Changes between Initial Version and Version 1 of Ticket #6200, comment 9


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Timestamp:
2021-09-13T21:40:24Z (4 years ago)
Author:
Francesco Casella

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  • Ticket #6200, comment 9

    initial v1  
    1 Another small example case: [https://libraries.openmodelica.org/branches/master/Buildings_7.0.0/files/Buildings_7.0.0_Buildings.Fluid.HeatExchangers.Validation.HeaterCooler_u.err Buildings.Fluid.HeatExchangers.Validation.HeaterCooler_u].
     1@Karim, maybe I got a good lead on this issue. Please check this example case: [https://libraries.openmodelica.org/branches/master/Buildings_7.0.0/files/Buildings_7.0.0_Buildings.Fluid.HeatExchangers.Validation.HeaterCooler_u.err Buildings.Fluid.HeatExchangers.Validation.HeaterCooler_u].
    22
    3 Diagnostics with {{{-d=bltdump}}}
     3Diagnostics with {{{-d=bltdump}}}:
    44{{{
    55[6] 22:35:32 Symbolic Error
    … …  
    1212  36: heaDyn.vol.dynBal.ports_mXi_flow[1,1]:VARIABLE(unit = "kg/s" protected = true final = true ) Buildings.Fluid.HeatExchangers.Validation.HeaterCooler_u, Buildings.Fluid.HeatExchangers.HeaterCooler_u, Buildings.Fluid.MixingVolumes.MixingVolume, Buildings.Fluid.Interfaces.ConservationEquation type: Real [2,1]
    1313}}}
     14Now, there are ''two equations'' stating that the derivative of a certain pressure is zero, one belonging to the "dynamic" set and the other belonging to the "initial" set.
     15
     16The initial one comes straight from the initial equations set. I tried to figure out where the dynamic one comes from. If I turn on {{{-d=optdaedump}}}, that equation first appears in the log immediately after "Index reduction done.". It shows up in the previous list, marked "pantelidesIndexReduction (unspecified partition)", as {{{der(heaDyn.vol.dynBal.medium.p) = 0.0}}}. As I understand, this equation comes from the fact that the medium pressure is equal to the fixed sink pressure because of the direct connection between the two volumes, so the Pantelides algorithm identifies this constraint and differentiates it.
     17
     18Now, the algorithm that identifies redundant initial conditions due to index reduction should detect this pair as such and remove one. For some reason, however, this pair escapes the detection. Can you try to figure out why?