Effects of grit roughness and pitch oscillations on the S801 airfoil

Ramsay, R.R.; Hoffman, Matthew J.; Gregorek, G. M.

doi:10.2172/204225

Cited by 20 publications

(35 citation statements)

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“…The mid-series airfoils were experimentally validated at The Ohio State University [22]. Grit with a k c = 0.0019 was attached in a distinct pattern of varying distribution based on measured wind turbine roughness, where k was the roughness height and c was the model chord.…”

Section: Ic Historical Airfoil Designmentioning

confidence: 99%

Effect of Surface Roughness on Wind Turbine Performance

Ehrmann

2017

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Wind farm operators observe production deficits as machines age. Quantifying deterioration on individual components is difficult, but one potential explanation is accumulation of blade surface roughness. Historically, wind turbine airfoils were designed for lift to be insensitive to roughness by simulating roughness with trip strips. However, roughness was still shown to negatively affect performance. Furthermore, experiments illustrated distributed roughness is not properly simulated by trip strips. To understand how real-world roughness affects performance, field measurements of turbine-blade roughness were made and simulated on a NACA 63 3-418 airfoil in a wind tunnel. Insect roughness and paint chips were characterized and recreated as distributed roughness and a forward-facing step. Distributed roughness was tested in three heights and five density configurations. The model chord Reynolds number was varied between 0.8 to 4.8 × 10 6. Measurements of lift, drag, pitching moment, and boundary-layer transition were completed. Results indicate minimal effect from paint-chip roughness. As distributed roughness height and density increase, lift-curve slope, maximum lift, and lift-to-drag ratio decrease. As Reynolds number increases, bypass transition occurs earlier. The critical roughness Reynolds number varies between 178 to 318, within the historical range. Little sensitivity to pressure gradient is observed. At a chord Reynolds number of 3.2 × 10 6 , the maximum lift-to-drag ratio decreases 40% for 140 µm roughness, corresponding to a 2.3% loss in annual energy production. Simulated performance loss compares well to measured performance loss on an in-service wind turbine.

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Section: Ic Historical Airfoil Designmentioning

confidence: 99%

Effect of Surface Roughness on Wind Turbine Performance

Ehrmann

2017

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“…For DU 93‐W‐210 and DU 91‐W2–250, the experimental data at angles of attack between −10 and 20° are used, and the data at other angles of attack are computed through AirfoilPrep.xls , which is a simple tool from NREL. The aerodynamic results of five airfoils (S801, S810, S813, S815, S825) under different Reynolds numbers are adopted, too. These data are obtained for airfoils under clean and roughness conditions and then expanded to large angles of attack by AirfoilPrep.xls .…”

Section: Modified Fixed Point Iterative Methods and Performance Testsmentioning

confidence: 99%

Improved fixed point iterative method for blade element momentum computations

2017

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The blade element momentum (BEM) theory is widely used in aerodynamic performance calculations and optimization applications for wind turbines. The fixed point iterative method is the most commonly utilized technique to solve the BEM equations. However, this method sometimes does not converge to the physical solution, especially for the locations near the blade tip and root where the failure rate of the iterative method is high. The stability and accuracy of aerodynamic calculations and optimizations are greatly reduced due to this problem. The intrinsic mechanisms leading to convergence problems are addressed through both theoretical analysis and numerical tests. A term from the BEM equations equals to zero at a critical inflow angle is the source of the convergence problems. When the initial inflow angle is set larger than the critical inflow angle and the relaxation methodology is adopted, the convergence ability of the iterative method will be greatly enhanced. Numerical tests have been performed under different combinations of local tip speed ratio, local solidity, local twist and airfoil aerodynamic data. Results show that the simple iterative methods have a good convergence ability which will improve the aerodynamic or structural design of wind turbines.

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“…Figure 5. Airfoils response reconstruction in comparison with the experimental data for S801 airfoil (Ramsay et al, 1996) applying only the first order correction and with inclusion of the second order term. (a) Lift, (b) drag and (c) pitching moment.…”

Section: Second Order Correctionmentioning

confidence: 99%

“…This onset may result in a significant drop of the lift coefficient (C L ) and can be dangerous for the blade structure itself. (Ramsay et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

An improved second order dynamic stall model for wind turbine airfoils

Bangga¹,

Lutz²,

Arnold³

2020

Preprint

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Abstract. Robust and accurate dynamic stall modeling remains one of the most difficult tasks in wind turbine load calculations despite its long research effort in the past. In the present paper, a new second order dynamic stall model is developed with the main aim to model the higher harmonics of the vortex shedding while retaining its robustness for various flow conditions and airfoils. Comprehensive investigations and tests are performed by varying many flow parameters. The occurring physical characteristics for each case are discussed and evaluated in the present studies. The improved model is also tested on four different airfoils with different relative thicknesses. The validation against measurement data demonstrates that the improved model is able to reproduce the dynamic polar accurately without airfoil specific parameter calibration for each investigated flow condition and airfoil. This can deliver further benefit to industrial applications where experimental/reference data for calibrating the model is not always available.

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Effects of grit roughness and pitch oscillations on the S801 airfoil

Cited by 20 publications

References 0 publications

Effect of Surface Roughness on Wind Turbine Performance

Effect of Surface Roughness on Wind Turbine Performance

Improved fixed point iterative method for blade element momentum computations

An improved second order dynamic stall model for wind turbine airfoils

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