Characteristic and propagation velocities of the two-fluid models (original) (raw)

Influence of the stiff inter-phase exchange source terms on the propagation velocities of the two fluid models is analyzed. If infinitely fast inter-phase exchange is assumed, i.e. instantaneous thermal and mechanical relaxation, the results of the two-fluid models should be similar to the results homogeneous-equilibrium model, despite different characteristic velocities of both models. Results of the present work show, that the propagation velocities of the two-fluid model with infinitely stiff relaxation terms are indeed equal to the propagation velocities of the homogeneous-equilibrium model - despite large differences in the eigen-structures of the two-fluid models and HEM model. It is known that the speed of sound in two-fluid model is not the same as the HEM speed of sound, however, the propagation speed of the sonic waves of the two-fluid models with infinitely stiff relaxation terms is close to the HEM speed of sound and not the speed of sound of the two-fluid model. For non-stiff relaxation source terms the characteristic velocities of the two-fluid model are approximately equal to the wave propagation velocities.