Page 336 - Process Modelling and Simulation With Finite Element Methods

Electrokinetic Flow 323

Init tab Y(tO) = 1
Subdomain 1 -sig*phix -sig*phiy 0 0
(potential mode)
0 Apply I OK

Note the space delimiter is necessary to specify T as a vector in species mode
and potential mode. There are few loose ends to tie up. Two expressions above
are undefined. As we are already in the Subdomain Mode, it is convenient to
define them now. Pull down the options menu and select Add/Edit
expressions. The Add/Edit expressions dialog box appears.

Now for the boundary cconditions.
Boundary Settings.

bnd 1 bnd 2 bnd 3 bnd 4
outflowtpressure u = zeta*phix u = zeta*phix outflowtpressure
p=o v = zeta*phiy v = zeta*phiy p=o

bnd 1 bnd 2 bnd 3 bnd 4
Dirichlet Neumann Neumann Neumann
G=0; R=-Y G=O G=O G = betael*zel*Y*phix

bnd 1 1 bnd2 1 bnd3 I bnd4
Dirichlet I Neumann I Neumann 1 Dirichlet
I G=0; R=3-phi I G=O I G=O 1 G=O; R= -phi

Accept the standard mesh parameters and hit the mesh button on the toolbar
(triangle). 87 nodes and 136 elements are created for us. Note that to produce
the desired Neumann boundary condition at the outlet boundary for species, G is
set to the expression that precisely eliminates the electrophoretic term from r in
the species equation.