RCAIDE.Library.Methods.Aerodynamics.Common.Drag.parasite_drag_pylon

parasite_drag_pylon

parasite_drag_pylon(state, settings, geometry)

Computes the parasite drag coefficient for pylons as a proportion of nacelle drag.

Parameters:

• state (Data) –

  Flight conditions and aerodynamic state containing:

  • conditions.aerodynamics.coefficients.drag.parasitedict

    Dictionary of parasite drag data indexed by nacelle tag containing:

    • totalfloat

      Total parasite drag coefficient [unitless]

    • wetted_areafloat

      Wetted area [m²]

    • skin_frictionfloat

      Skin friction coefficient [unitless]

    • compressibility_factorfloat

      Compressibility correction factor [unitless]

    • reynolds_factorfloat

      Reynolds number correction factor [unitless]

    • form_factorfloat

      Form factor [unitless]

• settings (dict) – Aerodynamic analysis settings and parameters. Not used.

• geometry (Data) –

  Aircraft geometry containing:

  • reference_areafloat

    Reference area for drag coefficient calculation [m²]

  • networkslist

    List of propulsion networks containing propulsors

    • propulsorslist

      List of propulsor objects with nacelle attributes

      • nacelleNacelle, optional

        Nacelle object containing:

        • diameterfloat

          Diameter of the nacelle [m]

        • has_pylonbool

          Flag indicating if nacelle has an associated pylon

        • tagstr

          Unique identifier for the nacelle

Returns:

Results are stored in state.conditions.aerodynamics.coefficients.drag.parasite[nacelle.tag + ‘_pylon’]

Return type:

None

Notes

This function calculates the parasite drag coefficient for pylons based on the corresponding nacelle drag characteristics. The pylon drag is estimated as a proportion of the nacelle drag, accounting for the relative size and aerodynamic characteristics of the pylon compared to the nacelle.

Major Assumptions

• Pylon drag is proportional to nacelle drag

• Pylon factor of 0.2 represents a typical pylon-to-nacelle drag ratio

• Pylon inherits aerodynamic characteristics from associated nacelle

• Pylon reference area is based on nacelle diameter

• Pylon drag scales with the ratio of pylon to aircraft reference areas

Theory

The pylon drag is calculated as a proportion of the nacelle drag:

\(C_{D,pylon} = f_{pylon} \cdot C_{D,nacelle} \cdot \frac{S_{ref,pylon}}{S_{ref,aircraft}}\)

where:

• \(f_{pylon} = 0.2\) is the pylon factor

• \(C_{D,nacelle}\) is the nacelle parasite drag coefficient

• \(S_{ref,pylon} = \frac{\pi d_{nacelle}^2}{4}\) is the pylon reference area

• \(S_{ref,aircraft}\) is the aircraft reference area

The pylon inherits the aerodynamic characteristics from the nacelle:

\(C_{f,pylon} = C_{f,nacelle}\)

\(k_{comp,pylon} = k_{comp,nacelle}\)

\(k_{reyn,pylon} = k_{reyn,nacelle}\)

\(FF_{pylon} = FF_{nacelle}\)

The pylon wetted area is scaled proportionally:

\(S_{wet,pylon} = f_{pylon} \cdot S_{wet,nacelle}\)

Definitions

‘Pylon’

Structural support connecting an engine nacelle to the aircraft wing or fuselage.

References

[1] Stanford AA241 Course Notes