- In most cases, sheet metal parts built with CAD sheet metal design features and design tables are not recommended.
- Sheet metal features such as corner features and bend radii cannot be removed and often cause the mesh size to be too large. This can lead to significantly longer analysis times, and reduced solution efficiency.
- The recommended approach is to build sheet metal parts as solid features in CAD. Omit detail that is not relevant to the flow and thermal simulation.
- Do not apply the following boundary conditions directly to the lighting fixture. (Only apply heat generation conditions):
- Film coefficient. Autodesk Simulation CFD computes the heat transfer between the device and the surrounding air.
- Pressure boundary conditions to internal slots. Because these surfaces are internal, the pressure is not known. A specified value will cause instability in the flow solution.
- Be careful not to run the analysis longer than necessary. When properly meshed, most lighting analyses reach convergence between 200 and 500 iterations.
- A coarse mesh is useful for predicting trends, but accuracy cannot be improved by running a coarse mesh additional iterations beyond convergence.
- In many analyses, temperatures are over-predicted within the first 100 iterations.
- As subsequent iterations are run, convergence is attained and resultant temperatures will converge at a lower value.
- If predicted temperature are significantly higher than expected in the early stages of the analysis (one or more orders of magnitude), check the model setup to ensure that all loads and materials are physically correct.
- If the resultant temperatures seem excessively high, enable radiation. In some models, neglecting the effects of radiation produces temperatures roughly 10-20% higher than actual values. A useful strategy is to run 200 iterations without radiation, and then enable radiation and continue. This reduces the analysis time, and provides insight into the effects of radiation. Be sure to specify appropriate emissivity material property values. For more about radiation.
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