sailfish.physics.circumbinary.Physics

class sailfish.physics.circumbinary.Physics(eos_type: EquationOfState = EquationOfState.GLOBALLY_ISOTHERMAL, sound_speed: float = 1.0, mach_number: float = 10.0, gamma_law_index: float = 1.6666666666666667, viscosity_model: ViscosityModel = ViscosityModel.NONE, viscosity_coefficient: float = 0.0, alpha: float = 0.0, buffer_is_enabled: bool = False, buffer_driving_rate: float = 1000.0, buffer_onset_width: float = 0.1, point_mass_function: Optional[Callable[[float], List[PointMass]]] = None, cooling_coefficient: float = 0.0, constant_softening: bool = True, diagnostics: List[Diagnostic] = [])[source]

Bases: NamedTuple

Physics configuration for the binary accretion solvers

Configuration categories are:

Equation of state: globally isothermal, locally isothermal, or gamma-law

In globally isothermal mode, a uniform sound speed is specified. In globally isothermal mode, an orbital mach number is specified, and used to assign the sound speed based on the local gravitational potential (this option only makes sense when gravitating point masses are provided). In gamma-law mode, the sound speed is determined self-consistently from the internal energy. The cbdiso_2d solver only supports the former two modes, and the cbdgam_2d solver only upports the last mode.
Gravitating point masses

Point masses can be optionally provided to model stars or black holes. The point mass properties include a point mass’s mass, and its x-y position. These properties fully determine the gravitational potential sourced by the particle. Point masses can also act as sinks of mass and momentum (see the PointMass struct above for details). The point masses are supplied to the solver implicitly through a callback function, mapping the simulation time to a sequence of particles. Currently, solvers support either zero, one, or two particles.
Viscosity model

Two different viscosity models are nominally supported: constant-nu, and constant alpha. Currently the isothermal solver only supports constant-nu viscosity.
Thermal cooling

Todo.
An outer buffer zone

For binary accretion problems in a square domain, it can be useful to impose a wave-damping zone (or sponge layer) to avoid artifacts fromt the outer boundary on the orbiting gas. The buffer zone, if enabled, will drive the solution outside a “buffer onset radius” toward an appropriate hydrodynamic state. This should be gas with uniform gas pressure and density (which may be sampled from the initial condition), and that gas should be on circular Keplerian orbits. The buffer_driving_rate parameter controls how fast the solution is driven toward the smooth one. The buffer is applied in a region between the domain radius (the half-width of a square domain), extending inwards by an amount specified by the buffer_onset_width parameter.

__init__()

Methods

`__init__`()
`count`(value, /)	Return number of occurrences of value.
`index`(value[, start, stop])	Return first index of value.
`point_masses`(time)	Generate two point masses from the simulation time and supplied callback.

Attributes

`alpha`	Alpha parameter, if viscosity model is alpha
`buffer_driving_rate`	Rate of driving toward target solution in the buffer region
`buffer_is_enabled`	Whether the buffer zone is enabled
`buffer_onset_width`	Distance over which the buffer ramps up
`constant_softening`	If local disk height is ignored in gravitational softening
`cooling_coefficient`	Strength of the cooling term
`diagnostics`	Physics diagnostics to be returned when reductions are computed
`eos_type`	EOS type: globally or locally isothermal
`gamma_law_index`	Adiabatic index, if the EOS type is not isothermal
`mach_number`	Square of the Mach number, if EOS type is locally isothermal
`num_particles`
`point_mass_function`	Callback function to supply point masses as a function of time
`sound_speed`	Isothermal sound speed, if EOS type is globally isothermal
`viscosity_coefficient`	Kinematic viscosity value (a^2 Omega) if viscosity is nu
`viscosity_model`	Which viscosity model to use (none, nu, alpha)

alpha: float: Alpha parameter, if viscosity model is alpha

buffer_driving_rate: float: Rate of driving toward target solution in the buffer region

buffer_is_enabled: bool: Whether the buffer zone is enabled

buffer_onset_width: float: Distance over which the buffer ramps up

constant_softening: bool: If local disk height is ignored in gravitational softening

cooling_coefficient: float: Strength of the cooling term

count(value, /): Return number of occurrences of value.

diagnostics: List[Diagnostic]: Physics diagnostics to be returned when reductions are computed

eos_type: EquationOfState: EOS type: globally or locally isothermal

gamma_law_index: float: Adiabatic index, if the EOS type is not isothermal

index(value, start=0, stop=9223372036854775807, /)

Return first index of value.

Raises ValueError if the value is not present.

mach_number: float: Square of the Mach number, if EOS type is locally isothermal

point_mass_function: Callable[[float], List[PointMass]]: Callback function to supply point masses as a function of time

point_masses(time)[source]: Generate two point masses from the simulation time and supplied callback.

sound_speed: float: Isothermal sound speed, if EOS type is globally isothermal

viscosity_coefficient: float: Kinematic viscosity value (a^2 Omega) if viscosity is nu

viscosity_model: ViscosityModel: Which viscosity model to use (none, nu, alpha)