Simulating Smoke Visibility

Because smoke visibility is derived from the flow results computed by Autodesk® CFD, it can be enabled either before running or after the solution is complete.

Basic analysis considerations

Flow

• Assign a Scalar boundary condition (value = 1) to indicate the location of the fire (smoke emission source). This can be on either a solid surface or a wall surface. The scalar value represents the mass concentration of the combustion products throughout the analysis region.
• Set up other boundary conditions, materials, mesh distributions, etc.
• On the Physics tab of the Solve dialog, click the Advanced button, and enable General Scalar. Specify a non-zero value for the diffusion coefficient.
• In many smoke visibility analyses, air movement is driven at least in part by natural convection. To enable material properties to vary with temperature, select Variable on the Environment dialog.

Thermal

• Specify the air temperature at all inlets. This is required.
• Specify known heat generation boundary conditions on lighting, electronics, and equipment. Do not specify temperatures on components that will be solved for in the simulation.
• Specify film coefficients (as needed) to exterior surfaces to simulate heat transfer with the surrounding environment. (External wall surfaces that do not have an applied heat transfer boundary condition are treated as perfectly insulated.)

On the Solve dialog, enable both Flow and Heat Transfer.

To enable Smoke visibility prior to running an analysis

1. On the Control tab of the Solve dialog, click the Results quantities button.
2. Check the Smoke visibility box.
3. To define the characteristics of the environment, click the Parameters button adjacent to the Smoke visibility check box.

To enable Smoke visibility for a completed analysis

1. Follow the preceding procedure to enable the Smoke visibility result quantity.
2. On the Control tab of the Solve dialog, leave the Continue From field at the last iteration.
3. Set the Iterations to run to be 0, and click Solve.

The analysis will appear to start, but will not solve any additional iterations. The smoke visibility results are then computed and made available for visualization.