LinAir 4

(Java -- available for most platforms)

LinAir calculates the aerodynamic characteristics of one or more lifting surfaces. The wings may be tapered, twisted, and swept with any dihedral angle. See the figure below for an example configuration. The input data may be specified interactively or read from a standard, XML input file. The program then computes the lift, drag, pitching moment, and lift distribution over each element. The angle of attack, twist, incidence angles, etc. may then be changed in order to trim the aircraft, to minimize drag, or simply to examine the effects of various design changes.

The program represents the lifting surfaces with discrete horseshoe vortices with strength determined by solution of a linear system of equations. Forces and moments are computed based on the velocities in the Trefftz plane, resulting in rapid turn-around and accurate induced drag (to within about 2%-4%). The effect of Mach number (in subsonic flow) is included as the program solves the Prandtl-Glauert equation. Parasite drag of the airfoil sections may be included with a quadratic curve fit of section drag versus lift coefficient. The program integrates the profile drag along the span and includes this in the total drag.

The program is ideal for computing the basic aerodynamics of a single wing or the interference of a wing and canard system, the effect of winglets on induced drag, or the tail size required for a given stability level. By placing several wing elements right behind each other, the effect of camber or control surface deflections can be evaluated. LinAir is used at NASA for quick analysis of unconventional configurations, at many major airframe companies, and several universities.

For version 4, LinAir has been re-written as a Java 2 application. Aside from the obvious benefit of cross-platform compatibility, this allows the code to be modular in nature and hence easily extensible, to the point that a user with some background in object-oriented programming and the LinAir SDK (release date still TBD) would be able to write custom plug-ins.

The changes and/or additions relative to LinAir 3 can be summarized as follows:

The user interface has received a complete overhaul.

• The number of panels allowed is now 60.
• An additional section property to define lift at zero angle of attack has been added.
• Section properties are now defined at both the panel root and tip.
• Panel twist is now defined by providing panel root and tip incidences (as in LinAir 1.4).
• Input file format is now XML.
• A file converter has been incorporated to translate from older style LinAir input files to the newer XML format.

The base distribution includes the following components:

• Geometry: Geometry provides facilities for generating and editing LinAir geometries and defining flow properties. An interactive 3-D view of the geometry is provided.
• Lift Distribution: Computes the lift and Cl distribution of each element. Provides both plots and a table of relevant results.
• Element Forces: Computes the forces and moments on each element and provides a table of relevant results.
• Alpha Sweep: Plots an alpha sweep of the geometry at a particular Mach number and over a given alpha range. The user has the option to plot any combination of the overall forces and moments.
• View XML Data: Analogous to the Input File component from previous versions of LinAir. Displays the input file in raw form.
• Convert Input Files: Imports older format (i.e. pre LinAir 4) input files and generates equivalent XML files.

Obtaining LinAir

Please contact Desktop Aeronautics directly regarding pricing and availability. Site licensing is also available.