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Single-Precision and Double-Precision Solvers
Both single-precision and double-precision versions of ANSYS FLUENT are available on all computer
platforms. For most cases, the single-precision solver will be sufficiently accurate, but certain types of
problems may benefit from the use of a double-precision version. Several examples are listed below:
1. If your geometry has features of very disparate length scales (e.g., a very long, thin pipe), single-
precision calculations may not be adequate to represent the node coordinates.
2. If your geometry involves multiple enclosures connected via small-diameter pipes (e.g.,
automotive manifolds), mean pressure levels in all but one of the zones can be quite large (since y o u
can set only one global reference pressure location). Double precision calculations may
therefore be necessary to resolve the pressure differences that drive the flow, since these will
typically be much smaller than the pressure levels.
3. For conjugate problems involving high thermal-conductivity ratios and/or high aspect-ratio
meshes, convergence and/or accuracy may be impaired with the single precision solver, due to
inefficient transfer of boundary information.

4. For multiphase problems where the population balance model is used to resolve particle size
distributions, which could have statistical moments whose values span many orders of
magnitude.

4.2.3 Starting ANSYS FLUENT
Using FLUENT Launcher

Whether you start ANSYS FLUENT either from
the Linux/UNIX or Windows command line
with no arguments, from the Windows
Programs menu, or from the Windows desktop,
FLUENT Launcher will appear, where you can
specify the dimensionality of the problem (2D
or 3D), as well as other options (e.g., whether
you want a single-precision or double-precision
calculation):
Under Dimension, select 3D for the three-
dimensional solver, or select 2D for the
two-dimensional solver.

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