Simcenter 3D Solutions Simcenter 3D - Overview of Thermal Solver files and how to use them​

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This article is about how to use thermal solver files and its overview in Simcenter 3D application


Simcenter 3D Part files:

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Assembly FEMs

The assembly FEM contains:
  • Occurrences of the component FEMs.
  • Properties overwritten on specific FEM occurrences.

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Solution Monitor

The Solver Monitor provides the following information from the solver during the analysis:
  • Solver version, run time, and run directory.
  • Model summary.
  • Status of the solution and current module being executed by the thermal solver.
  • Convergence residuals at each iteration during the analysis.
  • Warnings and errors.
You can abort or stop a solution using the Solution Monitor window. 
  • Abort terminates the analysis. All temporary files are removed, and the results are not post processed. You cannot restart or continue an aborted solution.
  • Stop ends the analysis before the final time step or steady state. The software keeps the temporary files, performs post-processing, and creates results output files. 
The solution monitor window is written to a <simulation/model name>-<solution/analysis name>.log file, located in the same directory as the SIM file.

Solver files

Solver Reference Manual
All the following information and much more can be found in the thermal solver reference manual:

Solution file: XML
<simulation/model name>-<solution/analysis name>.xml
The file contains the model and solution definition. The model definition includes meshes, elements, and model properties. The solution definition includes the boundary conditions and solution settings. 
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The CAE software launches the Monitor, where the file data is processed and prepared in a format (INPF file) that the thermal solver require to perform the solve.

Mapping file: MAP

<simulation name>-<solution name>.map

A mapping file is used by the solution file to retrieve the regions where mapping is defined in the source and target models. It also includes information about the mapping zones defined for the source and target model, such as thermal, transverse gradient, and axisymmetry mapping zones.

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Solution Monitor/Log file: Module description



Module description

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<simulation/model name>-<solution/analysis name>.log

At the end of a steady state run, the log file includes a summary of the heat flow:
  • Heat load is a directly applied heat load Q (through BCs: volumetric heat flows or surface heat fluxes). 
  • Heat flows are heat flows through conductance (because of temperature differences).
  • For a coupled thermal-flow (CFD) solution:
     Heat Imbalance = Total Heat Load on Elements + Heat Flow from Sinks – Heat Flow into Sinks

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  • Using the terminology in the log file we have:
    Total Heat Imbalance = Total heat load on non-fluid elements + (Heat flow from temperature B.C.s + Heat convected from fluid) – (Heat flow into temperature B.C.s + Heat convected to fluid)
  • The steady state Heat Imbalance solution is when the Total Heat Imbalance goes to 0.
  • The units on the log file are always the one defined in the Solution Units page. (Edit solution- Solution Units).
The log file also includes a summary of heat flow into various sinks (temperature boundary conditions):
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The information about the heat needed to keep the sink entities at these temperatures can be very useful when selecting the size of the heater.
INPF is the primary input file to the thermal solver. ASCII file that contains the nodes, elements, materials and boundary condition information for the thermal solver. 

You can solve directly from INPF, similarly to XML. Sometimes can be useful to modify manually or with a script to run batch runs.

Solver include files are in the INPF format. Can be used to write additional loads on groups or include reduced models into a larger model.

Binary files
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The VUFF file contains:
  • The model geometry elemental properties written by ECHOS. 
  • The view factors, heat flux view factors, solar view factors, albedo factors, and Earth view factors written by VUFAC. 
  • The IR and solar spectrum gray body view factor matrices written by GRAYB.  
This is a good file to look for view factor or radiation conductance between elements. It can be more complicated to understand when using the Oppenheim method.


MODLF contains all the thermal couplings, radiative, conductive, hydraulic, and convective conductance, element capacitances, and heat loads calculated from elemental geometry and material and physical properties by the COND, GRAYB, VUFAC, and POWER modules.

MODLCF is a condensed version of the MODLF file after addition of the Card 9 model parameters, element merging, sub-structuring, and combining of heat loads, capacitances, and conductance. 

MODLF and MODLCF are by default binary files, however, they can be translated into ASCII format using the AS option in the TMG Executive Menu or with an Advanced Controls simulation object in Simcenter 3D. Both binary and ASCII formats are equally acceptable to TMG; however, the binary is preferred, because there is no loss in precision.

For debugging or manual inspection, MODLCF should be used over MODLF.
REPF/<simulation/model name>-<solution/analysis name>_report.log
A log file that contains calculation details. This file is always appended to the solution. This file replaces the old REPF file.
The file contains information on:
  • Groups 
  • Thermostats 
  • Multilayer shells 
  • Oppenheim elements 
  • Solver created elements
Very useful information for understanding the model, especially when looking at other solver files.
MSGF/<simulation/model name>-<solution/analysis name>_verbose.log
A log file that contains messages regarding thermal solver routines, including their timing and memory statistics and verbose messages. By default, the basic level of verboseness is activated. This file replaces the old MSFG file.

The thermal solver has the capability of displaying different levels of messaging in the log files:
  • Level 1 only displays fatal errors.
  • Level 2 displays fatal errors and warning messages.
  • Level 3 displays fatal errors, warnings, and information messages. (This is the default.)
When you include the LEVEL OF VERBOSENESS OF MESSAGING OUTPUT advanced parameter into your solution, you can display:
  • Level 4 displays fatal errors, warnings, information messages, and key information from different thermal solver routines including convergence traces. The level 4 information is written to the verbose log file. This is the default.
  • Level 5 displays level 4 information and MPI secondary ranks. It also resolves messages by boundary conditions. All extra information from level 5 is written only to the verbose log file.
For levels 4 and 5, you can also request the timing and memory information in thermal solver modules that support it when you include the INCLUDE TIMING INFO IN VERBOSE OUTPUT and INCLUDE MEMORY INFO IN VERBOSE OUTPUT advanced parameters, respectively.

The TEMPF file contains the calculated temperatures at the end of a run. The Analyzer writes data on TEMPF at the printout intervals

  • I is the element number.
  • TEMP(I) is the temperature of element I.
  • If I is -99999, TEMP(I) is the printout time value for subsequent temperatures.
The file can be used for initial conditions or mapping.
Post Processing: Reports
Reports are used to extract specific information from the model.

The types of report available is dependent on the solver, the analysis type, and the solution selected.
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BC summary table

When you include the DISPLAY BC SUMMARY TABLES advanced parameter in a solution, the thermal solver generates the <simulation name>-<solution name>.bcdata file that outputs in the table format the time and evaluated boundary condition data for the following loads and simulation objects:
  • Thermal Stream loads
  • Thermal Convecting Zone loads
  • Thermal Void loads
  • Immersed Duct simulation objects
  • Heat Pipe type of Thermal Device simulation objects
The table also outputs the data for named points and groups of elements. (2306+)
This file is updated at each successful time step during the solve and stored in the run or scratch directory.
This table facilitates evaluation of the data related to the boundary condition.
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When you include the PLOT BC SUMMARY advanced parameter in the solution, the thermal solver generates the <simulation name>-<solution name>data.html file that displays graphs of thermal and fluid properties of the following loads and simulation objects included in the solution:
  • Thermal Stream loads
  • Thermal Convecting Zone loads
  • Thermal Void loads
  • Thermal Coupling simulation objects
  • Immersed Duct simulation objects
  • Heat Pipe type of Thermal Device simulation objects
You can also display graphs of thermal and fluid properties for named points and groups of elements.
This file is update during the run at each iteration.

The <simulation/model name>-<solution/analysis name>.bun is the results file in binary universal file format. This file can be read by NX/Simcenter 3D for post-processing.


KB Article ID# KB000128451_EN_US



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