User Specified AFT Arrow to Resolved Solution allowable mismatch was exceeded

A Transient Solver Error in AFT xStream

Full Message Text

Error occurred while running Transient Solver. A user specified "AFT Arrow To Resolved Solution allowable mismatch" was exceeded.

Explanation

This transient solver error indicates that one of the allowable mismatch values defined on the Transient Solver Initialization panel was exceeded. For an explanation of how the allowable mismatch values are applied and the transient solver initialization process please reference the discussion in the Transient Solver Initialization panel topic.

xStream prints a summary of the comparison between the AFT Arrow Steady and Resolved solutions in the Solution Progress window, which can be used to determine what parameters were violated. For example, see Figure 1 below which shows a model that met the velocity criteria, but did not meet the applied temperature criteria.

Required Action

To resolve a mismatch between the AFT Arrow Steady and Resolved solutions it is recommended to re-evaluate the initial conditions selected for the model to remove inconsistent inputs.

For instance, in the model used for Figure 1 there was an inlet tank defined at 300 deg. F. Pipe P1 connected to the inlet tank was defined to use convective heat transfer with the atmospheric temperature set at 70 deg. F. There was no flow in the pipe initially, so the pipe was fixed at the atmospheric temperature (70 deg. F) for the AFT Arrow Steady solution. During the artificial transient resolution process the pipe temperature was allowed to vary and increased to about 300 deg. F due to the tank temperature, creating a mismatch between the AFT Arrow Steady and Resolved solution temperatures in the pipe.

The error message in the example model was resolved by using the Temperature Override for Zero Flow option in the Pipe Properties window to set the pipe's temperature equal to the tank temperature during the AFT Arrow Steady solution.