory morphing, Macro-fiber composite (MFC) trailing edge. Correlation of the airfoil lift with the oscillatory input is presented. Modal analysis of the test airfoil and apparatus is used to determine the frequency response function. The effects of static MFC inputs on the FRF are presented and compared to the unactuated airfoil. The transfer function is then used to determine the lift component du...

Turbine airfoil having near-wall cooling insert

Science.gov (United States)

Martin, Jr., Nicholas F.; Wiebe, David J.

2017-09-12

A turbine airfoil is provided with at least one insert positioned in a cavity in an airfoil interior. The insert extends along a span-wise extent of the turbine airfoil and includes first and second opposite faces. A first near-wall cooling channel is defined between the first face and a pressure sidewall of an airfoil outer wall. A second near-wall cooling channel is defined between the second face and a suction sidewall of the airfoil outer wall. The insert is configured to occupy an inactive volume in the airfoil interior so as to displace a coolant flow in the cavity toward the first and second near-wall cooling channels. A locating feature engages the insert with the outer wall for supporting the insert in position. The locating feature is configured to control flow of the coolant through the first or second near-wall cooling channel.

Effects of grit roughness and pitch oscillations on the LS(1)-0417MOD airfoil

Energy Technology Data Exchange (ETDEWEB)

Janiszewska, J.M.; Ramsay, R.R.; Hoffman, M.J.; Gregorek, G.M. [Ohio State Univ., Columbus, OH (United States)

1996-01-01

Horizontal axis wind turbine rotors experience unsteady aerodynamics due to wind shear when the rotor is yawed, when rotor blades pass through the support tower wake, and when the wind is gusting. An understanding of this unsteady behavior is necessary to assist in the calculations of rotor performance and loads. The rotors also experience performance degradation caused by surface roughness. These surface irregularities are due to the accumulation of insect debris, ice, and/or the aging process. Wind tunnel studies that examine both the steady and unsteady behavior of airfoils can help define pertinent flow phenomena, and the resultant data can be used to validate analytical computer codes. An LS(l)-0417MOD airfoil model was tested in The Ohio State University Aeronautical and Astronautical Research Laboratory (OSU/AARL) 3{times}5 subsonic wind tunnel (3{times}5) under steady flow and stationary model conditions, as well as with the model undergoing pitch oscillations. To study the possible extent of performance loss due to surface roughness, a standard grit pattern (LEGR) was used to simulate leading edge contamination. After baseline cases were completed, the LEGR was applied for both steady state and model pitch oscillation cases. The Reynolds numbers for steady state conditions were 0.75, 1, 1.25, and 1.5 million, while the angle of attack ranged from {minus}20{degrees} to +40{degrees}. With the model undergoing pitch oscillations, data were acquired at Reynolds numbers of 0.75, 1, 1.25, and 1.5 million, at frequencies of 0.6, 1.2, and 1.8 Hz. Two sine wave forcing functions were used, {plus_minus} 5.5%{degrees} and {plus_minus} 10{degrees}, at mean angles of attack of 8{degrees}, 14{degrees}, and 20{degrees}. For purposes herein, any reference to unsteady conditions foil model was in pitch oscillation about the quarter chord.

Unsteady Thick Airfoil Aerodynamics: Experiments, Computation, and Theory

Science.gov (United States)

Strangfeld, C.; Rumsey, C. L.; Mueller-Vahl, H.; Greenblatt, D.; Nayeri, C. N.; Paschereit, C. O.

2015-01-01

An experimental, computational and theoretical investigation was carried out to study the aerodynamic loads acting on a relatively thick NACA 0018 airfoil when subjected to pitching and surging, individually and synchronously. Both pre-stall and post-stall angles of attack were considered. Experiments were carried out in a dedicated unsteady wind tunnel, with large surge amplitudes, and airfoil loads were estimated by means of unsteady surface mounted pressure measurements. Theoretical predictions were based on Theodorsen's and Isaacs' results as well as on the relatively recent generalizations of van der Wall. Both two- and three-dimensional computations were performed on structured grids employing unsteady Reynolds-averaged Navier-Stokes (URANS). For pure surging at pre-stall angles of attack, the correspondence between experiments and theory was satisfactory; this served as a validation of Isaacs theory. Discrepancies were traced to dynamic trailing-edge separation, even at low angles of attack. Excellent correspondence was found between experiments and theory for airfoil pitching as well as combined pitching and surging; the latter appears to be the first clear validation of van der Wall's theoretical results. Although qualitatively similar to experiment at low angles of attack, two-dimensional URANS computations yielded notable errors in the unsteady load effects of pitching, surging and their synchronous combination. The main reason is believed to be that the URANS equations do not resolve wake vorticity (explicitly modeled in the theory) or the resulting rolled-up un- steady flow structures because high values of eddy viscosity tend to \\smear" the wake. At post-stall angles, three-dimensional computations illustrated the importance of modeling the tunnel side walls.

The effects of NACA 0012 airfoil modification on aerodynamic performance improvement and obtaining high lift coefficient and post-stall airfoil

Science.gov (United States)

Sogukpinar, Haci

2018-02-01

In this study, aerodynamic performances of NACA 0012 airfoils with distinct modification are numerically investigated to obtain high lift coefficient and post-stall airfoils. NACA 0012 airfoil is divided into two part thought chord line then suction sides kept fixed and by changing the thickness of the pressure side new types of airfoil are created. Numerical experiments are then conducted by varying thickness of NACA 0012 from lower surface and different relative thicknesses asymmetrical airfoils are modified and NACA 0012-10, 0012-08, 0012-07, 0012-06, 0012-04, 0012-03, 0012-02, 0012-01 are created and simulated by using COMSOL software.

Airfoil shape for flight at subsonic speeds. [design analysis and aerodynamic characteristics of the GAW-1 airfoil

Science.gov (United States)

Whitcomb, R. T. (Inventor)

1976-01-01

An airfoil is examined that has an upper surface shaped to control flow accelerations and pressure distribution over the upper surface and to prevent separation of the boundary layer due to shock wave formulation at high subsonic speeds well above the critical Mach number. A highly cambered trailing edge section improves overall airfoil lifting efficiency. Diagrams illustrating supersonic flow and shock waves over the airfoil are shown.

Computational study of the Risoe-B1-18 airfoil with a hinged flap providing variable trailing edge geometry

Energy Technology Data Exchange (ETDEWEB)

Troldborg, N.

2005-03-01

A comprehensive computational study, in both steady and unsteady flow conditions, has been carried out to investigate the aerodynamic characteristics of the Risoe-B1-18 airfoil equipped with variable trailing edge geometry as produced by a hinged flap. The function of such flaps should be to decrease fatigue-inducing oscillations on the blades. The computations were conducted using a 2D incompressible RANS solver with a k-w turbulence model under the assumption of a fully developed turbulent flow. The investigations were conducted at a Reynolds number of Re = 1.6 - 10{sup 6}. Calculations conducted on the baseline airfoil showed excellent agreement with measurements on the same airfoil with the same specified conditions. Furthermore, a more widespread comparison with an advanced potential theory code is presented. The influence of various key parameters, such as flap shape, flap size and oscillating frequencies, was investigated so that an optimum design can be suggested for application with wind turbine blades. It is concluded that a moderately curved flap with flap chord to airfoil curve ratio between 0.05 and 0.10 would be an optimum choice. (author)

Airfoil flow instabilities induced by background flow oscillations

Energy Technology Data Exchange (ETDEWEB)

Selerowicz, W.C.; Szumowski, A.P. [Technical Univ. Warsaw (Poland)

2002-04-01

The effect of background flow oscillations on transonic airfoil (NACA 0012) flow was investigated experimentally. The oscillations were generated by means of a rotating plate placed downstream of the airfoil. Owing to oscillating chocking of the flow caused by the plate, the airfoil flow periodically accelerated and decelerated. This led to strong variations in the surface pressure and the airfoil loading. The results are presented for two angles of attack, {alpha}=4 and {alpha}=8.5 , which correspond to the attached and separated steady airfoil flows, respectively. (orig.)

VISUALISASI DISTRIBUSI TEKANAN PADA AIRFOIL JOUKOWSKY

OpenAIRE

Eddy Maryonoto

2009-01-01

The goal of this research is to develop a computer based system that can beused to visualize pressure distribution on the Joukowsky's airfoil and streamlinespattern around the airfoil. The pressure on the airfoil is calculdted usingformulasderived from potensial theory. Visualization of pressure distribution implementedby using color gradation technique and coded b.v using Borland Delphi 6programming language. The result of the test shotus lhat lhe system has performedperfectly. Pressure disl...

Optimization of wind turbine rotors

Energy Technology Data Exchange (ETDEWEB)

Nygaard, Tor Anders

1999-07-01

The Constrained Steepest Descent method has been applied to the optimization of wind turbine rotors through the development of a numerical model. The model consists of an optimization kernel, an aerodynamic model, a structural dynamic model of a rotating beam, and a cost model for the wind turbine. The cost of energy is minimized directly by varying the blade design, the rotational speed and the resulting design of the drive-train and tower. The aerodynamic model is a combination of a fast engineering model based on strip-theory and two and three-dimensional Euler solvers. The two-dimensional Euler solver is used for generation of pre-stall airfoil data. Comparisons with experimental data verify that the engineering model effectively approximates non-stalled flow, except at the blade tip. The three-dimensional Euler solver is in good agreement with the experimental data at the tip, and is therefore a useful supplement for corrections of the tip-loss model, and evaluation of an optimized design. The structural dynamic model evaluates stresses and deformations for the blade. It is based on constitutive relations for a slender beam that are solved with the equations of motions using a finite-difference method. The cost model evaluates the design change of the wind turbine and the resulting costs that occur when a change in blade design modifies the blade mass and the overall forces. The cost model is based on engineering design rules for the drive-train and tower. The model was applied using a Danish 600 kW wind turbine as a reference. Two rotors were optimized using traditional NACA airfoils and a new low-lift airfoil family developed specifically for wind turbine purposes. The cost of energy decreased four percent for the NACA rotor, and seven percent for the low-lift rotor. Optimizations with a high number of degrees of freedom show that a designer has considerable flexibility in choosing some primary parameters such as rated power and rotor diameter, if the rest

Flow control over a NACA 0012 airfoil using dielectric-barrier-discharge plasma actuator with a Gurney flap

Energy Technology Data Exchange (ETDEWEB)

Feng, Li-Hao [Beijing University of Aeronautics and Astronautics, Fluid Mechanics Key Laboratory of Education Ministry, Beijing (China); University of Nottingham, University Park, Faculty of Engineering, Nottingham (United Kingdom); Jukes, Timothy N. [University of Nottingham, University Park, Faculty of Engineering, Nottingham (United Kingdom); AIST, Research Centre for New Fuels and Vehicle Technology, Tsukuba (Japan); Choi, Kwing-So [University of Nottingham, University Park, Faculty of Engineering, Nottingham (United Kingdom); Wang, Jin-Jun [Beijing University of Aeronautics and Astronautics, Fluid Mechanics Key Laboratory of Education Ministry, Beijing (China)

2012-06-15

Flow control study of a NACA 0012 airfoil with a Gurney flap was carried out in a wind tunnel, where it was demonstrated that a dielectric-barrier-discharge (DBD) plasma actuator attached to the flap could increase the lift further, but with a small drag penalty. Time-resolved PIV measurements of the near-wake region indicated that the plasma forcing shifted the wake downwards, reducing its recirculation length. Analysis of wake vortex dynamics suggested that the plasma actuator initially amplified the lower wake shear layer by adding momentum along the downstream surface of the Gurney flap. This enhanced mutual entrainment between the upper and lower wake vortices, leading to an increase in lift on the airfoil. (orig.)

On the effects of leading edge vortex generators on an OA209 airfoil

OpenAIRE

Heine, Benjamin; Mulleners, Karen; Gardner, Anthony; Mai, Holger

2009-01-01

Leading edge vortex generators have been found to significantly increase the aerodynamic performance of an airfoil under dynamic stall conditions. However, the principle of operation of these devices is still unclear. Therefore static wind and water tunnel experiments as well as CFD simulations have been conducted on a rotary aircraft wing profile OA209. A POD analysis applied to the vector fields generated by PIV measurements showed that the vortex generators break larger flow structures...

Unsteady Aerodynamics of Deformable Thin Airfoils

OpenAIRE

Walker, William Paul

2009-01-01

Unsteady aerodynamic theories are essential in the analysis of bird and insect flight. The study of these types of locomotion is vital in the development of flapping wing aircraft. This paper uses potential flow aerodynamics to extend the unsteady aerodynamic theory of Theodorsen and Garrick (which is restricted to rigid airfoil motion) to deformable thin airfoils. Frequency-domain lift, pitching moment and thrust expressions are derived for an airfoil undergoing harmonic oscillations and def...

Study on Trailing Edge Ramp of Supercritical Airfoil

Science.gov (United States)

2016-03-30

China Abstract Trailing edge flow control method could improve the performance of supercritical airfoil with a small modification on the original...stall behaviour . As a result, the non-separation ramp could increase the thickness of airfoil, which benefits wing structure and aerodynamic...direction based on the original RAE2822 airfoil, which will thicken the airfoil. The interpolation is implemented as shown in Eqn. 1. This modification could

2D Numerical Investigation of the Laminar and Turbulent Flow Over Different Airfoils Using OpenFOAM

International Nuclear Information System (INIS)

Rahimi, H; Stoevesandt, B; Peinke, J; Medjroubi, W

2014-01-01

The aim of this work is to assess the prediction capabilities of the turbulence models and the transition model kkl-ω available in OpenFOAM and to achieve a database of airfoil aerodynamical characteristics. The airfoils chosen for the simulations are FX 79-W- 15A and NACA 63-430, which are widely used in wind turbines. The numerically obtained lift and drag coefficients are compared with available experimental results. A quantitative and qualitative study is conducted to determine the influence of meshing strategies, computational time step together with interpolation and temporal schemes. Two Reynolds Averaged Navier- Stokes models (RANS models) are used, which are the k-ω SST model by Menter and the kkl-ω model (which involves transition modeling) by Walters and Davor

Fluidic load control for wind turbines blades

NARCIS (Netherlands)

Boeije, C.S.; Vries, de H.; Cleine, I.; Emden, van E.; Zwart, G.G.M.; Stobbe, H.; Hirschberg, A.; Hoeijmakers, H.W.M.; Maureen Hand, xx

2009-01-01

This paper describes the initial steps into the investigation of the possibility of reducing fatigue loads on wind turbine blades by the application of fluidic jets. This investigation involves static pressure measurements as well as numerical simulations for a non-rotating NACA-0018 airfoil. The

Wind turbine

Science.gov (United States)

Cheney, Jr., Marvin C.

1982-01-01

A wind turbine of the type having an airfoil blade (15) mounted on a flexible beam (20) and a pitch governor (55) which selectively, torsionally twists the flexible beam in response to wind turbine speed thereby setting blade pitch, is provided with a limiter (85) which restricts unwanted pitch change at operating speeds due to torsional creep of the flexible beam. The limiter allows twisting of the beam by the governor under excessive wind velocity conditions to orient the blades in stall pitch positions, thereby preventing overspeed operation of the turbine. In the preferred embodiment, the pitch governor comprises a pendulum (65,70) which responds to changing rotor speed by pivotal movement, the limiter comprising a resilient member (90) which engages an end of the pendulum to restrict further movement thereof, and in turn restrict beam creep and unwanted blade pitch misadjustment.

Turbulent wind field characterization and re-generation based on pitot tube measurements mounted on a wind turbine

DEFF Research Database (Denmark)

Pedersen, Mads Mølgaard; Larsen, Torben J.; Aagaard Madsen, Helge

2015-01-01

models that compensate for axial and tangential induction, approximated by blade element momentum theory, radial expansion of the inflow, rotor tilt, dynamic and skew inflow, tip loss, as well as braking and circulation of the flow local to the airfoil. The wind speeds measured on the rotating blades...... the measured wind speeds at the recording position. In the theoretical part of this study a quite good agreement is seen between load sensors on a turbine model exposed to the reference and the re-generated turbulence field. Finally the method is applied to full scale measurements and reasonable wind shear...

Wind tunnel study of helical and straight-bladed vertical-axis wind turbine wakes

Science.gov (United States)

Bagheri, Maryam; Araya, Daniel

2017-11-01

It is hypothesized that blade curvature can serve as a passive means to control fluid entrainment and wake recovery in vertical-axis wind turbine (VAWT) arrays. We test this experimentally in a wind tunnel using two different VAWT configurations, one with straight blades and another with helical blades, keeping all other experimental parameters fixed. A small-scale, commercially available VAWT (15W max power) is used as the baseline wind tunnel model in each case. The commercial VAWT blades are replaced with either straight or helical blades that are 3D-printed extrusions of the same airfoil cross-section. Results from smoke flow visualization, three-component wake velocity measurements, and turbine power data are presented. These results give insight into the potential use of VAWTs with curved blades in utility-scale wind farms.

2D CFD Airfoil Analysis

Science.gov (United States)

Babb, Grace

2017-11-01

This work aims to produce a higher fidelity model of the blades for NASA's X-57 all electric propeller driven experimental aircraft. This model will, in turn, allow for more accurate calculations of the thrust each propeller can generate. This work uses computational fluid dynamics (CFD) to first analyze the propeller blades as a series of 11 differently shaped airfoils and calculate, among other things, the coefficients for lift and drag associated with each airfoil at different angles of attack. OpenFOAM-a C + + library that can be used to create series of applications for pre-processing, solving, and post-processing-is one of the primary tools utilized in these calculations. By comparing the data OpenFOAM generates about the NACA 23012 airfoil with existing experimental data about the NACA 23012 airfoil, the reliability of our model is measured and verified. A trustworthy model can then be used to generate more data and sent to NASA to aid in the design of the actual aircraft.

An Integrated Method for Airfoil Optimization

Science.gov (United States)

Okrent, Joshua B.

Design exploration and optimization is a large part of the initial engineering and design process. To evaluate the aerodynamic performance of a design, viscous Navier-Stokes solvers can be used. However this method can prove to be overwhelmingly time consuming when performing an initial design sweep. Therefore, another evaluation method is needed to provide accurate results at a faster pace. To accomplish this goal, a coupled viscous-inviscid method is used. This thesis proposes an integrated method for analyzing, evaluating, and optimizing an airfoil using a coupled viscous-inviscid solver along with a genetic algorithm to find the optimal candidate. The method proposed is different from prior optimization efforts in that it greatly broadens the design space, while allowing the optimization to search for the best candidate that will meet multiple objectives over a characteristic mission profile rather than over a single condition and single optimization parameter. The increased design space is due to the use of multiple parametric airfoil families, namely the NACA 4 series, CST family, and the PARSEC family. Almost all possible airfoil shapes can be created with these three families allowing for all possible configurations to be included. This inclusion of multiple airfoil families addresses a possible criticism of prior optimization attempts since by only focusing on one airfoil family, they were inherently limiting the number of possible airfoil configurations. By using multiple parametric airfoils, it can be assumed that all reasonable airfoil configurations are included in the analysis and optimization and that a global and not local maximum is found. Additionally, the method used is amenable to customization to suit any specific needs as well as including the effects of other physical phenomena or design criteria and/or constraints. This thesis found that an airfoil configuration that met multiple objectives could be found for a given set of nominal

Validation of a wind tunnel testing facility for blade surface pressure measurements

Energy Technology Data Exchange (ETDEWEB)

Fuglsang, P.; Antoniou, I.; Soerensen, N.N.; Madsen, H.A.

1998-04-01

This report concerns development and validation of a 2d testing facility for airfoil pressure measurements. The VELUX open jet wind tunnel was used with a test stand inserted. Reynolds numbers until 1.3 million were achieved with an airfoil chord of 0.45 m. The aerodynamic load coefficients were found from pressure distribution measurements and the total drag coefficient was calculated from wake rake measurements. Stationary inflow as well as dynamic inflow through pitching motion was possible. Wind tunnel corrections were applied for streamline curvature and down-wash. Even though the wind tunnel is not ideal for 2d testing, the overall quality of the flow was acceptable with a uniform flow field at the test stand position and a turbulence intensity of 1 % at the inlet of the test section. Reference values for free stream static and total pressure were found upstream of the test stand. The NACA 63-215 airfoil was tested and the results were compared with measurements from FFA and NACA. The measurements agreed well except for lift coefficient values at high angles of attack and the drag coefficient values at low angles of attack, that were slightly high. Comparisons of the measured results with numerical predictions from the XFOIL code and the EllipSys2D code showed good agreement. Measurements with the airfoil in pitching motion were carried out to study the dynamic aerodynamic coefficients. Steady inflow measurements at high angles of attack were used to investigate the double stall phenomenon. (au) EFP-94; EFP-95; EFP-97. 8 tabs., 82 ills., 16 refs.

A CFD Database for Airfoils and Wings at Post-Stall Angles of Attack

Science.gov (United States)

Petrilli, Justin; Paul, Ryan; Gopalarathnam, Ashok; Frink, Neal T.

2013-01-01

This paper presents selected results from an ongoing effort to develop an aerodynamic database from Reynolds-Averaged Navier-Stokes (RANS) computational analysis of airfoils and wings at stall and post-stall angles of attack. The data obtained from this effort will be used for validation and refinement of a low-order post-stall prediction method developed at NCSU, and to fill existing gaps in high angle of attack data in the literature. Such data could have potential applications in post-stall flight dynamics, helicopter aerodynamics and wind turbine aerodynamics. An overview of the NASA TetrUSS CFD package used for the RANS computational approach is presented. Detailed results for three airfoils are presented to compare their stall and post-stall behavior. The results for finite wings at stall and post-stall conditions focus on the effects of taper-ratio and sweep angle, with particular attention to whether the sectional flows can be approximated using two-dimensional flow over a stalled airfoil. While this approximation seems reasonable for unswept wings even at post-stall conditions, significant spanwise flow on stalled swept wings preclude the use of two-dimensional data to model sectional flows on swept wings. Thus, further effort is needed in low-order aerodynamic modeling of swept wings at stalled conditions.

Airfoil nozzle and shroud assembly

Science.gov (United States)

Shaffer, J.E.; Norton, P.F.

1997-06-03

An airfoil and nozzle assembly are disclosed including an outer shroud having a plurality of vane members attached to an inner surface and having a cantilevered end. The assembly further includes a inner shroud being formed by a plurality of segments. Each of the segments having a first end and a second end and having a recess positioned in each of the ends. The cantilevered end of the vane member being positioned in the recess. The airfoil and nozzle assembly being made from a material having a lower rate of thermal expansion than that of the components to which the airfoil and nozzle assembly is attached. 5 figs.

Turbine airfoil to shroud attachment method

Science.gov (United States)

Campbell, Christian X; Kulkarni, Anand A; James, Allister W; Wessell, Brian J; Gear, Paul J

2014-12-23

Bi-casting a platform (50) onto an end portion (42) of a turbine airfoil (31) after forming a coating of a fugitive material (56) on the end portion. After bi-casting the platform, the coating is dissolved and removed to relieve differential thermal shrinkage stress between the airfoil and platform. The thickness of the coating is varied around the end portion in proportion to varying amounts of local differential process shrinkage. The coating may be sprayed (76A, 76B) onto the end portion in opposite directions parallel to a chord line (41) of the airfoil or parallel to a mid-platform length (80) of the platform to form respective layers tapering in thickness from the leading (32) and trailing (34) edges along the suction side (36) of the airfoil.

Theory and Low-Order Modeling of Unsteady Airfoil Flows

Science.gov (United States)

Ramesh, Kiran

Unsteady flow phenomena are prevalent in a wide range of problems in nature and engineering. These include, but are not limited to, aerodynamics of insect flight, dynamic stall in rotorcraft and wind turbines, leading-edge vortices in delta wings, micro-air vehicle (MAV) design, gust handling and flow control. The most significant characteristics of unsteady flows are rapid changes in the circulation of the airfoil, apparent-mass effects, flow separation and the leading-edge vortex (LEV) phenomenon. Although experimental techniques and computational fluid dynamics (CFD) methods have enabled the detailed study of unsteady flows and their underlying features, a reliable and inexpensive loworder method for fast prediction and for use in control and design is still required. In this research, a low-order methodology based on physical principles rather than empirical fitting is proposed. The objective of such an approach is to enable insights into unsteady phenomena while developing approaches to model them. The basis of the low-order model developed here is unsteady thin-airfoil theory. A time-stepping approach is used to solve for the vorticity on an airfoil camberline, allowing for large amplitudes and nonplanar wakes. On comparing lift coefficients from this method against data from CFD and experiments for some unsteady test cases, it is seen that the method predicts well so long as LEV formation does not occur and flow over the airfoil is attached. The formation of leading-edge vortices (LEVs) in unsteady flows is initiated by flow separation and the formation of a shear layer at the airfoil's leading edge. This phenomenon has been observed to have both detrimental (dynamic stall in helicopters) and beneficial (high-lift flight in insects) effects. To predict the formation of LEVs in unsteady flows, a Leading Edge Suction Parameter (LESP) is proposed. This parameter is calculated from inviscid theory and is a measure of the suction at the airfoil's leading edge. It

Vibrational analysis of vertical axis wind turbine blades

Science.gov (United States)

Kapucu, Onur

The goal of this research is to derive a vibration model for a vertical axis wind turbine blade. This model accommodates the affects of varying relative flow angle caused by rotating the blade in the flow field, uses a simple aerodynamic model that assumes constant wind speed and constant rotation rate, and neglects the disturbance of wind due to upstream blade or post. The blade is modeled as elastic Euler-Bernoulli beam under transverse bending and twist deflections. Kinetic and potential energy equations for a rotating blade under deflections are obtained, expressed in terms of assumed modal coordinates and then plugged into Lagrangian equations where the non-conservative forces are the lift and drag forces and moments. An aeroelastic model for lift and drag forces, approximated with third degree polynomials, on the blade are obtained assuming an airfoil under variable angle of attack and airflow magnitudes. A simplified quasi-static airfoil theory is used, in which the lift and drag coefficients are not dependent on the history of the changing angle of attack. Linear terms on the resulting equations of motion will be used to conduct a numerical analysis and simulation, where numeric specifications are modified from the Sandia-17m Darrieus wind turbine by Sandia Laboratories.

Airfoil seal system for gas turbine engine

Science.gov (United States)

None, None

2013-06-25

A turbine airfoil seal system of a turbine engine having a seal base with a plurality of seal strips extending therefrom for sealing gaps between rotational airfoils and adjacent stationary components. The seal strips may overlap each other and may be generally aligned with each other. The seal strips may flex during operation to further reduce the gap between the rotational airfoils and adjacent stationary components.

Advanced Airfoils Boost Helicopter Performance

Science.gov (United States)

2007-01-01

Carson Helicopters Inc. licensed the Langley RC4 series of airfoils in 1993 to develop a replacement main rotor blade for their Sikorsky S-61 helicopters. The company's fleet of S-61 helicopters has been rebuilt to include Langley's patented airfoil design, and the helicopters are now able to carry heavier loads and fly faster and farther, and the main rotor blades have twice the previous service life. In aerial firefighting, the performance-boosting airfoils have helped the U.S. Department of Agriculture's Forest Service control the spread of wildfires. In 2003, Carson Helicopters signed a contract with Ducommun AeroStructures Inc., to manufacture the composite blades for Carson Helicopters to sell

High-efficiency airfoil rudders applied to submarines

Directory of Open Access Journals (Sweden)

ZHOU Yimei

2017-03-01

Full Text Available Modern submarine design puts forward higher and higher requirements for control surfaces, and this creates a requirement for designers to constantly innovate new types of rudder so as to improve the efficiency of control surfaces. Adopting the high-efficiency airfoil rudder is one of the most effective measures for improving the efficiency of control surfaces. In this paper, we put forward an optimization method for a high-efficiency airfoil rudder on the basis of a comparative analysis of the various strengths and weaknesses of the airfoil, and the numerical calculation method is adopted to analyze the influence rule of the hydrodynamic characteristics and wake field by using the high-efficiency airfoil rudder and the conventional NACA rudder comparatively; at the same time, a model load test in a towing tank was carried out, and the test results and simulation calculation obtained good consistency:the error between them was less than 10%. The experimental results show that the steerage of a high-efficiency airfoil rudder is increased by more than 40% when compared with the conventional rudder, but the total resistance is close:the error is no more than 4%. Adopting a high-efficiency airfoil rudder brings much greater lifting efficiency than the total resistance of the boat. The results show that high-efficiency airfoil rudder has obvious advantages for improving the efficiency of control, giving it good application prospects.

Experimental Studies of Flow Separation of the NACA 2412 Airfoil at Low Speeds

Science.gov (United States)

Seetharam, H. C.; Rodgers, E. J.; Wentz, W. H., Jr.

1997-01-01

Wind tunnel tests have been conducted on an NACA 2412 airfoil section at Reynolds number of 2.2 x 10(exp 6) and Mach number of 0.13. Detailed measurements of flow fields associated with turbulent boundary layers have been obtained at angles of attack of 12.4 degrees, 14.4 degrees, and 16.4 degrees. Pre- and post-separated velocity and pressure survey results over the airfoil and in the associated wake are presented. Extensive force, pressure, tuft survey, hot-film survey, local skin friction, and boundary layer data are also included. Pressure distributions and separation point locations show good agreement with theory for the two layer angles of attack. Boundary layer displacement thickness, momentum thickness, and shape factor agree well with theory up to the point of separation. There is considerable disparity between extent of flow reversal in the wake as measured by pressure and hot-film probes. The difference is attributed to the intermittent nature of the flow reversal.

Aeroelastic Stability of a 2D Airfoil Section equipped with a Trailing Edge Flap

DEFF Research Database (Denmark)

Bergami, Leonardo

Recent studies conclude that important reduction of the fatigue loads encountered by a wind turbine blade can be achieved using a deformable trailing edge control system. The focus of the current work is to determine the effect of this flap-like system on the aeroelastic stability of a 2D airfoil...... section. A simulation tool is implemented to predict the flow speed at which a flap equipped section may become unstable, either due to flutter or divergence. First, the stability limits of the airfoil without flap are determined, and, in the second part of the work, a deformable trailing edge flap...... is applied. Stability is investigated for the uncontrolled flap, and for three different control algorithms. The three controls are tuned for fatigue load alleviation and they are based on, respectively, measurement of the heave displacement and velocity, measurement of the local angle of attack, measurement...

Advances in wind turbine blade design and materials

DEFF Research Database (Denmark)

Wind energy is gaining critical ground in the area of renewable energy, with wind energy being predicted to provide up to 8% of the world’s consumption of electricity by 2021. Advances in wind turbine blade design and materials reviews the design and functionality of wind turbine rotor blades...... as well as the requirements and challenges for composite materials used in both current and future designs of wind turbine blades. Part one outlines the challenges and developments in wind turbine blade design, including aerodynamic and aeroelastic design features, fatigue loads on wind turbine blades......, and characteristics of wind turbine blade airfoils. Part two discusses the fatigue behavior of composite wind turbine blades, including the micromechanical modelling and fatigue life prediction of wind turbine blade composite materials, and the effects of resin and reinforcement variations on the fatigue resistance...

Estimation of supersonic fighter jet airfoil data and low speed aerodynamic analysis of airfoil section at the Mach number 0.15

Science.gov (United States)

Sogukpinar, Haci

2018-02-01

In this paper, some of the NACA 64A series airfoils data are estimated and aerodynamic properties are calculated to facilitate great understandings effect of relative thickness on the aerodynamic performance of the airfoil by using COMSOL software. 64A201-64A204 airfoils data are not available in literature therefore 64A210 data are used as reference data to estimate 64A201, 64A202, 64A203, 64A204 airfoil configurations. Numerical calculations are then conducted with the angle of attack from -12° to +16° by using k-w turbulence model based on the finite-volume approach. The lift and drag coefficient are one of the most important parameters in studying the airplane performance. Therefore lift, drag and pressure coefficient around selected airfoil are calculated and compared at the Reynolds numbers of 6 × 106 and also stalling characteristics of airfoil section are investigated and presented numerically.

Modeling and Grid Generation of Iced Airfoils

Science.gov (United States)

Vickerman, Mary B.; Baez, Marivell; Braun, Donald C.; Hackenberg, Anthony W.; Pennline, James A.; Schilling, Herbert W.

2007-01-01

SmaggIce Version 2.0 is a software toolkit for geometric modeling and grid generation for two-dimensional, singleand multi-element, clean and iced airfoils. A previous version of SmaggIce was described in Preparing and Analyzing Iced Airfoils, NASA Tech Briefs, Vol. 28, No. 8 (August 2004), page 32. To recapitulate: Ice shapes make it difficult to generate quality grids around airfoils, yet these grids are essential for predicting ice-induced complex flow. This software efficiently creates high-quality structured grids with tools that are uniquely tailored for various ice shapes. SmaggIce Version 2.0 significantly enhances the previous version primarily by adding the capability to generate grids for multi-element airfoils. This version of the software is an important step in streamlining the aeronautical analysis of ice airfoils using computational fluid dynamics (CFD) tools. The user may prepare the ice shape, define the flow domain, decompose it into blocks, generate grids, modify/divide/merge blocks, and control grid density and smoothness. All these steps may be performed efficiently even for the difficult glaze and rime ice shapes. Providing the means to generate highly controlled grids near rough ice, the software includes the creation of a wrap-around block (called the "viscous sublayer block"), which is a thin, C-type block around the wake line and iced airfoil. For multi-element airfoils, the software makes use of grids that wrap around and fill in the areas between the viscous sub-layer blocks for all elements that make up the airfoil. A scripting feature records the history of interactive steps, which can be edited and replayed later to produce other grids. Using this version of SmaggIce, ice shape handling and grid generation can become a practical engineering process, rather than a laborious research effort.

Airfoil optimization for morphing aircraft

Science.gov (United States)

Namgoong, Howoong

Continuous variation of the aircraft wing shape to improve aerodynamic performance over a wide range of flight conditions is one of the objectives of morphing aircraft design efforts. This is being pursued because of the development of new materials and actuation systems that might allow this shape change. The main purpose of this research is to establish appropriate problem formulations and optimization strategies to design an airfoil for morphing aircraft that include the energy required for shape change. A morphing aircraft can deform its wing shape, so the aircraft wing has different optimum shapes as the flight condition changes. The actuation energy needed for moving the airfoil surface is modeled and used as another design objective. Several multi-objective approaches are applied to a low-speed, incompressible flow problem and to a problem involving low-speed and transonic flow. The resulting solutions provide the best tradeoff between low drag, high energy and higher drag, low energy sets of airfoil shapes. From this range of solutions, design decisions can be made about how much energy is needed to achieve a desired aerodynamic performance. Additionally, an approach to model aerodynamic work, which would be more realistic and may allow using pressure on the airfoil to assist a morphing shape change, was formulated and used as part of the energy objective. These results suggest that it may be possible to design a morphing airfoil that exploits the airflow to reduce actuator energy.

First-stage high pressure turbine bucket airfoil

Science.gov (United States)

Brown, Theresa A.; Ahmadi, Majid; Clemens, Eugene; Perry, II, Jacob C.; Holiday, Allyn K.; Delehanty, Richard A.; Jacala, Ariel Caesar

2004-05-25

The first-stage buckets have airfoil profiles substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I wherein Z is a perpendicular distance from a plane normal to a radius of the turbine centerline and containing the X and Y values with the Z value commencing at zero in the X, Y plane at the radially innermost aerodynamic section of the airfoil and X and Y are coordinates defining the airfoil profile at each distance Z. The X, Y and Z values may be scaled as a function of the same constant or number to provide a scaled-up or scaled-down airfoil section for the bucket.

Multiple piece turbine engine airfoil with a structural spar

Science.gov (United States)

Vance, Steven J [Orlando, FL

2011-10-11

A multiple piece turbine airfoil having an outer shell with an airfoil tip that is attached to a root with an internal structural spar is disclosed. The root may be formed from first and second sections that include an internal cavity configured to receive and secure the one or more components forming the generally elongated airfoil. The internal structural spar may be attached to an airfoil tip and place the generally elongated airfoil in compression. The configuration enables each component to be formed from different materials to reduce the cost of the materials and to optimize the choice of material for each component.

The flow over a thin airfoil subjected to elevated levels of freestream turbulence at low Reynolds numbers

Energy Technology Data Exchange (ETDEWEB)

Ravi, Sridhar [University of Tuebingen, Tuebingen (Germany); Watkins, Simon; Watmuff, Jon; Massey, Kevin; Petersen, Phred; Marino, Matthew [RMIT University, Melbourne, VIC (Australia); Ravi, Anuradha [Vellore Institute of Technology, Vellore, Tamilnadu (India)

2012-09-15

Micro Air Vehicles (MAVs) can be difficult to control in the outdoor environment as they fly at relatively low speeds and are of low mass, yet exposed to high levels of freestream turbulence present within the Atmospheric Boundary Layer. In order to examine transient flow phenomena, two turbulence conditions of nominally the same longitudinal integral length scale (Lxx/c = 1) but with significantly different intensities (Ti = 7.2 % and 12.3 %) were generated within a wind tunnel; time-varying surface pressure measurements, smoke flow visualization, and wake velocity measurements were made on a thin flat plate airfoil. Rapid changes in oncoming flow pitch angle resulted in the shear layer to separate from the leading edge of the airfoil even at lower geometric angles of attack. At higher geometric angles of attack, massive flow separation occurred at the leading edge followed by enhanced roll up of the shear layer. This lead to the formation of large Leading Edge Vortices (LEVs) that advected at a rate much lower than the mean flow speed while imparting high pressure fluctuations over the airfoil. The rate of LEV formation was dependent on the angle of attack until 10 and it was independent of the turbulence properties tested. The fluctuations in surface pressures and consequently aerodynamic loads were considerably limited on the airfoil bottom surface due to the favorable pressure gradient. (orig.)

Acoustics of a Mixed Porosity Felt Airfoil

Science.gov (United States)

2016-06-06

NUWC-NPT Technical Report 12,212 6 June 2016 Acoustics of a Mixed Porosity Felt Airfoil Aren M. Hellum Undersea Warfare Weapons...Felt Airfoil 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Aren M. Hellum 5.d PROJECT NUMBER 5e...existing literature. Geyer et al. [5] measured a sound reduction of 5 to 15 dB for airfoils made entirely of porous material. A 1973 patent

Test results of NREL 10M, special-purpose family of thin airfoils

Energy Technology Data Exchange (ETDEWEB)

Starcher, K.L.; Nelson, V.C.; Wei, Jun [West Texas A& M Univ., Canyon, TX (United States)

1996-12-31

Two 25 kW Carter Wind Systems were tested to determine performance differences between production blades and rotors with NREL Special Purpose Thin Airfoils. Blade design, mold preparation, blade production, and testing were conducted. Design tools were created for computer modeling of the blade. The blades had the same twist, taper, and length as production blades. Flap natural frequency was adjusted to be as similar as possible between rotors, as was blade mass, blade center of gravity and rotor moment of inertia. Data collected were; wind speed at hub height, blade root flap & edgewise loads, main shaft torque, azimuth position, teeter angle, yaw angle and electrical power. These data were collected at 128 Hertz for data sets of eight seconds. This data set was then written to hard disk and the cycle repeated resulting in a file containing five and one half minutes of data. A data run consisted of; preflight checkout/warm-up of equipment, preflight calibration/verification of all sensors on both turbines, collection of five files of data (about thirty minutes of data), post flight calibration/verification of sensors. During this high speed data collection period there were a total of twenty-four data runs collected. Data were collected for wind speeds in the range about 7, 10 and 13 m/s. A data matrix was filled for clean, medium and heavy surface roughness. Baseline power curves, parametric pitch variation runs to establish testing pitch settings, high speed data collection runs with and without applied surface roughness were completed and analyzed. Data were compared using simple arithmetic mean, Fast Fourier Transform (FFT) analysis, rainflow counting algorithms and wavelet analysis. The NREL airfoils showed much less sensitivity to surface roughness. There were minimal root bending load differences. Annual energy production during long term operation is being determined. 9 refs., 7 figs.

Dynamic stall study of a multi-element airfoil

Science.gov (United States)

Tung, Chee; Mcalister, Kenneth W.; Wang, Clin M.

1992-01-01

Unsteady flow behavior and load characteristics of a VR-7 airfoil with and without a slat were studied in the water tunnel of the Aeroflightdynamics Directorate, NASA Ames Research Center. Both airfoils were oscillated sinusoidally between 5 and 25 degrees at a Reynolds number of 200,000 to obtain the unsteady lift, drag and pitching moment data. A fluorescing dye was released from an orifice located at the leading edge of the airfoil for the purpose of visualizing the boundary layer and wake flow. The flow field and load predictions of an incompressible Navier-Stokes code based on a velocity-vorticity formulation were compared with the test data. The test and predictions both confirm that the slatted VR-7 airfoil delays both static and dynamic stall as compared to the VR-7 airfoil alone.

Aeroelastic Optimization of MW Wind Turbines

DEFF Research Database (Denmark)

Hansen, Morten Hartvig; Zahle, Frederik

This report contains the results from the Energy Development and Demonstration Project “Aeroelastic Optimization of MW wind turbine” (AeroOpt). The project has had the following five Work Packages: 1. Geometric non-linear, anisotropic beamelement forHAWC2 2. Closed-loop eigenvalue analysis...... of controlled wind turbines 3. Resonant wave excitation of lateral tower bending modes 4. Development of next generation aerodynamic design tools 5. Advanced design and verification of airfoils The purposes of these Work Packages are briefly described in the Preface and a summary of the results are given...

A Wind Tunnel Model to Explore Unsteady Circulation Control for General Aviation Applications

Science.gov (United States)

Cagle, Christopher M.; Jones, Gregory S.

2002-01-01

Circulation Control airfoils have been demonstrated to provide substantial improvements in lift over conventional airfoils. The General Aviation Circular Control model is an attempt to address some of the concerns of this technique. The primary focus is to substantially reduce the amount of air mass flow by implementing unsteady flow. This paper describes a wind tunnel model that implements unsteady circulation control by pulsing internal pneumatic valves and details some preliminary results from the first test entry.

Effect of Geometric Uncertainties on the Aerodynamic Characteristic of Offshore Wind Turbine Blades

International Nuclear Information System (INIS)

Ernst, Benedikt; Schmitt, Henning; Seume, Jörg R

2014-01-01

Offshore wind turbines operate in a complex unsteady flow environment which causes unsteady aerodynamic loads. The unsteady flow environment is characterized by a high degree of uncertainty. In addition, geometry variations and material imperfections also cause uncertainties in the design process. Probabilistic design methods consider these uncertainties in order to reach acceptable reliability and safety levels for offshore wind turbines. Variations of the rotor blade geometry influence the aerodynamic loads which also affect the reliability of other wind turbine components. Therefore, the present paper is dealing with geometric uncertainties of the rotor blades. These can arise from manufacturing tolerances and operational wear of the blades. First, the effect of geometry variations of wind turbine airfoils on the lift and drag coefficients are investigated using a Latin hypercube sampling. Then, the resulting effects on the performance and the blade loads of an offshore wind turbine are analyzed. The variations of the airfoil geometry lead to a significant scatter of the lift and drag coefficients which also affects the damage-equivalent flapwise bending moments. In contrast to that, the effects on the power and the annual energy production are almost negligible with regard to the assumptions made

Parametric dependence of a morphing wind turbine blade on material elasticity

International Nuclear Information System (INIS)

Puterbaugh, Martin; Beyene, Asfaw

2011-01-01

A few recent works have suggested a morphing blade for wind turbine energy conversion. The concept is derived from fin and wing motions that better adapt to varying load conditions. Previous research has provided the fluid mechanic justification of this new concept. This paper establishes a parametric relationship between an asymmetric wind turbine blade and constituent material modulus to predict the geometric response of the morphing blade for a given material characteristic. The airfoil's trailing edge deflection is associated to a prescribed fluid exit angle via the Moment Area (MA) method. Subsequently, a mathematical model is derived to predict material deformation with respect to imparted aerodynamic forces. Results show that an airfoil, much like a tapered beam, can be modeled as a non-prismatic cantilevered beam using this well established method. -- Research highlights: →A mathematical model relating morphing airfoil thickness and elastic modulus was established. →For non-prismatic beam under a uniform distributive load, the slope and deflection of the airfoil's trailing edge were related to the fluid exit angle. →The main driver of blade deformation was the angular drag force. The Moment Area method was used, verified by Finite Element method. →Displacement to the exit angle is predicated upon the elastic modulus value given that other parameters are constant. →Optimum power output is obtained in part load conditions when the blade deforms to the applicable exit angle.

Transonic Shock-Wave/Boundary-Layer Interactions on an Oscillating Airfoil

Science.gov (United States)

Davis, Sanford S.; Malcolm, Gerald N.

1980-01-01

Unsteady aerodynamic loads were measured on an oscillating NACA 64A010 airfoil In the NASA Ames 11 by 11 ft Transonic Wind Tunnel. Data are presented to show the effect of the unsteady shock-wave/boundary-layer interaction on the fundamental frequency lift, moment, and pressure distributions. The data show that weak shock waves induce an unsteady pressure distribution that can be predicted quite well, while stronger shock waves cause complex frequency-dependent distributions due to flow separation. An experimental test of the principles of linearity and superposition showed that they hold for weak shock waves while flows with stronger shock waves cannot be superimposed.

Reversible airfoils for stopped rotors in high speed flight

International Nuclear Information System (INIS)

Niemiec, Robert; Jacobellis, George; Gandhi, Farhan

2014-01-01

This study starts with the design of a reversible airfoil rib for stopped-rotor applications, where the sharp trailing-edge morphs into the rounded leading-edge, and vice-versa. A NACA0012 airfoil is approximated in a piecewise linear manner and straight, rigid outer profile links used to define the airfoil contour. The end points of the profile links connect to control links, each set on a central actuation rod via an offset. Chordwise motion of the actuation rod moves the control and the profile links and reverses the airfoil. The paper describes the design methodology and evolution of the final design, based on which two reversible airfoil ribs were fabricated and used to assemble a finite span reversible rotor/wing demonstrator. The profile links were connected by Aluminum strips running in the spanwise direction which provided stiffness as well as support for a pre-tensioned elastomeric skin. An inter-rib connector with a curved-front nose piece supports the leading-edge. The model functioned well and was able to reverse smoothly back-and-forth, on application and reversal of a voltage to the motor. Navier–Stokes CFD simulations (using the TURNS code) show that the drag coefficient of the reversible airfoil (which had a 13% maximum thickness due to the thickness of the profile links) was comparable to that of the NACA0013 airfoil. The drag of a 16% thick elliptical airfoil was, on average, about twice as large, while that of a NACA0012 in reverse flow was 4–5 times as large, even prior to stall. The maximum lift coefficient of the reversible airfoil was lower than the elliptical airfoil, but higher than the NACA0012 in reverse flow operation. (paper)

Icing losses on wind turbines

Energy Technology Data Exchange (ETDEWEB)

Duncan, T.; Fotsing, I.; Pearson, S. [Garrad Hassan Canada Inc., Ottawa, ON (Canada)

2010-07-01

This PowerPoint presentation discussed some of the energy losses that can occur as a result of icing on wind turbines. Airfoil deterioration can occur in the presence of rime and glaze ice. Anemometers are also impacted by ice, and shut-downs can occur as a result of icing events. Availability deficits that occur during the winter months can lead to annual energy losses of 0.5 percent. The impact of icing events on total wind power energy production in Quebec is estimated at between 1.3 percent to 2.7 percent. Ice loss estimates are considered during the pre-construction phases of wind power projects. However, ice loss prediction methods are often inaccurate. Studies have demonstrated that preconstruction masts show a reasonable correlation with wind turbine icing, and that icing losses are site-specific. tabs., figs.

Numerical optimization of circulation control airfoils

Science.gov (United States)

Tai, T. C.; Kidwell, G. H., Jr.; Vanderplaats, G. N.

1981-01-01

A numerical procedure for optimizing circulation control airfoils, which consists of the coupling of an optimization scheme with a viscous potential flow analysis for blowing jet, is presented. The desired airfoil is defined by a combination of three baseline shapes (cambered ellipse, and cambered ellipse with drooped and spiralled trailing edges). The coefficients of these shapes are used as design variables in the optimization process. Under the constraints of lift augmentation and lift-to-drag ratios, the optimal airfoils are found to lie between those of cambered ellipse and the drooped trailing edge, towards the latter as the angle of attack increases. Results agree qualitatively with available experimental data.

An Experimental Investigation of Unsteady Surface Pressure on an Airfoil in Turbulence

Science.gov (United States)

Mish, Patrick F.; Devenport, William J.

2003-01-01

Measurements of fluctuating surface pressure were made on a NACA 0015 airfoil immersed in grid generated turbulence. The airfoil model has a 2 ft chord and spans the 6 ft Virginia Tech Stability Wind Tunnel test section. Two grids were used to investigate the effects of turbulence length scale on the surface pressure response. A large grid which produced turbulence with an integral scale 13% of the chord and a smaller grid which produced turbulence with an integral scale 1.3% of the chord. Measurements were performed at angles of attack, alpha from 0 to 20 . An array of microphones mounted subsurface was used to measure the unsteady surface pressure. The goal of this measurement was to characterize the effects of angle of attack on the inviscid response. Lift spectra calculated from pressure measurements at each angle of attack revealed two distinct interaction regions; for omega(sub r) = omega b / U(sub infinity) is less than 10 a reduction in unsteady lift of up to 7 decibels (dB) occurs while an increase occurs for omega(sub r) is greater than 10 as the angle of attack is increased. The reduction in unsteady lift at low omega(sub r) with increasing angle of attack is a result that has never before been shown either experimentally or theoretically. The source of the reduction in lift spectral level appears to be closely related to the distortion of inflow turbulence based on analysis of surface pressure spanwise correlation length scales. Furthermore, while the distortion of the inflow appears to be critical in this experiment, this effect does not seem to be significant in larger integral scale (relative to the chord) flows based on the previous experimental work of McKeough suggesting the airfoils size relative to the inflow integral scale is critical in defining how the airfoil will respond under variation of angle of attack. A prediction scheme is developed that correctly accounts for the effects of distortion when the inflow integral scale is small relative

Symmetric airfoil geometry effects on leading edge noise.

Science.gov (United States)

Gill, James; Zhang, X; Joseph, P

2013-10-01

Computational aeroacoustic methods are applied to the modeling of noise due to interactions between gusts and the leading edge of real symmetric airfoils. Single frequency harmonic gusts are interacted with various airfoil geometries at zero angle of attack. The effects of airfoil thickness and leading edge radius on noise are investigated systematically and independently for the first time, at higher frequencies than previously used in computational methods. Increases in both leading edge radius and thickness are found to reduce the predicted noise. This noise reduction effect becomes greater with increasing frequency and Mach number. The dominant noise reduction mechanism for airfoils with real geometry is found to be related to the leading edge stagnation region. It is shown that accurate leading edge noise predictions can be made when assuming an inviscid meanflow, but that it is not valid to assume a uniform meanflow. Analytic flat plate predictions are found to over-predict the noise due to a NACA 0002 airfoil by up to 3 dB at high frequencies. The accuracy of analytic flat plate solutions can be expected to decrease with increasing airfoil thickness, leading edge radius, gust frequency, and Mach number.

3D CFD Quantification of the Performance of a Multi-Megawatt Wind Turbine

Science.gov (United States)

Laursen, J.; Enevoldsen, P.; Hjort, S.

2007-07-01

This paper presents the results of 3D CFD rotor computations of a Siemens SWT-2.3-93 variable speed wind turbine with 45m blades. In the paper CFD is applied to a rotor at stationary wind conditions without wind shear, using the commercial multi-purpose CFD-solvers ANSYS CFX 10.0 and 11.0. When comparing modelled mechanical effects with findings from other models and measurements, good agreement is obtained. Similarly the computed force distributions compare very well, whereas some discrepancies are found when comparing with an in-house BEM model. By applying the reduced axial velocity method the local angle of attack has been derived from the CFD solutions, and from this knowledge and the computed force distributions, local airfoil profile coefficients have been computed and compared to BEM airfoil coefficients. Finally, the transition model of Langtry and Menter is tested on the rotor, and the results are compared with the results from the fully turbulent setup.

3D CFD Quantification of the Performance of a Multi-Megawatt Wind Turbine

International Nuclear Information System (INIS)

Laursen, J; Enevoldsen, P; Hjort, S

2007-01-01

This paper presents the results of 3D CFD rotor computations of a Siemens SWT-2.3-93 variable speed wind turbine with 45m blades. In the paper CFD is applied to a rotor at stationary wind conditions without wind shear, using the commercial multi-purpose CFD-solvers ANSYS CFX 10.0 and 11.0. When comparing modelled mechanical effects with findings from other models and measurements, good agreement is obtained. Similarly the computed force distributions compare very well, whereas some discrepancies are found when comparing with an in-house BEM model. By applying the reduced axial velocity method the local angle of attack has been derived from the CFD solutions, and from this knowledge and the computed force distributions, local airfoil profile coefficients have been computed and compared to BEM airfoil coefficients. Finally, the transition model of Langtry and Menter is tested on the rotor, and the results are compared with the results from the fully turbulent setup

Aeroacoustic Computations for Turbulent Airfoil Flows

DEFF Research Database (Denmark)

Shen, Wen Zhong; Zhu, Wei Jun; Sørensen, Jens Nørkær

2009-01-01

a NACA 0015 airfoil at a Mach number of 0.2 and a Reynolds number of 1.6 x 10(5) for different angles of attack. The flow solutions are validated by comparing lift and drag characteristics with experimental data. The comparisons show good agreements between the computed and measured airfoil lift...

Review Report on Design Study and Economic Assessment of Multi-Unit Offshore Wind Energy Conversion Systems Applications,

Science.gov (United States)

1977-03-21

meter turbine . Available from NTIS; $6.50. 113 pages. 7. SAND-76-0130 Wind Tunnel Performance Data for the Darrieus Wind Tur- bine with NACA-0012...2-meter-diameter Darrieus wind turbine have been tested in a low speed wind tunnel. The airfoil section for all configurations was NACA 0012. The... Darrieus Vertical-Axis Wind Turbine Program at Sandia Laboratories, Kadlec, E.G., published by Sandia Laboratories 1976. Contract No. AT(29-1)-789. From

Geometrical effects on the airfoil flow separation and transition

KAUST Repository

Zhang, Wei

2015-04-25

We present results from direct numerical simulations (DNS) of incompressible flow over two airfoils, NACA-4412 and NACA-0012-64, to investigate the effects of the airfoil geometry on the flow separation and transition patterns at Re=104 and 10 degrees incidence. The two chosen airfoils are geometrically similar except for maximum camber (respectively 4%C and 0 with C the chord length), which results in a larger projection area with respect to the incoming flow for the NACA-4412 airfoil, and a larger leeward surface curvature at the leading edge for the NACA-0012-64 airfoil. The governing equations are discretized using an energy conservative fourth-order spatial discretization scheme. An assessment on the two-point correlation indicates that a spanwise domain size of 0.8C is sufficiently large for the present simulations. We discuss flow separation at the airfoil leading edge, transition of the separated shear layer to three-dimensional flow and subsequently to turbulence. Numerical results reveal a stronger adverse pressure gradient field in the leading edge region of the NACA-0012-64 airfoil due to the rapidly varying surface curvature. As a result, the flow experiences detachment at x/C=0.08, and the separated shear layer transition via Kelvin-Helmholtz mechanism occurs at x/C=0.29 with fully developed turbulent flow around x/C=0.80. These flow development phases are delayed to occur at much downstream positions, respectively, observed around x/C=0.25, 0.71 and 1.15 for the NACA-4412 airfoil. The turbulent intensity, measured by the turbulent fluctuations and turbulent Reynolds stresses, are much larger for NACA-0012-64 from the transition onset until the airfoil trailing edge, while turbulence develops significantly downstream of the trailing edge for the NACA-4412 airfoil. For both airfoils, our DNS results indicate that the mean Reynolds stress u\\'u\\'/U02 reaches its maximum value at a distance from the surface approximately equal to the displacement

Analysis of Location of Laminar-Turbulent Transition on the FX 66-S-196 V1 Airfoil

Directory of Open Access Journals (Sweden)

Laurynas Naujokaitis

2011-04-01

Full Text Available The transition location on the FX 66‑S‑196 V1 wing section was analyzed with the using interactive program XFOIL of Mark Drela, MIT. Calculated results of transition location were compared with published measurement data from a wind tunnel at Delft University of Technology (Netherlands. The airfoil was analyzed at the Reynolds number Re = 0,5·106 and Re = 1,5·106. Article in Lithuanian

Damping element for reducing the vibration of an airfoil

Science.gov (United States)

Campbell, Christian X; Marra, John J

2013-11-12

An airfoil (10) is provided with a tip (12) having an opening (14) to a center channel (24). A damping element (16) is inserted within the opening of the center channel, to reduce an induced vibration of the airfoil. The mass of the damping element, a spring constant of the damping element within the center channel, and/or a mounting location (58) of the damping element within the center channel may be adjustably varied, to shift a resonance frequency of the airfoil outside a natural operating frequency of the airfoil.

Modeling unsteady forces and pressures on a rapidly pitching airfoil

Science.gov (United States)

Schiavone, Nicole K.; Dawson, Scott T. M.; Rowley, Clarence W.; Williams, David R.

2014-11-01

This work develops models to quantify and understand the unsteady aerodynamic forces arising from rapid pitching motion of a NACA0012 airfoil at a Reynolds number of 50 000. The system identification procedure applies a generalized DMD-type algorithm to time-resolved wind tunnel measurements of the lift and drag forces, as well as the pressure at six locations on the suction surface of the airfoil. Models are identified for 5-degree pitch-up and pitch-down maneuvers within the overall range of 0-20 degrees. The identified models can accurately capture the effects of flow separation and leading-edge vortex formation and convection. We demonstrate that switching between different linear models can give accurate prediction of the nonlinear behavior that is present in high-amplitude maneuvers. The models are accurate for a wide-range of motions, including pitch-and-hold, sinusoidal, and pseudo-random pitching maneuvers. Providing the models access to a subset of the measured data channels can allow for improved estimates of the remaining states via the use of a Kalman filter, suggesting that the modeling framework could be useful for aerodynamic control applications. This work was supported by the Air Force Office of Scientific Research, under Award No. FA9550-12-1-0075.

Self-sustained Flow-acoustic Interactions in Airfoil Transitional Boundary Layers

Science.gov (United States)

2015-07-09

AFRL-AFOSR-VA-TR-2015-0235 Self-sustained flow-acoustic interactions in airfoil transitional boundary layers Vladimir Golubev EMBRY-RIDDLE...From - To)      01-04-2012 to 31-03-2015 4.  TITLE AND SUBTITLE Self-sustained flow-acoustic interactions in airfoil transitional boundary layers 5a...complementary experimental and numerical studies of flow-acoustic resonant interactions in transitional airfoils and their impact on airfoil surface

Supercritical Airfoil Coordinates

Data.gov (United States)

National Aeronautics and Space Administration — Rectangular Supercritical Wing (Ricketts) - design and measured locations are provided in an Excel file RSW_airfoil_coordinates_ricketts.xls . One sheet is with Non...

Separation control of NACA0015 airfoil using plasma actuators

Science.gov (United States)

Harada, Daisuke; Sakakibara, Jun

2017-11-01

Separation control of NACA0015 airfoil by means of plasma actuators was investigated. Plasma actuators in spanwise intermittent layout on the suction surface of the airfoil were activated with spanwise phase difference φ = 0 or φ = π in the case of dimensionless burst frequencyF+ = 6 and F+ = 0.5 at Re = 6.3 ×104 . The lift and drag of the airfoil were measured using a two component force balance. The flow around the airfoil was measured by PIV analysis. In the condition of F+ = 6 and φ = π at around stall angle, which is 10 degrees, the lift-to-drag ratio was higher than that ofF+ = 6 and φ = 0 . Therefore, it was confirmed that aerodynamic characteristics of the airfoil improved by disturbances with temporal and spatial phase difference.

Numerical prediction of shock induced oscillations over a 2D airfoil: Influence of turbulence modelling and test section walls

Energy Technology Data Exchange (ETDEWEB)

Thiery, Mylene [Aerodynamics and Energetics Modelling Department, Turbulence Modelling and Prediction Unit, ONERA Toulouse, 2 avenue Edouard Belin, 31055 Toulouse Cedex 4 (France); Coustols, Eric [Aerodynamics and Energetics Modelling Department, Turbulence Modelling and Prediction Unit, ONERA Toulouse, 2 avenue Edouard Belin, 31055 Toulouse Cedex 4 (France)]. E-mail: Eric.Coustols@onera.fr

2006-08-15

The present study deals with recent numerical results from on-going research conducted at ONERA/DMAE regarding the prediction of transonic flows, for which shock wave/boundary layer interaction is important. When this interaction is strong enough (M {>=} 1.3), shock induced oscillations (SIO) appear at the suction side of the airfoil and lead to the formation of unsteady separated areas. The main issue is then to perform unsteady computations applying appropriate turbulence modelling and relevant boundary conditions with respect to the test case. Computations were performed with the ONERA elsA software and the URANS-type approach, closure relationships being achieved from transport-equation models. Applications are provided for the OAT15A airfoil data base, well documented for unsteady CFD validation (mean and r.m.s. pressure, phase-averaged LDA data, ...). In this paper, the capabilities of turbulence models are evaluated with two 2D URANS strategies, under free-stream or confined conditions. The latter takes into account the adaptive upper and lower wind-tunnel walls. A complete 3D URANS simulation was then performed to demonstrate the real impact of all lateral wind-tunnel walls on such a flow.

Numerical prediction of shock induced oscillations over a 2D airfoil: Influence of turbulence modelling and test section walls

International Nuclear Information System (INIS)

Thiery, Mylene; Coustols, Eric

2006-01-01

The present study deals with recent numerical results from on-going research conducted at ONERA/DMAE regarding the prediction of transonic flows, for which shock wave/boundary layer interaction is important. When this interaction is strong enough (M ≥ 1.3), shock induced oscillations (SIO) appear at the suction side of the airfoil and lead to the formation of unsteady separated areas. The main issue is then to perform unsteady computations applying appropriate turbulence modelling and relevant boundary conditions with respect to the test case. Computations were performed with the ONERA elsA software and the URANS-type approach, closure relationships being achieved from transport-equation models. Applications are provided for the OAT15A airfoil data base, well documented for unsteady CFD validation (mean and r.m.s. pressure, phase-averaged LDA data, ...). In this paper, the capabilities of turbulence models are evaluated with two 2D URANS strategies, under free-stream or confined conditions. The latter takes into account the adaptive upper and lower wind-tunnel walls. A complete 3D URANS simulation was then performed to demonstrate the real impact of all lateral wind-tunnel walls on such a flow

Correlation of theory to wind-tunnel data at Reynolds numbers below 500,000

Science.gov (United States)

Evangelista, Raquel; Mcghee, Robert J.; Walker, Betty S.

1989-01-01

This paper presents results obtained from two airfoil analysis methods compared with previously published wind tunnel test data at chord Reynolds numbers below 500,000. The analysis methods are from the Eppler-Somers airfoil design/analysis code and from ISES, the Drela-Giles Airfoil design/analysis code. The experimental data are from recent tests of the Eppler 387 airfoil in the NASA Langley Low Turbulence Pressure Tunnel. For R not less than 200,000, lift and pitching moment predictions from both theories compare well with experiment. Drag predictions from both theories also agree with experiment, although to different degrees. However, most of the drag predictions from the Eppler-Somers code are accompanied with separation bubble warnings which indicate that the drag predictions are too low. With the Drela-Giles code, there is a large discrepancy between the computed and experimental pressure distributions in cases with laminar separation bubbles, although the drag polar predictions are similar in trend to experiment.

Measuring Lift with the Wright Airfoils

Science.gov (United States)

Heavers, Richard M.; Soleymanloo, Arianne

2011-01-01

In this laboratory or demonstration exercise, we mount a small airfoil with its long axis vertical at one end of a nearly frictionless rotating platform. Air from a leaf blower produces a sidewise lift force L on the airfoil and a drag force D in the direction of the air flow (Fig. 1). The rotating platform is kept in equilibrium by adding weights…

Compressor airfoil tip clearance optimization system

Science.gov (United States)

Little, David A.; Pu, Zhengxiang

2015-08-18

A compressor airfoil tip clearance optimization system for reducing a gap between a tip of a compressor airfoil and a radially adjacent component of a turbine engine is disclosed. The turbine engine may include ID and OD flowpath boundaries configured to minimize compressor airfoil tip clearances during turbine engine operation in cooperation with one or more clearance reduction systems that are configured to move the rotor assembly axially to reduce tip clearance. The configurations of the ID and OD flowpath boundaries enhance the effectiveness of the axial movement of the rotor assembly, which includes movement of the ID flowpath boundary. During operation of the turbine engine, the rotor assembly may be moved axially to increase the efficiency of the turbine engine.

Surface pressure and aerodynamic loads determination of a transonic airfoil based on particle image velocimetry

International Nuclear Information System (INIS)

Ragni, D; Ashok, A; Van Oudheusden, B W; Scarano, F

2009-01-01

The present investigation assesses a procedure to extract the aerodynamic loads and pressure distribution on an airfoil in the transonic flow regime from particle image velocimetry (PIV) measurements. The wind tunnel model is a two-dimensional NACA-0012 airfoil, and the PIV velocity data are used to evaluate pressure fields, whereas lift and drag coefficients are inferred from the evaluation of momentum contour and wake integrals. The PIV-based results are compared to those derived from conventional loads determination procedures involving surface pressure transducers and a wake rake. The method applied in this investigation is an extension to the compressible flow regime of that considered by van Oudheusden et al (2006 Non-intrusive load characterization of an airfoil using PIV Exp. Fluids 40 988–92) at low speed conditions. The application of a high-speed imaging system allows the acquisition in relatively short time of a sufficient ensemble size to compute converged velocity statistics, further translated in turbulent fluctuations included in the pressure and loads calculation, notwithstanding their verified negligible influence in the computation. Measurements are performed at varying spatial resolution to optimize the loads determination in the wake region and around the airfoil, further allowing us to assess the influence of spatial resolution in the proposed procedure. Specific interest is given to the comparisons between the PIV-based method and the conventional procedures for determining the pressure coefficient on the surface, the drag and lift coefficients at different angles of attack. Results are presented for the experiments at a free-stream Mach number M = 0.6, with the angle of attack ranging from 0° to 8°

An Experimental Study on Active Flow Control Using Synthetic Jet Actuators over S809 Airfoil

International Nuclear Information System (INIS)

Gul, M; Uzol, O; Akmandor, I S

2014-01-01

This study investigates the effect of periodic excitation from individually controlled synthetic jet actuators on the dynamics of the flow within the separation and re-attachment regions of the boundary layer over the suction surface of a 2D model wing that has S809 airfoil profile. Experiments are performed in METUWIND's C3 open-loop suction type wind tunnel that has a 1 m × 1 m cross-section test section. The synthetic jet array on the wing consists of three individually controlled actuators driven by piezoelectric diaphragms located at 28% chord location near the mid-span of the wing. In the first part of the study, surface pressure, Constant Temperature Anemometry (CTA) and Particle Image Velocimetry (PIV) measurements are performed over the suction surface of the airfoil to determine the size and characteristics of the separated shear layer and the re-attachment region, i.e. the laminar separation bubble, at 2.3x10 5 Reynolds number at zero angle of attack and with no flow control as a baseline case. For the controlled case, CTA measurements are carried out under the same inlet conditions at various streamwise locations along the suction surface of the airfoil to investigate the effect of the synthetic jet on the boundary layer properties. During the controlled case experiments, the synthetic jet actuators are driven with a sinusoidal frequency of 1.45 kHz and 300Vp-p. Results of this study show that periodic excitation from the synthetic jet actuators eliminates the laminar separation bubble formed over the suction surface of the airfoil at 2.3x10 5 Reynolds number at zero angle of attack

Turbine airfoil with laterally extending snubber having internal cooling system

Science.gov (United States)

Scribner, Carmen Andrew; Messmann, Stephen John; Marsh, Jan H.

2016-09-06

A turbine airfoil usable in a turbine engine and having at least one snubber with a snubber cooling system positioned therein and in communication with an airfoil cooling system is disclosed. The snubber may extend from the outer housing of the airfoil toward an adjacent turbine airfoil positioned within a row of airfoils. The snubber cooling system may include an inner cooling channel separated from an outer cooling channel by an inner wall. The inner wall may include a plurality of impingement cooling orifices that direct impingement fluid against an outer wall defining the outer cooling channel. In one embodiment, the cooling fluids may be exhausted from the snubber, and in another embodiment, the cooling fluids may be returned to the airfoil cooling system. Flow guides may be positioned in the outer cooling channel, which may reduce cross-flow by the impingement orifices, thereby increasing effectiveness.

Turbine airfoil with controlled area cooling arrangement

Science.gov (United States)

Liang, George

2010-04-27

A gas turbine airfoil (10) includes a serpentine cooling path (32) with a plurality of channels (34,42,44) fluidly interconnected by a plurality of turns (38,40) for cooling the airfoil wall material. A splitter component (50) is positioned within at least one of the channels to bifurcate the channel into a pressure-side channel (46) passing in between the outer wall (28) and the inner wall (30) of the pressure side (24) and a suction-side channel (48) passing in between the outer wall (28) and the inner wall (30) of the suction side (26) longitudinally downstream of an intermediate height (52). The cross-sectional area of the pressure-side channel (46) and suction-side channel (48) are thereby controlled in spite of an increasing cross-sectional area of the airfoil along its longitudinal length, ensuring a sufficiently high mach number to provide a desired degree of cooling throughout the entire length of the airfoil.

Aerodynamic loading on a cylinder behind an airfoil

Energy Technology Data Exchange (ETDEWEB)

Zhang, H.J.; Huang, L.; Zhou, Y. [Hong Kong Polytechnic University, Department of Mechanical Engineering, Kowloon (Hong Kong)

2005-05-01

The interaction between the wake of a rotor blade and a downstream cylinder holds the key to the understanding and control of electronic cooling fan noise. In this paper, the aerodynamic characteristics of a circular cylinder are experimentally studied in the presence of an upstream NACA 4412 airfoil for the cylinder-diameter-based Reynolds numbers of Re{sub d}=2,100-20,000, and the airfoil chord-length-based Reynolds numbers of Re{sub c}=14,700-140,000. Lift and drag fluctuations on the cylinder, and the longitudinal velocity fluctuations of the flow behind the cylinder were measured simultaneously using a load cell and two hot wires, respectively. Data analysis shows that unsteady forces on the cylinder increase significantly in the presence of the airfoil wake. The dependence of the forces on two parameters is investigated, that is, the lateral distance (T) between the airfoil and the cylinder, and the Reynolds number. The forces decline quickly as Tincreases. For Re{sub c}<60,000, the vortices shed from the upstream airfoil make a major contribution to the unsteady forces on the cylinder compared to the vortex shedding from the cylinder itself. For Re{sub c}>60,000, no vortices are generated from the airfoil, and the fluctuating forces on the cylinder are caused by its own vortex shedding. (orig.)

Aerodynamic shape optimization for alleviating dynamic stall characteristics of helicopter rotor airfoil

Directory of Open Access Journals (Sweden)

Wang Qing

2015-04-01

Full Text Available In order to alleviate the dynamic stall effects in helicopter rotor, the sequential quadratic programming (SQP method is employed to optimize the characteristics of airfoil under dynamic stall conditions based on the SC1095 airfoil. The geometry of airfoil is parameterized by the class-shape-transformation (CST method, and the C-topology body-fitted mesh is then automatically generated around the airfoil by solving the Poisson equations. Based on the grid generation technology, the unsteady Reynolds-averaged Navier-Stokes (RANS equations are chosen as the governing equations for predicting airfoil flow field and the highly-efficient implicit scheme of lower–upper symmetric Gauss–Seidel (LU-SGS is adopted for temporal discretization. To capture the dynamic stall phenomenon of the rotor more accurately, the Spalart–Allmaras turbulence model is employed to close the RANS equations. The optimized airfoil with a larger leading edge radius and camber is obtained. The leading edge vortex and trailing edge separation of the optimized airfoil under unsteady conditions are obviously weakened, and the dynamic stall characteristics of optimized airfoil at different Mach numbers, reduced frequencies and angles of attack are also obviously improved compared with the baseline SC1095 airfoil. It is demonstrated that the optimized method is effective and the optimized airfoil is suitable as the helicopter rotor airfoil.

Outcomes of the DeepWind Conceptual Design

DEFF Research Database (Denmark)

Schmidt Paulsen, Uwe; Borg, Michael; Aagaard Madsen, Helge

2015-01-01

DeepWind has been presented as a novel floating offshore wind turbine concept with cost reduction potentials. Twelve international partners developed a Darrieus type floating turbine with new materials and technologies for deep-sea offshore environment. This paper summarizes results of the 5 MW...... the Deepwind floating 1 kW demonstrator. The 5 MW simulation results, loading and performance are compared to the OC3-NREL 5 MW wind turbine. Finally the paper elaborates the conceptual design on cost modelling....... DeepWind conceptual design. The concept was evaluated at the Hywind test site, described on its few components, in particular on the modified Troposkien blade shape and airfoil design. The feasibility of upscaling from 5 MW to 20 MW is discussed, taking into account the results from testing...

Software tool for horizontal-axis wind turbine simulation

Energy Technology Data Exchange (ETDEWEB)

Vitale, A.J. [Instituto Argentino de Oceanografia, Camino La Carrindanga Km. 7, 5 CC 804, B8000FWB Bahia Blanca (Argentina); Universidad Tecnologica Nacional Facultad Regional Bahia Blanca, GESE, 11 de Abril 461, B8000LMI Bahia Blanca (Argentina); Dpto. de Ing. Electrica y de Computadoras, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahia Blanca (Argentina); Rossi, A.P. [Universidad Tecnologica Nacional Facultad Regional Bahia Blanca, GESE, 11 de Abril 461, B8000LMI Bahia Blanca (Argentina); Dpto. de Ing. Electrica y de Computadoras, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahia Blanca (Argentina)

2008-07-15

The main problem of a wind turbine generator design project is the design of the right blades capable of satisfying the specific energy requirement of an electric system with optimum performance. Once the blade has been designed for optimum operation at a particular rotor angular speed, it is necessary to determine the overall performance of the rotor under the range of wind speed that it will encounter. A software tool that simulates low-power, horizontal-axis wind turbines was developed for this purpose. With this program, the user can calculate the rotor power output for any combination of wind and rotor speeds, with definite blade shape and airfoil characteristics. The software also provides information about distribution of forces along the blade span, for different operational conditions. (author)

Effects of Leading Edge Defect on the Aerodynamic and Flow Characteristics of an S809 Airfoil.

Science.gov (United States)

Wang, Yan; Zheng, Xiaojing; Hu, Ruifeng; Wang, Ping

Unexpected performance degradation occurs in wind turbine blades due to leading edge defect when suffering from continuous impacts with rain drops, hails, insects, or solid particles during its operation life. To assess this issue, this paper numerically investigates the steady and dynamic stall characteristics of an S809 airfoil with various leading edge defects. More leading edge defect sizes and much closer to practical parameters are investigated in the paper. Numerical computation is conducted using the SST k-ω turbulence model, and the method has been validated by comparison with existed published data. In order to ensure the calculation convergence, the residuals for the continuity equation are set to be less than 10-7 and 10-6 in steady state and dynamic stall cases. The simulations are conducted with the software ANSYS Fluent 13.0. It is found that the characteristics of aerodynamic coefficients and flow fields are sensitive to leading edge defect both in steady and dynamic conditions. For airfoils with the defect thickness of 6%tc, leading edge defect has a relative small influence on the aerodynamics of S809 airfoil. For other investigated defect thicknesses, leading edge defect has much greater influence on the flow field structures, pressure coefficients and aerodynamic characteristics of airfoil at relative small defect lengths. For example, the lift coefficients decrease and drag coefficients increase sharply after the appearance of leading edge defect. However, the aerodynamic characteristics could reach a constant value when the defect length is large enough. The flow field, pressure coefficient distribution and aerodynamic coefficients do not change a lot when the defect lengths reach to 0.5%c,1%c, 2%c and 3%c with defect thicknesses of 6%tc, 12%tc,18%tc and 25%tc, respectively. In addition, the results also show that the critical defect length/thickness ratio is 0.5, beyond which the aerodynamic characteristics nearly remain unchanged. In

Horn–Schunck optical flow applied to deformation measurement of a birdlike airfoil

Directory of Open Access Journals (Sweden)

Gong Xiaoliang

2015-10-01

Full Text Available Current deformation measurement techniques suffer from limited spatial resolution. In this work, a highly accurate and high-resolution Horn–Schunck optical flow method is developed and then applied to measuring the static deformation of a birdlike flexible airfoil at a series of angles of attack at Reynolds number 100,000 in a low speed, low noise wind tunnel. To allow relatively large displacements, a nonlinear Horn–Schunck model and a coarse-to-fine warping process are adopted. To preserve optical flow discontinuities, a nonquadratic penalization function, a multi-cue driven bilateral filtering and a principle component analysis of local image patterns are used. First, the accuracy and convergence of this Horn–Schunck technique are verified on a benchmark. Then, the maximum displacement that can be reliably calculated by this technique is studied on synthetic images. Both studies are compared with the performance of a Lucas–Kanade optical flow method. Finally, the Horn–Schunck technique is used to estimate the 3-D deformation of the birdlike airfoil through a stereoscopic camera setup. The results are compared with those computed by Lucas–Kanade optical flow, image correlation and numerical simulation.

A shape adaptive airfoil for a wind turbine blade

Science.gov (United States)

Daynes, Stephen; Weaver, Paul M.

2011-04-01

The loads on wind turbine components are primarily from the blades. It is important to control these blade loads in order to avoid damaging the wind turbine. Rotor control technology is currently limited to controlling the rotor speed and the pitch of the blades. As blades increase in length it becomes less desirable to pitch the entire blade as a single rigid body, but instead there is a requirement to control loads more precisely along the length of the blade. This can be achieved with aerodynamic control devices such as flaps. Morphing technologies are good candidates for wind turbine flaps because they have the potential to create structures that have the conflicting abilities of being load carrying, light-weight and shape adaptive. A morphing flap design with a highly anisotropic cellular structure is presented which is able to undergo large deflections and high strains without a large actuation penalty. An aeroelastic analysis couples the work done by aerodynamic loads on the flap, the flap strain energy and the required actuation work to change shape. The morphing flap is experimentally validated with a manufactured demonstrator and shown to have reduced actuation requirements compared to a conventional hinged flap.

Aerodynamic shape optimization of Airfoils in 2-D incompressible flow

Science.gov (United States)

Rangasamy, Srinivethan; Upadhyay, Harshal; Somasekaran, Sandeep; Raghunath, Sreekanth

2010-11-01

An optimization framework was developed for maximizing the region of 2-D airfoil immersed in laminar flow with enhanced aerodynamic performance. It uses genetic algorithm over a population of 125, across 1000 generations, to optimize the airfoil. On a stand-alone computer, a run takes about an hour to obtain a converged solution. The airfoil geometry was generated using two Bezier curves; one to represent the thickness and the other the camber of the airfoil. The airfoil profile was generated by adding and subtracting the thickness curve from the camber curve. The coefficient of lift and drag was computed using potential velocity distribution obtained from panel code, and boundary layer transition prediction code was used to predict the location of onset of transition. The objective function of a particular design is evaluated as the weighted-average of aerodynamic characteristics at various angles of attacks. Optimization was carried out for several objective functions and the airfoil designs obtained were analyzed.

Effects of surface roughness and vortex generators on the NACA 4415 airfoil

Energy Technology Data Exchange (ETDEWEB)

Reuss, R.L.; Hoffman, M.J.; Gregorek, G.M. [Ohio State Univ., Columbus, OH (United States)

1995-12-01

Wind turbines in the field can be subjected to many and varying wind conditions, including high winds with rotor locked or with yaw excursions. In some cases the rotor blades may be subjected to unusually large angles of attack that possibly result in unexpected loads and deflections. To better understand loadings at unusual angles of attack, a wind tunnel test was performed. An 18-inch constant chord model of the NACA 4415 airfoil section was tested under two dimensional steady state conditions in the Ohio State University Aeronautical and Astronautical Research Laboratory (OSU/AARL) 7 x 10 Subsonic Wind Tunnel (7 x 10). The objective of these tests was to document section lift and moment characteristics under various model and air flow conditions. These included a normal angle of attack range of {minus}20{degree} to +40{degree}, an extended angle of attack range of {minus}60{degree} to +230{degree}, applications of leading edge grit roughness (LEGR), and use of vortex generators (VGs), all at chord Reynolds numbers as high as possible for the particular model configuration. To realistically satisfy these conditions the 7 x 10 offered a tunnel-height-to-model-chord ratio of 6.7, suggesting low interference effects even at the relatively high lift and drag conditions expected during the test. Significantly, it also provided chord Reynolds numbers up to 2.0 million. 167 figs., 13 tabs.

Turbine airfoil with outer wall thickness indicators

Science.gov (United States)

Marra, John J; James, Allister W; Merrill, Gary B

2013-08-06

A turbine airfoil usable in a turbine engine and including a depth indicator for determining outer wall blade thickness. The airfoil may include an outer wall having a plurality of grooves in the outer surface of the outer wall. The grooves may have a depth that represents a desired outer surface and wall thickness of the outer wall. The material forming an outer surface of the outer wall may be removed to be flush with an innermost point in each groove, thereby reducing the wall thickness and increasing efficiency. The plurality of grooves may be positioned in a radially outer region of the airfoil proximate to the tip.

Development of a Wind Turbine Test Rig and Rotor for Trailing Edge Flap Investigation: Static Flap Angles Case

International Nuclear Information System (INIS)

Abdelrahman, Ahmed; Johnson, David A

2014-01-01

One of the strategies used to improve performance and increase the life-span of wind turbines is active flow control. It involves the modification of the aerodynamic characteristics of a wind turbine blade by means of moveable aerodynamic control surfaces. Trailing edge flaps are relatively small moveable control surfaces placed at the trailing edge of a blade's airfoil that modify the lift of a blade or airfoil section. An instrumented wind turbine test rig and rotor were specifically developed to enable a wide-range of experiments to investigate the potential of trailing edge flaps as an active control technique. A modular blade based on the S833 airfoil was designed to allow accurate instrumentation and customizable settings. The blade is 1.7 meters long, had a constant 178mm chord and a 6° pitch. The modular aerodynamic parts were 3D printed using plastic PC-ABS material. The blade design point was within the range of wind velocities in the available large test facility. The wind facility is a large open jet wind tunnel with a maximum velocity of 11m/s in the test area. The capability of the developed system was demonstrated through an initial study of the effect of stationary trailing edge flaps on blade load and performance. The investigation focused on measuring the changes in flapwise bending moment and power production for different trailing edge flap spanwise locations and deflection angles. The relationship between the load reduction and deflection angle was linear as expected from theory and the highest reduction was caused by the flap furthest from the rotor center. Overall, the experimental setup proved to be effective in measuring small changes in flapwise bending moment within the wind turbine blade and will provide insight when (active) flap control is targeted

Airfoil shape for flight at subsonic speeds

Science.gov (United States)

Whitcomb, Richard T.

1976-01-01

An airfoil having an upper surface shaped to control flow accelerations and pressure distribution over the upper surface and to prevent separation of the boundary layer due to shock wave formulation at high subsonic speeds well above the critical Mach number. A highly cambered trailing edge section improves overall airfoil lifting efficiency.

Modeling of Airfoil Trailing Edge Flap with Immersed Boundary Method

DEFF Research Database (Denmark)

Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær

2011-01-01

The present work considers incompressible flow over a 2D airfoil with a deformable trailing edge. The aerodynamic characteristics of an airfoil with a trailing edge flap is numerically investigated using computational fluid dynamics. A novel hybrid immersed boundary (IB) technique is applied...... to simulate the moving part of the trailing edge. Over the main fixed part of the airfoil the Navier-Stokes (NS) equations are solved using a standard body-fitted finite volume technique whereas the moving trailing edge flap is simulated with the immersed boundary method on a curvilinear mesh. The obtained...... results show that the hybrid approach is an efficient and accurate method for solving turbulent flows past airfoils with a trailing edge flap and flow control using trailing edge flap is an efficient way to regulate the aerodynamic loading on airfoils....

Analysis of jet-airfoil interaction noise sources by using a microphone array technique

Science.gov (United States)

Fleury, Vincent; Davy, Renaud

2016-03-01

The paper is concerned with the characterization of jet noise sources and jet-airfoil interaction sources by using microphone array data. The measurements were carried-out in the anechoic open test section wind tunnel of Onera, Cepra19. The microphone array technique relies on the convected, Lighthill's and Ffowcs-Williams and Hawkings' acoustic analogy equation. The cross-spectrum of the source term of the analogy equation is sought. It is defined as the optimal solution to a minimal error equation using the measured microphone cross-spectra as reference. This inverse problem is ill-posed yet. A penalty term based on a localization operator is therefore added to improve the recovery of jet noise sources. The analysis of isolated jet noise data in subsonic regime shows the contribution of the conventional mixing noise source in the low frequency range, as expected, and of uniformly distributed, uncorrelated noise sources in the jet flow at higher frequencies. In underexpanded supersonic regime, a shock-associated noise source is clearly identified, too. An additional source is detected in the vicinity of the nozzle exit both in supersonic and subsonic regimes. In the presence of the airfoil, the distribution of the noise sources is deeply modified. In particular, a strong noise source is localized on the flap. For high Strouhal numbers, higher than about 2 (based on the jet mixing velocity and diameter), a significant contribution from the shear-layer near the flap is observed, too. Indications of acoustic reflections on the airfoil are also discerned.

Laminar-Turbulent transition on Wind Turbines

DEFF Research Database (Denmark)

Martinez Hernandez, Gabriel Gerardo

The present thesis deals with the study of the rotational effects on the laminar-turbulent transition on wind turbine blades. Linear stability theory is used to formulate the stability equations that include the effect of rotation. The mean flow required as an input to stability computations...... parametrized and adapted to an wind turbine rotor geometry. The blade is resolved in radial sections along which calculations are performed. The obtained mean flow is classified according to the parameters used on the rotating configuration, geometry and operational conditions. The stability diagrams have been...... to define the resultant wave magnitude and direction. The propagation of disturbances in the boundary layers in three dimensional flows is relatively a complicated phenomena. The report discusses the available methods and techniques used to predict the transition location. Some common wind turbine airfoils...

Novel Design for a Wind Tunnel Vertical Gust Generator

Science.gov (United States)

Smith, Zachary; Jones, Anya; Hrynuk, John

2017-11-01

Gust response of MAVs is a fundamental problem for flight stability and control of such aircraft. Current knowledge about the gust response of these vehicles is limited and gust interaction often results in damage to vehicles. Studying isolated gust effects on simple airfoil models in a controlled environment is a necessity for the further development of MAV control laws. Gusts have typically been generated by oscillating an airfoil causing the shedding of vortices to propagate through the system. While effective, this method provides only a transient up and downdraft behavior with small changes in angle of attack, not suitable for studying MAV scale gust interactions. To study these interactions, a gust that creates a change in flow angle larger than the static stall angle of typical airfoils was developed. This work was done in a low speed, low turbulence wind tunnel at base operating speed of 1.5 m/s, generating a Reynolds number of 12,000 on a NACA 0012 wing. It describes the fundamental mechanisms of how this gust was generated and the results obtained from the gust generator. The gust, which can alter the flow field in less than 1 second, was characterized using PIV and the interactions with a stationary airfoil at several angles of attack are evaluated.

RANS study of unsteady flow around a profile blade : application to stall of horizontal axis wind turbine

Energy Technology Data Exchange (ETDEWEB)

Belkheir, N. [Khemis Miliana Univ., Ain Defla (Algeria); Dizene, R. [Univ. des Sciences et de la Technologie Houari Boumediene, Algiers (Algeria). Laboratoire de Mecanique Avancee; Khelladi, S.; Massouh, F.; Dobrev, I. [Arts et Metiers Paris Tech., Paris (France)

2010-07-01

The shape of an airfoil is designed to achieve the best aerodynamic performance. An aerofoil section undergoes dynamic stall when subjected to any form of unsteady angle of pitch. The study of a horizontal-axis wind turbine (HAWT) under wind operating conditions is complex because it is subject to instantaneous speed and wind direction variation. When turbine blades are driven into a dynamic stall, the lift coefficient drops suddenly resulting in a degradation in aerodynamic performance. This study presented steady and unsteady wind load predictions over an oscillating S809 airfoil tested in a subsonic wind tunnel. A model of sinusoidal pitch oscillations was used. The values for the angles of attack in steady state ranged from -20 to +40 degrees. The model considered 3 frequencies and 2 amplitudes. The two-dimensional numerical model simulated the instantaneous change of wind direction with respect to the turbine blade. Results were compared with data measurements of S809 aerofoil. Reasonable deviations were obtained between the predicted and experimental results for pitch oscillations. The URANS approach was used to predict the stall while the software FLUENT was used for the numerical solution. It was concluded that the behaviour of the unsteady flow in the wind farm must be considered in order to obtain an accurate estimate of the wind turbine aerodynamic load. 12 refs., 5 figs.

Optimized chord and twist angle distributions of wind turbine blade considering Reynolds number effects

Energy Technology Data Exchange (ETDEWEB)

Wang, L.; Tang, X. [Univ. of Central Lancashire. Engineering and Physical Sciences, Preston (United Kingdom); Liu, X. [Univ. of Cumbria. Sustainable Engineering, Workington (United Kingdom)

2012-07-01

The aerodynamic performance of a wind turbine depends very much on its blade geometric design, typically based on the blade element momentum (BEM) theory, which divides the blade into several blade elements. In current blade design practices based on Schmitz rotor design theory, the blade geometric parameters including chord and twist angle distributions are determined based on airfoil aerodynamic data at a specific Reynolds number. However, rotating wind turbine blade elements operate at different Reynolds numbers due to variable wind speed and different blade span locations. Therefore, the blade design through Schmitz rotor theory at a specific Reynolds number does not necessarily provide the best power performance under operational conditions. This paper aims to provide an optimal blade design strategy for horizontal-axis wind turbines operating at different Reynolds numbers. A fixed-pitch variable-speed (FPVS) wind turbine with S809 airfoil is chosen as a case study and a Matlab program which considers Reynolds number effects is developed to determine the optimized chord and twist angle distributions of the blade. The performance of the optimized blade is compared with that of the preliminary blade which is designed based on Schmitz rotor design theory at a specific Reynolds number. The results demonstrate that the proposed blade design optimization strategy can improve the power performance of the wind turbine. This approach can be further developed for any practice of horizontal axis wind turbine blade design. (Author)

Active Control of Flow Separation Over an Airfoil

Science.gov (United States)

Ravindran, S. S.

1999-01-01

Designing an aircraft without conventional control surfaces is of interest to aerospace community. In this direction, smart actuator devices such as synthetic jets have been proposed to provide aircraft maneuverability instead of control surfaces. In this article, a numerical study is performed to investigate the effects of unsteady suction and blowing on airfoils. The unsteady suction and blowing is introduced at the leading edge of the airfoil in the form of tangential jet. Numerical solutions are obtained using Reynolds-Averaged viscous compressible Navier-Stokes equations. Unsteady suction and blowing is investigated as a means of separation control to obtain lift on airfoils. The effect of blowing coefficients on lift and drag is investigated. The numerical simulations are compared with experiments from the Tel-Aviv University (TAU). These results indicate that unsteady suction and blowing can be used as a means of separation control to generate lift on airfoils.

NUMERICAL INVESTIGATION OF TWO ELEMENT CAMBER MORPHING AIRFOIL IN LOW REYNOLDS NUMBER FLOWS

Directory of Open Access Journals (Sweden)

RAJESH SENTHIL KUMAR T.

2017-07-01

Full Text Available Aerodynamic performance of a two-element camber morphing airfoil was investigated at low Reynolds number using the transient SST model in ANSYS FLUENT 14.0 and eN method in XFLR5. The two-element camber morphing concept was employed to morph the baseline airfoil into another airfoil by altering the orientation of mean-line at 35% of the chord to achieve better aerodynamic efficiency. NACA 0012 was selected as baseline airfoil. NACA 23012 was chosen as the test case as it has the camber-line similar to that of the morphed airfoil and as it has the same thickness as that of the baseline airfoil. The simulations were carried out at chord based Reynolds numbers of 2.5×105 and 3.9×105. The aerodynamic force coefficients, aerodynamic efficiency and the location of the transition point of laminar separation bubble over these airfoils were studied for various angles of attack. It was found that the aerodynamic efficiency of the morphed airfoil was 12% higher than that of the target airfoil at 4° angle of attack for Reynolds number of 3.9×105 and 54% rise in aerodynamic performance was noted as Reynolds number was varied from 2.5×105 to 3.9×105. The morphed airfoil exhibited the nature of low Reynolds number airfoil.

Aerodynamic and aeroacoustic performance of airfoils with morphing structures

OpenAIRE

Ai, Qing; Azarpeyvand, Mahdi; Lachenal, Xavier; Weaver, Paul M.

2016-01-01

Aerodynamic and aeroacoustic performance of airfoils fitted with morphing trailing edges are investigated using a coupled structure/fluid/noise model. The control of the flow over the surface of an airfoil using shape optimization techniques can significantly improve the load distribution along the chord and span lengths whilst minimising noise generation. In this study, a NACA 63-418 airfoil is fitted with a morphing flap and various morphing profiles are considered with two features that di...

Airfoil gust response and the sound produced by airifoil-vortex interaction

Science.gov (United States)

Amiet, R. K.

1986-01-01

This paper contributes to the understanding of the noise generation process of an airfoil encountering an unsteady upwash. By using a fast Fourier transform together with accurate airfoil response functions, the lift-time waveform for an airfoil encountering a delta function gust (the indicial function) is calculated for a flat plate airfoil in a compressible flow. This shows the interesting property that the lift is constant until the generated acoustic wave reaches the trailing edge. Expressions are given for the magnitude of this constant and for the pressure distribution on the airfoil during this time interval. The case of an airfoil cutting through a line vortex is also analyzed. The pressure-time waveform in the far field is closely related to the left-time waveform for the above problem of an airfoil entering a delta function gust. The effects of varying the relevant parameters in the problem are studied, including the observed position, the core diameter of the vortex, the vortex orientation and the airfoil span. The far field sound varies significantly with observer position, illustrating the importance of non-compactness effects. Increasing the viscous core diameter tends to smooth the pressure-time waveform. For small viscous core radius and infinite span, changing the vortex orientation changes only the amplitude of the pressure-time waveform, and not the shape.

Turbine airfoil fabricated from tapered extrusions

Science.gov (United States)

Marra, John J

2013-07-16

An airfoil (30) and fabrication process for turbine blades with cooling channels (26). Tapered tubes (32A-32D) are bonded together in a parallel sequence, forming a leading edge (21), a trailing edge (22), and pressure and suction side walls (23, 24) connected by internal ribs (25). The tapered tubes may be extruded without camber to simplify the extrusion process, then bonded along matching surfaces (34), forming a non-cambered airfoil (28), which may be cambered in a hot forming process and cut (48) to length. The tubes may have tapered walls that are thinner at the blade tip (T1) than at the base (T2), reducing mass. A cap (50) may be attached to the blade tip. A mounting lug (58) may be forged (60) on the airfoil base and then machined, completing the blade for mounting in a turbine rotor disk.

Sealing apparatus for airfoils of gas turbine engines

Science.gov (United States)

Jones, R.B.

1998-05-19

An improved airfoil tip sealing apparatus is disclosed wherein brush seals are attached to airfoil tips with the distal ends of the brush seal fibers sealingly contacting opposing wall surfaces. Embodiments for variable vanes, stators and both cooled and uncooled turbine blade applications are disclosed. 17 figs.

Numerical simulation of the RISOe1-airfoil dynamic stall

Energy Technology Data Exchange (ETDEWEB)

Bertagnolio, F.; Soerensen, N. [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark)

1997-12-31

In this paper we are concerned with the numerical computation of the dynamic stall that occur in the viscous flowfield over an airfoil. These results are compared to experimental data that were obtained with the new designed RISOe1-airfoil, both for a motionless airfoil and for a pitching motion. Moreover, we present some numerical computations of the plunging and lead-lag motions. We also investigate the possibility of using the pitching motion to simulate the plunging and lead-lag situations. (au)

Effects of Leading Edge Defect on the Aerodynamic and Flow Characteristics of an S809 Airfoil.

Directory of Open Access Journals (Sweden)

Yan Wang

Full Text Available Unexpected performance degradation occurs in wind turbine blades due to leading edge defect when suffering from continuous impacts with rain drops, hails, insects, or solid particles during its operation life. To assess this issue, this paper numerically investigates the steady and dynamic stall characteristics of an S809 airfoil with various leading edge defects. More leading edge defect sizes and much closer to practical parameters are investigated in the paper.Numerical computation is conducted using the SST k-ω turbulence model, and the method has been validated by comparison with existed published data. In order to ensure the calculation convergence, the residuals for the continuity equation are set to be less than 10-7 and 10-6 in steady state and dynamic stall cases. The simulations are conducted with the software ANSYS Fluent 13.0.It is found that the characteristics of aerodynamic coefficients and flow fields are sensitive to leading edge defect both in steady and dynamic conditions. For airfoils with the defect thickness of 6%tc, leading edge defect has a relative small influence on the aerodynamics of S809 airfoil. For other investigated defect thicknesses, leading edge defect has much greater influence on the flow field structures, pressure coefficients and aerodynamic characteristics of airfoil at relative small defect lengths. For example, the lift coefficients decrease and drag coefficients increase sharply after the appearance of leading edge defect. However, the aerodynamic characteristics could reach a constant value when the defect length is large enough. The flow field, pressure coefficient distribution and aerodynamic coefficients do not change a lot when the defect lengths reach to 0.5%c,1%c, 2%c and 3%c with defect thicknesses of 6%tc, 12%tc,18%tc and 25%tc, respectively. In addition, the results also show that the critical defect length/thickness ratio is 0.5, beyond which the aerodynamic characteristics nearly remain

Development of design tools for reduced aerodynamic noise wind turbines (draw)

NARCIS (Netherlands)

Wagner, S.; Guidati, G.; Ostertag, J.; Bareiss, R.; Wittum, G.; Huurdeman, B.; Braun, K.; Hirsch, C.; Kang, S.; Khodak, A.; Overmeire, M. van; Bladt, G.; Nienhaus, A.; Dassen, A.G.M.; Parchen, R.R.; Looijmans, K.

1997-01-01

The major aim of the present project was the development of new predictïon models for the aerodynamic noise generation at wind turbine blades. These models should be transferred to computer codes and should be sensitive enough to consider even small changes in the airfoil geometry. This accuracy is

Analysis of VAWT Efficiency of NACA00 Series Airfoil%NACA00系列翼型的VAWT效能影响因素分析

Institute of Scientific and Technical Information of China (English)

曹阳; 时玉娟; 吴国庆; 李巧梅

2017-01-01

采用滑移网格技术对不同参数下的小型垂直轴叶轮瞬态流场进行了数值计算,着重研究了不同安装角、翼型、叶片弦长、叶片数对叶轮功率的影响,得出不同转速下使叶轮获得最大功率的最佳翼型、叶片安装角、弦长和叶片数,并通过吹风实验验证了最佳叶片数和最佳弦长时的垂直轴风力机具有较优的气动性能.%Numerical simulation on unsteady rotated flow of vertical axis wind turbine with different parameters is done based on moving meshes,and it's mainly studied that power of vertical axis wind turbine is affected by different installation angles,airfoils,chord lengths,number of blades.It is proved that when the blade installation Angle,the chord length,the number of blade,and airfoil are best,vertical axis wind turbine can obtain maximum power.At last,the optimal number of blades and chord lengths are testified in the further blowing experiments,and now the optimal aerodynamic performance of vertical axis wind turbine is gotten.

Validation of the CQU-DTU-LN1 series of airfoils

DEFF Research Database (Denmark)

Shen, Wen Zhong; Zhu, Wei Jun; Fischer, Andreas

2014-01-01

The CQU-DTU-LN1 series of airfoils were designed with an objective of high lift and low noise emission. In the design process, the aerodynamic performance is obtained using XFOIL while noise emission is obtained with the BPM model. In this paper we present some validations of the designed CQU......, the designed Cl and Cl/Cd agrees well with the experiment and are in general higher than those of the NACA airfoil. For the acoustic features, the noise emission of the LN118 airfoil is compared with the acoustic measurements and that of the NACA airfoil. Comparisons show that the BPM model can predict...

Validations and improvements of airfoil trailing-edge noise prediction models using detailed experimental data

DEFF Research Database (Denmark)

Kamruzzaman, M.; Lutz, Th.; Würz, W.

2012-01-01

This paper describes an extensive assessment and a step by step validation of different turbulent boundary-layer trailing-edge noise prediction schemes developed within the European Union funded wind energy project UpWind. To validate prediction models, measurements of turbulent boundary-layer pr...... with measurements in the frequency region higher than 1 kHz, whereas they over-predict the sound pressure level in the low-frequency region. Copyright © 2011 John Wiley & Sons, Ltd.......-layer properties such as two-point turbulent velocity correlations, the spectra of the associated wall pressure fluctuations and the emitted trailing-edge far-field noise were performed in the laminar wind tunnel of the Institute of Aerodynamics and Gas Dynamics, University of Stuttgart. The measurements were...... carried out for a NACA 643-418 airfoil, at Re  =  2.5 ×106, angle of attack of −6° to 6°. Numerical results of different prediction schemes are extensively validated and discussed elaborately. The investigations on the TNO-Blake noise prediction model show that the numerical wall pressure fluctuation...

Progresses in application of computational ?uid dynamic methods to large scale wind turbine aerodynamics?

Institute of Scientific and Technical Information of China (English)

Zhenyu ZHANG; Ning ZHAO; Wei ZHONG; Long WANG; Bofeng XU

2016-01-01

The computational ?uid dynamics (CFD) methods are applied to aerody-namic problems for large scale wind turbines. The progresses including the aerodynamic analyses of wind turbine pro?les, numerical ?ow simulation of wind turbine blades, evalu-ation of aerodynamic performance, and multi-objective blade optimization are discussed. Based on the CFD methods, signi?cant improvements are obtained to predict two/three-dimensional aerodynamic characteristics of wind turbine airfoils and blades, and the vorti-cal structure in their wake ?ows is accurately captured. Combining with a multi-objective genetic algorithm, a 1.5 MW NH-1500 optimized blade is designed with high e?ciency in wind energy conversion.

Computational Acoustic Beamforming for Noise Source Identification for Small Wind Turbines.

Science.gov (United States)

Ma, Ping; Lien, Fue-Sang; Yee, Eugene

2017-01-01

This paper develops a computational acoustic beamforming (CAB) methodology for identification of sources of small wind turbine noise. This methodology is validated using the case of the NACA 0012 airfoil trailing edge noise. For this validation case, the predicted acoustic maps were in excellent conformance with the results of the measurements obtained from the acoustic beamforming experiment. Following this validation study, the CAB methodology was applied to the identification of noise sources generated by a commercial small wind turbine. The simulated acoustic maps revealed that the blade tower interaction and the wind turbine nacelle were the two primary mechanisms for sound generation for this small wind turbine at frequencies between 100 and 630 Hz.

Ice Accretions and Full-Scale Iced Aerodynamic Performance Data for a Two-Dimensional NACA 23012 Airfoil

Science.gov (United States)

Addy, Harold E., Jr.; Broeren, Andy P.; Potapczuk, Mark G.; Lee, Sam; Guffond, Didier; Montreuil, Emmanuel; Moens, Frederic

2016-01-01

This report documents the data collected during the large wind tunnel campaigns conducted as part of the SUNSET project (StUdies oN Scaling EffecTs due to ice) also known as the Ice-Accretion Aerodynamics Simulation study: a joint effort by NASA, the Office National d'Etudes et Recherches Aérospatiales (ONERA), and the University of Illinois. These data form a benchmark database of full-scale ice accretions and corresponding ice-contaminated aerodynamic performance data for a two-dimensional (2D) NACA 23012 airfoil. The wider research effort also included an analysis of ice-contaminated aerodynamics that categorized ice accretions by aerodynamic effects and an investigation of subscale, low- Reynolds-number ice-contaminated aerodynamics for the NACA 23012 airfoil. The low-Reynolds-number investigation included an analysis of the geometric fidelity needed to reliably assess aerodynamic effects of airfoil icing using artificial ice shapes. Included herein are records of the ice accreted during campaigns in NASA Glenn Research Center's Icing Research Tunnel (IRT). Two different 2D NACA 23012 airfoil models were used during these campaigns; an 18-in. (45.7-cm) chord (subscale) model and a 72-in. (182.9-cm) chord (full-scale) model. The aircraft icing conditions used during these campaigns were selected from the Federal Aviation Administration's (FAA's) Code of Federal Regulations (CFR) Part 25 Appendix C icing envelopes. The records include the test conditions, photographs of the ice accreted, tracings of the ice, and ice depth measurements. Model coordinates and pressure tap locations are also presented. Also included herein are the data recorded during a wind tunnel campaign conducted in the F1 Subsonic Pressurized Wind Tunnel of ONERA. The F1 tunnel is a pressured, high- Reynolds-number facility that could accommodate the full-scale (72-in. (182.9-cm) chord) 2D NACA 23012 model. Molds were made of the ice accreted during selected test runs of the full-scale model

OPTIMASI AIRFOIL MENGGUNAKAN PARTICLE SWARM DENGAN PARAMETERISASI CST (CLASS SHAPE TRANSFORMATION

Directory of Open Access Journals (Sweden)

Eva Hertnacahyani Herraprastanti

2017-11-01

Full Text Available Airfoil merupakan profil penampang yang diaplikasikan pada sarana transportasi maupun pembangkit energi sebagai penampang sudu turbin. Airfoil yang dirancang diharapkan menghasilkan gaya angkat (lift maksimal namun gaya hambat (drag seminimal mungkin. Tujuan penelitian 1 Validasi aerodinamika metode panel dengan Interaksi Viskos-Tak Viskos; 2 Analisis aerodinamika airfoil untuk menentukan koefisien lift dan drag; 3 Menerapkan metode optimasi Particle Swarm Optimization untuk mendapatkan geometri airfoil dengan rasio koefisien lift dan drag maksimum (CL/CD maks. Tahap pertama menentukan profil airfoil Class Shape Transformation (CST. Airfoil akan dianalisis menggunakan metoda panel selanjutnya diterapkan model aliran singularitas source dan doublet. Solusi yang diperoleh dari metode panel merupakan kondisi aliran yang dianggap tak viskos. Apabila sudut serang cukup tinggi solusi yang diperoleh dengan pendekatan tersebut sudah tidak akurat lagi. Untuk memperbaiki hasil maka diterapkan metode interaksi viskos-tak viskos kuasi simultan. Proses ini diulang sampai konvergensi dan diperoleh koefisien lift, dan drag. Dengan menggunakan optimasi Particle Swarm Optimization (PSO akan didapat profil airfoil dengan  koefisien lift dan drag maksimum. Namun apabila prosedur optimasi belum optimal, akan dilakukan update geometri, sampai didapat konvergensi. Kesimpulan penelitian :1 Metode panel dengan interaksi viskos tak viskos memberikan hasil yang cukup baik dan akurat, dengan rata-rata kesalahan dibawah 9.5%;  2 Semakin besar bilangan Reynold maka nilai CL/CD maksimum akan semakin tinggi; 3 Ketebalan (thickness dan camber maksimum cenderung meningkat dengan peningkatan bilangan Reynold; 4 Untuk airfoil CST optimasi dengan PSO memberikan hasil yang lebih baik.

Near-wall serpentine cooled turbine airfoil

Science.gov (United States)

Lee, Ching-Pang

2013-09-17

A serpentine coolant flow path (54A-54G) formed by inner walls (50, 52) in a cavity (49) between pressure and suction side walls (22, 24) of a turbine airfoil (20A). A coolant flow (58) enters (56) an end of the airfoil, flows into a span-wise channel (54A), then flows forward (54B) over the inner surface of the pressure side wall, then turns behind the leading edge (26), and flows back along a forward part of the suction side wall, then follows a loop (54E) forward and back around an inner wall (52), then flows along an intermediate part of the suction side wall, then flows into an aft channel (54G) between the pressure and suction side walls, then exits the trailing edge (28). This provides cooling matched to the heating topography of the airfoil, minimizes differential thermal expansion, revives the coolant, and minimizes the flow volume needed.

Aeroelastic optimization of MW wind turbines

Energy Technology Data Exchange (ETDEWEB)

Hartvig Hansen, M.; Zahle, F.

2011-12-15

This report contains the results from the Energy Development and Demonstration Project ''Aeroelastic Optimization of MW wind turbine'' (AeroOpt). The project has had the following five Work Packages: 1. Geometric non-linear, anisotropic beam element for HAWC2. 2. Closed-loop eigenvalue analysis of controlled wind turbines. 3. Resonant wave excitation of lateral tower bending modes. 4. Development of next generation aerodynamic design tools. 5. Advanced design and verification of airfoils. The purposes of these Work Packages are briefly described in the Preface and a summary of the results are given in Section 2. Thereafter, the results from each Work Package are described in eight subsequent chapters. (Author)

A Novel Dual-Rotor Turbine for Increased Wind Energy Capture

International Nuclear Information System (INIS)

Rosenberg, A; Selvaraj, S; Sharma, A

2014-01-01

Horizontal axis wind turbines suffer from aerodynamic inefficiencies in the blade root region (near the hub) due to several non-aerodynamic constraints. Aerodynamic interactions between turbines in a wind farm also lead to significant loss of wind farm efficiency. A new dual-rotor wind turbine (DRWT) concept is proposed that aims at mitigating these two losses. A DRWT is designed that uses an existing turbine rotor for the main rotor, while the secondary rotor is designed using a high lift-to-drag ratio airfoil. Reynolds Averaged Navier- Stokes computational fluid dynamics simulations are used to optimize the design. Large eddy simulations confirm the increase energy capture potential of the DRWT. Wake comparisons however do not show enhanced entrainment of axial momentum

On the effect of leading edge blowing on circulation control airfoil aerodynamics

Science.gov (United States)

Mclachlan, B. G.

1987-01-01

In the present context the term circulation control is used to denote a method of lift generation that utilizes tangential jet blowing over the upper surface of a rounded trailing edge airfoil to determine the location of the boundary layer separation points, thus setting an effective Kutta condition. At present little information exists on the flow structure generated by circulation control airfoils under leading edge blowing. Consequently, no theoretical methods exist to predict airfoil performance under such conditions. An experimental study of the flow field generated by a two dimensional circulation control airfoil under steady leading and trailing edge blowing was undertaken. The objective was to fundamentally understand the overall flow structure generated and its relation to airfoil performance. Flow visualization was performed to define the overall flow field structure. Measurements of the airfoil forces were also made to provide a correlation of the observed flow field structure to airfoil performance. Preliminary results are presented, specifically on the effect on the flow field structure of leading edge blowing, alone and in conjunction with trailing edge blowing.

Unsteady aerodynamic behavior of an airfoil with and without a slat

Science.gov (United States)

Tung, Chee; Mcalister, Kenneth W.; Wang, Clin M.

1993-01-01

Unsteady flow behavior and load characteristics of a 2D VR-7 airfoil with and without a leading-edge slat were studied in the water tunnel of the Aeroflightdynamics Directorate, NASA Ames Research Center. Both airfoils were oscillated sinusoidally between 5 and 25 deg at Re = 200,000 to obtain the unsteady lift, drag, and pitching moment data. A fluorescent dye was released from an orifice located at the leading edge of the airfoil for the purpose of visualizing the boundary layer and wake flow. The flowfield and load predictions of an incompressible Navier-Stokes code based on a velocity-vorticity formulation were compared with the test data. The test and predictions both confirm that the slatted VR-7 airfoil delays both static and dynamic stall as compared to the VR-7 airfoil alone.

Geometrical effects on the airfoil flow separation and transition

KAUST Repository

Zhang, Wei; Cheng, Wan; Gao, Wei; Qamar, Adnan; Samtaney, Ravi

2015-01-01

We present results from direct numerical simulations (DNS) of incompressible flow over two airfoils, NACA-4412 and NACA-0012-64, to investigate the effects of the airfoil geometry on the flow separation and transition patterns at Re=104 and 10

Sensitivity of Key Parameters in Aerodynamic Wind Turbine Rotor Design on Power and Energy Performance

International Nuclear Information System (INIS)

Bak, Christian

2007-01-01

In this paper the influence of different key parameters in aerodynamic wind turbine rotor design on the power efficiency, C p , and energy production has been investigated. The work was divided into an analysis of 2D airfoils/blade sections and of entire rotors. In the analysis of the 2D airfoils it was seen that there was a maximum of the local C p for airfoils with finite maximum C l /C d values. The local speed ratio should be between 2.4 and 3.8 for airfoils with maximum c l /c d between 50 and 200, respectively, to obtain maximum local C p . Also, the investigation showed that Re had a significant impact on CP and especially for Re p for rotors was made with three blades and showed that with the assumption of constant maximum c l /c d along the entire blade, the design tip speed ratio changed from X=6 to X=12 for c l /cd=50 and c l /c d =200, respectively, with corresponding values of maximum c p of 0.46 and 0.525. An analysis of existing rotors re-designed with new airfoils but maintaining the absolute thickness distribution to maintain the stiffness showed that big rotors are more aerodynamic efficient than small rotors caused by higher Re. It also showed that the design tip speed ratio was very dependent on the rotor size and on the assumptions of the airfoil flow being fully turbulent (contaminated airfoil) or free transitional (clean airfoil). The investigations showed that rotors with diameter D=1.75m, should be designed for X around 5.5, whereas rotors with diameter D=126m, should be designed for Xbetween 6.5 and 8.5, depending on the airfoil performance

Influences of surface temperature on a low camber airfoil aerodynamic performances

Directory of Open Access Journals (Sweden)

Valeriu DRAGAN

2016-03-01

Full Text Available The current note refers to the comparison between a NACA 2510 airfoil with adiabatic walls and the same airfoil with heated patches. Both suction and pressure sides were divided into two regions covering the leading edge (L.E. and trailing edge (T.E.. A RANS method sensitivity test has been performed in the preliminary stage while for the extended 3D cases a DES-SST approach was used. Results indicate that surface temperature distribution influences the aerodynamics of the airfoil, in particular the viscous drag component but also the lift of the airfoil. Moreover, the influence depends not only on the surface temperature but also on the positioning of the heated surfaces, particularly in the case of pressure lift and drag. Further work will be needed to optimize the temperature distribution for airfoil with higher camber.

Prediction of unsteady airfoil flows at large angles of incidence

Science.gov (United States)

Cebeci, Tuncer; Jang, H. M.; Chen, H. H.

1992-01-01

The effect of the unsteady motion of an airfoil on its stall behavior is of considerable interest to many practical applications including the blades of helicopter rotors and of axial compressors and turbines. Experiments with oscillating airfoils, for example, have shown that the flow can remain attached for angles of attack greater than those which would cause stall to occur in a stationary system. This result appears to stem from the formation of a vortex close to the surface of the airfoil which continues to provide lift. It is also evident that the onset of dynamic stall depends strongly on the airfoil section, and as a result, great care is required in the development of a calculation method which will accurately predict this behavior.

Airfoil

Science.gov (United States)

Ristau, Neil; Siden, Gunnar Leif

2015-07-21

An airfoil includes a leading edge, a trailing edge downstream from the leading edge, a pressure surface between the leading and trailing edges, and a suction surface between the leading and trailing edges and opposite the pressure surface. A first convex section on the suction surface decreases in curvature downstream from the leading edge, and a throat on the suction surface is downstream from the first convex section. A second convex section is on the suction surface downstream from the throat, and a first convex segment of the second convex section increases in curvature.

Numerical flow simulation over clean and iced wind turbine blades

Energy Technology Data Exchange (ETDEWEB)

Villalpando, F.; Reggio, M. [Ecole Polytechnique, Montreal, PQ (Canada); Ilinca, A. [Quebec Univ., Rimouski, PQ (Canada). Wind Energy Group

2009-07-01

The impact of ice accretion on the drag and lift coefficients of a wind turbine blade was studied. Computerized simulations were conducted for both clean and ice-accreted 2-D airfoils at various angles of attack. The finite volume-based commercial computational fluid dynamics (CFD) program FLUENT was used to simulate the 2-D geometries of turbulent, unsteady and incompressible flow around the airfoils. Pressure coefficients and the contribution of pressure and friction forces to the lift and drag coefficients were analyzed. The study showed that traditional calculations over-predict the lift and drag of ice-accreted airfoil profiles. Ice accreted over the profile's pressure side provoked a bigger lift reduction and drag increase than that caused by ice accreted on the suction side. The poor performance of the aerodynamic coefficients was attributed to the contribution of pressure forces. Further experimentation is required to determine if de-icing systems for turbine blades should be developed to prevent or melt ice over the profile pressure side. 11 refs., 7 tabs., 15 figs.

RANS Based Methodology for Predicting the Influence of Leading Edge Erosion on Airfoil Performance

Energy Technology Data Exchange (ETDEWEB)

Langel, Christopher M. [Univ. of California, Davis, CA (United States). Dept. of Mechanical and Aerospace Engineering; Chow, Raymond C. [Univ. of California, Davis, CA (United States). Dept. of Mechanical and Aerospace Engineering; van Dam, C. P. [Univ. of California, Davis, CA (United States). Dept. of Mechanical and Aerospace Engineering; Maniaci, David Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Wind Energy Technologies Dept.

2017-10-01

The impact of surface roughness on flows over aerodynamically designed surfaces is of interested in a number of different fields. It has long been known the surface roughness will likely accelerate the laminar- turbulent transition process by creating additional disturbances in the boundary layer. However, there are very few tools available to predict the effects surface roughness will have on boundary layer flow. There are numerous implications of the premature appearance of a turbulent boundary layer. Increases in local skin friction, boundary layer thickness, and turbulent mixing can impact global flow properties compounding the effects of surface roughness. With this motivation, an investigation into the effects of surface roughness on boundary layer transition has been conducted. The effort involved both an extensive experimental campaign, and the development of a high fidelity roughness model implemented in a R ANS solver. Vast a mounts of experimental data was generated at the Texas A&M Oran W. Nicks Low Speed Wind Tunnel for the calibration and validation of the roughness model described in this work, as well as future efforts. The present work focuses on the development of the computational model including a description of the calibration process. The primary methodology presented introduces a scalar field variable and associated transport equation that interacts with a correlation based transition model. The additional equation allows for non-local effects of surface roughness to be accounted for downstream of rough wall sections while maintaining a "local" formulation. The scalar field is determined through a boundary condition function that has been calibrated to flat plate cases with sand grain roughness. The model was initially tested on a NACA 0012 airfoil with roughness strips applied to the leading edge. Further calibration of the roughness model was performed using results from the companion experimental study on a NACA 63₃ -418 airfoil

The design, simulation and testing of an urban vertical axis wind turbine with the omni-direction-guide-vane

International Nuclear Information System (INIS)

Chong, W.T.; Fazlizan, A.; Poh, S.C.; Pan, K.C.; Hew, W.P.; Hsiao, F.B.

2013-01-01

Graphical abstract: Solar energy, renewable energy, urban wind energy, environment, augmented wind turbine. Highlights: ► A system for on-site wind–solar hybrid power generation and rain water collection. ► The omni-direction-guide-vane (ODGV) overcomes the weak wind and turbulence conditions in urban areas. ► The ODGV improves the wind turbine performance by speeding-up and guiding the wind. ► The ODGV is designed to blend into the building architecture with safety enhancement. ► The wind tunnel test and CFD simulation results are presented. - Abstract: A novel omni-direction-guide-vane (ODGV) that surrounds a vertical axis wind turbine (VAWT) is designed to improve the wind turbine performance. Wind tunnel testing was performed to evaluate the performance of a 5-bladed (Wortmann FX63-137 airfoil) H-rotor wind turbine, with and without the integration of the ODGV. The test was conducted using a scaled model turbine which was constructed to simulate the VAWT enclosed by the ODGV placed on a building. The VAWT shows an improvement on its self-starting behavior where the cut-in speed was reduced with the integration of the ODGV. Since the VAWT is able to self-start at a lower wind speed, the working hour of the wind turbine would increase. At a wind speed of 6 m/s and under free-running condition (only rotor inertia and bearing friction were applied), the ODGV helps to increase the rotor rotational speed by 182%. With extra load application at the same wind speed (6 m/s), the wind turbine power output was increased by 3.48 times at its peak torque with the aid of the ODGV. The working concept of the ODGV is to minimize the negative torque zone of a lift-type VAWT and to reduce turbulence and rotational speed fluctuation. It was verified by re-simulating the torque coefficient data of a single bladed (NACA 0015 airfoil) VAWT published by the Sandia National Laboratories. From the simulation results, with the presence of the ODGV, it was shown that the

Wind tunnels with adapted walls for reducing wall interference

Science.gov (United States)

Ganzer, U.

1979-01-01

The basic principle of adaptable wind tunnel walls is explained. First results of an investigation carried out at the Aero-Space Institute of Berlin Technical University are presented for two dimensional flexible walls and a NACA 0012 airfoil. With five examples exhibiting very different flow conditions it is demonstrated that it is possible to reduce wall interference and to avoid blockage at transonic speeds by wall adaptation.

Computational Simulation of the Flow Past an Airfoil for an Unmanned Aerial Vehicle

Directory of Open Access Journals (Sweden)

L. Velázquez-Araque

2013-08-01

Full Text Available This paper deals with the numerical simulation of the two-dimensional, incompressible, steady air flow past a NACA 2415 airfoil and four modifications of this one. The modification of this airfoil was made in order to create a blowing outlet with the shape of a step on the suction surface. Therefore, five different locations along the cord line for this blowing outlet were analyzed. This analysis involved the aerodynamic performance which meant obtaining lift, drag and pitching moment coefficients curves as a function of the angle of attack for the situation where the engine of the aerial vehicle is turned off called the no blowing condition by means computational fluid dynamics. The RNG k-ε model is utilized to describe the turbulent flow process. The simulations were held at a Reynolds number of 105. Results allowed obtaining lift and drag forces and pitching moment coefficient and also the location of the separation and reattachment point in some cases for different angles of attack, from 0 to 16 degrees with the smallest increment of 4 degrees. Finally, numerical results were compared with results obtained from wind tunnel tests by means of an aerodynamic balance and also oil and smoke visualization techniques and found to be in very good agreement.

Fiberglass Composite Blades for the 4 MW - WTS-4 Wind Turbine

Science.gov (United States)

Bussolari, R. J.

1982-01-01

The design and fabrication of composite blades for the WTS-4, a four-megawatt horizontal-axis wind turbine, is discussed. The blade consists of a two-cell, monolithic structure of filament-wound, fiberglass/epoxy composite. Filament winding is a low-cost process which can produce a blade with an aerodynamically efficient airfoil and planform with nonlinear twist to achieve high performance in terms of energy capture. Its retention provides a redundant attachment for long, durable life and safety. Advanced tooling concepts and as sophisticated computer control is used to achieve the unique filament-wound shape.

Unsteady flow model for circulation-control airfoils

Science.gov (United States)

Rao, B. M.

1979-01-01

An analysis and a numerical lifting surface method are developed for predicting the unsteady airloads on two-dimensional circulation control airfoils in incompressible flow. The analysis and the computer program are validated by correlating the computed unsteady airloads with test data and also with other theoretical solutions. Additionally, a mathematical model for predicting the bending-torsion flutter of a two-dimensional airfoil (a reference section of a wing or rotor blade) and a computer program using an iterative scheme are developed. The flutter program has a provision for using the CC airfoil airloads program or the Theodorsen hard flap solution to compute the unsteady lift and moment used in the flutter equations. The adopted mathematical model and the iterative scheme are used to perform a flutter analysis of a typical CC rotor blade reference section. The program seems to work well within the basic assumption of the incompressible flow.

Parametric analyses on dynamic stall control of rotor airfoil via synthetic jet

Directory of Open Access Journals (Sweden)

Qijun ZHAO

2017-12-01

Full Text Available The effects of synthetic jet control on unsteady dynamic stall over rotor airfoil are investigated numerically. A moving-embedded grid method and an Unsteady Reynolds Averaged Navier-Stokes (URANS solver coupled with k-ω Shear Stress Transport (SST turbulence model are established for predicting the complex flowfields of oscillatory airfoil under jet control. Additionally, a velocity boundary condition modeled by sinusoidal function has been developed to fulfill the perturbation effect of periodic jet. The validity of present CFD method is evaluated by comparisons of the calculated results of baseline dynamic stall case for rotor airfoil and jet control case for VR-7B airfoil with experimental data. Then, parametric analyses are conducted emphatically for an OA212 rotor airfoil to investigate the effects of jet control parameters (jet location, dimensionless frequency, momentum coefficient, jet angle, jet type and dual-jet on dynamic stall characteristics of rotor airfoil. It is demonstrated by the calculated results that efficiency of jet control could be improved with specific momentum coefficient and jet angle when the jet is located near separation point of rotor airfoil. Furthermore, the dual-jet could improve control efficiency more obviously on dynamic stall of rotor airfoil with respect to the unique jet, and the influence laws of dual-jet’s angles and momentum coefficients on control effects are similar to those of the unique jet. Finally, unsteady aerodynamic characteristics of rotor via synthetic jet which is located on the upper surface of rotor blade in forward flight are calculated, and as a result, the aerodynamic characteristics of rotor are improved compared with the baseline. The results indicate that synthetic jet has the capability in improving aerodynamic characteristics of rotor. Keywords: Airfoil, Dynamic stall characteristics, Flow control, Moving-embedded grid methodology, Navier-Stokes equations, Parametric

Influence of Reynolds Number on Multi-Objective Aerodynamic Design of a Wind Turbine Blade.

Science.gov (United States)

Ge, Mingwei; Fang, Le; Tian, De

2015-01-01

At present, the radius of wind turbine rotors ranges from several meters to one hundred meters, or even more, which extends Reynolds number of the airfoil profile from the order of 105 to 107. Taking the blade for 3MW wind turbines as an example, the influence of Reynolds number on the aerodynamic design of a wind turbine blade is studied. To make the study more general, two kinds of multi-objective optimization are involved: one is based on the maximum power coefficient (CPopt) and the ultimate load, and the other is based on the ultimate load and the annual energy production (AEP). It is found that under the same configuration, the optimal design has a larger CPopt or AEP (CPopt//AEP) for the same ultimate load, or a smaller load for the same CPopt//AEP at higher Reynolds number. At a certain tip-speed ratio or ultimate load, the blade operating at higher Reynolds number should have a larger chord length and twist angle for the maximum Cpopt//AEP. If a wind turbine blade is designed by using an airfoil database with a mismatched Reynolds number from the actual one, both the load and Cpopt//AEP will be incorrectly estimated to some extent. In some cases, the assessment error attributed to Reynolds number is quite significant, which may bring unexpected risks to the earnings and safety of a wind power project.

Influence of Reynolds Number on Multi-Objective Aerodynamic Design of a Wind Turbine Blade

Science.gov (United States)

Ge, Mingwei; Fang, Le; Tian, De

2015-01-01

At present, the radius of wind turbine rotors ranges from several meters to one hundred meters, or even more, which extends Reynolds number of the airfoil profile from the order of 105 to 107. Taking the blade for 3MW wind turbines as an example, the influence of Reynolds number on the aerodynamic design of a wind turbine blade is studied. To make the study more general, two kinds of multi-objective optimization are involved: one is based on the maximum power coefficient (C Popt) and the ultimate load, and the other is based on the ultimate load and the annual energy production (AEP). It is found that under the same configuration, the optimal design has a larger C Popt or AEP (C Popt//AEP) for the same ultimate load, or a smaller load for the same C Popt//AEP at higher Reynolds number. At a certain tip-speed ratio or ultimate load, the blade operating at higher Reynolds number should have a larger chord length and twist angle for the maximum C popt//AEP. If a wind turbine blade is designed by using an airfoil database with a mismatched Reynolds number from the actual one, both the load and C popt//AEP will be incorrectly estimated to some extent. In some cases, the assessment error attributed to Reynolds number is quite significant, which may bring unexpected risks to the earnings and safety of a wind power project. PMID:26528815

An airloads theory for morphing airfoils in dynamic stall with experimental correlation

Science.gov (United States)

Ahaus, Loren A.

Helicopter rotor blades frequently encounter dynamic stall during normal flight conditions, limiting the applicability of classical thin-airfoil theory at large angles of attack. Also, it is evident that because of the largely different conditions on the advancing and retreating sides of the rotor, future rotorcraft may incorporate dynamically morphing airfoils (trailing-edge aps, dynamic camber, dynamic droop, etc.). Reduced-order aerodynamic models are needed for preliminary design and ight simulation. A unified model for predicting the airloads on a morphing airfoil in dynamic stall is presented, consisting of three components. First, a linear airloads theory allows for arbitrary airfoil deformations consistent with a morphing airfoil. Second, to capture the effects of the wake, the airloads theory is coupled to an induced ow model. Third, the overshoot and time delay associated with dynamic stall are modeled by a second-order dynamic filter, along the lines of the ONERA dynamic stall model. This paper presents a unified airloads model that allows arbitrary airfoil morphing with dynamic stall. Correlations with experimental data validate the theory.

Recent progress in the analysis of iced airfoils and wings

Science.gov (United States)

Cebeci, Tuncer; Chen, Hsun H.; Kaups, Kalle; Schimke, Sue

1992-01-01

Recent work on the analysis of iced airfoils and wings is described. Ice shapes for multielement airfoils and wings are computed using an extension of the LEWICE code that was developed for single airfoils. The aerodynamic properties of the iced wing are determined with an interactive scheme in which the solutions of the inviscid flow equations are obtained from a panel method and the solutions of the viscous flow equations are obtained from an inverse three-dimensional finite-difference boundary-layer method. A new interaction law is used to couple the inviscid and viscous flow solutions. The newly developed LEWICE multielement code is amplified to a high-lift configuration to calculate the ice shapes on the slat and on the main airfoil and on a four-element airfoil. The application of the LEWICE wing code to the calculation of ice shapes on a MS-317 swept wing shows good agreement with measurements. The interactive boundary-layer method is applied to a tapered iced wing in order to study the effect of icing on the aerodynamic properties of the wing at several angles of attack.

Turbine Airfoil Leading Edge Film Cooling Bibliography: 1972–1998

Directory of Open Access Journals (Sweden)

D. M. Kercher

2000-01-01

Full Text Available Film cooling for turbine airfoil leading edges has been a common practice for at least 35 years as turbine inlet gas temperatures and pressures have continually increased along with cooling air temperatures for higher engine cycle efficiency. With substantial engine cycle performance improvements from higher gas temperatures, it has become increasingly necessary to film cool nozzle and rotor blade leading edges since external heat transfer coefficients and thus heat load are the highest in this airfoil region. Optimum cooling air requirements in this harsh environment has prompted a significant number of film cooling investigations and analytical studies reported over the past 25 years from academia, industry and government agencies. Substantial progress has been made in understanding the complex nature of leading edge film cooling from airfoil cascades, simulated airfoil leading edges and environment. This bibliography is a report of the open-literature references available which provide information on the complex aero–thermo interaction of leading edge gaseous film cooling with mainstream flow. From much of this investigative information has come successful operational leading edge film cooling design systems capable of sustaining airfoil leading edge durability in very hostile turbine environments.

Numerical Simulation of Airfoil Aerodynamic Penalties and Mechanisms in Heavy Rain

Directory of Open Access Journals (Sweden)

Zhenlong Wu

2013-01-01

Full Text Available Numerical simulations that are conducted on a transport-type airfoil, NACA 64-210, at a Reynolds number of 2.6×106 and LWC of 25 g/m3 explore the aerodynamic penalties and mechanisms that affect airfoil performance in heavy rain conditions. Our simulation results agree well with the experimental data and show significant aerodynamic penalties for the airfoil in heavy rain. The maximum percentage decrease in CL is reached by 13.2% and the maximum percentage increase in CD by 47.6%. Performance degradation in heavy rain at low angles of attack is emulated by an originally creative boundary-layer-tripped technique near the leading edge. Numerical flow visualization technique is used to show premature boundary-layer separation at high angles of attack and the particulate trajectories at various angles of attack. A mathematic model is established to qualitatively study the water film effect on the airfoil geometric changes. All above efforts indicate that two primary mechanisms are accountable for the airfoil aerodynamic penalties. One is to cause premature boundary-layer transition at low AOA and separation at high AOA. The other occurs at times scales consistent with the water film layer, which is thought to alter the airfoil geometry and increase the mass effectively.

NACA0015 measurements in LM wind tunnel and turbulence generated noise

Energy Technology Data Exchange (ETDEWEB)

Bertagnolio, Franck

2008-11-15

A NACA0015 airfoil section was instrumented with an array of highfrequency microphones mounted on its surface and measured in the wind tunnel at LM Glasfiber at various inflow speeds, angles of attack, and with different turbulent inflow conditions. The aim of this work is to analyze these measurement data, including the turbulent inflow characteristics. The airfoil surface pressure data are considered in the perspective of turbulent inflow noise in order to identify the potential for using these data to validate and possibly improve associated noise models from the literature. In addition, these data are further analyzed in the context of trailing edge noise modeling which is directly related to the surface pressure fluctuations in the vicinity of the trailing edge. (au)

Influence of Thickness Variation on the Flapping Performance of Symmetric NACA Airfoils in Plunging Motion

Directory of Open Access Journals (Sweden)

Liangyu Zhao

2010-01-01

Full Text Available In order to investigate the impact of airfoil thickness on flapping performance, the unsteady flow fields of a family of airfoils from an NACA0002 airfoil to an NACA0020 airfoil in a pure plunging motion and a series of altered NACA0012 airfoils in a pure plunging motion were simulated using computational fluid dynamics techniques. The “class function/shape function transformation“ parametric method was employed to decide the coordinates of these altered NACA0012 airfoils. Under specified plunging kinematics, it is observed that the increase of an airfoil thickness can reduce the leading edge vortex (LEV in strength and delay the LEV shedding. The increase of the maximum thickness can enhance the time-averaged thrust coefficient and the propulsive efficiency without lift reduction. As the maximum thickness location moves towards the leading edge, the airfoil obtains a larger time-averaged thrust coefficient and a higher propulsive efficiency without changing the lift coefficient.

Enhancements to NURBS-Based FEA Airfoil Modeler: SABER

Science.gov (United States)

Saleeb, A. F.; Trowbridge, D. A.

2003-01-01

NURBS (Non-Uniform Rational B-Splines) have become a common way for CAD programs to fit a smooth surface to discrete geometric data. This concept has been extended to allow for the fitting of analysis data in a similar manner and "attaching" the analysis data to the geometric definition of the structure. The "attaching" of analysis data to the geometric definition allows for a more seamless sharing of data between analysis disciplines. NURBS have become a useful tool in the modeling of airfoils. The use of NURBS has allowed for the development of software that easily and consistently generates plate finite element models of the midcamber surface of a given airfoil. The resulting displacements can then be applied to the original airfoil surface and the deformed shape calculated.

Investigation of Airfoil Aeroacoustics with Blowing Control Mechanism

Directory of Open Access Journals (Sweden)

Baha ZAFER

2016-11-01

Full Text Available In this investigation, it is dealt with computational aero-acoustic analysis of an airfoil with jet blowing. The airfoil shape is selected as NACA0015 profile with jet blowing on upper surface. The calculations of analysis are done by using commercial finite volume solver. The k-ε turbulence model is used for the turbulence modeling and the Ffowcs Williams and Hawking acoustic analogy model is run for determination of acoustic data. The numerical results are compared with experimental data for computed Sound Pressure Level without jet blowing and well agreement is observed. In the case of jet blowing, the effects of different jet angle, velocity ratio and angle of attack on airfoil are investigated and noise levels of non jet cases and jet blowing cases are studied.

Unsteady lift forces on highly cambered airfoils moving through a gust

Science.gov (United States)

Atassi, H.; Goldstein, M.

1974-01-01

An unsteady airfoil theory in which the flow is linearized about the steady potential flow of the airfoil is presented. The theory is applied to an airfoil entering a gust. After transformation to the W-plane, the problem is formulated in terms of a Poisson's equation. The solutions are expanded in a Fourier-Bessel series. The theory is applied to a circular arc with arbitrary camber. Closed form expressions for the velocity and pressure on the surface of the airfoil are obtained. The unsteady aerodynamic forces are then calculated and shown to contain two terms. One in an explicit closed analytical form represents the contribution of the oncoming vortical disturbance, the other depends on a single quadrature and accounts for the effect of the wake.

The effect of variations in first- and second-order derivatives on airfoil aerodynamic performance

Directory of Open Access Journals (Sweden)

Penghui Yi

2017-01-01

Full Text Available The geometric factors which influence airfoil aerodynamic performance are attributed to variations in local first- and second-order curvature derivatives. Based on a self-developed computational fluid dynamics (CFD program called UCFD, the influence of local profile variations on airfoil aerodynamic performance in different pressure areas is investigated. The results show that variations in first- and second-order derivatives of the airfoil profiles can cause fluctuations in airfoil aerodynamic performance. The greater the variation in local first- and second-order derivatives, the greater the fluctuation amplitude of the airfoil aerodynamic coefficients. Moreover, at the area near the leading edge and the shock-wave position, the surface pressure is more sensitive to changes in first- and second-order derivatives. These results provide a reference for airfoil aerodynamic shape design.

Ice accretion modeling for wind turbine rotor blades

Energy Technology Data Exchange (ETDEWEB)

Chocron, D.; Brahimi, T.; Paraschivoiu, I.; Bombardier, J.A. [Ecole Polytechnique de Montreal (Canada)

1997-12-31

The increasing application of wind energy in northern climates implies operation of wind turbines under severe atmospheric icing conditions. Such conditions are well known in the Scandinavian countries, Canada and most of Eastern European countries. An extensive study to develop a procedure for the prediction of ice accretion on wind turbines rotor blades appears to be essential for the safe and economic operation of wind turbines in these cold regions. The objective of the present paper is to develop a computer code capable of simulating the shape and amount of ice which may accumulate on horizontal axis wind turbine blades when operating in icing conditions. The resulting code is capable to predict and simulate the formation of ice in rime and glaze conditions, calculate the flow field and particle trajectories and to perform thermodynamic analysis. It also gives the possibility of studying the effect of different parameters that influence ice formation such as temperature, liquid water content, droplet diameter and accretion time. The analysis has been conducted on different typical airfoils as well as on NASA/DOE Mod-0 wind turbine. Results showed that ice accretion on wind turbines may reduce the power output by more than 20%.

Active Subspaces of Airfoil Shape Parameterizations

Science.gov (United States)

Grey, Zachary J.; Constantine, Paul G.

2018-05-01

Design and optimization benefit from understanding the dependence of a quantity of interest (e.g., a design objective or constraint function) on the design variables. A low-dimensional active subspace, when present, identifies important directions in the space of design variables; perturbing a design along the active subspace associated with a particular quantity of interest changes that quantity more, on average, than perturbing the design orthogonally to the active subspace. This low-dimensional structure provides insights that characterize the dependence of quantities of interest on design variables. Airfoil design in a transonic flow field with a parameterized geometry is a popular test problem for design methodologies. We examine two particular airfoil shape parameterizations, PARSEC and CST, and study the active subspaces present in two common design quantities of interest, transonic lift and drag coefficients, under each shape parameterization. We mathematically relate the two parameterizations with a common polynomial series. The active subspaces enable low-dimensional approximations of lift and drag that relate to physical airfoil properties. In particular, we obtain and interpret a two-dimensional approximation of both transonic lift and drag, and we show how these approximation inform a multi-objective design problem.

Airfoil noise prediction from 2D3C PIV data

NARCIS (Netherlands)

De Santana, Leandro Dantas; Schram, C.; Desmet, W.

2015-01-01

The noise emitted by incoming turbulence interacting with an airfoil has many technological applications, and has accordingly received much attention in the literature. While numerous developments are focused on the determination of the airfoil response to a given incoming gust, the characterization

Wind-tunnel Tests of a Hall High-life Wing

Science.gov (United States)

Weick, Fred E; Sanders, Robert

1932-01-01

Wind-tunnel tests have been made to find the lift, drag, and center-of-pressure characteristics of a Hall high-lift wing model. The Hall wing is essentially a split-flap airfoil with an internal air passage. Air enters the passage through an opening in the lower surface somewhat back of and parallel to the leading edge, and flows out through an opening made by deflecting the rear portion of the under surface downward as a flap. For ordinary flight conditions the front opening and the rear flap can be closed, providing in effect a conventional airfoil (the Clark Y in this case). The tests were made with various flap settings and with the entrance to the passage both open and closed. The highest lift coefficient found, C(sub L) = 2.08, was obtained with the passage closed.

Holography and LDV techniques, their status and use in airfoil research

Science.gov (United States)

Johnson, D. A.; Bachalo, W. D.

1978-01-01

The measurement capabilities of laser velocimetry and holographic interferometry in transonic airfoil testing were demonstrated. Presented are representative results obtained with these two nonintrusive techniques on a 15.24 cm chord airfoil section. These results include the density field about the airfoil, flow angles in the inviscid flow and viscous flow properties including the turbulent Reynolds stresses. The accuracies of the density fields obtained by interferometry were verified from comparisons with surface pressure and laser velocimeter measurements.

Computation of viscous transonic flow about a lifting airfoil

Science.gov (United States)

Walitt, L.; Liu, C. Y.

1976-01-01

The viscous transonic flow about a stationary body in free air was numerically investigated. The geometry chosen was a symmetric NACA 64A010 airfoil at a freestream Mach number of 0.8, a Reynolds number of 4 million based on chord, and angles of attack of 0 and 2 degrees. These conditions were such that, at 2 degrees incidence unsteady periodic motion was calculated along the aft portion of the airfoil and in its wake. Although no unsteady measurements were made for the NACA 64A010 airfoil at these flow conditions, interpolated steady measurements of lift, drag, and surface static pressures compared favorably with corresponding computed time-averaged lift, drag, and surface static pressures.

Boundary Layer Control on Airfoils.

Science.gov (United States)

Gerhab, George; Eastlake, Charles

1991-01-01

A phenomena, boundary layer control (BLC), produced when visualizing the fluidlike flow of air is described. The use of BLC in modifying aerodynamic characteristics of airfoils, race cars, and boats is discussed. (KR)

NUMERICAL INVESTIGATION OF TWO ELEMENT CAMBER MORPHING AIRFOIL IN LOW REYNOLDS NUMBER FLOWS

OpenAIRE

RAJESH SENTHIL KUMAR T.; V. SIVAKUMAR; BALAJEE RAMAKRISHNANANDA; ARJHUN A.K, SURIYAPANDIYAN

2017-01-01

Aerodynamic performance of a two-element camber morphing airfoil was investigated at low Reynolds number using the transient SST model in ANSYS FLUENT 14.0 and eN method in XFLR5. The two-element camber morphing concept was employed to morph the baseline airfoil into another airfoil by altering the orientation of mean-line at 35% of the chord to achieve better aerodynamic efficiency. NACA 0012 was selected as baseline airfoil. NACA 23012 was chosen as the test case as it has the camber-line s...

Numerical Investigation of an Oscillating Flat Plate Airfoil

Science.gov (United States)

Mohaghegh, Fazlolah; Janechek, Matthew; Buchholz, James; Udaykumar, Hs

2017-11-01

This research investigates the vortex dynamics of a plunging flat plate airfoil by analyzing the vorticity transport in 2D simulations. A horizontal airfoil is subject to a freestream flow at Re =10000. A prescribed vertical sinusoidal motion is applied to the airfoil. Smoothed Profile Method (SPM) models the fluid-structure interaction. SPM as a diffuse interface model considers a thickness for the interface and applies a smooth transition from solid to fluid. As the forces on the airfoil are highly affected by the interaction of the generated vortices from the surface, it is very important to find out whether a diffuse interface solver can model a flow dominated by vorticities. The results show that variation of lift coefficient with time agrees well with the experiment. Study of vortex evolution shows that similar to experiments, when the plate starts moving downward from top, the boundary layer is attached to the surface and the leading-edge vortex (LEV) is very small. By time, LEV grows and rolls up and a secondary vortex emerges. Meanwhile, the boundary layer starts to separate and finally LEV detaches from the surface. In overall, SPM as a diffuse interface model can predict the lift force and vortex pattern accurately.

Ice Roughness and Thickness Evolution on a Swept NACA 0012 Airfoil

Science.gov (United States)

McClain, Stephen T.; Vargas, Mario; Tsao, Jen-Ching

2017-01-01

Several recent studies have been performed in the Icing Research Tunnel (IRT) at NASA Glenn Research Center focusing on the evolution, spatial variations, and proper scaling of ice roughness on airfoils without sweep exposed to icing conditions employed in classical roughness studies. For this study, experiments were performed in the IRT to investigate the ice roughness and thickness evolution on a 91.44-cm (36-in.) chord NACA 0012 airfoil, swept at 30-deg with 0deg angle of attack, and exposed to both Appendix C and Appendix O (SLD) icing conditions. The ice accretion event times used in the study were less than the time required to form substantially three-dimensional structures, such as scallops, on the airfoil surface. Following each ice accretion event, the iced airfoils were scanned using a ROMER Absolute Arm laser-scanning system. The resulting point clouds were then analyzed using the self-organizing map approach of McClain and Kreeger to determine the spatial roughness variations along the surfaces of the iced airfoils. The resulting measurements demonstrate linearly increasing roughness and thickness parameters with ice accretion time. Further, when compared to dimensionless or scaled results from unswept airfoil investigations, the results of this investigation indicate that the mechanisms for early stage roughness and thickness formation on swept wings are similar to those for unswept wings.

Comparison of CFD simulations to non-rotating MEXICO blades experiment in the LTT wind tunnel of TUDelft

International Nuclear Information System (INIS)

Zhang, Ye; Van Zuijlen, Alexander; Van Bussel, Gerard

2014-01-01

In this paper, three dimensional flow over non-rotating MEXICO blades is simulated by CFD methods. The numerical results are compared with the latest MEXICO wind turbine blades measurements obtained in the low speed low turbulence (LTT) wind tunnel of Delft University of Technology. This study aims to validate CFD codes by using these experimental data measured in well controlled conditions. In order to avoid use of wind tunnel corrections, both the blades and the wind tunnel test section are modelled in the simulations. The ability of Menter's k – ω shear stress transport (SST) turbulence model is investigated at both attached flow and massively separated flow cases. Steady state Reynolds averaged Navier Stokes (RANS) equations are solved in these computations. The pressure distribution at three measured sections are compared under the conditions of different inflow velocities and a range of angles of attack. The comparison shows that at attached flow condition, good agreement can be obtained for all three airfoil sections. Even with massively separated flow, still fairly good pressure distribution comparison can be found for the DU and NACA airfoil sections, although the RISØ section shows poor comparison. At the near stall case, considerable deviations exists on the forward half part of the upper surface for all three sections

Experimental study of pitching and plunging airfoils at low Reynolds numbers

Energy Technology Data Exchange (ETDEWEB)

Baik, Yeon Sik; Bernal, Luis P. [University of Michigan, Department of Aerospace Engineering, Ann Arbor, MI (United States)

2012-12-15

Measurements of the unsteady flow structure and force time history of pitching and plunging SD7003 and flat plate airfoils at low Reynolds numbers are presented. The airfoils were pitched and plunged in the effective angle of attack range of 2.4 -13.6 (shallow-stall kinematics) and -6 to 22 (deep-stall kinematics). The shallow-stall kinematics results for the SD7003 airfoil show attached flow and laminar-to-turbulent transition at low effective angle of attack during the down stroke motion, while the flat plate model exhibits leading edge separation. Strong Re-number effects were found for the SD7003 airfoil which produced approximately 25 % increase in the peak lift coefficient at Re = 10,000 compared to higher Re flows. The flat plate airfoil showed reduced Re effects due to leading edge separation at the sharper leading edge, and the measured peak lift coefficient was higher than that predicted by unsteady potential flow theory. The deep-stall kinematics resulted in leading edge separation that led to formation of a large leading edge vortex (LEV) and a small trailing edge vortex (TEV) for both airfoils. The measured peak lift coefficient was significantly higher ({proportional_to}50 %) than that for the shallow-stall kinematics. The effect of airfoil shape on lift force was greater than the Re effect. Turbulence statistics were measured as a function of phase using ensemble averages. The results show anisotropic turbulence for the LEV and isotropic turbulence for the TEV. Comparison of unsteady potential flow theory with the experimental data showed better agreement by using the quasi-steady approximation, or setting C(k) = 1 in Theodorsen theory, for leading edge-separated flows. (orig.)

Integration of Airfoil Design during the design of new blades

Energy Technology Data Exchange (ETDEWEB)

Sartori, L.; Bottasso, L.; Croce, A. [Politecnico di Milano, Milan (Italy); Grasso, F. [ECN Wind Power, Petten (Netherlands)

2013-09-15

Despite the fact that the design of a new blade is a multidisciplinary task, often the different disciplines are combined together at later stage. Looking at the aerodynamic design, it is common practice design/select the airfoils first and then design the blade in terms of chord and twist based on the initial selection of the airfoils. Although this approach is quite diffused, it limits the potentialities of obtaining optimal performance. The present work is focused on investigating the benefits of designing the external shape of the blade including the airfoil shapes together with chord and twist. To accomplish this, a design approach has been developed, where an advanced gradient based optimization algorithm is able to control the shape of the blade. The airfoils described in the work are the NACA 4 digits, while the chord distribution and the twist distribution are described through Bezier curves. In this way, the complexity of the problem is limited while a versatile geometrical description is kept. After the details of the optimization scheme are illustrated, several numerical examples are shown, demonstrating the advantages in terms of performance and development time of integrating the design of the airfoils during the optimization of the blade.

WIND TUNNEL EVALUATION FOR CONTROL TRANSITION FROM ELEVATOR TO STABILATOR OF SMALL UAV

Directory of Open Access Journals (Sweden)

ZULHILMY SAHWEE

2017-06-01

Full Text Available Faulty control surface actuator in a small Unmanned Aerial Vehicles (sUAV could be overcome with a few techniques. Redundant actuators, analytical redundancy or combination of both are normally used as fault accommodation techniques. In this paper, the accommodation technique of faulty elevator actuator is presented. This technique uses a standby control surface as temporary control reallocation. Wind tunnel measurement facility is set up for the experimental validation and it is compared with FoilSim software. Flat plate airfoil which was used as horizontal stabilizer, is simulated using numerical model and it is validated using the wind tunnel test. Then, a flat airfoil is designed to be used as stabilator for the recovery of faulty elevator actuator. Results show the different deflection angle is needed when transferring from one control surface to another. From the analysis, the proposed method could be implemented without affecting the pitch stability during control surface transition. The alternate control surface accommodation technique proves to be promising for higher reliability sUAV in the case of a faulty on-board actuator.

Quasisolutions of Inverse Boundary-Value Problem of Aerodynamics for Dense Airfoil Grids

Directory of Open Access Journals (Sweden)

A.M. Elizarov

2016-12-01

Full Text Available In the process of turbomachinery development, it is of great importance to accurately design impellers and select their blade shape. One of the promising approaches to solving this problem is based on the theory of inverse boundary-value problems in aerodynamics. It helps to develop methods for profiling airfoil grids with predetermined properties in the same way as it is done for isolated airfoils. In this paper, methods have been worked out to find quasisolutions of the inverse boundary-value problem in aerodynamics for a plane airfoil grid. Two methods of quasisolution have been described. The first “`formal” method is similar, in its essence, to the method used for construction of quasisolution for an isolated airfoil. It has been shown that such quasisolutions provide satisfactory results for grids having a sufficiently large relative airfoil pitch. If pitch values are low, this method is unacceptable, because “modified” velocity distribution in some areas is significantly different from the original one in this case. For this reason, areas with significant changes in the angle of the tangent line appear in the airfoil contour and the flow region becomes multivalent. To satisfy the conditions of solvability in the case of grids having a small airfoil pitch, a new quasisolution construction method taking into account the specifics of the problem has been suggested. The desired effect has been achieved due to changes in the weighting function of the minimized functional. The comparison of the results of construction of the new quasisolution with the results obtained by the “formal” method has demonstrated that the constructed airfoils are very similar when the pitch is large. In the case of dense grids, it is clear that preference should be given to the second method, as it brings less distortion to the initial velocity distribution and, thus, allows to physically find an actual airfoil contour.

The future of utility-scale wind power

International Nuclear Information System (INIS)

Hock, S.; Thresher, R.; Williams, T.

1992-01-01

The U.S. Department of Energy (DOE) estimates that by 2030, wind power could potentially displace between 3 and 4 quadrillion (10 15 ) Btus (quads) of primary energy, with an installed electrical generation capacity of 120,000 to 160,000 MW. This forecast is based upon economic analyses indicating that the costs of wind-generated electricity could be cost competitive with conventional fossil-fuel-based generation by early next century. The key to realizing this objective is overcoming technical challenges to the development of a next-generation of advanced wind turbines. These challenges include the detailed characterization of wind inflow to turbines at wind-power-plant sites, an understanding of unsteady aerodynamics, the development of sophisticated computer models of all aspects of turbine operation, and the application of a better understanding of component and system fatigue to new designs. Advanced wind systems will include such new technologies as blade designs incorporating advanced airfoils and new materials, variable-speed operation, advanced power electronics, rotor-hub enhancements, tall towers, aerodynamic controls, advanced drive trains, and expert control systems. A larger market share for wind energy will also require the resolution of issues surrounding transmission, storage, and the integration of an intermittent energy source into the utility grid

KNOW-Blade Task-2 report - Aerodynamic accessories[Wind turbines

Energy Technology Data Exchange (ETDEWEB)

Johansen, J.; Soerensen, N.N.; Zahle, F.; Kang, S.; Nikolaou, I.; Politis, E.S.; Chaviaropoulos, P.K.; Ekaterinaris, J.

2004-11-01

In the EC project KNOW-BLADE a work package has been defined to investigate the possibility to numerically model aerodynamic accessories in existing Navier-Stokes solvers. Four different aerodynamic accessories have been investigated. Firstly, the potential of applying active flow control by means of a pulsating jet placed at the leading edge in order to enhance mean lift. The general trend is that increased pulsation frequency is beneficial, in that it reduces the oscillation amplitude and raises the mean lift level while lowering the mean drag level. An increased jet exit velocity has a tendency to increase the oscillation amplitude, which is not very attractive for load control on wind turbines. Secondly, the effect of vortex generators has been modelled using two phenomenological vortex generator models. The models have been applied to three airfoil configurations. For all cases investigated the models shows qualitatively the correct behaviour, even though there are a considerable spread in the degree of success. Thirdly, the influence of adding a stall strip for changing the airfoil characteristics was investigated. Stall strips at three different positions were directly modelled by changing the airfoil geometry. In general the 7mm stall strips placed at P00 and P-02 had the greatest effect on the max lift followed by stall strip P02. Unfortunately, there was not sufficient agreement between the experimental results and the simulations to draw any conclusions of optimum position and geometry of the stall strip. Finally, the effect of surface roughness was modelled by either modifying the boundary condition of the turbulence model or by modifying the airfoil geometry. Using the roughness model gave relatively good agreement with measurements and it must be concluded that the effect of using roughness tape can be better predicted with a roughness model compared to using a modified airfoil surface. (au)

Boundary Layer Transition, Separation and Flow Control on Airfoils, Wings and Bodies in CFD, Wind-Tunnel and In-Flight Studies

Czech Academy of Sciences Publication Activity Database

Popelka, Lukáš; Matějka, M.; Šimurda, David; Součková, Natálie

2011-01-01

Roč. 35, č. 4 (2011), s. 97-104 ISSN 0744-8996 R&D Projects: GA MŠk(CZ) 1M06031; GA AV ČR IAA2076403; GA ČR GA101/08/1112 Institutional research plan: CEZ:AV0Z20760514 Keywords : airfoil * wing-fuselage interaction * flow control Subject RIV: BK - Fluid Dynamics