RCAIDE.Library.Methods.Aerodynamics.Common.Drag.parasite_drag_fuselage

parasite_drag_fuselage

parasite_drag_fuselage(state, settings, fuselage)

Computes the parasite drag coefficient for a fuselage or boom accounting for compressibility effects.

Parameters:

• state (Data) –

  Flight conditions containing:

  • conditions.freestream.mach_numberfloat

    Freestream Mach number [unitless]

  • conditions.freestream.temperaturefloat

    Freestream static temperature [K]

  • conditions.freestream.reynolds_numberfloat

    Freestream Reynolds number per unit length [unitless/m]

• settings (dict) –

  Aerodynamic analysis settings containing:

  • fuselage_parasite_drag_form_factorfloat

    Form factor for fuselage parasite drag [unitless]

  • supersonic.fuselage_parasite_drag_begin_blend_machfloat

    Mach number at which supersonic blending begins [unitless]

  • supersonic.fuselage_parasite_drag_end_blend_machfloat

    Mach number at which supersonic blending ends [unitless]

• fuselage (Data) –

  Fuselage geometry containing:

  • tagstr

    Unique identifier for the fuselage

  • areas.front_projectedfloat

    Front projected area [m²]

  • areas.wettedfloat

    Wetted area [m²]

  • lengths.totalfloat

    Total length of fuselage [m]

  • effective_diameterfloat

    Effective diameter of fuselage [m]

Returns:

Results are stored in state.conditions.aerodynamics.coefficients.drag.parasite[fuselage.tag]

Return type:

None

Notes

This function calculates the parasite drag coefficient for a fuselage or boom using compressible turbulent flat plate theory with form factor corrections. The calculation accounts for compressibility effects through Mach number-dependent form factors and uses cubic spline blending for the transonic regime.

Major Assumptions

• Fully turbulent boundary layer over the entire fuselage

• Cylindrical body approximation for form factor calculations

• Compressible turbulent flat plate skin friction correlation

• Cubic spline blending smooths transition between subsonic and supersonic regimes

• Form factor accounts for pressure drag due to body shape

Theory

The fuselage Reynolds number is:

\(Re_{fus} = Re \cdot l_{fus}\)

where \(Re\) is the freestream Reynolds number per unit length and \(l_{fus}\) is the fuselage length.

The skin friction coefficient is calculated using compressible turbulent flat plate theory:

\(C_f = f(Re_{fus}, M, T)\)

The diameter-to-length ratio is:

\(d/l = \frac{d_{fus}}{l_{fus}}\)

For subsonic flow (M ≤ 1.0), the form factor parameters are:

\(D = \sqrt{1 - (1-M^2)(d/l)^2}\) for M < 0.95

\(D = \sqrt{1 - (d/l)^2}\) for M ≥ 0.95

\(a = \frac{2(1-M^2)(d/l)^2(\text{arctanh}(D)-D)}{D^3}\) for M < 0.95

\(a = \frac{2(d/l)^2(\text{arctanh}(D)-D)}{D^3}\) for M ≥ 0.95

The maximum velocity perturbation is:

\(\frac{\Delta u_{max}}{u_{\infty}} = \frac{a}{(2-a)\sqrt{1-M^2}}\) for M < 0.95

\(\frac{\Delta u_{max}}{u_{\infty}} = \frac{a}{2-a}\) for M ≥ 0.95

The form factor is:

\(k_{fus} = (1 + FF \cdot \frac{\Delta u_{max}}{u_{\infty}})^2\)

where \(FF\) is the user-specified form factor.

For supersonic flow, the form factor is calculated using cubic spline blending between subsonic and supersonic correlations.

The parasite drag coefficient is:

\(C_{D,parasite} = k_{fus} \cdot C_f \cdot \frac{S_{wet}}{S_{ref}}\)

Definitions

‘Parasite Drag’

Drag component caused by viscous effects and pressure forces on the aircraft surface.

‘Form Factor’

Multiplier accounting for the increase in drag due to body shape compared to a flat plate.

‘Compressibility Effects’

Changes in aerodynamic characteristics due to compressible flow effects at high Mach numbers.

References

[1] Stanford AA241 Course Notes

See also

RCAIDE.Library.Methods.Aerodynamics.Common.Drag.compressible_turbulent_flat_plate, RCAIDE.Library.Methods.Utilities.Cubic_Spline_Blender