@hirnyk I changed one of the IBCs and recieve this:

Error, (in pdsolve/numeric/plot) unable to compute solution for t<HFloat(0.0):
unable to store HFloat(undefined)+HFloat(undefined)*I when datatype=float[8]

(Not sure if that is progress...)

What is the HFloat paramater? Is it caused from a bad solution?

I have attached my maple file if it is of any use

Thank-you for your continued help

Cation_exchange_mode.mw

@hirnyk I changed one of the IBCs and recieve this:

Error, (in pdsolve/numeric/plot) unable to compute solution for t<HFloat(0.0):
unable to store HFloat(undefined)+HFloat(undefined)*I when datatype=float[8]

(Not sure if that is progress...)

What is the HFloat paramater? Is it caused from a bad solution?

I have attached my maple file if it is of any use

Thank-you for your continued help

Cation_exchange_mode.mw

@hirnyk Thanks for your help, the pdes now solve.

For anyone interested, here is the working code:

equations:={ diff(c(t,z),t)+16/9*diff(q(t,z),t)+7.24+1.74e13*c(t,z)^12*diff(c(t,z),z)=300+7.4e14*c(t,z)^12*diff(c(t,z),z,z), diff(q(t,z),t)=(1.35e10*c(t,z)^13*(1-q(t,z))-q(t,z))/(2/3+1.35e14*c(t,z)^12*(1-1/100*q(t,z))) };

ibc := {c(t,0)=1, c(0,z)=0, q(0,z)=0, D[2,2](c)(t,0)=0};

variables := {q(t,z),c(t,z)};

sol:=pdsolve(equations, ibc, numeric, variables, time=t, range=0..25); 

@hirnyk Thanks for your help, the pdes now solve.

For anyone interested, here is the working code:

equations:={ diff(c(t,z),t)+16/9*diff(q(t,z),t)+7.24+1.74e13*c(t,z)^12*diff(c(t,z),z)=300+7.4e14*c(t,z)^12*diff(c(t,z),z,z), diff(q(t,z),t)=(1.35e10*c(t,z)^13*(1-q(t,z))-q(t,z))/(2/3+1.35e14*c(t,z)^12*(1-1/100*q(t,z))) };

ibc := {c(t,0)=1, c(0,z)=0, q(0,z)=0, D[2,2](c)(t,0)=0};

variables := {q(t,z),c(t,z)};

sol:=pdsolve(equations, ibc, numeric, variables, time=t, range=0..25); 

Thank-you for your reply.

I have now defined the q[1] terms

equations:={

diff(c[1](t,z),t)+16/9*diff(q[1](t,z),t)+7.24+1.74e13*c[1](t,z)^12*diff(c[1](t,z),z)=

300+7.4e14*c[1](t,z)^12*diff(c[1](t,z),z,z),

diff(q[1](t,z),t)=(1.35e10*c[1](t,z)^13*(1-q[1](t,z))-q[1](t,z))/(2/3+1.35e14*c[1](t,z)^12*(1-1/100*q[1](t,z)))

};

and added the diff(c[1](t,z),z,z) term to the ibc

ibc := {c[1](t,0)=1, q[1](0,z)=0, 'diff(c[1](t,z),z,z)=0'};

however I still encounter the same error..... any ideas?

Thanks

variables := {q[1](t,z),c[1](t,z)};

sol:=pdsolve(equations, ibc, numeric, variables);

Thank-you for your reply.

I have now defined the q[1] terms

equations:={

diff(c[1](t,z),t)+16/9*diff(q[1](t,z),t)+7.24+1.74e13*c[1](t,z)^12*diff(c[1](t,z),z)=

300+7.4e14*c[1](t,z)^12*diff(c[1](t,z),z,z),

diff(q[1](t,z),t)=(1.35e10*c[1](t,z)^13*(1-q[1](t,z))-q[1](t,z))/(2/3+1.35e14*c[1](t,z)^12*(1-1/100*q[1](t,z)))

};

and added the diff(c[1](t,z),z,z) term to the ibc

ibc := {c[1](t,0)=1, q[1](0,z)=0, 'diff(c[1](t,z),z,z)=0'};

however I still encounter the same error..... any ideas?

Thanks

variables := {q[1](t,z),c[1](t,z)};

sol:=pdsolve(equations, ibc, numeric, variables);