## 5.6. Troubleshooting and Error Messages

Data Input Errors:

Where a numerical value is required as an input but a text or blank entry is made, an error message similar to the following will appear at the bottom of dialog box:

    Invalid input for mass flow rate. Please check the value and try again.

This indicates exactly which input is causing the problem and suggests revision. Often this will be where the letter “O” has been typed rather than the number “0”. To rectify the problem, click OK to enable the user interface, then edit the value that contains the error.

A different error message, similar to the following, will appear where an input value lies outside of the advised range in the tooltip:

    mass flow rate must be > 0. Please check the value and try again.

This is similarly specific and similarly resolved.

Calculation Errors:

During the meanline calculation, where the geometry has no OGV, the following error may appear:

Figure 5.11: Meanline Calculation Error Message

The usual cause of this error is that the specified mass flow rate is too large for the size of the machine. In this situation, either gradually increasing the outer diameter or reducing the mass flow rate should give a valid meanline calculation.

This error may also occur during the design calculation. This is because the meanline calculation is updated using a new efficiency estimate during the design calculation outer loop. This suggests that the initial efficiency estimate is too high and lowering this in the meanline calculation may give the same error. Again increasing the outer diameter or reducing the mass flow rate should resolve the problem.

During the design or analysis calculation, the following error message may occasionally appear:

Figure 5.12: Design Calculation Error Message

Even though the results of the meanline calculation will seem to be fine, with all parameters within the recommended guideline, the throughflow code may still fail. It is important to note that the blade geometry (number of vanes, aspect ratio, and profile trim) does not influence the meanline calculation but has a significant impact on the throughflow calculation.

Less aggressive settings for the geometry parameters (a larger number of vanes, lower aspect ratio, and profile trim closer to 1) should lead to a successful design/analysis calculation. Exploring the design space around the desired geometry in this manner will give a good indication of why the calculation fails under such conditions and what can be done to remedy the situation.

During the design and analysis calculations, a number of files associated with the throughflow are created in subdirectories below the case name directory. Should the design and/or analysis calculation fail and prove difficult to remedy using the above techniques, these files will prove helpful to technical support in diagnosing the issue.

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