Multicomponent Mixing

5.8 Multicomponent Mixing

Multicomponent flows consist of different chemical species (components) that are mixed at the molecular level and generally share the same velocity and temperature. They differ from multiphase flows (described in Multiphase module), where the different phases are intrinsically immiscible (though turbulent mixing can occur), and each phase only occupies a fraction of the total volume. For example, the air surrounding us consists of two main chemical species of oxygen and nitrogen, and some water vapor depending on humidity. They are fully mixed together and occupy the same space. The air movement (wind) is thus a multicomponent flow. On the other hand, when oil and water are injected into a container, the water and oil are separated by a clear interface with the water at the bottom due to gravity. The oil-water motions are liquid-liquid two-phase flows. Furthermore, the chemical species may also interact through chemical reactions and the resulting multicomponent reactive flows are observed in various natural phenomena and engineering applications. Therefore, it is very important to consider multicomponent flows in a CFD solver.

Without the consideration of chemical reactions, Simerics-MP offers a modelling capability to predict the mixing and transport of multiple components by solving conservation equations describing convection and diffusion for each component species. In this module, Multicomponent Mixing, the fundamental theory of species transport in multicomponent flows is described. The model parameters and settings, the work flow and the post-processing quantities are also discussed in detail.

To activate the Multicomponent Mixing module:

Click Select Modules in the Model Panel. The Physical Model Selection dialog box opens.
Select the Multicomponent Mixing module from Available Modules.
Specify species (component) name in the Module Name box and click Add.
Click Model Panel to see assigned physical modules for the simulation.

Figure 5.176 - Multicomponent mixing

The module is explained as follows:

Definitions: Terminologies relevant to the Multicomponent Mixing module.
Physics: Models, methods and constants used in Multicomponent Mixing module.
Conditions: Specifying conditions for the entities-boundaries, interfaces, volumes under the Multicomponent Mixing module.
Output Variables: Outputs from the Multicomponent Mixing module.