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Average Demand Calculation and Fire Flow

My model is fine and everything works fine however the design criteria for demand is 2.1 multiply by the average demand  + Fire Flow (as indicated in the snapshot)
I have setup the Scenarios and alternative for this criteria based on the BASED DEMAND (as PHASE 5_UNSPLIT_OPTION A_BASE_DD as shown in the snapshot)
My Question are as follows
1. I am going to multiply the all the base demand for each nodes (junctons) with 2.1 to achieve the new demand alternative (average demand  + Fire Flow)
2. Create a snapshot for the time when average demand occur in the model and multiply this by 2.1 
3. I need clarification and best method to set this up
4. Which of these element is better to use for fire flow analysis Junction or Hydrants
Thanks 
Mayowa
  • Regarding item 4 - please also see the below article:

    Junction Vs. Hydrant


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

  • 1.  Here is a link to a wiki technote that will show you how to multiply 2.1 with the base demand.  Make sure you have the scenario set up to use the desired demand alternative.

    communities.bentley.com/.../how-to-edit-demands-globally.aspx

    You can also use a multiplier in the calculation options.

    communities.bentley.com/.../10333.aspx

    If this does not answer question number one, please give us more clarification on what you are looking to do.

    2. To get the snapshot, you would go to Analysis > Calculation Options.  Set the Time Analysis Type to steady state.  Set Is EPS Snapshot to True if this is an EPS snapshot, not a regular steady state run.  An EPS snapshot is a steady state run, but it considers the starting date and time of the analysis and applies the appropriate pattern multipliers for that time.

    NOTE:  Since an EPS is not run, attributes such as tank levels are derived from the same initial conditions as a steady state run.

    3.  See numbers 1 and 2.

    4.  As for using a hydrant versus a junction, it depends on what you are looking for in the node.  They are both non-storage nodes.  With a hydrant, you can enter a hydrant flow curve.  The hydrant flow curve allows you to find the flow the distribution system can deliver at the specified residual pressure, helping you identify the system's capacity to deliver water to that node in the network.  Both nodes can have an unlimited number of demands associated with them.

    Terry Foster
    Technical Support
    Hydraulics and Hydrology product line
    Bentley Systems, Inc.