pyairpar

Author: Matthew G Lauer

Source code can be found here. Documentation can be found here.

Welcome

To the documentation page for pyairpar, an object-oriented Python 3 package for single- and multi-element Bézier-parametrized airfoil design. This Bézier parametrization framework is being presented at the 2022 AIAA Aviation Conference in Chicago, IL under the title "A Parametrization Framework for Multi-Element Airfoil Systems Using Bézier Curves."

Motivation

The creation of this package was motivated by a research aircraft application: the aerodynamic design of a propulsion-airframe-integrated commercial transport aircraft. The cross-section of a wing or fuselage with integrated propulsors can be represented, with some sacrifice in fidelity, as a quasi-2D multi-element airfoil system. This multi-element airfoil system is comprised of a main airfoil (either the fuselage or main airfoil element), a hub airfoil (representing the cross-section of an axisymmetric hub), and a nacelle airfoil (representing the cross-section of an axisymmetric nacelle).

By using a well-defined parametrization framework, this airfoil system can be morphed or deformed in a variety of ways simply by changing the value of any of the input parameters. These parameters are represented by pyairpar.core.param.Param objects in this framework. Defining the airfoil system in this way provides an intuitive I/O interface for shape optimization or parametric sweeps.

In pyairpar, airfoils are comprised of a set of connected, arbitrary-order Bézier curves. Because Bézier curves have the property that they always pass through their starting and ending control points, Bézier curve "joints" can be used to force the airfoil surface to pass through a particular point in space. pyairpar forces all Bézier curve joints within an airfoil to be G⁰, G¹, and G² continuous, which is useful in general for surface smoothness and in particular for computational fluid dynamics (CFD) packages where a discontinuity in the curvature value at a point can cause undesired flow properties or even unconverged results.

Applications

It is the hope of the author that pyairpar is sufficiently flexible to be used for airfoil applications of varying complexities, from simple, single-airfoil design to high-fidelity, multi-element airfoil shape optimization. Other common multi-element airfoil systems, such as the high-lift configuration on an aircraft, are also target applications for this software package.

One utility provided in this software package which may be useful in the start-up phase of airfoil design is pyairpar.utils.airfoil_matching.match_airfoil(). This modules allows the matching of a particular parametrization to any public airfoil geometry at airfoiltools.com using the gradient-based "SLSQP" optimizer.

Acknowledgments

This work was supported by NASA under award number 80NSSC19M0125 as part of the Center for High-Efficiency Electrical Technologies for Aircraft (CHEETA). Logo courtesy of NASA.

Contact Information

Author: Matthew G Lauer

Email: mlauer2015@gmail.com

Version Notes

1.1.1

• Corrections to README.md for PyPi long project description (images not showing properly)

1.1.0

• Made corrections on BaseAirfoilParams and AnchorPoint Args domains
• Added support for zero-curvature anchor points using 180-degree curvature control arm angles (or 90-degree curvature control arm angles for the leading edge)
• Added support for sharp-juncture anchor points with R=0 or R_{LE}=0. Adding multiple consecutive sharp juncture anchor points creates line segments. Adding sharp-juncture anchor points violates the principle of slope and curvature continuity, but may be useful in some cases.