February 2026 critical fixes

Bug 102875: Fix the flow solver regression where the energy equation plateaus and fails to converge

Fixed versions: 2512.3, 2506.7, 2412.15

A regression was identified in the flow solver affecting the computation of residuals for the energy equation. Due to this defect, convergence was not properly detected in certain cases, which could lead to convergence stagnation and increased solve times. This issue has been corrected. Following the fix, a decrease in the number of solver iterations required for convergence may be observed. The final solution results remain unchanged.

Bug 115820: Elemental convection coefficient results are incorrectly reported as zero on thermal exchange co-simulation interfaces when using the finite element method

An issue was identified in finite element simulations using co-simulation thermal exchange boundary conditions where elemental convection coefficient results were incorrectly computed and reported as zero. Nodal convection coefficient results were not impacted. This issue has been resolved.

User Story 117418: Thermal-mechanical models show inconsistent nodal convection coefficient results for thermal-mechanical contacts when running in parallel

Fixed versions: 2512.4

A defect in the thermal parallel solver caused inconsistent nodal convection coefficient results when models with thermal-mechanical contact interfaces were executed using multiple CPUs. The root cause was related to errors in internal averaging and gap distance calculations during the parallel distribution of thermal-mechanical data. This issue has been fixed, ensuring parallel and serial executions now produce consistent and identical convection coefficient results across all supported CPU configurations.

Bug 117516: Convection to environment uses an incorrect user-specified temperature when convection to a fluid ambient or radiative ambient environment is included earlier in the solution

A bug was discovered in the NX2TMG module related to convection to environment constraints. Specifically, when a constraint utilizing a fluid ambient or radiative ambient environment temperature was defined prior to one using a user-specified value, the latter could erroneously inherit the ambient environment temperature rather than applying its intended value. As a result, convection to environment constraints configured with a specified environment temperature may have used an incorrect value during solver execution, resulting in inaccurate solution results. This issue has been resolved.

Bug 119890: Improve precision in the evaluation of the convective area on free edges of axisymmetric elements and on the edges of hole or bolt elements

Fixed versions: 2512.3, 2506.7

Two issues were identified and have been resolved.

Axisymmetric free edge behavior

Axisymmetric free edges were incorrectly treated as plane stress when computing the convective area in the thermal solver. This could result in small differences in key simulation results, such as temperatures.

Convective and thermal coupling boundary conditions (BCs) on holes and bolts

For convective or thermal coupling BCs applied to hole or bolt edges, the convective area was evaluated incorrectly. The calculation used a thickness-only evaluation rather than the true coupled surface area that accounts for the curvature of the hole or bolt geometry. This discrepancy was more significant for linear elements, where the evaluated area could differ substantially from the correct convective area. For parabolic elements, the impact was less pronounced.

Both issues have been corrected. Axisymmetric edges are now handled properly, and convective and thermal coupling BCs accurately account for the full curved surface area of holes and bolts, ensuring reliable simulation results.