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Parameters are being changed to default zero values at initialization!
Parameters are being changed to default zero values at initialization!
Jun-22-17 21:24:08
Hi,
I'm trying to simulate a rather highly non linear dynamic system. I started with a steady state model and got the values. I then made a dynamic model and set the derivatives to zero in the 'initial equation' section. I gave the initial guesses based on the steady state model result. Now, when I run the dynamic model, it gives the following warning:
Code:
[1] 02:46:30 Translation Notification
It was not possible to analyze the given system symbolically, because the relevant equations are part of an algebraic loop. This is not supported yet.
[2] 02:46:30 Translation Warning
Assuming redundant initial conditions for the following 30 initial equations:
P[5] = P_condenser + 10.0 * Pressure_drop + (P_condenser + Pressure_drop - (P_condenser + 10.0 * Pressure_drop)) * 0.4444444444444444
comp[2].HOV[1] = propanol.HOV[1]
comp[2].VapCp[6] = propanol.VapCp[6]
comp[2].VP[2] = propanol.VP[2]
comp[1].VP[2] = ethanol.VP[2]
comp[2].LiqDen[1] = propanol.LiqDen[1]
comp[2].LiqDen[4] = propanol.LiqDen[4]
comp[2].HOV[2] = propanol.HOV[2]
comp[1].HOV[2] = ethanol.HOV[2]
comp[2].VP[4] = propanol.VP[4]
comp[2].HOV[5] = propanol.HOV[5]
comp[2].HOV[6] = propanol.HOV[6]
comp[2].LiqDen[3] = propanol.LiqDen[3]
comp[2].VP[3] = propanol.VP[3]
comp[2].VP[5] = propanol.VP[5]
comp[1].Tc = ethanol.Tc
comp[2].VP[6] = propanol.VP[6]
comp[2].LiqDen[6] = propanol.LiqDen[6]
comp[2].LiqDen[5] = propanol.LiqDen[5]
comp[2].HOV[4] = propanol.HOV[4]
comp[1].VP[3] = ethanol.VP[3]
comp[1].VP[4] = ethanol.VP[4]
comp[1].VP[5] = ethanol.VP[5]
comp[1].VP[6] = ethanol.VP[6]
comp[2].VapCp[4] = propanol.VapCp[4]
comp[1].HOV[4] = ethanol.HOV[4]
comp[1].HOV[5] = ethanol.HOV[5]
comp[1].HOV[6] = ethanol.HOV[6]
comp[1].VapCp[6] = ethanol.VapCp[6]
comp[2].Tc = propanol.Tc
[3] 02:46:30 Translation Warning
Iteration variables with default zero start attribute in torn nonlinear equation system:
$DER.x[2,2]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10,2]
$DER.x[3,2]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10,2]
$DER.x[4,2]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10,2]
$DER.x[5,2]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10,2]
$DER.x[6,2]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10,2]
$DER.x[7,2]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10,2]
$DER.x[8,2]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10,2]
$DER.x[9,2]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10,2]
$DER.x[10,2]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10,2]
$DER.x[1,2]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10,2]
comp[1].VP[5]:VARIABLE() = ethanol.VP[5] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[2].HOV[6]:VARIABLE() = propanol.HOV[6] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[2].VapCp[6]:VARIABLE() = propanol.VapCp[6] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[2].HOV[4]:VARIABLE() = propanol.HOV[4] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
$DER.T[10]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10]
comp[2].VP[3]:VARIABLE() = propanol.VP[3] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
$DER.T[9]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10]
comp[2].HOV[2]:VARIABLE() = propanol.HOV[2] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[2].LiqDen[1]:VARIABLE() = propanol.LiqDen[1] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[2].LiqDen[3]:VARIABLE() = propanol.LiqDen[3] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[1].VP[3]:VARIABLE() = ethanol.VP[3] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[2].VP[5]:VARIABLE() = propanol.VP[5] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[2].LiqDen[4]:VARIABLE() = propanol.LiqDen[4] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[1].Tc:VARIABLE() = ethanol.Tc .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [2]
comp[1].VP[6]:VARIABLE() = ethanol.VP[6] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
$DER.T[5]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10]
comp[2].HOV[5]:VARIABLE() = propanol.HOV[5] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
$DER.T[7]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10]
comp[1].VapCp[6]:VARIABLE() = ethanol.VapCp[6] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[1].HOV[6]:VARIABLE() = ethanol.HOV[6] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
$DER.T[8]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10]
$DER.M[7]:VARIABLE() .DistillationDynamic, .Real type: Real [10]
P[5]:VARIABLE() = P_condenser + 10.0 * Pressure_drop + (P_condenser + Pressure_drop - (P_condenser + 10.0 * Pressure_drop)) * 0.4444444444444444 .DistillationDynamic, .Real type: Real [10]
$DER.M[10]:VARIABLE() .DistillationDynamic, .Real type: Real [10]
comp[2].LiqDen[6]:VARIABLE() = propanol.LiqDen[6] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[2].LiqDen[5]:VARIABLE() = propanol.LiqDen[5] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
$DER.T[2]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10]
comp[1].HOV[5]:VARIABLE() = ethanol.HOV[5] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[1].HOV[2]:VARIABLE() = ethanol.HOV[2] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
$DER.T[3]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10]
comp[2].HOV[1]:VARIABLE() = propanol.HOV[1] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
$DER.T[6]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10]
$DER.T[4]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10]
comp[2].Tc:VARIABLE() = propanol.Tc .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [2]
$DER.T[1]:DUMMY_DER(fixed = false ) .DistillationDynamic, .Real type: Real [10]
comp[1].HOV[4]:VARIABLE() = ethanol.HOV[4] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
$DER.M[3]:VARIABLE() .DistillationDynamic, .Real type: Real [10]
comp[2].VP[4]:VARIABLE() = propanol.VP[4] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[2].VP[6]:VARIABLE() = propanol.VP[6] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[2].VapCp[4]:VARIABLE() = propanol.VapCp[4] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[2].VP[2]:VARIABLE() = propanol.VP[2] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[1].VP[2]:VARIABLE() = ethanol.VP[2] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
comp[1].VP[4]:VARIABLE() = ethanol.VP[4] .DistillationDynamic, .Chemsep_Database.General_Properties, .Real type: Real [6]
$DER.M[1]:VARIABLE() .DistillationDynamic, .Real type: Real [10]
$DER.M[4]:VARIABLE() .DistillationDynamic, .Real type: Real [10]
$DER.M[2]:VARIABLE() .DistillationDynamic, .Real type: Real [10]
$DER.M[5]:VARIABLE() .DistillationDynamic, .Real type: Real [10]
$DER.M[6]:VARIABLE() .DistillationDynamic, .Real type: Real [10]
$DER.M[8]:VARIABLE() .DistillationDynamic, .Real type: Real [10]
$DER.M[9]:VARIABLE() .DistillationDynamic, .Real type: Real [10]
Here almost all the values that are being set to default zero are parameters for which the values are available at t=0, but still they are being dropped.
(the system is exactly same as steady state one, except derivatives are added but they are kept as zero in initial equation section)
Any ideas how to solve this issue?
-Swaroop
- swaroop.katta
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- 23 Posts
Thank you
Re: Parameters are being changed to default zero values at initialization!
Jun-22-17 21:35:08
Why is the initialization problem over-determined? Did you set `fixed=true` while setting the initial guess?
- lochel
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- 45 Posts
Re: Parameters are being changed to default zero values at initialization!
Jun-22-17 21:42:22
No, I did not use 'fixed = true'. I just gave whatever initial values that I gave for steady state model. I think parameters have default values of 'fixed = true' right? Is there any reason why they are being changed to zero?
-Swaroop
- swaroop.katta
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- 23 Posts
Re: Parameters are being changed to default zero values at initialization!
Jun-22-17 21:46:01
Can you share the model?
- lochel
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- 45 Posts
Re: Parameters are being changed to default zero values at initialization!
Jun-22-17 22:04:44
- swaroop.katta
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- 23 Posts
Re: Parameters are being changed to default zero values at initialization!
Jun-23-17 11:41:02
It seems that the dynamic model contains too much initial equations. Maybe this is because of index reduction. You should try to define less initial equations because otherwise OpenModelica will try to remove some by itself which might lead to strange results.
It simulates with the following initial equations, but I don’t know if this is what you want.
Code:
initial equation
for i in 1:N_Trays loop
der(M[i]*x[i,:].*hl[i,:]) = {0,0};
end for;
- lochel
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- 45 Posts
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