aerosandbox.library.aerodynamics.inviscid#

Module Contents#

Functions#

induced_drag(lift, span, dynamic_pressure[, ...])

Computes the induced drag associated with a lifting planar wing.

oswalds_efficiency(taper_ratio, aspect_ratio[, sweep, ...])

Computes the Oswald's efficiency factor for a planar, tapered, swept wing.

optimal_taper_ratio([sweep])

Computes the optimal (minimum-induced-drag) taper ratio for a given quarter-chord sweep angle.

CL_over_Cl(aspect_ratio[, mach, sweep, Cl_is_compressible])

Returns the ratio of 3D lift coefficient (with compressibility) to the 2D lift coefficient.

induced_drag_ratio_from_ground_effect(h_over_b)

Gives the ratio of actual induced drag to free-flight induced drag experienced by a wing in ground effect.

Attributes#

machs

aerosandbox.library.aerodynamics.inviscid.induced_drag(lift, span, dynamic_pressure, oswalds_efficiency=1)[source]#

Computes the induced drag associated with a lifting planar wing.

Parameters:

  • lift – Lift force [Newtons]

  • span – Wing span [meters]

  • dynamic_pressure – Dynamic pressure [Pascals]

  • oswalds_efficiency – Oswald’s efficiency factor [-]

Returns: Induced drag force [Newtons]

aerosandbox.library.aerodynamics.inviscid.oswalds_efficiency(taper_ratio, aspect_ratio, sweep=0.0, fuselage_diameter_to_span_ratio=0.0, method='nita_scholz')[source]#

Computes the Oswald’s efficiency factor for a planar, tapered, swept wing.

Based on “Estimating the Oswald Factor from Basic Aircraft Geometrical Parameters” by M. Nita, D. Scholz; Hamburg Univ. of Applied Sciences, 2012. https://www.fzt.haw-hamburg.de/pers/Scholz/OPerA/OPerA_PUB_DLRK_12-09-10.pdf

Implementation of Section 5 from the above paper.

Only valid for backwards-swept wings; i.e. 0 <= sweep < 90.

Parameters:

  • taper_ratio (float) – Taper ratio of the wing (tip_chord / root_chord) [-]

  • aspect_ratio (float) – Aspect ratio of the wing (b^2 / S) [-]

  • sweep (float) – Wing quarter-chord sweep angle [deg]

  • fuselage_diameter_to_span_ratio (float) –

Return type:

float

Returns: Oswald’s efficiency factor [-]

aerosandbox.library.aerodynamics.inviscid.optimal_taper_ratio(sweep=0.0)[source]#

Computes the optimal (minimum-induced-drag) taper ratio for a given quarter-chord sweep angle.

Based on “Estimating the Oswald Factor from Basic Aircraft Geometrical Parameters” by M. Nita, D. Scholz; Hamburg Univ. of Applied Sciences, 2012.

Only valid for backwards-swept wings; i.e. 0 <= sweep < 90.

Parameters:

sweep – Wing quarter-chord sweep angle [deg]

Return type:

float

Returns: Optimal taper ratio

aerosandbox.library.aerodynamics.inviscid.CL_over_Cl(aspect_ratio, mach=0.0, sweep=0.0, Cl_is_compressible=True)[source]#

Returns the ratio of 3D lift coefficient (with compressibility) to the 2D lift coefficient.

Specifically: CL_3D / CL_2D

Parameters:

  • aspect_ratio (float) – The aspect ratio of the wing.

  • mach (float) – The freestream Mach number.

  • sweep (float) – The sweep of the wing, in degrees. To be most accurate, this should be the sweep at the locus of

  • wing. (thickest points along the) –

  • Cl_is_compressible (bool) – This flag indicates whether the 2D airfoil data already has compressibility effects

  • modeled. –

    For example:

    • If this flag is True, this function returns: CL_3D / CL_2D, where CL_2D is the sectional lift

    coefficient based on the local profile at the freestream mach number.

    • If this flag is False, this function returns: CL_3D / CL_2D_at_mach_zero, where CL_2D_… is the

    sectional lift coefficient based on the local profile at mach zero.

    For most accurate results, set this flag to True, and then model profile characteristics separately.

Return type:

float

aerosandbox.library.aerodynamics.inviscid.induced_drag_ratio_from_ground_effect(h_over_b)[source]#

Gives the ratio of actual induced drag to free-flight induced drag experienced by a wing in ground effect. Artificially smoothed below around h/b == 0.05 to retain differentiability and practicality. Source: W. F. Phillips, D. F. Hunsaker, “Lifting-Line Predictions for Induced Drag and Lift in Ground Effect”.

Using Equation 5 from the paper, which is modified from a model from Torenbeek:

Torenbeek, E. “Ground Effects”, 1982.

Parameters:

h_over_b (float) – (Height above ground) divided by (wingspan).

Returns:

Ratio of induced drag in ground effect to induced drag out of ground effect [unitless]

aerosandbox.library.aerodynamics.inviscid.machs[source]#