# Geometry

# Mesh Unit

The Mesh Unit is the length unit used in the mesh file. It can be m (meter), cm (centimeter), mm (millimeter), inch, or feet. Used to calculate which is the length in meters of one grid unit, e.g. for grid unit mm.

# Reference area

The Reference Area, is used to non-dimensionalize lift coefficient (CL), drag coefficient (CD), force, and moment coefficients. For example:

Here, is the freestream density and is the reference velocity calculated by , where is the freestream speed of sound, and by default, the reference Mach number, MachRef, is set to be equal to the freestream Mach number, Mach. However, when Mach, MachRef needs to be specified explicitly. In this case, it is equivalent to an explicitly set non-zero reference velocity in the next section for freestream parameters. Note, that reference area, refArea, as input to the JSON file is non-dimensionalized by .

# Moment Center

The Moment Center is the location about which all aerodynamic moments are calculated.

For example:

  1. A positive z-directional force acting at an x-coordinate greater than the x-coordinate of the Moment Center would generate a negative y-moment.
  2. A positive x-directional force acting at an z-coordinate greater than the z-coordinate of the Moment Center would generate a positive y-moment.
  3. A positive x-directional force acting at an y-coordinate greater than the y-coordinate of the Moment Center would generate a negative z-moment.
  4. A positive y-directional force acting at an x-coordinate greater than the x-coordinate of the Moment Center would generate a positive z-moment.
  5. A positive y-directional force acting at an z-coordinate greater than the z-coordinate of the Moment Center would generate a negative x-moment.
  6. A positive z-directional force acting at an y-coordinate greater than the y-coordinate of the Moment Center would generate a positive x-moment.

# Moment Length

The moment reference lengths are used to non-dimensionalize moment coefficients, according to the definitions below. For example:

Here, are the moment components with respect to the Moment Center, is the freestream density. Notably, is the reference velocity calculated by , where is the freestream speed of sound. By default, the reference Mach number, MachRef, is set to be equal to the freestream Mach number (Mach). However, when Mach==0, MachRef needs to be specified explicitly. In this case, it is equivalent to an explicitly set non-zero reference velocity in the next section for freestream parameters.

← Freestream →