Unit 1: Modeling Strategy-- Geometry and Boundary Conditions

LED and Fluorescent Lighting systems can be mounted in a variety of physical configurations. The model setup depends on the configuration, so it is helpful to understand how and where the device will be mounted as you set up your analysis model.

Configuration 1:Bulbs

Configuration 2:Wall Mounted

Configuration 3:Ceiling Mounted

Configuration 4:Pole-Mounted

Configuration 5:Ground-Based

Technique: Creating the Flow Volume

There are two primary ways to create the surrounding flow volume:

• Build it in the CAD model.
  • If the fixture must contact a surface of the region, this is the recommended approach.
  • A good technique is to create a cavity that surrounds the fixture. This region will be filled automatically when the model is launched, and will be meshed. It serves as a mesh refinement region, and because it eliminates the interference between the fixture and the surrounding air volume, the part names will not be modified.
• Use the External Volume Geometry tool in Autodesk Simulation CFD.
  • This eliminates the need to add an "Air" part to the CAD model.
  • Note that this technique should not be used if the fixture must contact a side of the air volume (as in the Wall-Mounted configuration).

A useful technique that can reduce the model size and analysis time is to take advantage of symmetry. If the device is half- or even quarter-symmetric, the overall model size can be reduced significantly. For more about symmetry.