Multiphase Flow

Numerous CFD applications involve not just a single fluid phase but, rather, multiple phases. ANSYS CFX is a leader in multiphase modeling technology. Its varied capabilities allow engineers to gain insight into equipment that is often difficult to probe. A complete suite of models allows ANSYS CFX to capture the interplay between multiple fluid phases like gases and liquids, dispersed particles and droplets, and free surfaces. All of these models benefit strongly from the coupled solver technology to achieve robust and scalable multiphase flow solutions.

The free surface flow option in ANSYS CFX allows the simulations of open channel flow, flow around ship hulls, tank filling and sloshing, Pelton turbines, and many other situations. A special compressive discretization scheme is used to maintain a sharp interface at the free surface. Optionally, users can have two distinct velocity fields, to allow for separation to be simulated in conjunction with strong mixing or entrainment.

The Lagrangian particle transport model users to simulate disperse phases discretely distributed in a continuous phase, such as liquid sprays or airborne solid particles. The functionality is extended by a large number of additional models for phenomena such as primary and secondary spray break-up, particle-wall interaction, wall erosion due to particle impact, particle-particle collision, and coal combustion.

The Eulerian multiphase model features a wealth of options to capture the exchange of mass, momentum and energy. This includes numerous drag and non-drag force models as well as robust models for phase change due to cavitation, evaporation, condensation and boiling. Additionally, the multiple size group (MUSIG™) model allows the simulation of the effect of turbulent breakup and coalescence of different bubble sizes.

For disperse phases that equilibrate quickly with their surroundings, such as small bubbles or particles rising in tundishes or settling under gravity in clarifiers, the Algebraic Slip Model is a very efficient option available in ANSYS CFX.

 

View Larger Image Nucleate boiling downstream of spacers in fuel rod bundle assemblyCourtesy Dr. E. Krepper, FZ Dresden.