Setting up the Models

Models define the primary variables of the simulation, including pressure, temperature and velocity, and what mathematical formulation will be used to generate the solution. In this example, the flow involves a turbulent, compressible, multi-component gas whose components are reacting chemically. The Segregated Flow model will be used together with the standard K-Epsilon turbulence model and the PPDF reaction model.

Open the Continua node, right-click on the Physics 1 node and select item Select models...

In the Physics Model Selection dialog, select the Stationary radio button in the Motion group box.

Select the Multi-Component Gas radio button in the Material group box.

The Physics Model Selection dialog will guide you through the model selection process by showing only the options appropriate to the initial choices made. Using the same technique as in the previous step:

Select Reacting in the Reaction Regime group box.

Select Non-Premixed Combustion in the Combustion group box.

Select Adiabatic PPDF in the Non-Premixed Combustion group box.

Select PPDF Flamelet in the Ppdf Reaction group box.

Select Segregated Flow in the Flow group box.

Select Steady in the Time group box.

Select Turbulent in the Viscous Regime group box.

Select K-Epsilon Turbulence in the Reynolds-Averaged Turbulence group box.

Select Standard K-Epsilon in the K-Epsilon Turbulence group box.

Select High y+ Wall Treatment in the K-Epsilon High y+ Wall Treatment group box

The Standard K-Epsilon model is preferred to the default Realizable Two-layer K-Epsilon model for this case because the near-wall mesh is too coarse to properly resolve the boundary layer. Two-layer models are not recommended for meshes without refined near-wall layers.

The Physics Model Selection dialog should look as shown below when you are done.

Note that the color of the Physics 1 node has turned from gray to blue to indicate that models have been activated.

Open the Physics 1 node and the Models node. The selected models now appear within that node.

The case will be run using first-order differencing schemes, allowing for faster solution convergence.

To change the differencing schemes, select the Adiabatic PPDF node.

In the Properties window, change the Convection property to 1st-order.

Repeat this process for the Segregated Flow node.

Make sure that the Standard K-Epsilon node has its Convection property set at 2nd-order.

Save the simulation by clicking on the

(Save) button.