Category: Chapter 1: OpenVSP Fundamentals

Introduction

The NACA 5-Series airfoil is automatically generated from the ideal lift coefficient, maximum camber location, and thickness to chord ratio parameters by the functions that define the shape. The name of the airfoil will also be automatically updated according to convention. Additional details about the naming convention and shape functions can be found in “Theory of Wing Sections” by Abbott and von Doenhoff.

Introduction

The NACA 6-Series airfoil profile is automatically generated from the series designation (63, 64, 65, etc.) indicating the location of minimum pressure, the ideal lift coefficient, and the thickness to chord ratio according to the functions that specify the airfoil shape. The airfoil name will also automatically be altered as these parameters are changed according to convention. Note that you also have control over the mean line x/c = a value which indicates the location along the chord where the  chordwise loading changes from uniform to linearly decreasing toward the trailing edge.

The “6A” series aims to alleviate the sharp trailing edge cusp that is present in normal 6-series airfoils. It is important to note that for 6A series airfoils, the upper and lower surfaces are relatively straight from about 0.8c to the trailing edge which implies that a = 0.8 for this class of airfoils by definition. An update in OpenVSP v.3.31.0 fixed a = 0.8 and disabled the parameter for all NACA 6A airfoils.

[Abbot and Doenhoff, “Theory of Wing Sections”, section 6.8, 1959]

Introduction

The NACA 4-Series airfoil section automatically creates the profile based on the camber, location of maximum camber, and thickness to chord ratio based on the functions that define the shape. The NACA naming designation will be automatically set according to the convention for this airfoil. You may also choose a sharp or blunt trailing edge for this section type.

Introduction

The General Fuselage cross-section is a powerful tool for creating a variety of profiles using few parameters. Similar to the Superellipse, the height, width, and maximum width location may be set to create antisymmetric top and bottom halves if desired. Additional control has been provided in the form of the side tangency angles and the top/bottom/upper/lower strengths. Note that the top and bottom angle cannot be altered from zero. As with most of the “customizable” cross-sections, the simplest approximation is likely the best for modeling and analysis. Typically, you will find that the Edit Curve cross-section is the most-powerful type while leveraging a relatively few number of points.

Introduction

The Fuse File cross-section type applies a spline through a specified set of points in a formatted FXS file. The points will follow a closed path starting from the positive X-intercept and move clockwise about the coordinate plane until returning to the original, first point. The first and last points in this file MUST be the same for the file to work. The height and width of the cross-section will be automatically calculated and applied to your model once a FXS file is chosen. An example FXS file is given below.

In general, users should attempt to use the Edit Curve type rather than a Fuse File to match a particular profile. Edit Curve has significant advantages in fine control, point matching, and spline variation and will typically result in a much more accurate representation of the desired shape than with a Fuse File.

Example FXS File

OPENVSP_XSEC_FILE_V1
1.0  0.0
0.0  -1.0
-1.0   0.0
0.0   1.0
1.0  0.0