Modelling isolation in Epanet 1

[mksamas]

Hello everyone.

I am struggling to model isolation correctly in Epanet for a water network of about 4000 pipes. I need to isolate a block within the water network to see how pressure is affected. I have tried using control valves and flow control valves with minimal flow e.g. 0.005 l/s. When I do this I get reasonable pressure head values however, I get flows of e.g 0.65 l/s in one of the pipes in the isolated network. How is this possible? Should the flow not be close to the entered value of 0.005 l/s? I have also ensured that the setting on all FCVs to the network are 0.005 l/s?

 

[hydrae]

My first thought is you have a large network and are concentrating on a small area with small flows.
The engine runs until it gets target values near calculated values on the whole matrix, it maybe your small flows are not forcing the engine to continue to run until the numbers at that location are reasonable.
Try increasing the accuracy located in the option-hydraulics

Hydrae

 

[mksamas]

Ok thanks hydrae. Maybe I should rephrase my question. I have a water network for an area. This network has been divided into six sub-blocks. These sub-blocks must be isolated individually from the rest of the network. This will be to see how the pressure varies within the network for example if the sub-block is closed for maintenance. So how do I model the isolation. Right now I am using control valves and flow control valves to close the links that feed the sub block. The control valves are positioned in such a way that they prevent flow into the sub- block. Where there are flow control valves the setting has been to minimal flow e.g 0.005 l/s in a pipe of 315mm. However when I run the model I will get a pipe within the isolated sub-block having a flow of for example of 0.74l/s in a pipe of 200mm. The total inflow into the sub-block is 0.088l/s. Some of the pipes have a flow of 0 l/s which is more accurate in my opinion. I would greatly appreciate any assistance or explanation on how this occurs.

 

[coloeng]

Why not just eliminate the demand in the sub-block, close all the pipes except one and then run the simulation. Leaving one pipe open will prevent it from having a disconnected portion of the distribution system.

 

[hydrae]

Any pipe can be closed by setting an attribute, this can model the isolation.
try not to use control valves or flow control valve where you do not have them in the system, e.g. build the model as the system is.

 

[mksamas]

Thank you so much guys. Compliments of the new season was away on holiday. I will try what you have just suggested now.