September 2025 critical fixes

September 2025 fixes were published on 18 September 2025.

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

Fixed versions: 2506.4, 2412.12

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 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

Fixed versions: 2506.4, 2412.12

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.

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

Fixed versions: 2506.4, 2412.12

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.