Page 86 - Process Modelling and Simulation With Finite Element Methods

Partial Differential Equations and the Finite Element Method 13

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

Add/Edit Constants
Name of constant: a1
Expression: 1.172E-3
Name of constant: a2
Expression: 7.995E-7
Name of constant: F400
Expression: 421.5
Apply
OK
Pull down the Subdomain menu and select Subdomain mode. Before setting
the equations, it is useful to define some intermediate variables to make the data
entry more concise. Pull down the options menu and select Add/Edit
expressions.

AddEdit Expressions
Variable name: FofT
Variable type: subdomain
Ada
Now click on the definition tab.
Enter expression: (u+273)/( l+al *u+a2*uA2)/F400
Apply
0 OK
Now pull down the Subdomain menu, select Coefficient View, and select
Subdomain settings.

Subdomain Mode
Select domain 1
Set f=O; c=l; d,=l/Foff
Apply
Select the init tab; set u(t0)=500-100*x
Apply
OK

Click on the mesh triangle on the toolbar, and then refine the mesh twice to 60
elements. Click on the = button on the toolbar to solve (stationary linear solver).
The steady state solution is unchanged from the initial condition, since for long
enough times, the accumulation term is immaterial. It certainly is for the