Page 217 - Process Modelling and Simulation With Finite Element Methods

204 Process Modelling and Simulation with Finite Element Methods

Pull down the options menu and select Add/Edit constants. The Add/Edit
constants dialog box appears.

AddEdit Constants
Name of constant: R; Expression: 3
0 Name of constant: Pe; Expression: 100

Pull down the Mesh menu and select the Parameters option.
Mesh Parameters
Set symmetry boundaries: 1 4
0 Total elements 2000
ApplyIOK
Now for the boundary conditions. Pull down the Boundary menu and select
Boundary Settings.

Boundary Mode
For both modes mom and condiff, specify:
Set bnd 2&3 as Neumann (no flux, no penetration) q=g=O
Set bnd 1 h=l, r=O
0
Set bnd 4 h=-1, r=O
Amlv/OK
As we have seen before, symmetry boundaries with these h-values result in
periodic boundary conditions.

Now pull down the Subdomain menu, and select Subdomain settings.

Subdomain Model Coefficient View
Select domain 1
mom mode, set c=-1, w0 0, 0 0, P=R*cx R*cy, f=-R*cy
condiff mode, set c=l/Pe, da=l, a=O 0, 0 0, p=siy -six,
f=O
init tab: (condiff) erfcnois(x,y)
Apply/OK
erfcn0is.m is a m-file function
function a=erfcnois (x,y)
)
)
b=-O.5*erfc (40* (x + 0.1) * (1.+0.02*randn(l) ;
c=O .5*erf c (40* (x - 0.1) ) * (1. +O .02*randn (1) ) ;
a=b+c;
which creates an appropriate slug of concentration unity that rapidly smooths out
in either horizontal direction, superposed with random (normally distributed) noise.