September 2025 critical fixes

Bug 106922: An incorrect flow return temperature is computed when the convective heat exchange type is used in a recirculation loop boundary condition

A bug related to the log-mean temperature method for recirculation loop boundary conditions using the convective heat exchange type was identified and corrected. The flow return temperature is now calculated as intended. The flow solver reference guide now provides additional details regarding the assumptions used in calculating temperature changes caused by convective heat exchange in recirculation loop boundary conditions.

Bug 110856: The contact solution is not reliably transferred from the Simcenter Nastran solver to the Simcenter 3D Thermal solver across all coupling time intervals in a thermal-mechanical run

Fixed versions: 2512.0

This is a critical fix for the Simcenter Nastran solver that directly impacts thermo-mechanical runs in the Simcenter 3D Multiphysics environment. The contact solution is now reliably transferred from the structural solver to the thermal solver across all coupling time intervals in a multiphysics run. Prior to the Simcenter Nastran fix, the output of contact distance and contact pressure values, as well as final contact separation results was inconsistent, with some values missing or present when not appropriate. For thermo-mechanical contact boundary conditions, the thermal solver’s calculation for thermal couplings depends on contact distance and contact pressure values provided by the structural solver. Consequently, convection coefficient results and other related outputs such as temperatures and convective heat fluxes may differ before and after this fix. Additionally, for gap distance co-simulation interface boundary conditions, the gap distance values sent to the external solver may also change following the implementation of this fix, which is reflected in the co-simulation log and overall results.

Bug 111444: Incorrect coupling areas for plane stress edges with both thermal coupling and enclosure radiation, and for thermal couplings where the primary region includes plane stress, axisymmetric, or chocking elements much larger than those in the secondary region

This critical fix addresses two defects:

1. In scenarios where both a thermal coupling and an enclosure radiation are applied to the same plane stress element edge, the thermal solver computed the incorrect coupling area. This error occurred during the process that determines the minimum overlap area between the primary and secondary selections of the thermal coupling.
2. When a thermal coupling is applied, a coupling resolution is defined that triggers a subdivision of the primary selection for accurate overlap area computation. If the primary element is significantly larger than the secondary element, the thermal solver performs an additional subdivision of the primary element. However, when the primary selection involves plane stress, axisymmetric, or chocking elements, the area comparison logic governing this extra subdivision was not properly evaluated. As a result, the computed overlap area lacked precision, negatively impacting the accuracy of thermal coupling results.

Users may observe differences in temperature, convective heat flux, and coupling area results after this correction.

Bug 114630: Relative temperature difference defined as a 4D field is ignored and set to zero for void regions

Fixed versions: 2512.0, 2506.5, 2412.13

When the Swirl Input Type was set to Relative Temperature Difference and defined using a 4D field, void regions were incorrectly assigned a zero value because the corresponding table was ignored. This resulted in incorrect calculations of total absolute fluid temperature on walls. This issue has now been resolved.

User Story 115002: Unexpected fluid cooling in a coupled thermal-flow simulation with a convective rotating flow surface

A bug was identified in the flow solver regarding its treatment of convective walls exchanging heat with the thermal solver, as opposed to flow-only simulations. Specifically, the viscous work term was not computed on these convective walls during coupled thermal-flow simulations. This issue has been resolved; the viscous heating surface source term is now correctly calculated for convective walls, thereby ensuring accurate temperature and convection coefficient results in coupled thermal-flow simulations.