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UNH-CORE / RM2-tow-tank

Repository for UNH RM2 tow tank experiments.
MIT License
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Check NACA formulas #4

Closed petebachant closed 9 years ago

petebachant commented 9 years ago

Just double-check that the NACA profile formulas are correct in the 3D models.

petebachant commented 9 years ago

Root blade profile:

"root_chord"*0.21/0.2*(0.2969*((x+"root_chord"/2)/"root_chord")^0.5 - 0.1260*((x+"root_chord"/2)/"root_chord") - 0.3516*((x+"root_chord"/2)/"root_chord")^2 + 0.2843*((x+"root_chord"/2)/"root_chord")^3 - 0.1015*((x+"root_chord"/2)/"root_chord")^4)

Tip blade profile:

"tip_chord"*0.21/0.2*(0.2969*((x+"tip_chord"/2)/"tip_chord")^0.5 - 0.1260*((x+"tip_chord"/2)/"tip_chord") - 0.3516*((x+"tip_chord"/2)/"tip_chord")^2 + 0.2843*((x+"tip_chord"/2)/"tip_chord")^3 - 0.1015*((x+"tip_chord"/2)/"tip_chord")^4)

Strut profile:

"chord"*0.21/0.2*(0.2969*((x+"chord"/2)/"chord")^0.5 - 0.1260*((x+"chord"/2)/"chord") - 0.3516*((x+"chord"/2)/"chord")^2 + 0.2843*((x+"chord"/2)/"chord")^3 - 0.1015*((x+"chord"/2)/"chord")^4)

Blade mount spacer profile

"strut_chord"*0.21/0.2*(0.2969*((x+"strut_chord"/2)/"strut_chord")^0.5 - 0.1260*((x+"strut_chord"/2)/"strut_chord") - 0.3516*((x+"strut_chord"/2)/"strut_chord")^2 + 0.2843*((x+"strut_chord"/2)/"strut_chord")^3 - 0.1015*((x+"strut_chord"/2)/"strut_chord")^4)
petebachant commented 9 years ago

The formula for a NACA 0020 is shown below. This is where the 0.21/0.20 factor comes from.

image

NACA Report No. 460, "The characteristics of 78 related airfoil sections from tests in the variable-density wind tunnel"

petebachant commented 9 years ago

Note that these points form a flat trailing edge. Rev3 drawings for the blade, strut, and blade mount spacer have the thickness corrected to account for this, and the trailing edge fillets start where the flat edge would be.