Built-In Variables

This section provides information on System Coupling's built-in variables that can be used in expressions or Python scripts.

For information on the different categories of variables, see:

Solution Variables

Solution variables are single-valued variables that define various solution settings for use in scripts and expressions.

Variable	Description
Iteration	Description Provides access within an expression to the current coupling iteration of the coupled analysis. For a step-based analysis, refers to the current coupling iteration within the current coupling step. For a steady iteration-based analysis, refers to the current coupling iteration. Values Defines the coupling iteration using positive integer values within the range of iterations defined for the analysis: *`1 < x ≤ <FinalIteration>`. Defaults to `1`. Example* 0.5*force.x if Iteration == 1 else force.x
Time	Description Available only for transient analyses. Provides access within an expression to the current analysis time. Within a step, its value is the time at the end of the last completed coupling step — that is, it reflects the current time according to the time step size and time units defined for the analysis. For example, if the TimeStepSize setting is set to *`0.1 [s]`, then the value of the Time* variable is *`0.1 [s]`* for the first coupling step, *`0.2 [s]`* for the second coupling step, and so on. Values Defines the current time using values within the time range of the coupled analysis: *`<TimeStepSize> < x ≤ <EndTime>`. Defaults to the value of the TimeStepSize* setting in the time unit defined for the analysis. Example 400 [K] if Time if < 1 [s] else temperature
Step	Description Available only for step-based coupled analyses. Provides access within an expression to the current coupling step of the coupled analysis. Values Defines the coupling step using positive integer values within the range of steps defined for the analysis: *`1 < x ≤ <FinalStep>`. Defaults to `1`. Example* 400 [K] Step if < 1 else temperature
PreviousTimestepSize	Description Available only for transient step-based coupled analyses. Provides access within an expression to the time interval of the previous coupling step. Values Defines the length of the time step using values within the duration defined for the analysis: *`0.0 < x ≤ <EndTime>`* Defaults to *`1`. Example* 400 [K] PreviousTimestepSize if < 1 [s] else temperature

Region Variables

Region variables are field variables that define various region settings for use in scripts and expressions.

Variable	Description
Area	Description Available only for transfers of element data from surfaces. That is, the source participant must have the following settings: Region.Topology = `Surface` Variable.Location = `Element` Provides access within an expression to the area of the region(s) corresponding to the source variable. Values Defines the area using real area values *`0.0 < x`* and an area unit. Example Force / Area
Normal	Description Available only for surface regions. Provides access within an expression to the normal vector for a specified variable surface. Values Defines the normal vector at each location of the region. The individual components may be accessed as Normal.x, Normal.y, and Normal.z. Example Force * Normal.y / 0.5 [m]
Position	Description Available only for vector regions Provides access within an expression to the position of the region(s) corresponding to the source variable. Coordinates are expressed as three Cartesian components which have either nodal or element centroids, depending on the topology of the data transfer region(s). Values Defines the position vector. The individual components may be accessed as Position.x, Position.y, and Position.z. Example Force * Position.x / 1 [m]
Volume	Description Available only for volume regions. Provides access within an expression to the volume of the region(s) corresponding to the source variable. Values Defines the area using real values *`0.0 < x`* and a volume unit. Example Heat_Rate / Volume