On 10/15/2018 05:27 AM, Jane Lee wrote:
> 
> I see what you mean though I am confused how you got to the equation for 
> the displacement? Surely there needs to be some time dependence 
> somewhere at least for it to make sense dimensionally?

I may have used the wrong terminology and forgotten a factor of delta t. 
But if you start here:

>      > However, I realised that this moves each vertex by the velocity
>     at that point,
>      > but I need, for example, a vertex on the top boundary to have
>     moved as much as
>      > the ones below it has moved as well as the velocity at the points
>     itself.

...then you get to an equation like this:

>         d(x,y,z) = \int_z^0 v(x,y,zeta) dzeta 

...where d(...) is the *cumulative displacement* by which you want to 
move the vertex and v(...) is the individual displacement you get. If 
you differentiate the formula by z, then you get

  d/dz d(x,y,z) = -v(x,y,z)

which is the advection equation I mentioned in my previous post, and for 
which it is substantially easier to solve than to compute the integral.

Best
  W.

-- 
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Wolfgang Bangerth          email:                 [email protected]
                            www: http://www.math.colostate.edu/~bangerth/

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