[FLASH-USERS] fixed boundary condition

[Klaus Weide]

On Wed, 5 Oct 2011, Asif ud-Doula wrote:

> Hello Everyone,
> I am a regular user of Zeus-MP, but I have decided to try out FLASH4-a. To
> start with a very simple problem, I wanted to simulate a colliding wind
> scenario in 2D in Cartesian coordinates wherein two opposing flows with fixed
> density and equal speed collide. But when I wanted to set the boundary
> condition to 'fixed', I was quite surprised that FLASH did not have it. It has
> 'outflow', 'reflect' and several sophisticated boundary conditions, but seems
> to be missing the simple 'fixed' condition. Am I missing something here? Or
> did anyone already write a subroutine for fixed b.c.. I appreciate your help
> in this.
> Asif

Asif,

We don't provide simple 'fixed' boundary conditions for Hydro etc. out of 
the box, but they are easy to implement as a USER_DEFINED type in your 
simulation directory.  Here are a couple of examples:

  source/Simulation/SimulationMain/WindTunnel/Grid_applyBCEdge.F90

  source/Simulation/SimulationMain/ShuOsher/Grid_bcApplyToRegionSpecialized.F90

To adapt one of those examples for your purposes, you will also need to copy/adapt
related parts of Config, flash.par, Simulation_*.F90 files - mostly for definition
and initialization of sim_ runtime parameters (to set your fixed b.c. values).
For the WindTunnel way of doing this, the line
   
  REQUIRES Grid/GridBoundaryConditions/OneRow

in the Config is essential.

Klaus