4.2.10. Surface Configuration and Naming

Cart3D has an optional (but very useful and thus highly recommended) input file called Config.xml that allows a user to define specific names for components and also group them together. The “Config” section of the pyCart.json master settings file points to this file (which can have a different name but will always be saved as Config.xml in the run directories) and also defines reference length and area. Finally, this section also tells flowCart what points to report force and moment histories for and defines moment reference points where necessary.

The following pyCart.json snippet shows all the options in action and lists the defaults.

"Config": {
    // Config file
    "File": "Config.xml",
    // Reference values
    "RefArea": 1.0,
    "RefLength": {
        "total": 0.5,
        "wing": 1.0
    },
    // Moment history requests with MRP
    "RefPoint": {
        "total": "MRP",
        "wing": "MRP"
    },
    // Force history requests
    "Force": ["entire", "total", "wing"],
    // Coordinates at which to output volume slices
    "Xslices": [],
    "Yslices": [],
    "Zslices": [],
    // Locations at which to sample flow state
    "PointSensors": []
}

These are indeed the defaults, but this example is misleadingly simple. The capabilities of the “Config” section are much better demonstrated by the following example.

"Config": {
    "RefArea": {"default": 18.0, "Rudder": 1.2},
    "RefLength": {"default": 2.6, "Rudder": 0.6},
    "RefPoint": {
        "Wings": [7.0, 0.0, -0.2],
        "Rudder": [12.5, 0.0, 2.1],
        "Body": [0.0, 0.0, 0.0]
    },
    "Force": ["Wings", "Body", "Rudder", "Tail"]
}

In this example, a default value is specified for both the reference area and reference length, but a different value is defined for the "Rudder" component. Moment histories are requested for three components, and all of them use a different moment reference point. Finally, the force histories are requested for four components.

The full dictionary of “Config” options is shown below.

File: {Config.xml} | str

Name of XML file containing component names and groupings

Force: {["entire"]} | list (str)

List of components on which to request force history

Points: {{}} | dict (list)

Dictionary of named points and their coordinates

PointSensors: {[]} | list (list | str)

List of named points or point coordinates

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

Reference area or dict of reference areas for different components

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

Reference length or dict of reference lengths for different components

RefPoint: {[0.0, 0.0, 0.0]} | dict | list

Three-dimensional float specifying global reference point or dict of components and their moment reference points

Xslices: {[]} | [0.0] | list (float)

List of x-coordinates at which to extract cut planes

Yslices: {[]} | [0.0] | list (float)

List of y-coordinates at which to extract cut planes

Zslices: {[]} | [0.0] | list (float)

List of z-coordinates at which to extract cut planes