Hello,

my problem is that I want to define in a model a boundary condition (BC) with zero gradient flux condition. I have several species in a table, and I want the first derivative for them to be zero. For a single species I don’t have the problem, but I can’t transfer it to get it for a longer list.

This how I write it down for the single species

"Zero Gradient condition" BC = Derivative[1, 0]  [Cl][L, t] == 0

For more species I define first a BC for each species and then write all in a list

dspecies = {Cl, Ca, Na}
BC[Cl] = 0;
BC[Ca] = 0;
BC[Na] = 0;

BCdspecies = Table[dspecies[[i]][L, t] == BC[dspecies[[i]]], {i, 1,Length[dspecies]}];

I don't see where I can get here the first derivative. May someone know how this works?

Cheers Chris