Domain

The Domain statistics provide time-resolved quantities describing the motion of the simulation reference frame. These outputs capture applied translations, rotations, and orientation changes associated with external acceleration models. These statistics describe how the domain itself is moving or accelerating over time. The name of this file is Domain.txt. The data is written as a time series, with each row corresponding to a simulation time. The output file is updated at the Statistics Output Write Interval.

The specific columns that appear depend on the external acceleration model applied to the domain (e.g., translation, rotation, or ball-joint motion). Only quantities relevant to the selected motion model are reported.

The reported quantities fall into several categories:

• Angular Motion Metrics: Angular position and rotational velocity describe the rotational state of the domain.

• Rotational Definition Metrics: Rotation axis and rotation point define the geometry about which rotation occurs.

• Translational Motion Metrics: Translation and translational velocity describe the linear motion of the domain.

• Orientation Metrics (Ball Joint): Ball joint direction and reference axis define the orientation of the domain when using ball-joint motion models.

Statistics Table

The index table below shows the statistics that can appear in the Domain Statistics output file. Within this table, each statistic corresponds to a column in the output table that evolves with the time column.

Statistics	Units	Details	When Appears
Time	s	simulation time
Angular Position	rad	angular position
Ball Joint Direction X	Dimensionless	orietation of ball joint
Ball Joint Direction Y	Dimensionless	orietation of ball joint
Ball Joint Direction Z	Dimensionless	orietation of ball joint
Ball Joint Reference Axis X	Dimensionless	axis to which ball joint is relative to
Ball Joint Reference Axis Y	Dimensionless	orietation of ball joint
Ball Joint Reference Axis Z	Dimensionless	orietation of ball joint
Rotation Axis X	Dimensionless	axis about which rotation occurs
Rotation Axis Y	Dimensionless	axis about which rotation occurs
Rotation Axis Z	Dimensionless	axis about which rotation occurs
Rotation Point X	m	point about which rotation occurs
Rotation Point Y	m	point about which rotation occurs
Rotation Point Z	m	point about which rotation occurs
Rotational Velocity	rpm	rotational velocity about rotation point and axis
Rotational Velocity X	rad/s	rotational velocity about rotation point
Rotational Velocity Y	rad/s	rotational velocity about rotation point
Rotational Velocity Z	rad/s	rotational velocity about rotation point
Translation X	m	total translation
Translation Y	m	total translation
Translation Z	m	total translation
Translational Velocity X	m/s	translational velocity
Translational Velocity Y	m/s	translational velocity
Translational Velocity Z	m/s	translational velocity

Usage and Interpretation

Domain statistics are used primarily to verify prescribed motion and to understand the simulation reference frame. Users can confirm that imposed motions—such as rotational speed, translation profiles, or oscillatory inputs—are being correctly applied. For example, comparing the reported Rotational Velocity or Translational Velocity against the intended inputs ensures that the simulation is executing as expected. Because many simulations are performed in non-inertial or moving frames, these statistics provide the necessary context for interpreting results. Quantities such as fluid velocity, acceleration, and force are often reported relative to the domain.