Buildings.Fluid.FixedResistances.BuriedPipes.Examples.TwoPipesConduit may be ill posed

[mwetter]

The model Buildings.Fluid.FixedResistances.BuriedPipes.Examples.TwoPipesConduit may be ill-posed:

On Dymola 2024x Refresh1 beta 1 (and likely older versions) it seems to simulate fine. See for example

On OpenModelica, the model stops with an assertion and the above temperature looks like

The assertion is

The following assertion has been violated at time 48565440.000000 ((noEvent(pipRet.vol_a.dynBal.medium.T <= 403.15))) --> "In TwoPipesConduit.pipRet.vol_a.dynBal.medium: Temperature T = 404.546 K exceeded its maximum allowed value of 130 degC (403.15 Kelvin) as required from medium model "Buildings.Media.Water"."

On OCT, the model fails to translate with

Error in flattened model:
  The system is structurally singular. The following variable(s) could not be matched to any equation:
     _eventIndicator_3
     _eventIndicator_6

  The following equation(s) could not be matched to any variable:
    der(pipSup.timDel.x) = der(pipSup.timDel.x)
    der(pipRet.timDel.x) = der(pipRet.timDel.x)

This issue is to analyze what the underlying cause is for this model to fail with two tools.

Note that various models in Buildings.Fluid.FixedResistances.BuriedPipes are on the exlude list in conf.yml.

[EttoreZ]

Hey Michael.

Trying to replicate your errors, I am using Ubuntu 22: OpenModelica 1.22.2~3-g9f40725 :

• Model does not converge when run with cvode (not your error though)
• Model does simulate using dassl, but results look a bit strange (see figure). . Optimica 1.4:
• I get the same error you mentioned I will take a look the following days to see if I notice anything strange in the formulation.