Sam Ziemann From - Region of Waterloo

August 26, 2011Sam ZiemannPage 4 of 12Reference: Fluid Transient Analysis for Strange Street Raw Water Supply System – Draft TechnicalMemorandumPer information provided in the Tier 3 Water Budget and Water Quantity RiskAssessment Strange Street Well Field Characterization Study, the first wells wereconstructed around 1910. It is assumed the cast iron piping was manufactured to meetAmerican Water Works Association (AWWA) Specification C106 and that Class 150pipe was installed.Preliminary Transient CalculationsPrior to assessing the performance of the raw water supply system using the hydraulictransient model, two significant transient parameters were calculated: the critical timeperiod of the raw water supply system, and the Joukowsky Head.Joukowsky HeadTo aid in the understanding of the expected pressure changes in the system that couldbe caused by a surge event, the Joukowsky Head was calculated for the raw watersupply system. The Joukowsky Head is the initial rise or drop in head caused by aninstantaneous change in the flow velocity and is determined using the followingequation:a∆v∆ h = ,g∆his the Joukowsky Head, a is the wave speed in metres per second,∆vis thewherechange in velocity in metres per second, and g is the acceleration due to gravity, whichis equal to 9.81 metres per second 2 .The Joukowsky Head within the raw water supply system was calculated for using adischarge of 140 L/ for current operating conditions and 227 L/s for anticipated futureoperating conditions. For current operating conditions a wave speed of 1183 m/s wasused to represent cast iron (CI) and ductile iron (DI) pipe whereas a wave speed of 337m/s, which is representative of PVC pipe, was used to calculate the Joukowsky Headfor anticipated future conditions. Calculation results are shown in Table 2 below:Table 2 - Joukowsky Head for Strange StreetRaw Water Supply SystemOperatingConditionJoukow skyHeadmEquivalentPressure kPaCurrent 106 1,041Future 49 481