Hello team,

First of all, thank you for the work on this OpenFOAM/GUI integration — it is very helpful for running and monitoring cases interactively.

I would like to raise a feature request / gap that I encountered while working on a coupled thermal problem.

In the current build (OpenFOAM v2412, GUI-based execution), it appears that patch-based expression boundary conditions are not supported, specifically:

patchExprFixedValue is not available

Expression access to other patches (e.g. patch(otherPatch).T)

Patch-level operators like areaAverage(patch(...)) or equivalent

timeVaryingUniformFixedValue is also not available in this build

Because of this, it is not possible to define boundary conditions such as:

Exhaust temperature = average suction temperature + ΔT

directly inside the case using expressions.

Impact / Why this matters

For coupled HVAC / data-center / ventilation simulations, patch-to-patch coupling is a very common requirement.
Without expression-based patch access, the only workaround is to:

run an external outer loop (Python / script)

read values from postProcessing/surfaceFieldValue

manually update the boundary condition file during runtime

While this workaround functions, it:

adds unnecessary complexity,

breaks the “single-solver-run” workflow,

and defeats some of the advantages of using a GUI-driven solver.