 # Demand calculation with Continuous vs Stepwise patterns

 Applies To Product(s): WaterCAD, WaterGEMS Version(s): 08.11.XX.XX, 10.XX.XX.XX Area: Output and Reporting Original Author: Mark Pachlhofer, Bentley Technical Support Group

# Problem Description

What is the difference between a continuous pattern vs. a stepwise pattern?

Why doesn't the demand at a particular timestep in an EPS appear to be calculated based on the multiplier on its pattern?

# Solution

Stepwise—The multiplier values are considered to be the average value for the interval between the specified time and the next time. Patterns using this format will have a staircase appearance. Multipliers are set at the specified time and held constant until the next point in the pattern.

Continuous—The multipliers are considered to be the instantaneous values at a particular time. Patterns using this format will have a curvilinear appearance. Multipliers are set at the specified time, and are linearly increased or decreased to the next point in the pattern.

With a continuous pattern the calculated demand at a particular timestep is equal to the average of the calculated demand for that timestep and the next one (for a "smoothing" effect). For example, assume the base demand on a given junction is 500gpm, the hydraulic time timestep in the calculation options is set to 1 hour, the pattern multiplier for timestep 8 is 1.0 and for time step 9 is 1.945, and the Start Time field would be 8 am (assuming the simulation was started at 12 am). The total calculated demand at the junction shown for timestep 8 will be (500 * 1) + (500 * 1.945) / 2 = 736.25.

For the continuous pattern, if you want to achieve a demand that is very close to the one specified in the pattern you can try a smaller Hydraulic Time Step.

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