Changing the solver engine and time step!

Mo7amed,

I'd like to see your model files before I comment on why the results you're seeing are different. What you should be certain of first is that you're comparing values at the same time steps when you're looking at the results of elements. If you're looking at two different time steps then it's possible the results could have changed pretty dramatically because something in your network could have changed, e.g. a pump turning on/off or a valve switching statuses. An important setting to check in your calculation options in order to make sure you're seeing all the time steps the "reporting time step". If you set that to <All> instead of Constant or Variable that might help out. I also noticed that you said you're using a time step of .02 hours and .01 hours, which are relatively small time steps. Do you have very fast changes in flows that you need to capture? If you don't you might want to consider using a slightly larger time step like 5 minutes.

If the above doesn't help there are two options for sharing your model on Communities. Either way, be sure to zip your files first. The first option is to attach to your reply on the forum using the Advanced Reply Editor (see link below and to the right of the reply box). If your data is confidential, use the instructions in the link below to send it via Bentley Sharefile. Files uploaded to Sharefile can only be viewed by Bentley.

communities.bentley.com/.../7079.be-communities-secure-file-upload

If you upload the file to Sharefile, please post here with the name of the file so that we know it is available

We have a wiki article that I've linked to below that explains the user notification that you're seeing and how it can be resolved.

communities.bentley.com/.../24830.pumps-are-operating-at-a-much-higher-rate-than-the-design-point-pump-exceeds-the-maximum-operating-point-specified-for-the-pump-curve

Regards,
Mark

Hello
I uploaded the file and linked it to this URL.

please check why the model works fine when using WaterGEMS solver engine and with problems while using epanet solver engine (both under the same time step and other conditions)?

Thank you in advance

Hello,

We see that you uploaded the .WTG and .WTG.DWH files, but we will also need the .WTG.SQLITE file (typically the largest in terms of file size) in order to open the model. Please upload a copy of that.

In general (and to add to what Mark posted), if you're seeing large differences in results between timesteps, solver versions/types and other calculation options, it's an indication that the model is unstable and likely has a problem with the configuration. There could be conflicting controls, valves fighting against each other, etc. If you see a User Notification stating that the network is unbalanced, check this article:

WaterGEMS/WaterCAD user notification: Network Unbalanced

Regarding EPANET vs WaterGEMS solver - there are some differences between them which can sometimes cause differences in results. You can read more here:

Should the EPANET solver and the WaterGEMS/CAD solver give the same results for a model?

Thanks for your fast respond ,
I uploaded .WTG.SQLITE file.
This system is very simple, 5 pumps and 1 demand node, if you used the WaterGEMS solver, the system is balanced while if you used EPAnet, the pump will not work because it couldn't deliver head or flow. (there are not any control is the system)
Why is that and how can i overcome this problem while using the EPAnet solver.
Thanks

The solution is simple--use WaterGEMS instead of EPANET. The WaterGEMS solver has some features that make it more robust.

Plus WaterGEMS has a whole array of features that do things better than EPANET (e.g. symbology) or things that EPANET can't do at all (e.g. criticality, pressure zone manager).