The Comp Geom tool is a geometry intersection and analysis algorithm that will compute the theoretical and wetted areas and volumes of your OpenVSP model, producing an intersected triangulated mesh. Comp Geom is widely integrated into other analyses and functions within OpenVSP such as VSPAERO’s Panel mode and the Parasite Drag tool.
The chordwise length and end angles may be further refined for Control Surfaces (CS). The chordwise length may be set as constant for the span of the surface or may have different lengths depending on your application. The end angles may also be set manually and either set to be equal or different than each other. By default, the angles are defined to align with the component X-axis. The leading or trailing edge is the reference for these angles. For example, an angle setting of 90° will result in the CS end to be normal to the trailing or leading edge of the wing. This is very easily visualized with highly swept wings. By leveraging unique lengths and angles at the start and end of a CS, users are capable of defining a variety of interesting deflection surfaces for analysis, export, or visualization.
Users should also be aware that the Num Points in the Surface End Angle box sets the number of points used to spline the UW curve for the CS. Very low numbers of points will result in a curved or “wiggled” CS boundary in some cases but you’ll find that the default value of 15 will result in a generally straight side. Highly variable or stretched surfaces such as a heavily swept vertical tail root fairing or tip will potentially lead to odd deflections in the CS boundary. In these cases, try adjusting the length or Num Points to clean up the edges.
Subsurface Finite Lines are similar to subsurface Lines except that the start and end U and W locations may be controlled independently at any points on a component surface. Finite Lines are an excellent way to mark regions where you want to include additional feature lines or intersections, particularly when working with exported file formats. Note that Finite Lines do not have the ability to section off regions of the surface in the same way as other types because they typically will not completely enclose or split the surface. Similar to Lines, Finite Line subsurfaces are an interesting way of visualizing the surface Bezier curves defined by the component parameters.
In this tutorial, the Snap-To feature is used to demonstrate how a model may be queried for component collision in a “real-world” application such as rotor strike. The demonstration shows how a seemingly small change to a model parameter, from a certain orientation, can have a significant impact on the aircraft. Snap-To can be a very powerful tool for checking a model for impact and clearance.
Working from the Snap-To window, you will have access to all of the settings that drive the collision detection process including the geometry Set, the target distance, and the manipulated parameter. You may also check the clearance of all components in the Set with a single click!
To perform a manual collision detection or Snap operation, select the desired parameter to be altered from the dropdown menus or simply drag the parameter button to the window to select automatically. Choose your desired target minimum distance and Set and then click “Increase” or “Decrease” as needed to change the model.
Note that the manual collision detection method tends to be more reliable than the interactive “click-and-drag” mode because the manual mode is not dependent on the slider range for updates.
