Restarting a solution using the thermal solver

The thermal solver uses the data in the following files for a restart:

• tmggeom.dat

• MODLF

• VUFF

• INPF

Note:

Because the thermal solver supports large ID numbers starting in NX 9, you cannot restart simulations using solver files that you generated in NX 8.5 or earlier. The upper limit for element and node labels is now 100 million.

You cannot stop an analysis that is thermal only before the specified end.

Supported modifications to the model

You can make some modifications to your model and still perform a restart using a previous analysis.

You can change:

• Thermal boundary condition values and options

• Solver attributes and parameters

You cannot change:

• The geometry

• The mesh

• Modeling objects

• The solution units

Advanced restart options

On occasion, a series of thermal analyses may be performed using the same geometry and mesh. If a new thermal analysis is started each time, the solver has to repeat much of the same calculation. In order to minimize solution time and recover as much previously calculated data as possible, use Restart Options.

The following options are especially useful when restarting complex radiation models, but can also be useful for restarting any complex thermal and/or duct network model. 3D flow calculations are not affected by these options.

Note:

These options are only supported for advanced thermal licenses.

• Conduction, Capacitances and Duct NetworkSelect Delete previous — Calculate new when you change the conductivity, specific heat, density, physical property, or fluid properties of at least one material in the model.

• Thermal CouplingsSelect Delete previous — Calculate new when you modify at least one of the following parameters of your existing Thermal Coupling simulation object:Type or value of the thermal coupling.Primary or secondary region.Coupling resolution.

• Convection CouplingsSelect Delete previous — Calculate new when you modify:Any parameter of your existing Thermal Coupling — Convection simulation object.Ambient conditions when your model includes a Convection to Environment constraint.

• Black Body View FactorsSelect Delete previous — Calculate new when you change the selection or modify parameters on the Radiation simulation object.Select Reuse previous — Do not calculate when there is no change in the model affecting black body view factors.Select Reuse previous — Calculate new when you have added an enclosure to a different region of the model. You must deactivate previously calculated regions of the model by selecting Deactivate Radiation option in the Deactivation Set or Deactivation Set Advanced simulation object. When you select this option for both Black Body View Factors and Radiative Conductances, the thermal solver computes the radiative conductances twice for the original thermal enclosure.

• Radiative ConductancesSelect Delete previous — Calculate new when you modify the Radiation or Thermal Coupling — Radiation simulation objects, or the emissivity of any elements.Select Reuse previous — Do not calculate when there is no change in the model affecting radiative conductances.Select Reuse previous — Calculate new when you want to reuse the radiative conductances from the previous solution and calculate radiative conductances for all active elements in the current solution. You must deactivate previously calculated regions of the model by selecting Deactivate Radiation option in the Deactivation Set or Deactivation Set Advanced simulation object. When you select this option for both Black Body View Factors and Radiative Conductances, the thermal solver computes the radiative conductances twice for the original thermal enclosure.Note: You should always recalculate radiative conductances if you recalculate black body view factors.

• Solar and Orbital View FactorsSolar view factors are geometry dependent. They must be recalculated if the position of the source or of the selected elements has changed. Most modifications to Solar Heating or Orbital Heating options cause changes in the relative position of the model and the source. For example, you cannot change the day of the analysis since this will modify the source position.Select Delete previous — Calculate new when you modify the parameters or the selection of the following simulation objects:Orbital HeatingRadiative HeatingSolar HeatingSelect Reuse previous — Do not calculate when you made no change in the model affecting solar and orbital view factors. Changes in solar flux, albedo or ground reflectance values do not affect solar or orbital view factors.Select Reuse previous — Calculate new when you want to reuse the solar, IR, and orbital view factors from the previous solution and calculate the solar, IR, and orbital view factors for all active elements in the current solution. You must deactivate previously calculated regions of the model by selecting Deactivate Radiation option in the Deactivation Set or Deactivation Set Advanced simulation object.

• Solar and Orbital Heat FluxesSelect Delete previous — Calculate new when you:Modify the solar spectrum properties of one of your materials.Modify the source fluxes.Calculate new solar, IR, or orbital view factors.Select Reuse previous — Do not calculate when there is no change in the model affecting solar or orbital heat fluxes.Select Reuse previous — Calculate new when you want to reuse the solar and orbital heat fluxes from the previous solution and calculate the solar and orbital heat fluxes for all active elements in the current solution. You must deactivate previously calculated regions of the model by selecting Deactivate Radiation option in the Deactivation Set or Deactivation Set Advanced simulation object.Warning: You should always recalculate solar and orbital heat fluxes if you recalculate solar, IR, and orbital view factors.

How do I

Continue a transient solution

Restart a steady state solution

Reuse thermal solution data in a modified or different solution

Learn more

Restarting a solution using the serial flow solver

Restarting a solution using the parallel flow solver

Solving the model

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Restarting a solution using the thermal solver, Simcenter 3D 2021.1 Series

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