**Reacting Systems Handled By FlUENT/UNS****Reaction modeling options****Speices Transport Equations****Mathematical Modeles****General Steps to follow in Modeling Speices Transport and Reaction****return to summary**

**Reacting
Systems Handled By FlUENT/UNS**

Fluent can simulate the folowing cases :

1. Fluid phase reactions that may involve multiple chimical reactions.

2. Liquid fuel reactions in witch fuel vapor is generated via evaporation of lquid droplets and combustion reaction occur in the gas phase.

3. Surface reactions in witch reaction occur at solid wall boundary.

4. Particulate reactions in witch reaction occurs by the evolution of a combustible gas and/or combustion occurs at the surface of a solid particule.

Fluent Uns provides two reaction modeling approaches :

1. Generalized Finit Rate Formulation

This approch is based on of the solution of speices transport for reaction and product concentration, with the chemical mechanism defined by the user2. Mixture fraction /PDF Formulation

2. Mixture Fraction /PDF Formulation

In this case Individual scalar (mixture fraction) equation is solved. this approach is specially used for turbulent diffusion flames.

fluent/uns solve a reaction diffusion equation wich have the folloween form

R and S are respectively puit and source terms. they give the evolution of mass fractions of different speices involved in the reactions.

there two models used with fluent/uns to give there expresions.

there is two ways to modelise the source term : two modeles could

- Arrhenius Rate modele and,

- Eddy Dissipation modele.

in each case a number of parameteres should be fixed by the user

**General
Steps to follow in Modeling Speices Transport and Reaction**

1. Enable finit rate reaction or non-reacting speices transport.

2. Specifying the mixture material and defining the properties of the mixture wich include informations about :

- speices in the mixture.
- reactions.
- other physical properties.

3. Defining properties of each reactant in the mixture.

4. Set speices boundary conditions.