AMReX-Astro/Castro: Castro 20.01

A new option castro.limit_fluxes_on_large_vel has been added. It is similar to the existing option limit_fluxes_on_small_dens -- fluxes are limited to prevent the velocity in any zone from getting too high. The largest legal speed is set by castro.speed_limit. (#712) This is more general than the previous solution proposed by castro.riemann_speed_limit, so that parameter has been removed. (#714)

The AMR parameter amr.compute_new_dt_on_regrid is now on by default. This avoids crashes that result from the CFL number being too large after regridding, because we update the timestep after seeing that larger velocity. You can still opt to set this off if you want to in your inputs file. (#720)

We have added calls into Hypre that only exist as of version 2.15.0, so that is the new minimum requirement for Castro radiation. Note that Hypre is now hosted on GitHub at https://github.com/hypre-space/hypre.

A new option castro.limit_fluxes_on_large_vel has been added. It is similar to the existing option limit_fluxes_on_small_dens -- fluxes are limited to prevent the velocity in any zone from getting too high. The largest legal speed is set by castro.riemann_speed_limit. (#712)

A new option castro.apply_sources_consecutively has been added. By default we add all source terms together at once. This option, if enabled, adds the sources one at a time, so that each source sees the effect of the previously added sources. This can matter, as an example, for the sponge source term, which may be more effective if it is added after source terms such as gravity that update the velocity. (#710)

A new option castro.ext_src_implicit has been added. The external source terms were previously only implemented as an explicit predictor-corrector scheme. The new option, if turned on, changes the handling of the external source terms to allow an implicit solve. This is done by subtracting the full old-time source and adding the full new-time source in the corrector, rather than -0.5 and +0.5 of each, respectively. It is still up to the individual problem to make sure it is consistent with this scheme if the option is turned on. (#709)

Add option for using monopole BCs in 3D. By setting gravity.max_multipole_order to a negative number, you can use monopole gravity to fill the boundary conditions, rather than the multiple BCs. This is useful for debugging purposes. To make the behavior consistent, we now use multipole BCs by default in 2D as well. (#716)