The Following Pipes Have Vapor Volumes in Computing Stations Greather Than 100% of the Liquid Computing Volume

A Critical Warning message in AFT Impulse

Full Message Text

The following pipes have vapor volumes in computing stations greater than 100% of the liquid computing volume:

Pipe X (Name), Stations: Y (Z%)

Explanation

This Critical Warning is part of a series of Output Messages meant to convey increasing uncertainty in results as Percent Vapor Volume increases.

• Caution - greater than 0.1% but less than 10%

• Warning - greater than 10% but less than 100%

• Critical Warning - greater than 100%

A detailed explanation about the Percent Vapor Volume parameter, section volume, and assumptions can be found on the Interpreting Cavitation Predictions topic. In summary, Impulse's solution methodology assumes that pipe sections are 100% liquid-full. This warning is stating that for the listed pipe stations, the Percent Vapor Volume was greater than 100% of the section volume at some point during the transient, which is fully violating the 100% liquid-full assumption.

Vapor volumes larger than the total volume in the pipe section are physically unrealistic and indicate that full column separation and extensive transient cavitation are likely occurring in the system at that point. In this situation, the cavitation models are no longer physically meaningful, and the conditions in the model may be outside of the single-phase assumption that Impulse is based on.

Required Action

Users should explore the various cavitation topics - and in particular the Interpreting Cavitation Predictions topic - to better understand what is causing these results, why they are possible, and how to interpret results in scenarios with this critical warning. If all else fails, users should treat systems with these results with extreme caution.