RCAIDE.Library.Methods.Aerodynamics.Common.Drag.windmilling_drag

windmilling_drag#

windmilling_drag(geometry, state)[source]#

Computes windmilling drag coefficient for turbofan engines in windmilling condition.

Parameters:

  • geometry (Vehicle) –

    Vehicle geometry object containing:
    • reference_areafloat, optional

      Reference area for drag coefficient calculation [m^2]

    • wingslist

      List of wing objects with sref attribute [m^2]

    • networkslist
      List of propulsion networks containing propulsors
      • propulsorslist
        List of propulsor objects with nacelle attributes
        • nacelleNacelle, optional

          Nacelle object with areas.wetted attribute [m^2]

  • state (State) – State object to store results in conditions.aerodynamics.coefficients.drag.windmilling

Returns:

windmilling_drag_coefficient – Windmilling drag coefficient [unitless]

Return type:

float

Notes

This function calculates the windmilling drag coefficient for turbofan engines when they are not producing thrust but are still rotating due to incoming airflow. The calculation is based on empirical correlations from wind tunnel testing.

Major Assumptions

  • Turbofan engines are in windmilling condition

  • Drag is primarily due to nacelle wetted area

  • Linear relationship between wetted area and drag coefficient

Theory

The windmilling drag coefficient is calculated using an empirical correlation:

\(C_{D,windmilling} = 0.007274 \frac{S_{wet,nacelle}}{S_{ref}}\)

where:

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

  • \(S_{wet,nacelle}\) is the total wetted area of all nacelles [m²]

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

Definitions

‘Windmilling’

Condition where a turbofan engine is not producing thrust but continues to rotate due to incoming airflow, typically during engine failure or shutdown scenarios.

‘Wetted Area’

Total surface area of the nacelle exposed to the airflow, used as a proxy for the drag-producing surface area.

References

[1] Askin, T. (2002). “Aircraft Engine Integration and Installation Effects.” Virginia Tech Thesis. http://www.dept.aoe.vt.edu/~mason/Mason_f/AskinThesis2002_13.pdf

See also

RCAIDE.Library.Components.Wings.Main_Wing