naca0012

naca0012

naca0012

Table of Contents

• 1. NACA0012 lift and drag from 0-180
  • 1.1. Data– Cl Cd vs. aoa
• 2. Naca0012 Stall
  • 2.1. dynamic stall
• 3. Numerical Modelling for naca0012 at Stalled AOAs
  • 3.1. Turbulence Model for Stalled airfoil
• 4. free surface & naca 0012
• 5. References

1 NACA0012 lift and drag from 0-180

naca0012 polar.doc

drag polar

Cl vs Cd at AOA 0-90 degree

numerical results of lift, drag, and presure coefficients at Re=1e5 based on RANS Spalart– Allmaras turbulence model, two peak Cl at AOA 11.5 and 42 degree ¹

Re - 2-88 x 106 and 1.44 x 10 6³

experimental data ⁴

naca 0018 comparing experimental vs cfd vs post-stall correction ⁵

² Marco 2016 Direct numerical simulation of an aerofoil at high angle of

1.1 Data– Cl Cd vs. aoa

Sheldahl, 1981 Sheldahl, Robert E., and Paul C. Klimas. Aerodynamic characteristics of seven symmetrical airfoil sections through 180-degree angle of attack for use in aerodynamic analysis of vertical axis wind turbines. No. SAND-80-2114. Sandia National Labs., Albuquerque, NM (USA), 1981. Re=4e4 AOA Cl Cd 0 0 0.0175 1 0.11 0.0177 2 0.22 0.0181 3 0.3376 0.0189 4 0.4464 0.0199 5 0.5276 0.0218 6 0.6115 0.0232 8 0.0615 0.072 10 0.0344 0.1 11 0.0869 0.117 12 0.1406 0.134 13 0.1945 0.152 14 0.2484 0.171 15 0.3024 0.19 16 0.3563 0.21 17 0.4107 0.231 18 0.4644 0.252 19 0.5178 0.274 20 0.5708 0.297 21 0.6232 0.32 22 0.6755 0.344 23 0.7283 0.369 24 0.7809 0.394 25 0.834 0.42 26 0.8873 0.446 27 0.9407 0.473 30 0.915 0.57 35 1.02 0.745 40 1.075 0.92 45 1.085 1.075 50 1.04 1.215 55 0.965 1.345 60 0.875 1.47 65 0.765 1.575 70 0.65 1.665 75 0.515 1.735 80 0.37 1.78E+00 85 0.22 1.8 90 0.07 1.8 95 -0.07 1.78 100 -0.22 1.75 105 -0.37 1.7 110 -0.51 1.635 115 -0.62 1.555 120 -0.735 1.465 125 -0.84 1.35 130 -0.91 1.225 135 -0.945 1.085 140 -0.945 0.925 145 -0.91 0.755 150 -0.85 0.575 155 -0.74 0.42 160 -0.66 0.32 165 -0.675 0.23 170 -0.85 0.14 175 -0.69 0.055 180 0 0.025

2 Naca0012 Stall

stall angle vs Re: stall angle is a function of Re

• 8 at Re=135k (Shen's data, used in BEM)
• 10 at Re=1e5 (Xfoil)
• 12 at Re=2e5 (Xfoil)
• 5-6 at Re=4e4 (Sheldahl 1981) ⁴
• aoa< 10 degree:
  • no flow separation of the mean flow⁶
  • time avergaged shear stress is positive at every point on the airfoil surface
• Stall angle is around 13 degree

stall types?

More detail, refer to "stall" in theory.html

thin airfoil stall

flow separation at the LE with reattachment

at a point which moves progressively rearward with increasing AOA.

Is nacaoo12 thin airfoil stall or not?

Turbulence Models for stall simulation?

• B. Stockdill et al⁶. studied naca0012 at AOA 20 degrees and Re_c = 1e5 with Spalart Almaras, Speziable k-τ model and adaptive k-τ model in both

steady and unsteay cases. unsteady >> k-τ model and adaptive k-τ model steady >> Spalart Almaras The numerical results show that adaptive k-τ model produces non-periodic lift and drag, while k-τ model yields purely periodic lift and drag.

2.1 dynamic stall

NASA Techical note D-8382 (Carr 1977 )⁷

3 Numerical Modelling for naca0012 at Stalled AOAs

NACA0012 at AOA 20 (⁸, Computational Fluid Dynamics Journal ) steady and unsteady behavior of NACA0012 at AOA 20 using 3 different turbulence models, namely Spalart Allmaras, Spezialek−τ model, and adaptive k−τ model. Unsteady results of Speziable k -τ model and Adaptive k -τ model were compared.

3.1 Turbulence Model for Stalled airfoil

keywords: Turbulence model; Flow separation; Stall SST K-ω

1. The k-o SST model overpredict the drag coefficient when AOA vairies between 30 and 150 degree.⁵
2. failed to capture the lift at AOA between 150 and 180 degrees. ⁵

Stall is difficult to quantify experimentally

Post stall data >> Extrapolation

Extraplolation methods:

• Viterna and Corrigan

4 free surface & naca 0012

Adjali, Saadia, et al. "A numerical study of steady 2D flow around NACA 0015 and NACA 0012 hydrofoil with free surface using VOF method." EPJ Web of Conferences. Vol. 92. EDP Sciences, 2015. Numerical Study of Unsteady Wave-Generation for Flow Around NACA 0024 Airfoil

5 References

 

Footnotes:

¹

Park, Byung Ho, and Yong Oun Han. "Steady Aerodynamic Characteristics of Two-Dimensional NACA0012 Airfoil for One Revolution Angle of Attack." International Journal of Aeronautical & Space Sciences (2018): 1-14. ² Timmer WA (2010) Aerodynamic characteristics of wind turbine blade airfoils at high angles-of-attack. European Wind Energy Association

²

DEFINITION NOT FOUND.

³

Gregory, Nigel, and C. L. O'reilly. Low-Speed aerodynamic characteristics of NACA 0012 aerofoil section, including the effects of upper-surface roughness simulating hoar frost. London: HM Stationery Office, 1973.

⁴

Sheldahl, Robert E., and Paul C. Klimas. Aerodynamic characteristics of seven symmetrical airfoil sections through 180-degree angle of attack for use in aerodynamic analysis of vertical axis wind turbines. No. SAND-80-2114. Sandia National Labs., Albuquerque, NM (USA), 1981.

2D NACA 0012 Airfoil Validation Case nasa

Selig, Michael S., ed. Summary of low speed airfoil data. Vol. 1. SoarTech, 1995.

Timmer, W. A., and R. P. J. O. M. Van Rooij. "Summary of the Delft University wind turbine dedicated airfoils." Journal of solar energy engineering 125.4 (2003): 488-496.

Selig, Michael S., and James J. Guglielmo. "High-lift low Reynolds number airfoil design." Journal of aircraft 34.1 (1997): 72-79

⁵

> Bianchini, Alessandro, et al. "An Experimental and Numerical Assessment of Airfoil Polars for Use in Darrieus Wind Turbines—Part II: Post-stall Data Extrapolation Methods." Journal of Engineering for Gas Turbines and Power 138.3 (2016): 032603.

⁶

Stockdill, B., et al. "Simulation of unsteady turbulent flow over a stalled airfoil." Computational Fluid Dynamics Journal 14.4 (2006): 359.

⁷

Carr, Lawrence W., Kenneth W. McAlister, and William J. McCroskey. "Analysis of the development of dynamic stall based on oscillating airfoil experiments." (1977).

⁸

DEFINITION NOT FOUND.

Author: kemina

Created: 2019-03-26 Tue 20:57

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