Negative Operating Point on an External Fan Boundary Condition
Issue
An External Fan boundary condition is applied just upstream of a diffuser section. After running the analysis, the resultant operating point was not on the specified fan curve, and indicated a negative flow rate.
Solution
The Solver was unable to determine a realistic operating point because the external fan boundary condition is too close to the diffuser section. The solution is to extend the geometry upstream to separate the External Fan boundary condition from the diffuser section.
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