NacaDiscipline

from philote_examples import NacaDiscipline

Philote discipline that generates NACA 4-digit airfoil coordinates.

Produces airfoil coordinates in XFOIL Selig format (TE -> upper -> LE -> lower -> TE), compatible with the XfoilDiscipline inputs.

Inherits from: philote_mdo.general.ExplicitDiscipline

Constructor

NacaDiscipline(n_points: int)

Parameters

Name	Type	Description
n_points	int	Total number of coordinate points in the output contour

Properties set by constructor

Property	Value	Description
_is_continuous	True	Discipline outputs are continuous
_is_differentiable	True	Discipline outputs are differentiable
_provides_gradients	True	Discipline provides analytical gradients

Methods

setup()

Defines inputs and outputs for the NACA discipline.

Inputs:

Name	Shape	Units	Description
camber	(1,)	--	Maximum camber (1st NACA digit)
camber_loc	(1,)	--	Location of maximum camber (2nd NACA digit)
thickness	(1,)	--	Maximum thickness (3rd-4th NACA digits)

Outputs:

Name	Shape	Units	Description
airfoil_x	(n_points,)	--	Airfoil x-coordinates in Selig format
airfoil_y	(n_points,)	--	Airfoil y-coordinates in Selig format

setup_partials()

Declares all partial derivatives. Declares partials of both outputs (airfoil_x, airfoil_y) with respect to all three inputs (camber, camber_loc, thickness).

compute(inputs, outputs)

Generates NACA 4-digit airfoil coordinates.

The input values are internally rescaled:

• camber is divided by 100 (e.g., 2 becomes 0.02)
• camber_loc is divided by 10 (e.g., 4 becomes 0.4)
• thickness is divided by 100 (e.g., 12 becomes 0.12)

Coordinates are computed using cosine-spaced x-stations and output in Selig format (upper surface reversed, concatenated with lower surface).

compute_partials(inputs, partials)

Computes analytical partial derivatives via chain rule through the NACA 4-digit thickness distribution and mean camber line formulas.

The Jacobian includes scaling factors for the input transformations:

• $\partial / \partial\text{camber}$: scaled by 0.01
• $\partial / \partial\text{camber\_loc}$: scaled by 0.1
• $\partial / \partial\text{thickness}$: scaled by 0.01

Module-Level Functions

The following functions in philote_examples.naca support the discipline:

_thickness_poly(x)

NACA 4-digit thickness polynomial (without the $5t$ scaling factor).

$$\text{poly}(x) = 0.2969\sqrt{x} - 0.1260\,x - 0.3516\,x^2 + 0.2843\,x^3 - 0.1015\,x^4$$

_thickness(x, t)

Full NACA 4-digit thickness distribution: $y_t = 5t \cdot \text{poly}(x)$.

_camber(x, m, p)

Mean camber line $y_c$ and its slope $dy_c/dx$ for given max camber $m$ and position $p$.

_camber_partials(x, m, p)

Partial derivatives of the camber line and slope with respect to $m$ and $p$:

• dyc_dm, dyc_dp -- partials of $y_c$
• ddyc_dm, ddyc_dp -- partials of $dy_c/dx$

_selig(upper, lower)

Combines upper and lower surface arrays in Selig order: upper reversed, concatenated with lower (excluding the shared leading-edge point).

Example

from philote_examples import NacaDiscipline
from philote_mdo.general import run_server

# Create discipline with 100 contour points
discipline = NacaDiscipline(n_points=100)

# Serve over gRPC
run_server(discipline, port=50051)