accretion rate

[migueldvb]

I wonder if there is a test problem that includes removing part of material that accumulates in some fraction of the Roche lobe of an object every time step to calculate the accretion rates onto the object.

[gawrysz]

I think it is not general enough to be eligible for being a test problem, unless there is some standard defined in the literature.

Such things can be implemented in routines in initproblem.F90 and hooked through problem_customize_solution.

[migueldvb]

Thank you, I will try to do that.

Is there a way in piernik that I could use to monitor the mass flux through a sphere centered on one of the stellar components?

[gawrysz]

I see two ways:

• Clean one: integrate mass over particular volume in a way similar to what write_timeslice in src/IO/dataio.F90 does. Hook that routine to problem_customize_solution
• Risky/tricky one: define a map of cell interfaces that have to be monitored and modify the hydro solver(s) (currently src/scheme/rtvd_split/rtvd.F90) to integrate fluxes on that interface. You can do it in similar way as the flux matching for AMR was implemented, except that you don't need to communicate thing as much - only do a single global reduce. Looks pretty easy to implement for single, convex surface, a bit more complicated if you want general things like multiple or non-convex thingies.