What does the sign of the unbalanced flow at grid point means

FLAC3D
1

Hi,

In flac 2d and 3d using fish you can access the unbalanced flow at a gridpoint with gp.flow when you are running a fluid model.

My question is:

  • what does the sign of the unbalanced flow means. I am guessing from the documentation it means between inflow and outflow but what is the reference for inflow and outflow?

Is it linked to the discharge vector and I need to get it to figure out what the sign means?

Thank you in advance!

2
  • gp.flow intrinsic returns the total out-of-balance flow at a grid point. This includes both the applied discharge and any flow into or out of the grid point occurring during fluid calculations.
  • A positive value indicates inflow, while a negative value indicates outflow.
  • A fixed-pp grid point is a special case because it is not considered a “free” grid point. For these fixed-pp grid points, there should be flow interaction between the model and the external environment. If we interpret this flow (flux) as an applied discharge, it corresponds exactly to the discharge. Summing up gp.flow() at all fixed-pp grid points gives the net discharge of the model.
3

Thank you.

Then It seemed I had misunderstood the documentation and gp.flow is only what I need in the special case of a fixed-pp.

If I understood correctly, it means that if I want to get the volumetric flow rate in the direction of the discharge vector at a given position in the model, I need to use zone.flow or is there another fish function that is better for this job.
If I want to use zone.flow, I need to convert the discharge vector to a volumetric value by multiplying it by the area the flow is passing through.
What would be the correct area to use to compute a volumetric flow rate? Should it be an average section of the zone?