FLASH provides support for solving the equations of special relativistic hydrodynamics (RHD) in one, two and three spatial dimensions.
Relativistic fluids are characterized by at least one of the following two behaviors: (i) bulk velocities close to the speed of light (kinematically relativistic regime), (ii) internal energy greater than or comparable to the rest mass density (thermodynamically relativistic regime). As can be seen from the equations in Sec:RHD_equations, the two effects become coupled by the presence of the Lorentz factor; as a consequence, transverse velocities do not obey simple advection equations. Under these circumstances, Newtonian hydrodynamics is not adequate and a correct description of the flow must take relativistic effects into account.
The motion of an ideal fluid in special relativity is described by the system of conservation laws
At present, only Cartesian (1, 2 and 3-D), 2-D cylindrical (,
)
and 1-D spherical (1-D,
) geometries are supported by
FLASH. Gravity is not included, although it can be easily added
with minor modifications.
An equation of state (Eos) provides an additional relation between
thermodynamic quantities and closes the system of
conservation laws ((15.14)). The current version of
FLASH supports only the ideal equation of state, for which
the specific enthalpy may be expressed as
As in classical hydrodynamics, relativistic fluids may be
described in terms of a state vector of
conservative,
, or primitive,
, variables.
The connection between the two sets is given by
REQUIRES physics/Eos/EosMain/Gamma/RHD
For this specific purpose, the current RHD implementation supports MODE_DENS_EI (a default mode) and MODE_DENS_PRES only (but not MODE_DENS_TEMP) in making a Eos_wrapped call.