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# guidelines for the configuration of pressure dependent demand analysis

Hi, I have my data of pressures in different points and I would like to configure my model to have more real data, how I configure the function which is the most optimal if power function or piecewise linear what the difference and how the table of percent of reference pressure vs demand works in a period eps...

thank you very much for your guide ...

Parents
• Hello Leonidas,

Using Pressure Dependent Demands

This is also a lot of good information in the help topics "Pressure Dependent Demands" and "Method for Modeling Pressure Dependent Demand" (see subtopics as well). Regards,

Craig Calvin

Bentley Technical Support

• • Hello Leonidas,

- The differences between the function that is the most optimal if the power function is linear or by parts, what is the difference and how the table of percentages of reference pressure vs. demand works in a period eps.

The curve generated for the power function will depend on the power function exponent (generally smoother). However, if you have specific values of percentage of demand to be supplied for a certain percentage of reference pressure you can generate the curve based on your own values. The power function is determined by observing field data and developing a relation to conform the equation for an orifice which will help you calculate the power exponent. If the values found on field so not conform to a specific equation (and a power exponent) you can input the percentages in a piecewise linear function.

When running an EPS analysis the "Demand (Target)" in junction properties would change as per the demand pattern specified. Hence, for every time step the target demand would change, the percentage of reference pressure would be calculated (i.e. pressure at the node for that demand / threshold pressure) and based on the piecewise function specified the appropriate percentage of total demand would be provided.

How to load several real points let's say 200 so to speak ...

I do not understand this question. Are you asking how to load piecewise function data containing 200 points i.e percentage pressures and demands between 0 to 100% with 200 points (200 rows of data)?. It is possible if you have extensive data. You can copy the data from excel and simply paste it.

If you are inquiring about the number of nodes you can assign PDD function to then its is possible to do so by creating a selection set and the globally assigning the PDD function in the PDD alternative. You can assign it to any number of nodes.

If this doesn't answer you question kindly clarify.

As pointed out by my colleagues the tech-note provided has detailed information to use Pressure Dependent Demands in WaterGEMS along with several topics in the Help section.

Regards,

Yashodhan Joshi

Bentley Technical Support

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