Flushing Area Options
When the flushing area is selected in the left pane, the user can set up global options for the events within that area. Most of these are set in the options tab in the right pane for the area. The most important is the Representative Scenario which establishes the boundary conditions (tank levels, pump status, demands) for the area.
The Output Scenario is the scenario where the results of the flushing analysis will be stored. The output scenario is created automatically the first time the area is computed.
The Target Velocity is the velocity that should be exceeded for the flushing to be considered successful for that pipe. The user may specify a Target Shear Stress as well as a Target Velocity or in addition to a Target Velocity. If both are specified, both must be satisfied for a pipe to be considered successfully flushed.
The Safety Factor (Flushing Time, Volume) is a multiplier by which the Time (Minimum Flushing) and Volume (Minimum Flushing) are multiplier to obtain Time (Recommended Flushing) and Volume (Recommended Flushing) in the Flushing Results Browser.
The Pipe Set is the collection of pipes for which the target velocity will be compared with the maximum velocity achieved by flushing. It is created by clicking the ellipse button and entering the pipe set dialog. To create a Pipe Set, pick the ellipse button and then the Select from Drawing button. Picking the Select from Drawing button enables the user to select the pipes to be included in the set using the standard element selection dialog.
The first toolbar button is used to select elements from the drawing. The standard select from drawing toolbar is displayed when in selection mode. Only pipes can be selected for this dialog.
(It may be advisable to create a selection set of pipes before entering the flushing manager.) The delete button can remove individual elements while the Remove All button removes all at once.
The Nodes of Interest ellipse operates similar to the Pipe Set except that it selects nodes that will always appear in the auxiliary results. Most nodes will not have data saved for each flushing event. Only those that meet the auxiliary results criteria or appear in the Nodes of Interest will be included.
Boundary elements are pipes or isolation valves which are closed for all of the events in an area. This is used for "back door" feeds to the area to ensure that all of the flow will enter the pipe run from the desired direction.
Under flushing flows, the user can specify either the emitter coefficient for the hydrant or junction being flowed or the actual flow rate. Because flow rate depends on pressure and the user does not usually know the flow rate ahead of time, it is usually more accurate to specify and emitter coefficient. Typical values in North America are 250 gpm/psi0.5 (20 L/s/m0.5). See page 453 of Advanced Water distribution Modeling and Management (Bentley). Do not specify both an emitter coefficient and a flow.
Depending on the selection from the drop down menu "Apply Flushing Flow By", the hydrant flow can be added to the node demand or used in place of the nodal demand.
Under Auxiliary Output, the user can save values for all elements for each event. However, in most cases the user is not interested in values for properties in elements far from the flushing. The user must therefore specify condition for which element data are saved and available for display for individual events. If the box, "Includes nodes with pressure less than?" is checked, properties for elements with pressure less than the specified value are saved for display/ If the box, "Include pipes with velocity greater than?" is checked, properties of pipes with high velocity are saved. This makes it possible to use color coding to display results of flushing without saving a great deal of unneeded values.
The Events tab enables the user to get a quick view of the events that are contained in the area and if desired, make events active or inactive for the next run. Click the Conventional Event Quick Edit button to open the Conventional Event Quick Edit dialog, allowing you to globally edit local flows and emitter coefficients across multiple events.
The Notes tab enables the user to enter a text description of the area.
Right clicking on an area in the left pane opens the following options
- Add - create new event
- Delete - delete the area
- Rename - renames the area
- Compute - computes all of the active events in the area
- Shift Up - moves the area up the list of areas
- Shift Down - moves the area down the list of areas
- Zoom To - zooms to the extents of the elements in the area
- Highlight - highlights the elements in the area
- Expand Children - expands the tree view of areas in the area
- Collapse Children - collapses the tree view of areas in the area
In the left pane, the type of event and its status is designated by the icon representing that event
The event Active check box is on the top of the right pane when the event is highlighted in the left pane. Inactive events are not computed.