dolfin team mailing list archive

[Johan Hake <johan.hake@xxxxxxxxx>]

On Friday October 8 2010 00:12:26 Anders Logg wrote:
> Question #128351 on DOLFIN changed:
> https://answers.launchpad.net/dolfin/+question/128351
> 
>     Status: Open => Answered
> 
> Anders Logg proposed the following answer:
> 
> On Thu, Oct 07, 2010 at 08:01:27PM -0000, Sungick Kim wrote:
> > New question #128351 on DOLFIN:
> > https://answers.launchpad.net/dolfin/+question/128351
> > 
> > Let  'u' be a scalar nodal value.
> > Now I want to construct a nodal vector field as below.
> > 
> > velocity = Expression(('u', '0.0', '0.0'))
> > 
> > There comes no error related this.
> > However, it seems that velocity = (0,0,0) all throughout domain.
> > Can anyone help me to know the right way to do this?
> 
> Have you set the value of u?

I am not exactly sure what you want to do, but if you just have a scalar 
value, you need to initilize u in your Expression. 

This can be done in two ways:

  velocity = Expression(('u', '0.0', '0.0'), {'u':value})

or
  
  velocity = Expression(('u', '0.0', '0.0'))
  velocity.u = value

There are no errors because u is initialized to Zero. Take a look in the 
docstring of Expression.

Johan