[petsc-users] Newton methods that converge all the time

[Adrian Croucher]

hi Henrik,


On 01/12/17 22:24, Buesing, Henrik wrote:

> The beauty of the pressure-enthalpy formulation is that you do not 
> need to initialize the saturations with small epsilon when you go into 
> two-phase. You can directly compute a correct enthalpy (and from it a 
> saturation) and "jump" into the two-phase region.
> Anyhow, no one says that you are not jumping in and out of the two-phase region. Consequently, there are examples for which either method works best.
>
> I am trying to simulate a supercritical reservoir (T>450 °C, p>35 MPa) from surface down to 3.5 km depth. (It is in Italy so geothermal gradient is large).
>
> There is a steam region, which forms and either I get osciallations in enthalpy (saturations) or small time-steps kill me. I want to simulate a quasi steady-state after 1 million years.

We regularly simulate systems like this, with steam zones near the top, 
and sometimes supercritical fluid at the bottom. We generally run steady 
states up to time step sizes of 1E15 s or more. We have done quite a bit 
of work on getting the variable-switching approach to work well under 
these conditions.

- Adrian

-- 
Dr Adrian Croucher
Senior Research Fellow
Department of Engineering Science
University of Auckland, New Zealand
email: a.croucher at auckland.ac.nz
tel: +64 (0)9 923 4611