How to read and understand the solver log file?
This article explains how to read and interpret Simcenter 3D Thermal/Flow solver log files, including information about solution setup, boundary conditions, solver iterations, and convergence results.
Model summary
- Simulation setup summary
-
- Solver type
- Analysis type
- Solution type
- Model path
- Solver run directory
- Mesh and model statistics
-
- Nodes: 100,992
- Thermal elements: 53,050
- Flow elements: 0
- Surface coating elements: 17,095
Finite Element Model
--------------------
Solver type: Simcenter 3D Thermal/Flow
Analysis type: Thermal
Solution type: Thermal
Simulation File: C:\simulation_file.sim
Solution: Steady
Number of nodes in thermal model: 10636
Number of elements in thermal model: 35643
Number of nodes in flow model: 0
Number of elements in flow model: 0
Number of elements created for surface coating: 8191 Use this information to confirm that the model size, element counts, and analysis type match your intended setup.
Solution options
Solution Options
----------------
Steady-State Analysis
Solving Thermal Only
Ambient Temperature: 2.000E+01 C
Ambient Pressure: 1.014E+02 mN/mm^2
Gravitational Acceleration: 9.810E+03 mm/s^2
Gravity Direction: X: 0.000E+00 Y: 0.000E+00 Z:-1.000E+00 Boundary conditions
Number of thermal boundary conditions: 4
Thermal Boundary Condition Type Value FSF TCP
----------------------------------------------------------------------
1 - 2000 W Heat Load 2.000E+09 mN-mm/s No All
1 - INIT_BC Initial Temp 2.000E+01 C No Yes
2 - tire_convection_to_outs Convective 2.500E+01 C No No
1 - wheel_convection_to_out Convective 2.500E+01 C No No
3 - wheel_and_brake_convect Convective 2.500E+01 C No No Number of thermal couplings: 1
Thermal Coupling Name Value Units
----------------------------------------------------------------------
1 - Brake_wheel_TC 2.000E+04 mN/mm-s-C
Type: Contact,Heat Transfer Coefficient
Primary Area: 1.455E+05 mm^2
Secondary Area: 1.560E+05 mm^2 These entries describe how heat is exchanged through applied boundary conditions and conductive interfaces.
Solver modules
| Module | Purpose |
|---|---|
| MAIN | Performs data checking, determines which modules to run. |
| DATACH | Performs data checking, and orbit creation. |
| ECHOS | Calculates each element's CG, element center, area or volume, hydraulic diameter, and surface normal along with the location of the nodes. |
| CONDN | Calculates capacitances, hydraulic resistances, and conductive conductances from geometry. |
| VUFAC | Calculates view factors, solar view factors, albedo factors, Earth view factors, heat flux view factors, and thermal couplings from geometry. |
| GRAYB | Calculates radiative conductances and gray body view factor matrices from view factors. |
| POWER | Calculates IR and solar spectrum heat loads from view factors and gray body view factor matrices. |
| MEREL | Performs model simplification, merging, substructuring, and combines parameters. |
| ANALYZER | Calculates temperatures and total pressures. |
| RSLTPOST | Transforms results into I-deas Universal file format. |
If the analysis fails, identify which module was running at the time to diagnose whether the issue is due to geometry, boundary setup, or solver convergence.
Information about convergence
When you select the Convergence Trace option, the solver writes detailed information about convergence. The log file contains:
- Per-iteration residuals
- Residuals values for every ILU/CG iteration, allowing you to track how the
residual drops as the solution converges.
When solving the thermal equations, the solver uses an iterative approach based on two combined algorithms: ILU (Incomplete LU factorization) and CG (Conjugate Gradient). Each ILU/CG iteration refines the temperature field until the residual falls below the specified convergence target.
ILU iteration 1 Residual= 7.67E-01 ILU iteration 2 Residual= 5.91E-01 ILU iteration 3 Residual= 7.48E-01 ILU iteration 4 Residual= 9.81E-01 ILU iteration 5 Residual= 7.17E-01 ILU iteration 6 Residual= 6.56E-01 ILU iteration 7 Residual= 5.29E-01 ILU iteration 8 Residual= 2.57E-01 ILU iteration 9 Residual= 3.45E-01 ILU iteration 10 Residual= 2.35E-01- The iteration number shows the step count of the solver.
- The residual value shows how far the current solution is from satisfying the governing equations.
- A decreasing residual means the solver is moving toward convergence. If residuals stall or increase, it signals difficulty in solving.
- Automatic restarts
- If the solver cannot reach the target residual within the allowed number of
iterations, it automatically restarts with updated
parameters:
After 100 iterations the Conjugate-Gradient solver did not converge. Residual= 2.197E-04, target residual= 1.000E-05, matrix fill= 20. The solution is restarting with matrix fill= 20, iteration limit= 200.The solver reached the iteration limit before convergence and is restarting with a higher matrix fill or a larger iteration limit to improve stability. You can change these settings in the Solver Parameters dialog box. For more information, see Troubleshooting thermal convergence issues and invalid temperature distribution.
- DTmax lines with element IDs
- During each ILU step, the solver reports the maximum temperature change,
DTmax, and the element ID where it
occurs:
ILU iteration 37 DTmax= 9.12E-03 at 39851 ILU iteration 38 Residual= 9.74E-06 ILU iteration 38 DTmax= 3.36E-04 at 39851This tells you which element in the model is most strongly influencing convergence at that step.
- Convergence confirmation
- Once the residual falls below the target threshold, the solver reports
successful
convergence:
Conjugate-Gradient solver successfully converged after 38 iterations. Residual= 9.738E-06, target residual= 1.000E-05, matrix fill= 20. - Final iteration summary
- The solver prints:
- A summary of the last few iterations, showing temperature extremes
and convergence
indicators:
Iter Tmax At Tmin At TDmax At T(TDmax) Time 1 70.95 49599 19.99 74891 5.10E+01 49599 70.95 0.000000E+00 ILU iteration 1 Residual= 4.65E-06 ILU iteration 1 DTmax= 1.11E-04 at 56061 Iter Tmax At Tmin At TDmax At T(TDmax) Time 2 70.95 49599 19.99 74891 1.11E-04 56061 26.52 0.000000E+00 No. of iterations = 2 TDmax = 1.107E-04 at element 56061- Tmax / Tmin — maximum and minimum temperatures, with their element IDs.
- TDmax — maximum temperature change across the model for that iteration.
- T(TDmax) — the temperature value at the element where TDmax occurred.
- Minimum and maximum temperatures and the elements where they
occur:
Minimum temperature = 19.993 at element 74891 INIT_BC Maximum temperature = 70.934 at element 68009 INIT_BC - Heat balance deviation identifying the element most responsible for
imbalance in the energy
equation:
Maximum heat balance deviation occurs at element 77931 Coil_2
- A summary of the last few iterations, showing temperature extremes
and convergence
indicators:
Heat flow summary
- Heat load is a directly applied heat load Q, through boundary conditions: volumetric heat flows or surface heat fluxes.
- Heat flows are heat flows through conductances due to temperature differences.
- Units correspond to those defined in the Solution Units page of the Solution dialog box.
For a coupled thermal-flow solution:
Heat Imbalance = Total Heat Load on Elements + Heat Flow from Sinks – Heat Flow into SinksUsing the terminology from the log file:
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)At steady state, Total Heat Imbalance equals zero. Therefore:
Total heat load on non-fluid elements = (Heat flow into temperature B.C.s + Heat convected to fluid) - (Heat flow from temperature B.C.s + Heat convected from fluid) Summary for thermal elements:
Maximum heat balance deviation occurs at element 68723
Heat flow into sinks = 2.000E+09
Heat flow from non-fluid sinks = 1.000E-10
Heat load into elements = 2.000E+09
Heat load into sinks = 0.000E+00
Heat flow from fluid sinks = 0.000E+00
Deviation from heat balance =-2.094E+04
Heat Flow+Load Summary Into Different Sink Entities:
Sink Entity Temperature Heat Energy absorbed
Flow+Load since start
Sink elements with no entity names: 2.500E+01 2.000E+09 0.000E+00