3.7.6. Solution Configuration & Component Names

The "Config" section of a Cape JSON file is used to give definitions of components, parts of vehicles, points, and similar things. This is generally pretty customized for each solver, but some very common options are defined here in cape to reduce duplicated code.

The JSON syntax with some nontrivial values is below.

"Config": {
    "Components": ["total", "wing"],
    "File": "Config.xml",
    "RefArea": 1.57,
    "RefLength": {
        "total": 0.5,
        "wing": 1.0
    },
    "RefPoint": "MRP",
    "Points": {
        "MRP": [0.0, 0.0, 0.0],
        "CG": [2.5. 0.0, 0.2]
    }
}

Links to additional options for each specific solver are found below.

• Cart3D

• FUN3D

The Components parameter defines a list of components that the user wants Cape to know about. Quite often, the meaning of the named component is actually defined in the ConfigFile, for example the way it is done in Cart3D with Config.xml. In most cases, these Components refer to subsets of the surface mesh(es), and they can be used to define components that pyCart, pyOver, or pyFun can move around.

The RefArea and RefLength parameters are universal enough to be included in the base cape module because almost any CFD solver or code that uses CFD results will utilize reference length and reference area. The RefPoint parameter is used to define moment reference points and, for some solvers, also the list of components for which moments should be reported. In addition, it is possible to define different reference areas/lengths for different components using a dict as in the example RefLength above.

Finally, the Point parameter is a unique capability of Cape that allows points to be conveniently defined in one spot. This can be convenient for a list of components that have the same moment reference point. Furthermore, it is essential for configurations that have multiple translations and/or rotations. Since the rotation point and rotation axis may move, Cape automatically updates Points according to the definition of those translations and/or rotations.

The dictionary of options is given below.

Components: {[]} | list (str)

List of components for Cape to know about, usually surface subsets

File: {"Config.xml"} | str

Name of file defining surface and/or volume grid subsets

Points: {{}} | dict (list)

Dictionary of named points and their coordinates

RefArea: {3.14159} | float | dict (float)

Reference area or dictionary of reference areas for each component

RefLength: {1.0} | float | dict (float)

Reference length or dictionary of reference lengths for each component

RefPoint: {null} | dict (list) | list

Moment reference point or dictionary of moment reference points

RefSpan: {null} | float | dict (float)

Reference span; falls back to RefLength if not specified