Hi, why an Error occurred while flattening??
model betondechanvreFINAL
parameter DomainLineSegment1D wall (L=0.36,N=20) "domain";
field Real teta (domain=wall);
field Real T (doamin=wall);
parameter Real rholiquid = 1000; //material density rholiquide beton de chanvre
parameter Real rhosurface = 0.011;//material density du beton de chanvre
  parameter Real rhogaz = 0.011; //material density du beton de chanvre
  parameter Real Rhoambiant = 1.25; //material density de l'air
  parameter Real Cp = 1000; //specific heat capacity
  parameter Real L = 0.36; //length of the wall
  parameter Real lambda = 0.1; //heat conductivity
  parameter Real Tinit = 296.15;//the wall is at 20 degree initialy
  parameter Real Text = 303.15; //the wall is at 20 degree initialy
  parameter Real tetainit = 0.012; //the wall is at 40% final relative humidity
  parameter Real Tfinal = 303.15; //the wall is at 30 degree final
  parameter Real Dteta = 1.16e-9;
  parameter Real Dtemp = 1.02e-12;
  parameter Real Dtetav = 1.07e-9;
  parameter Real Dtempv = 1.02e-12;
  parameter Real Lv = 2500; //specific heat capacity
  parameter Real hMassique = 0.0025;//coefficient d'echange massique
  parameter Real coefficientThermique = 3; //heat transfert coefficient intern

initial equation//initialise the state of variable of the module
T=Tinit indomain wall;
teta=tetainit indomain wall;

equation
der(teta)=Dtemp*pder(T,x2)+Dteta*pder(teta,x2) indomain wall;
rhogaz*Cp*der(T)=lamb*pder(T,D,x2)+Lv*rholiquid*Dtempv*pder(T,x2)+Dteta*pder(teta,x2) indomain wall;

//boundaries
-rholiquid*Dtemp*pder(T,x)=0 indomain wall.left;
-rholiquid*Dtemp*pder(T,x)-rholiquid*Dteta*pder(teta,x)=hMassique*(rhosurface-Rhoambiant) indomain wall.right;
end betondechanvreFINAL;

model betondechanvrehome
parameter Real rho=1000;//material density
parameter Real rhosurface=413;//material density
parameter Real Rhoambiant=0.007;//material density
parameter Real Cp=1000;//specific heat capacity
parameter Real L=0.1;//length of the wall
parameter Real lambda=0.11;//heat conductivity
parameter Real Tinit=293.15;//the wall is at 20 degree initialy
parameter Real Text=293.15;//the wall is at 20 degree initialy
parameter Real Tint=293.15;//the wall is at 20 degree initialy
parameter Real Thi=293.15;//the wall is at 20 degree initialy
parameter Real tetainit=0.4;//the wall is at 40% final volume specifique d'humidite
parameter Real tetaext=0.4;//the wall is at 40% final volume specifique d'humidite
parameter Real Tfinal=303.15;//the wall is at 30 degree final
parameter Real tetafinal=0.7;//the wall is at 70% final volume specifique d'humidite
parameter Integer N=10;
parameter Real deltax=L/N;//Discretisation
parameter Real Dteta=1.16e-9;
parameter Real Dtemp=1.02e-12;
parameter Real Dtetav=1.07e-9;
parameter Real Dtempv=1.02e-12;
parameter Real Lv=1000;//specific heat capacity
parameter Real hMassique=0.003;//coefficient d'echange massique
parameter Real coefficientThermique=3;//coefficient d'echange thermique

Real T[N];
Real teta[N];

initial equation//initialise the state of variable of the module

for i in 1:N-1 loop
T[i]=Tinit;
teta[i]=tetainit;
end for;

equation
-rho*(T[1]*Dtemp+Dteta*teta[1])=0;
-rho*(T[N]*Dtemp+Dteta*teta[N])=hMassique*(rhosurface-Rhoambiant);
-lambda*T[1]-Lv*rho*(Dtempv*T[1]+Dtetav*teta[1])=0;
-lambda*T[N]-Lv*rho*(Dtempv*T[N]+Dtetav*teta[N])=coefficientThermique*(Tinit-Tfinal)+Lv*hMassique*(rhosurface-Rhoambiant);


for i in 2:N-1 loop
der(teta[i])=Dtemp*(T[i+1]-2*T[i]+T[i-1])/(L/N)^2 +Dteta*(teta[i+1]-2*teta[i]+teta[i-1])/(L/N)^2;
rhosurface*Cp*der(T[i])=lambda*(T[i+1]-2*T[i]+T[i-1])/(L/N)^2 +Lv*Dtempv*(T[i+1]-2*T[i]+T[i-1])/(L/N)^2 + Dteta*(teta[i+1]-2*teta[i]+teta[i-1])/(L/N)^2;
end for;


end betondechanvrehome;



the output error is

[1] 11:28:24 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] 11:28:24 Translation Warning
Assuming redundant initial conditions for the following 2 initial equations:
         T[1] = Tinit
         teta[1] = tetainit
what is the problem? can anyone help?

i should simulate heat and humidity through a single layer wall in openmoldelica...there is a problem the partial differential equation  i downloaded from internet model a model but pder (u,x) is not the function do do partial differential equation!
i download this script but it cam't run in openmodelica why?

model advection
parameter DomainlineSegment1D omega(L=5, N=200);
Real u(domain=omega);
initial equation
equation
der(u)+2*pder(u,x)=0;
u=0;
u=extrapolatefield();
end advection;