View Full Version : Numerical correction and Priessmann slot

Eva Choudalaki
July 27, 2016, 06:33 AM
Hey everyone,

There is something that has been troubling us and there is no clear explanation within the InfoWorks ICM Help file.

When numerical correction is applied to compensate for the effects of the Priessmann Slot, InfoWorks ICM reduces the cross section area of a manhole to provide a reduction in volume equal to the volume of the slot. As mentioned in the help file, it is possible for the sum of all storage compensation parameters to be negative.
The Minimum Plan Area at Nodes values in the Simulation Parameters, ensure that the effective plan area of a node can never fall to zero.

What happens then with the extra volume (the amount that would cause the node to have a negative area) that is not reduced? Is it “unavoidable” extra storage that is added in the system? Is there a way around it?

Thank you for any help,

Rui Daniel Pina
August 15, 2016, 06:29 AM
Hi Eva,

Thanks for the post.

The volume correction only applies to the nodes connected to conduits. If the corrected area is lower than the defined “Minimum Plan Area at Nodes” in the Simulation Parameters, this value is considered and no extra compensation is applied.
Other possible option to reduce the Preissmann slot is to the change of the Celerity ratio in the Simulation Parameters. If you are modelling modelling conduits with pressure flow, you can also consider the use of the “Pressure” or “ForceMain” solution models that do not use the Preissmann slot.

I hope this helps.

Rui Daniel Pina