When a fixture is ground-based, surrounding air can only flow from the sides and above the fixture. The simulation model is larger than the vertical and test box configurations, and only open at the top. This simulates the ground plane and the open air above the fixture.
Examples include garden lights, and bollards.
Geometry
- Construct an enclosure around the device. The device usually touches the lower surface of the enclosure.
- Base the enclosure dimensions on the average of the three dimensions of the device. The stability of the flow is dependent on the aspect ratio of the enclosure. In the case of a long skinny device, this ensures that the environment has a reasonable aspect ratio.
- The side view is shown on the left; the front view is shown on the right:
Note: The top face is open. Air enters and exits from the top. For more about the ideal flow profile and troubleshooting...
Boundary Conditions
- To define an opening (usually the top surface), assign Static Gage Pressure = 0.
- To assign a temperature constraint to the opening, specify a Film coefficient = 2 W/m²K and Reference Temperature = ambient temperature.
- Leave the bottom surface unspecified to simulate an insulated surface.
- Heat loading is specific to the lighting type. Click for LED. Click for fluorescent.