Yaw Aerodynamics Analyzed With Three Codes in Comparison With Experiment

2003 ◽  
Author(s):  
Helge Aagaard Madsen ◽  
Niels N. So̸rensen ◽  
Scott Schreck
Keyword(s):  
Element Model ◽  
Navier Stokes ◽  
Local Flow ◽  
Flow Angle ◽  
Comparison With Experiment ◽  
Actuator Disc ◽  
Grid Points ◽  
Yaw Angle ◽  
Angle Interval ◽  
Blade Element

Yaw aerodynamics were computed with three codes of different complexity; 1) The 3D Navier Stokes solver Ellipsys3D using 5–8 million grid points; 2) HAWC3D which is a 3D actuator disc model coupled to a blade element model and using 20–30.000 grid points and 3) HAWC, a finite element based aeroelastic code using The Blade Element Momentum (BEM) model for the aerodynamics. Simulations were performed for two experiments. The first is the field rotor measurements on a 100 kW turbine at Risoe where local flow angle (LFA) and local relative velocity (LRV) at one radial station have been measured in a yaw angle interval of ±60°. The other experiment is the NREL measurements on a 10 m rotor in the NASA Ames 80 ft × 120 ft wind tunnel. LFA were measured at five radial stations and data for the 45° yaw case were analyzed. The measured changes in LFA caused by the yawing were used as the main parameter in the comparison with the models. In general a good correlation was found comparing the Ellipsys3D results with the LFA measured on the NREL rotor whereas a systematic underestimation of the amplitude in LFA as function of azimuth was observed for the two other models. This could possibly be ascribed to upwash influence on the measured LFA.

scholarly journals Evaluation of Tip Loss Corrections to AD/NS Simulations of Wind Turbine Aerodynamic Performance

2019 ◽  
Vol 9 (22) ◽  
pp. 4919 ◽  
Author(s):  
Wei Zhong ◽  
Tong Guang Wang ◽  
Wei Jun Zhu ◽  
Wen Zhong Shen
Keyword(s):  
Wind Turbine ◽  
Wind Farm ◽  
Relative Difference ◽  
Superior Performance ◽  
Navier Stokes ◽  
Special Focus ◽  
Actuator Disc ◽  
Blade Tip ◽  
Blade Loads ◽  
Blade Element

The Actuator Disc/Navier-Stokes (AD/NS) method has played a significant role in wind farm simulations. It is based on the assumption that the flow is azimuthally uniform in the rotor plane, and thus, requires a tip loss correction to take into account the effect of a finite number of blades. All existing tip loss corrections were originally proposed for the Blade-Element Momentum Theory (BEMT), and their implementations have to be changed when transplanted into the AD/NS method. The special focus of the present study is to investigate the performance of tip loss corrections combined in the AD/NS method. The study is conducted by using an axisymmetric AD/NS solver to simulate the flow past the experimental NREL Phase Ⅵ wind turbine and the virtual NREL 5MW wind turbine. Three different implementations of the widely used Glauert tip loss function F are discussed and evaluated. In addition, a newly developed tip loss correction is applied and compared with the above implementations. For both the small and large rotors under investigation, the three different implementations show a certain degree of difference to each other, although the relative difference in blade loads is generally no more than 4%. Their performance is roughly consistent with the standard Glauert correction employed in the BEMT, but they all tend to make the blade tip loads over-predicted. As an alternative method, the new tip loss correction shows superior performance in various flow conditions. A further investigation into the flow around and behind the rotors indicates that tip loss correction has a significant influence on the velocity development in the wake.

Tip Loss Correction for Actuator/Navier–Stokes Computations

2005 ◽  
Vol 127 (2) ◽  
pp. 209-213 ◽  
Author(s):  
Wen Zhong Shen ◽  
Jens Nørkær Sørensen ◽  
Robert Mikkelsen
Keyword(s):  
Experimental Data ◽  
New York ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Tip Speed Ratio ◽  
Actuator Disk ◽  
Axisymmetrical Flow ◽  
Actuator Disc ◽  
The Difference ◽  
Blade Element

A new tip loss correction, initially developed for 1D Blade Element/Momentum (BEM) computations (submitted to Wind Energy), is now extended to 2D Actuator Disc/Navier–Stokes (AD/NS) computations and 3D Actuator Line/Navier–Stokes (AL/NS) computations. In the paper, it is shown that the tip loss correction is an important and necessary step for actuator/Navier–Stokes models. Computed results are compared to experimental data and to results from BEM computations using the new tip correction as well as the original one of Glauert (Aerodynamic Theory, Dover, New York, Chap. VII, Div. L, pp. 251–268). From the results it is concluded that the tip loss correction has been correctly employed in the Navier–Stokes based actuator models. The results also demonstrate that the difference between actuator line and actuator disk-based models may increase, especially for flows at a low tip speed ratio. Since the flows at a low tip speed ratio are too far to be considered as axisymmetrical flows, the actuator disk models that are based on axisymmetrical flow behaviors may not be valid.

Correcting Inflow Measurements From Wind Turbines Using a Lifting-Surface Code

2000 ◽  
Vol 122 (4) ◽  
pp. 196-202 ◽  
Author(s):  
J. Whale ◽  
C. J. Fisichella ◽  
M. S. Selig
Keyword(s):  
Angle Of Attack ◽  
Three Dimensional ◽  
Correction Method ◽  
Local Flow ◽  
Flow Angle ◽  
Lifting Surface ◽  
Surface Code ◽  
Turbine Design ◽  
The Relationship ◽  
Blade Element

In order to provide accurate blade element data for wind turbine design codes, measured three-dimensional (3D) field data must be corrected in terms of the (sectional) angle of attack. A 3D Lifting-Surface Inflow Correction Method (LSIM) has been developed with the aid of a vortex-panel code in order to calculate the relationship between measured local flow angle and angle of attack. The results show the advantages of using the 3D LSIM correction over 2D correction methods, particularly at the inboard sections of the blade where the local flow is affected by post-stall effects and the influence of the blade root. [S0199-6231(00)00604-3]

A multi-fidelity modelling approach for evaluation and optimization of wing stroke aerodynamics in flapping flight

2013 ◽  
Vol 721 ◽  
pp. 118-154 ◽  
Author(s):  
Lingxiao Zheng ◽  
Tyson L. Hedrick ◽  
Rajat Mittal
Keyword(s):  
Parameter Space ◽  
Computational Models ◽  
Computational Modelling ◽  
Element Model ◽  
Flapping Wing ◽  
Navier Stokes ◽  
Specific Flow ◽  
Wing Stroke ◽  
Modelling Approach ◽  
Blade Element

AbstractThe aerodynamics of hovering flight in a hawkmoth (Manduca sexta) are examined using a computational modelling approach which combines a low-fidelity blade-element model with a high-fidelity Navier–Stokes-based flow solver. The focus of the study is on understanding the optimality of the hawkmoth-inpired wingstrokes with respect to lift generation and power consumption. The approach employs a tight coupling between the computational models and experiments; the Navier–Stokes model is validated against experiments, and the blade-element model is calibrated with the data from the Navier–Stokes modelling. In the first part of the study, blade-element and Navier–Stokes modelling are used concurrently to assess the predictive capabilities of the blade-element model. Comparisons between the two modelling approaches also shed insights into specific flow features and mechanisms that are lacking in the lower-fidelity model. Subsequently, we use blade-element modelling to explore a large kinematic parameter space of the flapping wing, and Navier–Stokes modelling is used to assess the performance of the wing-stroke identified as optimal by the blade-element parameter survey. This multi-fidelity optimization study indicates that even within a parameter space constrained by the animal’s natural flapping amplitude and frequency, it is relatively easy to synthesize a wing stroke that exceeds the aerodynamic performance of the hawkmoth wing stroke. Within the prescribed constraints, the optimal wing stroke closely approximates the condition of normal hover, and the implications of these findings on hawkmoth flight capabilities as well as on the issue of biomimetic versus bioinspired design of flapping wing micro-aerial vehicles, are discussed.

Through Flow Flange-to-Flange Turbine and Diffuser Analysis

2012 ◽  
Author(s):  
Andrei Granovskiy ◽  
Mikhail Kostege ◽  
Vladislav Krupa ◽  
Sergey Rudenko
Keyword(s):  
Gas Turbines ◽  
Power Plants ◽  
Gas Flow ◽  
Optimal Solution ◽  
Integrated Approach ◽  
Combined Cycle ◽  
Navier Stokes ◽  
Local Flow ◽  
Flow Angle ◽  
Part Load

At the present time an important aspect of power generation in combined cycle power plants is to keep part load performance of heavy duty gas turbines sufficiently high. Therefore it is a matter of importance to ensure the aerodynamic alignment between the turbine and exhaust diffuser, allowing potential increase in both turbine efficiency and diffuser pressure recovery. The benefit of such alignment could be noticed at numerical analysis accuracy of part-load conditions in particular due to the change in gas flow angle downstream of the turbine and resulting in an incidence on the diffuser struts. This incidence, in its turn, often causes local flow separation and an associated loss increase. This paper presents an integrated approach of the turbine and diffuser aerodynamic design by means of use of a single 3D Navier-Stokes CFD model. This model explores an automatic interface between the turbine and diffuser calculation domains. Furthermore, whilst gas turbine part load performance has been improved thanks to last stage turbine blade redesign, the above-mentioned integrated turbine & diffuser numerical modelling was used as working instrument to reach the optimal solution in terms of flange-to-flange efficiency in a broad operation range. Following test results, comparison against the numerical prediction fully proved the validity of chosen analytical approach.

Effects of Particle-Particle Collisions on Particle Concentration in a Turbulent Channel Flow

2006 ◽  
Author(s):  
H. Nasr ◽  
G. Ahmadi ◽  
J. B. McLaughlin
Keyword(s):  
Particle Concentration ◽  
Random Distribution ◽  
Pseudospectral Method ◽  
Time History ◽  
Turbulent Channel Flow ◽  
Navier Stokes ◽  
Particle Collisions ◽  
Navier Stokes Equation ◽  
History Of ◽  
Grid Points

This study is concerned with the effect of inter particle collisions on the particle concentration in turbulent duct flows. The time history of the instantaneous turbulent velocity vector was generated by the two-way coupled direct numerical simulation (DNS) of the Navier-Stokes equation via a pseudospectral method. The particle equation of motion included the Stokes drag, the Saffman lift, and the gravitational forces. The effect of particles on the flow is included in the analysis via a feedback force on the grid points. Several simulations for three classes of particles (28 μm Lycopodia, 50μm glass and 70μm copper) and different mass loadings were performed, and the effect of inter particle collisions on the particle concentration was evaluated and discussed. It was found that the particle-particle collisions reduce the tendency of particles to accumulate near the wall. This might be because collisions decorrelate particles with coherent eddies which are responsible for accumulation of particles near the wall. The spatial distribution of particles at the channel centerplane was compared with the experimental results of Fessler et al. (1994). The simulation results showed that the copper and glass particles had a random distribution while Lycopodium particles showed a non-random distribution with bands of particles that were preferentially concentrated.

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

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

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

The Development of an Aerodynamic Performance Prediction Tool for Modern Axial Flow Compressor Profiles

2006 ◽  
Author(s):  
Dario Bruna ◽  
Carlo Cravero ◽  
Mark G. Turner
Keyword(s):  
Performance Prediction ◽  
Parametric Design ◽  
Flow Analysis ◽  
Axial Flow ◽  
Navier Stokes ◽  
Flow Angle ◽  
Flow Solver ◽  
Aerodynamic Loss ◽  
Axial Flow Compressor ◽  
Flow Compressor

The development of a computational tool (MP-LOS) for the aerodynamic loss modeling and prediction for axial-flow compressor blade sections is presented in this paper. A state-of-the-art quasi 3-D flow solver, MISES, has been used for the flow analysis on existing airfoil geometries in many working conditions. Different values of inlet flow angle, inlet Mach number, AVDR, Reynolds number and solidity have been chosen to investigate a possible working range. The target is a loss prediction formulation that will be introduced into throughflow or axisymmetric Navier-Stokes codes for the performance prediction of multistage axial flow compressors. The loss coefficient has been correlated to the flow parameters that have shown an influence on the profile loss for the blades under study. The proposed correlation, using the described computational approach, can be extended to any profile family with the aid of any code for the parametric design of blade profiles.

Forced Response Assessment Using Modal Force Based Indicator Functions

2008 ◽  
Author(s):  
M. Vahdati ◽  
C. Breard ◽  
G. Simpson ◽  
M. Imregun
Keyword(s):  
Finite Element ◽  
Structural Model ◽  
Stokes Equations ◽  
Linear Time ◽  
Response Assessment ◽  
Element Model ◽  
Forced Response ◽  
Navier Stokes ◽  
Modal Force ◽  
Indicator Functions

This paper will focus on core-compressor forced response with the aim to develop two design criteria, the so-called chordwise cumulative modal force and heightwise cumulative force, to assess the potential severity of the vibration levels from the correlation between the unsteady pressure distribution on the blade’s surface and the structural modeshape. It is also possible to rank various blade designs since the proposed criterion is sensitive to changes in both unsteady aerodynamic loads and the vibration modeshapes. The proposed methodology was applied to a typical core-compressor forced response case for which measured data were available. The Reynolds-averaged Navier-Stokes equations were used to represent the flow in a non-linear time-accurate fashion on unstructured meshes of mixed elements. The structural model was based on a standard finite element representation from which the vibration modes were extracted. The blade flexibility was included in the model by coupling the finite element model to the unsteady flow model in a time-accurate fashion. A series of numerical experiments were conducted by altering the stator wake and using the proposed indicator functions to minimize the rotor response levels. It was shown that a fourfold response reduction was possible for a certain mode with only a minor modification of the blade.

Development and Validation of a CFD Technique for the Aerodynamic Analysis of HAWT

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
S. Gómez-Iradi ◽  
R. Steijl ◽  
G. N. Barakos
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Turbine Blades ◽  
Wind Tunnel Test ◽  
Unsteady Aerodynamics ◽  
Tunnel Wall ◽  
Local Flow ◽  
Flow Angle ◽  
Thrust And Torque

This paper demonstrates the potential of a compressible Navier–Stokes CFD method for the analysis of horizontal axis wind turbines. The method was first validated against experimental data of the NREL/NASA-Ames Phase VI (Hand, et al., 2001, “Unsteady Aerodynamics Experiment Phase, VI: Wind Tunnel Test Configurations and Available Data Campaigns,” NREL, Technical Report No. TP-500-29955) wind-tunnel campaign at 7 m/s, 10 m/s, and 20 m/s freestreams for a nonyawed isolated rotor. Comparisons are shown for the surface pressure distributions at several stations along the blades as well as for the integrated thrust and torque values. In addition, a comparison between measurements and CFD results is shown for the local flow angle at several stations ahead of the wind turbine blades. For attached and moderately stalled flow conditions the thrust and torque predictions are fair, though improvements in the stalled flow regime are necessary to avoid overprediction of torque. Subsequently, the wind-tunnel wall effects on the blade aerodynamics, as well as the blade/tower interaction, were investigated. The selected case corresponded to 7 m/s up-wind wind turbine at 0 deg of yaw angle and a rotational speed of 72 rpm. The obtained results suggest that the present method can cope well with the flows encountered around wind turbines providing useful results for their aerodynamic performance and revealing flow details near and off the blades and tower.

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