[Unknown properties in Hydraulic Option]

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[Unknown properties in Hydraulic Option]

Minh Thai
I'm using the Windows version of EPANET 2.
In the property window of Hydraulics Options, I notice that there are 3 properties really strange, I can't find the explanation of them in EPANET manual nor in EPANET Toolkit help file. They are CHECKFREQ, MAXCHECK  and  DAMPLIMIT
Can anyone explain these properties for me ? What are they ? The unit of them ? How are they used in simulation ?Any help would be welcomed.
Thanks in advance.
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Re: [Unknown properties in Hydraulic Option]

The Community Engineer
Administrator
These are simulation parameters.

EPANET solver sometimes experiences difficulty with convergence to solution or the solution might differ from the expected. In such cases simulation parameters can be modified to solve the instability.


CHECKFREQ
This sets the number of solution trials that pass during hydraulic balancing before the status of pumps, check valves, flow control valves and pipes connected to tanks are once again updated. The default value is 2, meaning that status checks are made every other trial. A value equal to the maximum number of trials would mean that status checks are made only after a system has converged. (Whenever a status change occurs the trials must continue since the current solution may not be balanced.) The frequency of status checks on pressure reducing and pressure sustaining valves (PRVs and PSVs) is determined by the DAMPLIMIT option (see below).

 
MAXCHECK
This is the number of solution trials after which periodic status checks on pumps, check valves flow control valves and pipes connected to tanks are discontinued. Instead, a status check is made only after convergence is achieved. The default value is 10, meaning that after 10 trials, instead of checking status every CHECKFREQ trials, status is checked only at convergence.
 
DAMPLIMIT
This is the accuracy value at which solution damping and status checks on PRVs and PSVs should begin. Damping limits all flow changes to 60% of what they would otherwise be as future trials unfold. The default is 0 which indicates that no damping should be used and that status checks on control valves are made at every iteration. Damping might be needed on networks that have trouble converging, in which case a limit of 0.01 is suggested.