Moving Inlet/Outlet¶

The Moving Inlet/Outlet statistics provide time-resolved quantities describing the state, motion, and flow behavior of each moving inlet or outlet in the simulation. These outputs characterize how the inlet or outlet interacts with the surrounding fluid, including its position, orientation, flow rate, and local thermofluid properties. This output produces a tab-separated ASCII .txt file named MovingInletOutlet_{DynamicName}.txt, where the dynamic name corresponds to the name of the Moving Inlet/Outlet in the Model Tree.

The data is written as a time series, where each row corresponds to a simulation time, and each column corresponds to a statistic listed in the table below. Each row in the output file corresponds to a new statistics output time and is appended at the Statistics Output Write Interval.

The reported quantities fall into several categories:

Kinematics: Position, translation, and orientation vectors describe how the outlet moves and is oriented within the domain.
Flow Quantities: Flow rate and velocity components describe the magnitude and direction of fluid passing through the outlet.
Thermofluid Properties: Pressure, density, temperature, and scalar field values represent spatial averages at the outlet and provide insight into local flow conditions.
Geometry and State: Diameter defines the outlet size, while the open/close indicator specifies whether the outlet is actively passing flow.

Statistics Table¶

The index table below shows the statistics that will appear in the Moving Inlet/Outlet output file. Within this table, each statistic corresponds to a column in the output table that evolves with the time column.

Statistics	Units	Details
Time	s	simulation time
Diameter	m	diameter
Flow Rate	m^3/s	flow rate
LB Density	Dimensionless	spatial-mean of LB density
Open/Close	Dimensionless	1 for open, 0 for closed
Orientation X	Dimensionless	orientation vector
Orientation Y	Dimensionless	orientation vector
Orientation Z	Dimensionless	orientation vector
Position X	m	position of center
Position Y	m	position of center
Position Z	m	position of center
Pressure	Pa	spatial-mean of pressure
Scalar Field	[dynamic]	scalar field value
Thermal Field Temperature	K	temperature
Translation X	m	translation relative to initial position
Translation Y	m	translation relative to initial position
Translation Z	m	translation relative to initial position
Velocity Magnitude	m/s	flow velocity magnitude
Velocity X	m/s	flow velocity vector
Velocity Y	m/s	flow velocity vector
Velocity Z	m/s	flow velocity vector

Usage and Application¶

The Moving Inlet/Outlet statistics are used to quantify how flow, motion, and local thermofluid conditions evolve at a moving boundary. Because both the outlet geometry and surrounding flow field are time-dependent, these outputs are particularly useful for analyzing transient behavior and verifying boundary condition performance.

The reported Flow Rate corresponds to the surface integral:

\[Q(t) = \int_{A(t)} \mathbf{u} \cdot \mathbf{n} \, dA\]

where \(A(t)\) is the moving outlet surface, \(u\) is the local fluid velocity, and \(n\) is the outward normal defined by the Orientation (X, Y, Z) vector. This quantity is directly used to track volumetric throughput and enforce system-level mass balance.

The Velocity (X, Y, Z) and Velocity Magnitude provide the local flow direction and intensity at the outlet, while Pressure, LB Density, Thermal Field Temperature, and Scalar Field represent spatially averaged thermofluid properties at the boundary. These quantities are useful for diagnosing local flow conditions and ensuring consistency with prescribed boundary behavior.

The outlet motion is described by Position (X, Y, Z) and Translation (X, Y, Z), with the translational velocity implicitly given by

\[v(t) = \frac{dx_c}{dt}\]

where \(xc(t)\) is the outlet center position. The Orientation (X, Y, Z) vector defines the direction of the outlet normal. The position and orientation are defined relative to the world origin and reference vectors.

The Diameter defines the characteristic size of the outlet, while the Open/Close indicator (1 = open, 0 = closed) determines whether flow is actively permitted through the boundary at a given time.