Hi Francisco,
In FiPy, it is necessary to add both a TransientTerm and a source term
for terms such as,
density (times) (\partial f[x]/\partial t)
So, the code will look something like this,
TransientTerm(var=var, coeff=density) - field * (density - density.old) / dt
There may be ways to improve the convergence with implicit sources,
but I haven't investigated that. For example, the "field * density.old
/ dt" part could become implicit in "field" and the the "field *
density / dt" could be implicit for "density" and coupled with an
equation solving for density.
Cheers,
Daniel
On Mon, May 16, 2016 at 1:30 PM, Francisco Vega Reyes wrote:
> Hello,
>
> a very common term in the Navier-Stokes equations for a gas is of the form:
>
> density (times) (\partial f[x]/\partial t),
>
> where f[x] is a hydrodynamic field (for instance, temperature). however, it
> appears in the Fipy manual that the transient terms that express time
> derivatives have no multiplying coefficients. I’d like to solve the transient
> Navier Stokes equations for a gas without having to divide the whole balance
> equations by density, which is of course also an unknown.
>
> How can I express then a term of the form above in Fipy?
>
> Thank you very much,
>
>
> Dr. Francisco Vega Reyes
>
> Departamento de Física,
> Universidad de Extremadura,
> 06071 Badajoz, Spain
>
> fv...@unex.es
>
>
>
>
>
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Daniel Wheeler
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