Linear parameter linking in OpenVSP establishes a linear relationship between any two parameters according to a scale and offset by B = A*Scale + Offset where B is the dependent variable and A is the independent or driving variable. Note that you should use Links when specific linear relationships, including equality, are needed in your model but should avoid linking every parameter by default. As with many features in OpenVSP, less is often more.
The topics below demonstrate how to use the Snap-To feature in OpenVSP. Snap-To is an interactive collision detection function that enables placing components at a fixed surface normal distance from one another or to check for clearance or collision in a model. For example, a component may be rotated or translated through a range of motion to ensure that adjacent parts are not struck. Alternatively, a component may be placed a fixed distance relative to another set of components with a single click.
User Parameters are unique variables that you can leverage to control or link your model in ways that aren’t available by default in OpenVSP. There are always 16 predefined user parameters that will always have the same Group, Name, and ParmID regardless of which model you are using. This makes them very robust in scripting and automation. Perhaps of greater interest to the designer is the ability to create custom parameters and adjust them from this menu. Once a user parameter has been created, the parameter is available for adjustment or linking as with any other model parameter. For example, a wing may be sized according to gross weight and wing loading rather than by span and area. An propeller may be sized according to the thrust, disk loading, tip speed, etc. So you can see how leveraging User Parameters in your model can enable a wider variety of parametric variation than would otherwise be available by default.
The Wedge airfoil enables users to set sharp, wedged leading and trailing edges based on a maximum thickness to chord ratio and the chord location of this maximum thickness. Users may also choose to set a section along the chord of constant thickness with the Flat Up parameter which results in a six-sided section rather than a traditional wedge. The U-location of feature points on this cross-section may also be modified to attach to associated points on neighboring cross-sections.
Variable Presets are an incredibly versatile and powerful function within OpenVSP that enable multiple, preconfigured parameter settings to be swapped with the click of a button. Variable Presets differ from Design Variables in that the presets are not intended to be interacted with or altered outside of OpenVSP for large design space explorations. Rather, the presets are intended to act as stored configurations of various settings that can be quickly switched within the GUI. For example, you can use the basic frame of a transport aircraft and variable presets to switch between different manufacturers and passenger classes in a single model. You can quickly switch between low, medium, and high resolution surface tessellation. You can also save analysis input settings (such as VSPAERO) to quickly set up and run different conditions. The possibilities are relatively boundless with this feature.
