[esp-r] Re: Contamination modelling reveals multiple issues

[Aizaz Samuel]

Christian,

In my experience the problem is not with the way ESP simulates but in results 
display. I have noticed that if mass flow network results are viewed in a 
random way then unrealistic values may sometimes be observed. Contaminant 
simulation is based on network mass flow and therefore contaminant results 
may also appear different from expected when not viewed in sequential order. 
As far as I know the bug has not been resolved. The work around is to view 
all flows, concentrations etc. in order. 

Solver instability has been reported in the past for contaminant modelling, 
try reducing your timestep to few minutes.

Although it may not have been tried before flow networks, plant and 
contaminants should work together - I plan to build such a model soon.

Regards,
Aizaz

On Friday 13 June 2008 17:55, Christian Anker Hviid wrote:
> Dear ESP-r community
>
> I am puzzled byt the contamination feature. Here are my findings:
>
> I have a model of a building where I use a combined air flow network (AFN)
> and plant system (PLANT) with a control law that acts on the air flow
> network. I introduce a contamination model CONT with CO2. The contamination
> model and the building have the same timestep /hour.
>
> I have included an examplar file in the results: cellular_contam_bc which
> contains AFN and CONT.
>
> With timestep averaged output (hourly integration)
> AFN + PLANT: Flow looks fine. Flow is controlled by the ctrl law and shows
> high value in day and low at night. AFN + CONT: Flow is wrong with jagged
> spikes and values beyond reality. CO2 is also jagged. AFN + PLANT + CONT:
> Flow is obviously wrong with jagged spikes. CO2 levels are also jagged
> spikes. EXAMPLAR: CO2 is fine if plotted first, flow is oscillating.
>
> Output saved at each timestep:
> AFN + PLANT : Flow is not correct, shows almost constant value. Not
> possible to plot results when a plant model is included here? AFN + CONT:
> Flow is correct and CO2 is correct if I plot CO2 before flow. Plotting flow
> first spoils the y-axis scale of CO2. Adjusting scale does not bring CO2
> curve back. AFN + PLANT + CONT: Flow is not correct, almost constant value.
> CO2 seems ok if I consider the flow results. EXAMPLAR: CO2 looks fine, Flow
> looks nice.
>
> What am I doing wrong? Contamination works ok fine with AFN, but not with a
> combined AFN+PLANT. Why does AFN+CONT only work when I save output at each
> timestep? Anybody with experience in contamination modelling? Thank you for
> your help.
>
>
> Best regards
> Christian Anker Hviid
>
> Civ. ing., Erhvervsph.d.-studerende
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