Hi,
I am modelling a simple system to compare the results to some codes that I have. But, despite having all the configurations similar to codes, I cannot get similar pressure fluctuation. Could you please have a look and let me know the reason?
Thanks in advance.
Regards,
Example 1.xlsx8233.Example 1.zip
Hello Hiwa,
Do you know what calculation method was used with the other results in the spreadsheet? This may be a case where the comparison is not apt. If different calculation methods are used, different results would be expected.
Another thing you can consider is using your own valve characteristic curve for the GPV. It is possible that the valve characteristic curve assumed by HAMMER will be different from the ball valve used in the valve in the field. Including a user-defined valve characteristic curve may improve the results compared to field data. More information on modeling valve closures in HAMMER can be found here: Model Reference - Valves.
Otherwise, more information would be needed about what the results in the spreadsheet are from and how they were determined.
Scott
As Scott mentioned, the calculation methodology used to generate your "code" may be different from HAMMER. HAMMER uses the Method of Characteristics, which you can read about in the Help and in the below articles. I suspect that a simplistic assumption was made in the results you are comparing to.
Numerical method used for transient simulations in HAMMER
Method of Characteristics vs. Wave Plan Method
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.
Dear Scott,
Thanks for your response. I am using the MOC and I wrote the code in Matlab. I compare my code to some results from other researchers that are very close as you see in the spreadsheet. I want to develop my code more for some research purposes and compare them to results from Hammer. I tried to use the same valve pattern and other specifications. But still, the Hammer result is far from other cases (please see the attached graph too). I am trying to understand how to calibrate the Hammer model with some real or reliable data. I appreciate more comments on this issue.
HAMMER models cavitation (vapor pocket formation) when the pressure reaches vapor pressure (set to -10m by default). That's why your HAMMER pressures stop going down at -10m and instead start to 'flat line'. Then later when the vapor pocket collapses you get a pressure spike.
I assume the other calculations you are using don't attempt to model cavitation, which may explain the difference. As a quick workaround you can change the vapor pressure value in the calculation options to some large value (like -100m).
Answer Verified By: Hiwa