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;