10.3.2 The Mixing Plane Model

The mixing plane model in ANSYS FLUENT provides an alternative to the multiple reference frame and sliding mesh models for simulating flow through domains with one or more regions in relative motion. This section provides a brief overview of the model and a list of its limitations.

Overview

As discussed in Section  10.3.1, the MRF model is applicable when the flow at the interface between adjacent moving/stationary zones is nearly uniform ("mixed out''). If the flow at this interface is not uniform, the MRF model may not provide a physically meaningful solution. The sliding mesh model (see this section in the separate Theory Guide) may be appropriate for such cases, but in many situations it is not practical to employ a sliding mesh. For example, in a multistage turbomachine, if the number of blades is different for each blade row, a large number of blade passages is required in order to maintain circumferential periodicity. Moreover, sliding mesh calculations are necessarily unsteady, and thus require significantly more computation to achieve a final, time-periodic solution. For situations where using the sliding mesh model is not feasible, the mixing plane model can be a cost-effective alternative.

In the mixing plane approach, each fluid zone is treated as a steady-state problem. Flow-field data from adjacent zones are passed as boundary conditions that are spatially averaged or "mixed'' at the mixing plane interface. This mixing removes any unsteadiness that would arise due to circumferential variations in the passage-to-passage flow field (e.g., wakes, shock waves, separated flow), thus yielding a steady-state result. Despite the simplifications inherent in the mixing plane model, the resulting solutions can provide reasonable approximations of the time-averaged flow field.

Limitations

Note the following limitations of the mixing plane model:

• The LES turbulence model cannot be used with the mixing plane model.

• The models for species transport and combustion cannot be used with the mixing plane model.

• The VOF multiphase model cannot be used with the mixing plane model.

• The discrete phase model cannot be used with the mixing plane model for coupled flows. Non-coupled computations can be done, but you should note that the particles leave the domain of the mixing plane.

For more information about rotor and stator domains, see this section in the separate Theory Guide.

For more information about the mixing plane concept, see this section in the separate Theory Guide.

For more information about choosing an averaging method, see this section in the separate Theory Guide.

For more information about ANSYS FLUENT's mixing plane algorithm, see this section in the separate Theory Guide.

For more information about mass conservation, see this section in the separate Theory Guide.

For more information about swirl conservation, see this section in the separate Theory Guide.

For more information about total enthalpy conservation, see this section in the separate Theory Guide.