Boundary conditions low Mach number flow
 

Hi,

I'm trying to study a low Mach number flow with variable density using the SIMPLER algorithm. The real problem is that of a spherically expanding flame from a point source in an unconfined space.

The physical boundary conditions are the velocity u=0 at the origin and u=0 at the far-field and pressure p=p0 at the far-field. The problem is essentially 1-D so I use a 1-D domain with a staggered grid for computations.

It is my understanding that for such a problem I only have to define either pressure or velocity at the boundaries. I seem to be getting incorrect results and I think I have issues with boundary conditions. Right now I have,

at the centre, r=0, u=0

at the far-field, r=R, du/dr = 0

I use the discretised pressure equation to obtain the pressures at the boundary using the velocities calculated at the boundary, i.e. I don't specify a particular pressure value at the boundary, it is taken from the solution.

Can anyone tell me if I'm doing anything wrong? Thanks.