RCAIDE.Library.Methods.Aerodynamics.Common.Drag.miscellaneous_drag

miscellaneous_drag

miscellaneous_drag(state, settings, geometry)

Computes the miscellaneous drag coefficient associated with aircraft components and configurations.

Parameters:

• state (Data) –

  Flight conditions containing:

  • conditions.freestream.mach_numberfloat

    Freestream Mach number [unitless]

• settings (dict) – Aerodynamic analysis settings and parameters

• geometry (Data) –

  Aircraft geometry containing:

  • reference_areafloat

    Reference area for drag coefficient calculation [m²]

  • landing_gearslist

    List of landing gear objects containing:

    • gear_extendedbool

      Flag indicating if landing gear is deployed

    • fairingbool

      Flag indicating if landing gear has fairings

    • wheelsint

      Number of wheels on the landing gear

    • tire_diameterfloat

      Diameter of landing gear tires [m]

    • tire_widthfloat

      Width of landing gear tires [m]

  • wingslist

    List of wing objects containing:

    • areas.wettedfloat

      Wetted area of the wing [m²]

  • fuselageslist

    List of fuselage objects containing:

    • areas.wettedfloat

      Wetted area of the fuselage [m²]

  • boomslist

    List of boom objects containing:

    • areas.wettedfloat

      Wetted area of the boom [m²]

  • networkslist

    List of propulsion networks containing propulsors

    • propulsorslist

      List of propulsor objects with nacelle attributes

      • nacelleNacelle, optional

        Nacelle object containing:

        • areas.wettedfloat

          Wetted area of the nacelle [m²]

        • diameterfloat

          Diameter of the nacelle [m]

Returns:

Results are stored in state.conditions.aerodynamics.coefficients.drag.miscellaneous.total

Return type:

None

Notes

This function calculates the miscellaneous drag coefficient including landing gear drag, subsonic miscellaneous drag based on wetted area, and supersonic nacelle base drag and fuselage upsweep drag. The calculation method varies between subsonic and supersonic flight regimes.

Major Assumptions

• Landing gear drag is proportional to tire frontal area

• Subsonic miscellaneous drag correlates with total wetted area

• Supersonic drag includes nacelle base drag and fuselage upsweep effects

• Landing gear fairings reduce drag by approximately 50%

• Basic empirical correlations are valid for typical transport aircraft

Theory

Landing Gear Drag: The landing gear drag coefficient is calculated as:

\(C_{D,LG} = \sum_{i=1}^{n} N_{wheels,i} \cdot C_{D,i} \cdot \frac{D_i \cdot W_i}{S_{ref}}\)

where:

• \(N_{wheels,i}\) is the number of wheels on landing gear \(i\)

• \(C_{D,i}\) is 0.15 for faired landing gear or 0.30 for unfaired

• \(D_i\) and \(W_i\) are the tire diameter and width [m]

• \(S_{ref}\) is the reference area [m²]

Subsonic Miscellaneous Drag: For Mach ≤ 1.0, the miscellaneous drag is:

\(C_{D,misc} = \frac{0.40(0.0184 + 0.000469 S_{wet} - 1.13 \times 10^{-7} S_{wet}^2)}{S_{ref}}\)

where \(S_{wet}\) is the total wetted area [m²].

Supersonic Miscellaneous Drag: For Mach > 1.0, the drag includes nacelle base drag and fuselage upsweep:

\(C_{D,nacelle} = \sum_{i=1}^{n} \frac{0.5}{12} \pi D_i \cdot 0.2 / S_{ref}\)

\(C_{D,upsweep} = \frac{0.006}{S_{ref}}\)

\(C_{D,misc} = C_{D,nacelle} + C_{D,upsweep}\)

Definitions

‘Miscellaneous Drag’

Drag component not accounted for by other drag categories, including landing gear, nacelle base, and fuselage upsweep effects.

‘Landing Gear Drag’

Additional drag caused by deployed landing gear, proportional to tire frontal area.

‘Nacelle Base Drag’

Drag caused by the base area of nacelles in supersonic flow.

References

[1] Stanford AA241 Course Notes. http://aerodesign.stanford.edu/aircraftdesign/aircraftdesign.html