How does the Unit Line LoadBuilder method work?

Applies To 
Product(s): WaterGEMS, WaterCAD, HAMMER
Version(s): CONNECT Edition
Area:  Layout and Data Input
Original Author: Scott Kampa, Bentley Technical Support Group


How To

How does the Unit Line LoadBuilder method work?

Steps to Accomplish

The Unit Line method in LoadBuilder divides the total demand in the system (or in a section of the system) into two parts: known demand (metered) and unknown demand (leakage and unmeasured user demand). The known demands are included from existing Demand alternatives in the model. Unknown demand from leakage on only one side of the pipe (for example, pipes along a river), K is 0.5. If both sides of the pipe supply water to users, K is 1. The unknown demand is entered in a table in LoadBuilder. Details on the methodology and theory can be found in the Help topic "Unit Line Method".

The following screenshot shows LoadBuilder using the Unit Line method:


The "Include known demands in results" item allow the user to retain demands that are already in a given demand alternative. By selecting this option the user can choose a Demand alternative from the drop down menu.

The "K-factor field" select allows the user to define how unknown demands are accounted for in the model. By click the ellipsis ("...") button, the user can add a K-factor they want to use during demand allocation. This will automatically create a User Data Extension (UDX) with the K-factor used in the model. The user can also go to Tools > User Data Extensions to create the User Data Extension. When the K-factor UDX attribute is created by the user through the UDX manager, a Real/Unitless ("None" dimension) attribute is expected. Using this method allows the user to enter values through the element FlexTables or properties grid, or even importing them through ModelBuilder. It also allows the user to define the name of the field, since creating the K-factor UDX in the LoadBuilder dialog will yield a default name. Once it is created, the K-factor UDX attribute will be available in Unit line method wizard in LoadBuilder.

The "Unaccounted-for Demand by Selection Set" table allows the user to assign unaccounted-for demands for the system by selection set. Click the New button to add a row to the table, then choose a selection set (or Entire Network to include all applicable elements) and specify an unaccounted-for demand value. Highlight a row and click the Delete button to remove it.

After the data is entered, click Next. This will list the different load types. The screenshot below shows an unaccounted-for demand of 100 gpm across the entire network and a known demand from an existing Demand alternative (which was included when the "Include known demands in results" checkbox was selected). You can also include a multiplier or a pattern in this step.

Click Next again, and you will see how the demands will be allocated in for the junctions. The demand will be based on the equations found in the Help documentation under the section "Unit Line Method". 

Click Next again. This step will allow you to the select a label for the LoadBuilder item and decide if the input will overwrite or append an existing Demand alternative, or if it will be assigned to a new Demand alternative.

For information on the theory and equations used for this method, please review the Help topic "Unit Line Method" 

See Also

How do each of the Loadbuilder methods work?

Troubleshooting and Understanding LoadBuilder