All other features available in Ansys Fluent can be used in conjunction with the Eulerian multiphase model, except for the following limitations:
The Reynolds Stress turbulence model is not available on a per phase basis.
Particle tracking (using the Lagrangian dispersed phase model) interacts only with the primary phase.
Streamwise periodic flow with specified mass flow rate cannot be modeled when the Eulerian model is used (you are allowed to specify a pressure drop).
Inviscid flow is not allowed.
Melting and solidification are not allowed.
When tracking particles with the DPM model in combination with the Eulerian multiphase model, the Shared Memory method cannot be selected (Parallel Processing for the Discrete Phase Model). (Note that using the Message Passing or Hybrid method enables the compatibility of all multiphase flow models with the DPM model.)
The Eulerian multiphase model is not compatible with non-premixed, partially premixed, and premixed combustion models.
To change from a single-phase model to a multiphase model, you
will have to do this in a series of steps. You will have to set
up a mixture solution and then a multiphase solution. However,
since multiphase problems are strongly linked, it is better to start
directly solving a multiphase problem with an initial conservative
set of parameters (first order in time and space). This is of
course problem dependent. The modifications involve, among other things,
the introduction of the volume fractions 
for the multiple phases, as well
as mechanisms for the exchange of momentum, heat, and mass between
the phases.