Configuration

Configuration#

Upon first import, osyris will create a configuration file located in /home/user/.osyris/config_osyris.py. This will then be loaded by osyris, and allows easy configuration for units, constants and additional derived variables.

Configure constants#

This function creates additional constants or units that you use often, and do not wish to re-defined all the time. The syntax is the following:

[ ]:

def configure_constants(units):
    units.define("solar_mass = 1.9889e+33 * g = M_sun = M_sol")
    units.define("radiation_constant = 7.5659146e-015 * erg / cm^3 / K^4 = ar")

Configure units#

This function defines which units should be used for the different variables that are loaded when reading a Ramses output. They are used to convert between code units and CGS.

Converting from code units requires the density, length and time scale factors unit_d, unit_l and unit_t, found in the simulation info file. Those are then used to define conversion factors for each variable, e.g. density or position. The conversion factors are stored in a dictionary that is returned by the function (and subsequently stored in the Dataset).

An example snippet could look like this:

[ ]:

def configure_units(units, unit_d, unit_l, unit_t):
    density = unit_d * units("g / cm**3")
    velocity = (unit_l / unit_t) * units("cm / s")
    momentum = density * velocity

    library = defaultdict(lambda: 1.0 * units("dimensionless"))

    library.update(
        {
            "density": density,
            "velocity": velocity,
            "velocity_x": velocity,
            "velocity_y": velocity,
            "velocity_z": velocity,
            "momentum": momentum,
            "momentum_x": momentum,
            "momentum_y": momentum,
            "momentum_z": momentum,
        }
    )
    return library

Additional variables#

It is often useful to define some additional variables that are to be computed every time data is loaded. These commonly include cell-centered magnetic field, or temperature.

It is recommended to place your variables in a try/except block, which will prevent errors if the variables are not found, for instance when loading data from a different simulation.

For instance

[ ]:

def additional_variables(data):
    # Magnetic field
    try:
        data["hydro"]["B_field"] = 0.5 * (
            data["hydro"]["B_left"] + data["hydro"]["B_right"]
        )
    except KeyError:
        pass

    # Mass
    try:
        data["hydro"]["mass"] = (data["hydro"]["density"] * data["amr"]["dx"] ** 3).to(
            "M_sun"
        )
    except KeyError:
        pass
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