For inviscid flows, Ansys Fluent solves the Euler equations. The mass conservation equation is the same as for a laminar flow, but the momentum and energy conservation equations are reduced due to the absence of molecular diffusion.
In this section, the conservation equations for inviscid flow in an inertial (non-rotating) reference frame are presented. The equations that are applicable to non-inertial reference frames are described in Flows with Moving Reference Frames. The conservation equations relevant for species transport and other models will be discussed in the chapters where those models are described.
The equation for conservation of mass, or continuity equation, can be written as follows:
 | (1–33) |
Equation 1–33 is the general form of
the mass conservation equation and is valid for incompressible as
well as compressible flows. The source 
is the mass
added to the continuous phase from the dispersed second phase (for
example, due to vaporization of liquid droplets) and any user-defined
sources.
For 2D axisymmetric geometries, the continuity equation is given by
 | (1–34) |
where 
is the axial coordinate, 
is the radial coordinate, 
is the axial velocity, and 
is the radial velocity.
Conservation of momentum is described by
 | (1–35) |
where 
is the static pressure and 
and 
are the gravitational body force
and external body forces (for example, forces that arise from interaction
with the dispersed phase), respectively. 
also contains
other model-dependent source terms such as porous-media and user-defined
sources.
For 2D axisymmetric geometries, the axial and radial momentum conservation equations are given by
 | (1–36) |
and
 | (1–37) |
where
 | (1–38) |
