Air Flow Curves not providing expected results.

Hello Felipe, 

Please see the section "Using a Custom Air Flow Curve" of the article we had linked to, if not already to make sure you defined the air flow curve correctly for the air valve. Like positive flows and pressures should be entered for outflow and negative flows and pressures should be entered for inflow.

You should also check to make sure that the flows you have entered in the custom air flow curves represent "free air" flow rates, at atmospheric pressure.

If this is set up correctly and if still the results do not make sense, then please upload model files for our review. 

Thanks Sushma.

I have reviewed the article and the curves were properly inserted.

I just uploaded the files for your review.

Could you please also check why is giving the following warning "Combined pump and motor efficiency should be between 30% and 95% inclusive."; even though the pump definition clearly has the combined efficiency within in the range.

Thanks.

Felipe

Hello Felipe,

The following link has information on the assumptions involved with air valves, including information on extended CAV: Assumptions and limitations of tracking air or vapor pockets in HAMMER. Extended CAV is mainly used to track the air-water interface in pipes adjacent to the air valve. It will not track beyond this point, and the air still will only provide protection at the location of the air valve.

Using Extended CAV increases the complexity of the calculation, so that may account for the results that you are seeing. Given the limitation of Extended CAV, you may want to consider not using this feature.

As for the other questions:

1. Increasing the time step or decreasing the run time would help with the simulation time. For instance, if you run this for 300 seconds, and find the the simulation reaches equilibrium after 150 seconds, you may be able to reasonable decrease the run time. Another option could be to decrease the report points you are selecting. There are currently over 100 report points. While it would compute in the same amount of time, the processing time for the results would be less, thus lowering the overall run time.

2. The air flow results can be found in the Transient Analysis Detailed Report. The following link has information on this: How to view extended node transient results for hydropneumatic tanks, pumps, or turbines. Air valve results are not in the Extended Node Data tab, but you can use the steps in the section on air valves and older versions to graph the results in an outside program, like Excel.

3. I don't believe that there is a way to display the percent open for air valves. For other valves, an FCV (or other valve) can report a relative closure for the initial conditions calculation, but the valve will not change the relative closure unless you put in an operating rule to change the relative closure of the valve.

4. The following link has information on the user notification: User notification: "Pump Efficiency must be between X% and Y% inclusive." I would check the pump definition and the speed you are using the Transient tab of the pump definition dialog.

Regards,
Scott

Thanks Scott,

This is very helpful!!!

Felipe

Scott,

It seems that my last reply was deleted.

Here it is again.

I have a couple of comments for questions 3 and 4:
3. Is there any place where I can check the relative closure of the FCV at the end of the simulation? Without any operating rule. Just to confirm that the relative closure remains the same at the end of the
simulation as it was at the beginning.
4. Could you please take a look of those parameters in my model, because I checked the info in the link, reviewed my pump definition and speed in the Transient tab, and everything seems to be ok.
Thanks again.
Felipe

Felipe, since you are asking about a new topic, I split your post to a new thread here: FCV closure reporting and pump efficiency error

Please see the answer I just posted in this separate thread.

Thanks Jesse!!!

Regards.

Felipe

Thanks Jesse!!!

Regards.

Felipe