  This work presents a new multiphase SPH model that includes the shifting
algorithm and a variable smoothing length formalism to simulate multi-phase
flows with accuracy and proper interphase management. The implementation was
performed in the DualSPHysics code and validated for different canonical
experiments, such as the single-phase and multiphase Poiseuille and Couette
test cases. The method is accurate even for the multiphase case for which two
phases are simulated. The shifting algorithm and the variable smoothing length
formalism has been applied in the multiphase SPH model to improve the numerical
results at the interphase even when it is highly deformed and non-linear
effects become important. The obtained accuracy in the validation tests and the
good interphase definition in the instability cases indicate an important
improvement in the numerical results compared with single-phase and multiphase
models where the shifting algorithm and the variable smoothing length formalism
are not applied.
