Heritage OpenVSP v2 models may be imported from the Import… menu. In most cases, the translation from OpenVSP v2 components to their OpenVSP 3 counterparts is very straightforward and has been automated as much as possible. For example, version 2 parameters defining a Wing will be directly applied to the matching parameters in version 3. A similar process occurs for fuselages cross-sections and skinning parameters. However, some VSP2 parameters or methods do not exist in VSP3 models or components and may require some manual iteration to match the design exactly. In such cases, it is recommended that the VSP2 model is imported along with a mesh from OpenVSP v2 to provide a guide for any required corrections.
Wireframes of Hermite (HRM) or Plot3D (P3D) format may be imported to OpenVSP models from the Import… menu. Hermite files have the option of importing as triangulated meshes or as wireframes. Note that some Hermite components may import with the reflected surface normals inverted which will be easily identified by shading the surface, resulting in a dark or shadowed effect.
Surface meshes such as *.tri files may be imported to your OpenVSP model under the Import… menu. In the case of meshes, both those created within OpenVSP and imported from elsewhere, if the OpenVSP model is saved with a MeshGeom present, the entire mesh file is appended to the VSP3 file which can quickly lead to excessively large file sizes. OpenVSP is also capable of importing and operating on open or non-watertight meshes.
When creating meshes outside of OpenVSP with the intent of importing into a model, you may sometimes find that surface normals are flipped or there are gaps in the mesh. In some cases, the mesh will fail to import altogether. In these cases, you should try to export the mesh in ASCII format which has been demonstrated to be a more reliable import format.
Excrescence adds drag components from features that are difficult or unrealistic to model such as antennae, sensors/probes, access panels, surface roughness, ice, bugs, etc. To account for these “real world” features of a model’s parasitic drag, users may apply drag excrescence in a variety of ways. Drag counts (CD x 10^4) and drag coefficient (CD) may be added as fixed amounts to the total. Percentages may also be added as either a percent of geometric drag coefficient (% of CD_Geom) or as percent margin (% Margin) which may only be added once and will remain a fixed percentage of the Total CD rather than being relative to the geometric CD. Excrescence may also be added as a fixed drag area (D/q) which is invariant with the input flow conditions. By leveraging drag excrescence, a parasitic drag model may be tuned to very accurately match existing aircraft or test data and account for non-ideal geometric features.
Model components may be grouped with model tree ancestors of the same type in the Parasite Drag tool so that individual wetted area contributions are summed and form factors are applied to the group. Grouped components may be viewed by clicking the component name where (+) is displayed. For Wings that are generally reflected across XZ by default, the right and left sides are automatically grouped. To group a component with an ancestor, click the drop-down menu in the component row and select on of the available ancestors. The grouped component will contribute its wetted area to that of the ancestor and inherit the ancestor’s form factor, reference length, etc. An example of this would be to group a canopy with a fuselage such that the canopy is included in the fuselage parasitic drag component.
