Expected Profiles

Wall-mounted, ceiling-mounted, and pole-mounted / test box configurations

Ideally, the flow should enter through the bottom surface of the region, curve around the fixture, and accelerate in a plume above the fixture:

Flow should not enter from the top opening:

If the flow does enter from the top, there are several recommended corrective actions:

• Apply a Film Coefficient boundary condition to the top surface. Specify the Film coefficient = 2 W/m²K and Reference Temperature = ambient temperature + 1 degree.
• Refine the mesh above the fixture. A convenient method is to create a mesh refinement region directly above the fixture. The flow gradients will be computed more accurately by focusing the mesh in this region.
• Reduce the Local stretching from 1.1 to 1.08. If the problem persists, reduce to 1.05:
  1. On the Mesh task, right click, and select Edit.
  2. On the Mesh quick edit dialog, click the Advanced button.
  3. Change the value in the Local stretching field.

If one or both of these modifications is made to a scenario, apply the same modification to all scenarios. This ensures consistency across the entire design study.

Ground Based

Ideally the flow should enter from the sides of the opening, and exit through the center(forming the plume from the fixture), as shown on the left. Flow should not enter from just one side and exit near the other side, as shown on the right:

If the flow enters from one side and exits through the other, the recommended action is to refine the mesh above the fixture. A convenient method is to create a mesh refinement region directly above the fixture. The flow gradients will be computed more accurately by focusing the mesh in this region.

Unit 4 |Things to Avoid