Solution dialog box — Transient Setup

The options on the Transient page are available when Solution Type is set to Transient on the Solution Details page.

Option	Analysis/Solution Type	Description
Solution Time Interval
Start Time	all	Sets the start time for the simulation.
End	Thermal Coupled Thermal-Flow	Specifies how the end time for the transient analysis is determined.At Specified TimeEnds the transient analysis at the time you set.Based on Orbit PeriodEnds the transient analysis at the end of the specified number of orbits or when the temperature change between two orbits falls below the specified value if periodic convergence is enable. You set the number of time steps in each orbit using the options in the Time Integration Control group.Based on Cyclic CriterionEnds the transient analysis when the temperature change between two cycles falls below the specified value or at the end of the specified number of cycles. You set the number of time steps in each cycle using the options in the Time Integration Control group.Run to Steady StateEnds the transient analysis when the temperature change between two intervals falls below the specified value or at the end of the specified number of intervals. You set the number of time steps in each interval using the options in the Time Integration Control group.Based on TemperatureEnds the transient analysis when the elements in one or more groups reach the specified temperature. The first group that reaches its target value ends the analysis. You select the group and set its target temperature value in the Target Temperature modeling object. For more information, see Target Temperature and Target Temperature Change.You can define multiple modeling objects of the same type in your solution.Based on Temperature ChangeEnds the transient analysis when the elements in one or more groups reach the specified temperature change between two consecutive time steps. The first group that reaches its target value ends the analysis. You select the group and set its target temperature change value in the Target Temperature Change modeling object. For more information, see Target Temperature and Target Temperature Change.You can define multiple modeling objects of the same type in your solution.Note: Based on Orbit Period, Based on Cyclic Criterion, and Run to Steady State are available only for Thermal analysis types.
End Time	all	Sets the end time for the simulation.
Maximum Number of Orbits	Space Systems Thermal	Appears only when you select Based on Orbit Period from the End list.Specifies the maximum number of orbits for the transient thermal analysis.
Enable Periodic Convergence	Appears only when you select Based on Orbit Period from the End list.Controls when the simulation stops.Select the Enable Periodic Convergence check box if you want the simulation to stop when the temperature change between orbits is less than the specified value. Clear the Enable Periodic Convergence check box if you want the simulation to stop at the maximum number of orbits specified. The simulation runs until to the Maximum Number of Orbits even if periodic convergence is achieved.
End Solve if Temperature Between Orbits less than	Appears when you select Based on Orbit Period from the End list.Specifies the maximum permissible temperature difference of each element at the end of two successive orbits.
Maximum Number of Cycles	Thermal	Appears only when you select Based on Cyclic Criterion from the End list.Specifies the maximum number of cycles for the transient thermal analysis.
End Solve if Temperature Change Between Cycles less than	Appears only when you select Based on Cyclic Criterion from the End list.Specifies the maximum permissible temperature difference of each element at the end of two successive cycles.
Specify Cycle Period	Appears only when you select Based on Cyclic Criterion from the End list.Specifies the value for the cycle period. Enter the value in time units.
Maximum Number of Intervals	Thermal	Appears only when you select Run to Steady State from the End list.Specifies the maximum number of intervals for the transient thermal analysis.
End Solve if Temperature Between Time Intervals less than	Appears only when you select Run to Steady State from the End list.Specifies the maximum permissible temperature difference of each element at the end of two successive intervals.
Specify Time Interval	Appears only when you select Run to Steady State from the End list.Specifies the size of the time interval.
Time Integration Control
Integration Method	Advanced Thermal****Space Systems Thermal	Controls how the solution is advanced in time.Implicit solution method is the implicit difference scheme.Semi–Implicit solution method is the Crank-Nicholson method.Explicit solution method is a fully explicit integration scheme.Exponential Explicit solution method is an explicit scheme where the element temperature profile over an integration time step is assumed to be an exponential decay.Fully Implicit solution method is the fully implicit difference scheme where the thermal solver treats all non-linear terms implicitly.Note: When you model the material ablation, select only implicit time integration methods.See Card 2b — Analyzer Control Card in the Simcenter 3D Thermal Solver Reference Manual for more information.
Thermal Time Step Option	Coupled Thermal-Flow	Controls how the thermal solver calculates the time step. Smaller time steps always give more accurate results but require increased computation time. The solution time is inversely proportional to the size of the time step.Number of Time Steps lets the solver calculate the time step size by dividing the simulation time interval by the number of time steps.Constant lets you define a constant size for the time step.Time Varying lets you define a time step size that varies with time. The time step size is a linear interpolation of the table data. This is an effective way to refine the time mesh for only those portions of the solution interval where the temperatures change rapidly. For more information, see Understanding time-varying time step.
Number of Thermal Time Steps	Coupled Thermal-Flow	Appears only when you select Number of Time Steps from the Thermal Time Step Option list.Specifies the number of time steps for the thermal part of the analysis.
Thermal Time Step	Coupled Thermal-Flow	Appears only when you select Constant from the Thermal Time Step Option list.Specifies the size of the thermal time step.Note: For models involving phase change reduce the time step to a value equal or lower to the following relationship:Time Step=CpWelemNexposed/(*Pinput**100)Where Cp is the heat capacity of the material changing phase, Welem is the weight of one element, Nexposed is the approximate amount of elements exposed to phase change, and Pinput is the approximate power input in the volume changing phase.
Thermal Time Step Variation Specify Field	Coupled Thermal-Flow	Appears only when you select Time Varying from the Thermal Time Step Option list. Lets you select or create a thermal time step list that varies with time. The time step size is a linear interpolation of the table data. See Specify Field options, below.Scale Factor lets you uniformly increase or decrease the dependent variable in a field by the factor you specify.For more information, see Understanding time-varying time step.
Flow Time Integration Method	Advanced Thermal-FlowAdvanced FlowAdvanced Thermal-Flow with ESC	Specifies the integration method for the parallel flow solver.ImplicitA first-order accurate temporal discretization method.The serial flow solver always uses this method.Semi-implicit Second-orderResolves transient flow features with a significantly greater accuracy than the Implicit method for a given timestep size using the parallel flow solver. This method is a second-order accurate temporal discretization method. Because LES simulations accurately capture flow structures with a wide range of associated time scales, use this method when you model flow fields using the LES turbulence model.This method is not supported by the serial flow solver.
Flow Time Step Option	Coupled Thermal-Flow	Controls how the flow solver calculates the time step. Smaller time steps always give more accurate results but require increased computation time. The solution time is inversely proportional to the size of the time step.Same as Thermal lets you set the flow time step size to be the same as the thermal time step size at each time step.Number of Time Steps lets the solver calculate the time step size by dividing the simulation time interval by the number of time steps.Constant lets you define a constant size for the time step.Time Varying lets you define a time step size that varies with time. The time step size is a linear interpolation of the table data. This is an effective way to refine the time mesh for only those portions of the solution interval where the flow quantities change rapidly.For more information, see Understanding time-varying time step.
Number of Flow Time Steps	Coupled Thermal-Flow	Appears only when you select Number of Time Steps from the Flow Time Step Option list.Specifies the number of time steps for the flow part of the analysis.
Flow Time Step	Coupled Thermal-Flow	Appears only when you select Constant from the Flow Time Step Option list.Specifies the value for the size of the flow time step.
Flow Time Step Variation Specify Field	Coupled Thermal-Flow	Appears only when you select Time Varying from the Flow Time Step Option list.Lets you select or create a flow time step list that varies with time. The time step size is a linear interpolation of the table data. See Specify Field options, below.Scale Factor lets you uniformly increase or decrease the dependent variable in a field by the factor you specify.For more information, see Understanding time-varying time step.
Time Step Option	Thermal****Flow	Controls how the solver calculates the time step. Smaller time steps always give more accurate results but require increased computation time. The solution time is inversely proportional to the size of the time step.Number of Time Steps lets the solver calculate the time step size by dividing the simulation time interval by the number of time steps.Constant lets you define a constant size for the time step.Time Varying lets you define a time step size that varies with time. The time step size is a linear interpolation of the table data. This is an effective way to refine the time mesh for only those portions of the solution interval where the temperatures change rapidly.Automatic lets the solver calculate the time step size automatically based on the temperature error tolerance. The time step is kept between the specified minimum and maximum values. See Adaptive time stepping method for more information. This option appears only when you select the Thermal analysis type.
Number of Time Steps	Thermal****Flow	Appears only when you select Number of Time Steps from the Time Step Option list.Specifies the number of time steps for the analysis.
Time Step	Thermal****Flow	Appears only when you select Constant from the Time Step Option list.Specifies the value for the size of the time step.
Time Step Variation Specify Field	Thermal****Flow	Appears only when you select Time Varying from the Time Step Option list.Lets you select or create a time step list that varies with time. The time step size is a linear interpolation of the table data. See Specify Field options, below.Scale Factor lets you uniformly increase or decrease the dependent variable in a field by the factor you specify.
Temperature Error Tolerance	Thermal	Appears only when you select Automatic from the Time Step Option list.Specifies the value for the temperature error tolerance of the estimated error between the analytical solution and the simulation. The error is the difference between a fit quadratic function and a linear variation through three consecutively computed temperature values for two consecutive time steps.
Maximum Time Step****Minimum Time Step	Thermal	Appears only when you select Automatic from the Time Step Option list.Specifies the values for the maximum and minimum time step sizes.
Results Sampling
Thermal Results Type	Coupled Thermal-Flow	Controls when the thermal solver calculates results for post processing. Results are always produced at the start and end times.At Constant Time Intervals produces thermal model results (analysis data sets) at the constant intervals that you specify.Total Number produces thermal model results for the number of times that you specify. The results are calculated at equal time intervals over the course of the analysis.At Specified Times produces thermal results at the times set by the Thermal Output Times option.Time Varying produces thermal results at intervals that vary with time. The time step size is a linear interpolation of the table data.Match Integration Times produces thermal results at the same times as the thermal calculation times set by the Time Integration Control group.
Thermal Time Interval	Coupled Thermal-Flow	Appears only when you select At Constant Time Intervals from the Thermal Results list.Specifies the time interval between two sets of thermal results. Enter the value in units of time.
Number of Thermal Results	Coupled Thermal-Flow	Appears only when you select Total Number from the Thermal Results list.Specifies the number of thermal result sets.
Thermal Output Times	Coupled Thermal-Flow	Appears when Thermal Results is set to At Specified Times.Sets the discrete post processing output times for the thermal part of the run. In addition to the specified times, the solver also outputs results sets at the initial time step.Only for thermal runs, if the final transient run time value exceeds the largest specified post processing output time value, then the solver considers the specified post processing output times list to be periodic.Example: If the solution start time is 0, the final time is 25000, and the output times are 3000 and 5000, the results are computed and stored at the following times: 0, 3000, 5000, 8000, 10000, 13000, 15000, 18000, 23000, and 25000. To avoid the periodic behavior, specify the final transient run time in your output times list.The values must be separated by commas or they must be entered on different lines. You can use Cut , Copy , and Paste commands.
Flow Results Type	Coupled Thermal-Flow	Controls when the flow solver calculates results for post processing. Results are always produced at the start and end times.Same as Thermal produces flow model results at the same times as thermal model results. At Constant Time Intervals produces flow model results (analysis data sets) at the constant intervals that you specify.Total Number produces flow model results for the number of times that you specify. The results are calculated at equal time intervals over the course of the analysis.At Specified Times produces flow results at the times set by the Flow Output Times option.Time Varying produces flow results at intervals that vary with time. The time step size is a linear interpolation of the table data.Match Integration Times produces flow results at the same times as the flow calculation times set by the Time Integration Control group.
Flow Time Interval	Coupled Thermal-Flow	Appears only when you select At Constant Time Intervals from the Flow Results list.Specifies the time interval between two sets of flow results. Enter the value in units of time.
Number of Flow Results	Coupled Thermal-Flow	Appears only when you select Total Number from the Flow Results list.Specifies the number of flow result sets.
Flow Output Times	Coupled Thermal-Flow	Appears when Flow Results is set to At Specified Times.Sets the discrete post processing output times for the flow part of the run. In addition to the specified times, the solver also outputs results sets at the initial time step.The values must be separated by commas or they must be entered on different lines. You can use Cut , Copy , and Paste commands.
Results	Thermal****Flow	Controls when the solver calculates results for post processing. Results are always produced at the start and end times.At Constant Time Intervals produces model results (analysis data sets) at the constant intervals that you specify.Total Number produces model results for the number of times that you specify. The results are calculated at equal time intervals over the course of the analysis.Number per Orbit produces results specified number of times per orbit. This option is available only when you select Based on Orbit Period from the End list.Number per Cycle produces results specified number of times per cycle. This option is available only when you select Based on Cycle Criterion from the End list.Number per Time Interval produces results specified number of times per interval. This option is available only when you select Run to Steady State from the End list.Results at Final Time Only produces one results set at the end of the transient analysis. This option is available only when you select Run to Steady State from the End list.At Specified Times produces results at the times set by the Output Times option.Time Varying produces results at intervals that vary with time. The time step size is a linear interpolation of the table data.Match Integration Times produces results at the same times as the calculation times set by the Time Integration Control group.
Time Interval	Thermal****Flow	Appears only when you select At Constant Time Intervals from the Results list.Specifies the time interval between two sets of results. Enter the value in units of time.
Number of Results	Thermal****Flow	Appears only when you select Total Number from the Results list.Specifies the number of result sets.
Number per Orbit	Space Systems Thermal	Appears only when you select Number per Orbit from the Results list.Specifies the number of results sets you want per orbit.
Results for Last Orbit only	Space Systems Thermal	Appears only when you select Based on Orbit Period from the End list.Select this option if you only want the results for the last orbit.
Number per Cycle	Thermal****Flow	Appears only when you select Number per Cycle from the Results list.Specifies the number of results sets you want per cycle.
Results for Last Cycle Only	Appears only when you select Based on Cycle Criterion from the End list.Specifies that you only want the results for the last cycle.
Number per Time Interval	Appears only when you select Number per Time Interval from the Results list.Specifies the number of results sets you want per interval.
Output Times	Appears only when Results is set to At Specified Times.Sets the discrete post processing output times for the run. In addition to the specified times, the solver also outputs results sets at the initial time step.Only for thermal runs, if the final transient run time value exceeds the largest specified post processing output time value, then the solver considers the specified post processing output times list to be periodic.Example: If the solution start time is 0, the final time is 25000, and the output times are 3000 and 5000, the results are computed and stored at the following times: 0, 3000, 5000, 8000, 10000, 13000, 15000, 18000, 23000, and 25000. To avoid the periodic behavior, specify the final transient run time in your output times list.The values must be separated by commas or they must be entered on different lines. You can use Cut , Copy , and Paste commands.
Output Times Variation****Specify Field	ThermalFlowCoupled Thermal-Flow	Appears only when you select Time Varying from the Thermal Results, Flow Results, or Results list.Lets you select or create a table containing the desired output time intervals at specified times. The time step size is a linear interpolation of the table data. See Specify Field options, below.Scale Factor lets you uniformly increase or decrease the dependent variable in a field by the factor you specify.
Articulation Parameters
The options in this group are also available when Solution Type is set to Steady State on the Solution Details page.
Times and Calculation Interval	Space Systems Thermal	Controls how the articulation time step is specified.Match Orbit sets the articulation time step to the orbit time step.Specify lets you define the articulation time step.
Time Step Option	Advanced ThermalAdvanced Thermal-FlowAdvanced Thermal-Flow with ESC****Space Systems Thermal	Controls how the thermal solver calculates the time steps for the articulation modeling. The view factors, radiative conductances, and thermal couplings are recomputed at the specified time interval.At Constant Time Intervals lets you define a constant size for the articulation time step.Total Number lets the solver calculate the time step size by dividing the articulation simulation time interval by the number of articulation time steps.At Specified Times lets you define specific articulation calculation times.Interval versus Time Table lets you define an articulation time step size that varies with time.
Start Time****End Time	Appears only when you select At Constant Time Intervals or Total Number from the Time Step Option list.Specifies values for the start and end times for the articulation calculation process.
Calculation Interval	Appears only when you select At Constant Time Intervals from the Time Step Option list.Specifies the time interval between two sets of articulation calculation. Enter the value in units of time.
Number of Time Steps	Appears only when you select Total Number from the Time Step Option list.Specifies the number of articulation calculation times.
Articulation Times	Appears only when you select At Specified Times from the Time Step Option list.Let you specify the time units for the discrete articulation calculation times that you enter in the text box.
Articulation times text box	Appears only when you select At Specified Times from the Time Step Option list.Let you specify the discrete articulation calculation times. The values must be separated by commas or they must be entered on different lines. You can use Cut , Copy , and Paste commands.
Time Step Variation	Appears only when you select Interval versus Time Table from the Time Step Option list.Lets you select or create a table containing the desired articulation calculation time intervals at specified times.For example, if you specify the following time step variation.TimeInterval0.01.06.02.016.03.4The solver performs the articulation calculation at the following times:0.01.02.03.04.05.06.08.010.012.014.016.0 The last row of the table indicates the last articulation calculation time; the interval value is a placeholder number.Specify Field lets you select or create the time step variation table. See Specify Field options.Scale Factor lets you uniformly increase or decrease the dependent variable in a field by the factor you specify.	Time	Interval	0.0	1.0	6.0	2.0	16.0	3.4	0.0	1.0	2.0	3.0	4.0	5.0	6.0	8.0	10.0	12.0	14.0	16.0
Time	Interval
0.0	1.0
6.0	2.0
16.0	3.4
0.0	1.0	2.0	3.0	4.0	5.0	6.0	8.0	10.0	12.0	14.0	16.0

Specify Field options

These options are available when the magnitude is defined as Field.
Select Existing Field from List	Lets you select an existing field.
Formula Constructor	Lets you use a formula to construct a field. For more information, see Define a boundary condition using a formula field.
Table Constructor	Lets you use a table to construct a field.For more information, see Define a boundary condition using a table field and Define a material property using a table field.
Link Constructor	Lets you reference an existing field. You can override the field's spatial map to use the field in another location.For more information, see Linked Field dialog box.
Plot(XY)	Plots the field as an XY graph.For more information, see: Plot functions, Graph overview, and Edit display properties of graph objects.
Overlay(XY)	Available when a plot is already displayed. Overlays a plot on an existing plot. You can overlay up to 50 plots. For more information, see Overlay plots.

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Solution options

Look up more details

Solution dialog box —Solution Details

Solution dialog box — Solution Units

Solution dialog box — Ambient Conditions

Solution dialog box — Initial Conditions

Solution dialog box —Restart

Solution dialog box —Thermal

Solution dialog box —3D Flow

Solution dialog box — Results Options

Solution dialog box (Mapping) — Mapping Details

Solution dialog box (Mapping) — Optional Output

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Solution dialog box — Transient Setup , Simcenter 3D 2021.1 Series

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