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AFT Blog

Welcome to the Applied Flow Technology Blog where you will find the latest news and training on how to use AFT Fathom, AFT Arrow, AFT Impulse, AFT xStream and other AFT software products.
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Exhaustive Tolerance Criteria

AFT Arrow uses Newton iteration to find a simultaneous solution for all junction pressures. Well, maybe not all junctions. When “Use Exhaustive Tolerance Criteria” is NOT selected, AFT Arrow will only check junction pressures that find their way into the solution matrix.

The AFT Arrow solver builds a matrix of equations based on the number of flow splits in the model. Each flow split must have a common pressure that is consistent with the flow and pressure drop in all of the connected pipes. Finding the right pressure for each flow split can become rather tricky. To find the pressure using iteration, an appropriate stopping point (i.e. tolerance) must be established. The conventional tolerance method will check only the junction pressures in the solution matrix. In some cases, however, a more rigorous approach is needed. When “Exhaustive Tolerance Criteria” is used, every junction is checked, regardless of whether or not it exists in the solution matrix. In addition to checking the complete set of junctions, “Exhaustive Tolerance Criteria” automatically tightens the tolerance that is specified in the solution control window.

“Use Exhaustive Tolerance Criteria” can be found on the Tolerance tab in the solution control window.

Solution Control Window

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Friday, 19 August 2022
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