Numerical Investigation of Airfoil Dynamic Stall in Simultaneous Harmonic Oscillatory and Translatory Motion

1998 ◽  
Vol 120 (1) ◽  
pp. 75-83 ◽  
Author(s):  
J. A. Ekaterinaris ◽  
N. N. So̸rensen ◽  
F. Rasmussen
Keyword(s):  
Wind Turbine ◽  
Numerical Solution ◽  
Turbine Blades ◽  
Harmonic Oscillation ◽  
Dynamic Stall ◽  
Transitional Flow ◽  
Flow Conditions ◽  
Complex Flow ◽  
Numerical Predictions ◽  
Translatory Motion

Wind turbine blades are subject to complex flow conditions. For operation in yaw and turbulent inflow, the blade sections appear to execute a motion more complex than a harmonic blade oscillation, which causes dynamic stall. Predictions of dynamic stall caused by simple harmonic oscillation are crucial to efforts in understanding and improving wind turbine performance. Investigation of dynamic stall development caused by a combined oscillatory and translatory motion contributes to better understand blade loading under complex flow conditions. In this paper, numerical predictions of light and deep stall caused by simple oscillatory motion are obtained first. The ability of the numerical solution to predict dynamic stall loads caused by a combined motion is further investigated. The numerical solution is obtained with a factorized, upwind-biased numerical scheme. The turbulent flow region is computed with a one-equation turbulence model. A transition model is used to simulate the transitional flow effects, which play an important role to the overall unsteady flowfield development. The computed results are compared with available experimental data.

scholarly journals Stochastic Model for Aerodynamic Force Dynamics on Wind Turbine Blades in Unsteady Wind Inflow

2015 ◽  
Vol 10 (4) ◽  
Author(s):  
M. R. Luhur ◽  
J. Peinke ◽  
M. Kühn ◽  
M. Wächter
Keyword(s):  
Stochastic Model ◽  
Wind Turbine ◽  
Aerodynamic Force ◽  
Turbine Blades ◽  
Stochastic Approach ◽  
Simulation Software ◽  
Dynamic Stall ◽  
Wind Turbine Blades ◽  
Full Field ◽  
Blade Element

The paper presents a stochastic approach to estimate the aerodynamic forces with local dynamics on wind turbine blades in unsteady wind inflow. This is done by integrating a stochastic model of lift and drag dynamics for an airfoil into the aerodynamic simulation software AeroDyn. The model is added as an alternative to the static table lookup approach in blade element momentum (BEM) wake model used by AeroDyn. The stochastic forces are obtained for a rotor blade element using full field turbulence simulated wind data input and compared with the classical BEM and dynamic stall models for identical conditions. The comparison shows that the stochastic model generates additional extended dynamic response in terms of local force fluctuations. Further, the comparison of statistics between the classical BEM, dynamic stall, and stochastic models' results in terms of their increment probability density functions (PDFs) gives consistent results.

Water channel experiments of dynamic stall on Darrieus wind turbine blades

1986 ◽  
Vol 2 (5) ◽  
pp. 445-449 ◽  
Author(s):  
G. Brochier ◽  
P. Fraunie ◽  
C. Beguier ◽  
I. Paraschivoiu
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Water Channel ◽  
Dynamic Stall ◽  
Wind Turbine Blades

2D Numerical Simulations of Blade-Vortex Interaction in a Darrieus Turbine

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
E. Amet ◽  
T. Maître ◽  
C. Pellone ◽  
J.-L. Achard
Keyword(s):  
Numerical Analysis ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Water Channel ◽  
Dynamic Stall ◽  
Speed Ratio ◽  
Secondary Effects ◽  
Time Step ◽  
Tip Speed Ratio ◽  
Lift And Drag

The aim of this work is to provide a detailed two-dimensional numerical analysis of the physical phenomena occurring during dynamic stall of a Darrieus wind turbine. The flow is particularly complex because as the turbine rotates, the incidence angle and the blade Reynolds number vary, causing unsteady effects in the flow field. At low tip speed ratio, a deep dynamic stall occurs on blades, leading to large hysteresis lift and drag loops (primary effects). On the other hand, high tip speed ratio corresponds to attached boundary layers on blades (secondary effects). The optimal efficiency occurs in the middle range of the tip speed ratio where primary and secondary effects cohabit. To prove the capacity of the modeling to handle the physics in the whole range of operating condition, it is chosen to consider two tip speed ratios (λ=2 and λ=7), the first in the primary effect region and the second in the secondary effect region. The numerical analysis is performed with an explicit, compressible RANS k-ω code TURBFLOW, in a multiblock structured mesh configuration. The time step and grid refinement sensitivities are examined. Results are compared qualitatively with the visualization of the vortex shedding of Brochier (1986, “Water channel experiments of dynamic stall on Darrieus wind turbine blades,” J. Propul. Power, 2(5), pp. 445–449). Hysteresis lift and drag curves are compared with the data of Laneville and Vitecoq (1986, “Dynamic stall: the case of the vertical axis wind turbine,” Prog. Aerosp. Sci., 32, pp. 523–573).

Experimental and Numerical Analysis of the Flow Structure and Dust Separation Inside a Pre-Swirl Cooling Air System

2003 ◽  
Author(s):  
O. Schneider ◽  
H. J. Dohmen ◽  
F.-K. Benra ◽  
D. Brillert
Keyword(s):  
Numerical Analysis ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Flow Conditions ◽  
Test Rig ◽  
Complex Flow ◽  
Air System ◽  
Cooling Air

Improvements in efficiency and performance of gas turbines require a better understanding of the internal cooling air system which provides the turbine blades with cooling air. With the increase of cooling air passing through the internal air system, a greater amount of air borne particles is transported to the film cooling holes at the turbine blade surface. In spite of their small size, these holes are critical for blockage. Blockage of only a few holes could have harmful effects on the cooling film surrounding the blade. As a result, a reduced mean time between maintenance or even unexpected operation faults of the gas turbine during operation could occur. Experience showed a complex interaction of cooling air under different flow conditions and its particle load. To get more familiar with all these influences and the system itself, a test rig has been built. With this test rig, the behavior of particles in the internal cooling air system can be studied at realistic flow conditions compared to a modern, heavy duty gas turbine. It is possible to simulate different particle sizes and dust concentrations in the coolant air. The test rig has been designed to give information about the quantity of separated particles at various critical areas of the internal air system [1]. The operation of the test rig as well as analysis of particles in such a complex flow system bear many problems, addressed in previous papers [1,2,3]. New theoretical studies give new and more accurate results, compared to the measurements. Furthermore the inspection of the test rig showed dust deposits at unexpected positions of the flow path, which will be discussed by numerical analysis.

Dynamic Stall on Rotating Airfoils: A Look at the N-Sequence Data from the NREL Phase VI Experiment

2013 ◽  
Vol 569-570 ◽  
pp. 611-619 ◽  
Author(s):  
Srinivas Guntur ◽  
Niels N. Sørensen ◽  
Scott Schreck
Keyword(s):  
Wind Turbine ◽  
Large Scale ◽  
Sequence Data ◽  
Turbine Blades ◽  
Angle Of Attack ◽  
Dynamic Stall ◽  
Wind Turbine Blades ◽  
Flow Solver ◽  
The Mean ◽  
Nrel Phase Vi

This paper presents an investigation on the combined effect of dynamic stall and rotational augmentation on wind turbine blades. Dynamic stall and rotational augmentation have previously been studied independently. The NREL Phase VI experiment was one large scale experiment that recorded 3D measurements on rotating and pitching airfoils, and using some these data the behaviour of the unsteady CL-α polars under the influence of rotation is investigated. Unsteady DES CFD computations of the Phase VI rotor in axial operation and continuous pitching conditions (reproducing conditions similar to the N-sequence experiments) for select cases have also been carried out using the in-house flow solver EllipSys3D. The resulting set of CL-α curves for the airfoils in rotation operating at various values of the frequency, the mean, and the amplitude of the angle of attack resulting from the CFD computations as well as those from the experiments are presented and discussed. Qualitative differences between dynamic stall occurrence on rotating and stationary airfoils are highlighted, procedures employed to extract the mean angle of attack from the available experimental data are discussed, and comments are made on the application of dynamic stall models in conjunction with 3D augmentation models on the rotating wind turbine blades.

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