Page 295 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

JWCL344_ch07_230-264.qxd 8/2/10 8:44 PM Page 255

7.7 Automated Optimization 255

EXAMPLE 7.5 MODEL CALIBRATION USING DARWIN CALIBRATOR
WaterGEMS has the ability to use measured field data to calibrate a model. In many cases, data that
are entered into the model are an approximation or guess. When the model results do not match
field data, then parameters in the model are adjusted. Also, using the Darwin Calibrator and field
data, we can locate potential differences between the real network and the model that could be
caused by problems in the system (blockages, closed valves, etc.).
Adjust the Hazen-Williams C factor (roughness factor) for pipes P-2, P-1, and P-8 for the pipe
network from Example 7.2. During the field measurements, the tank level was 3.93 m, the pump
was off, and a hydrant with a measured flow of 3,400 L/min at junction 7 (J-7) was opened to in-
crease the head loss in the pipe network. The measured field data are shown below:

Junction Pressure (kPa)

J-7 296.0
J-6 406.5
J-1 263.5
J-2 327.0

Solution:
• Open Tutorial 2 (from Example 7.2).
• From the Analysis menu, select Scenarios. Create a new base scenario named “Calibrator
Analysis.”
• Click on the Calculation Options tab at the bottom of the window. Create a new Calculation
Option by clicking the New button and enter “Calibrator Calculation Options” as the name.
Double-click the calculation options you just created. The Time Analysis Type is Steady State.
• Go back to the Scenarios tab and right-click the Calibrator Analysis scenario and select
Make Current. The red check should now be on the Calibrator Analysis scenario.
Double-click on the Calibrator Analysis scenario and select the Calibrator Calculation
Options in the Calculation Options field. Click the Compute button.
• Click the Darwin Calibrator button to create a calibration study to determine the
pipe roughness factors. Click the New button to select New Calibration Study. Check to
make sure the Representative Scenario window has Calibrator Analysis selected.
• Enter the field data in the Field Data Snapshots tab. Click the New button to enter new
data. Enter the measured pressures on the Observed Target tab. Select the junctions
from the drawing by clicking the Select button then clicking junctions J-7 J-6, J-l,
and J-2 from the drawing. Click the green check in the Select dialog. Select Pressure
(kPa) for each junction in the Attribute field. Enter the measured pressure for each
junction in the Value field.
• Enter the tank level in the Boundary Overrides tab. Select the tank from the drawing by
clicking the Select button then clicking the tank. Click the green check in the Select
dialog. Select Tank Level (m) in the Attribute field, then enter 3.93 m in the Value field.
• To make sure the pump is off, click the New button in the Boundary Overrides tab. Select the
pump by clicking the Select button , then clicking the pump. Click the green check in
the Select dialog. Select Pump Status in the Attribute field, then select Off in the Value field.
• Enter the additional demand at junction 7 in the Demand Adjustments tab. Select this
junction from the drawing by clicking the Select button , then clicking J-7. Click the
green check in the Select dialog. Enter 3400 L/min in the Value field.
• Select the pipes where the roughness values are to be determined in the Roughness
Groups tab. Pipes with similar roughness can be grouped together, or the software can