In this case, PLANT is used to introduce a turbulence model for concentration fluctuations which employs no conservation equations for statistical properties of the fluctuations. It is a variant of Multi-Fluid concept of Spalding as used by S.V. Zhubrin, 1997.

The 17-fluid model is considered here to simulate the turbulent mixing resulting from the admission of two separate, isothermal coaxial jets of different composition into a concentric duct as depicted diagrammatically below.

Entrance ///////////////////// Duct wall //////////////////Exit ---> :::::::::::: -> surrounding ---> :::::::::: --> jet --------->::::::::: Mixing layer spreading to wall---> " ---------> ----> central jet --------->-.-.-.-.-.-.- Symmetry axis .-.-.-.-.-.-.----->

In parallel with above model, the conservation equation for the transport of the square of fluctuating concentration component is also PLANTed for comparative purposes.

At the final stage of computations the results are processed to get the Fluid Population Distribution histogram which may be viewed by PHOTON. The use file for the latter is supplied.

The example employs the number of PLANT features:

- specific sources introduction,

- reference residuals calculations,

- intervention in calculation,

- processing the results and

- special print-out preparations.

- Single-fluid central-jet concentration contours.
- Averaged 17 fluid central jet concentration contours.
- Concentration fluctuations as predicted by transport equation.
- RMS concentration fluctuations by multi-fluid model.
- Fluid Population Distribution (PDF)at selected cell.