APPENDIX B – MOC and its Struggles to Compete with WPM
Surge Analysis and the Wave Plan Method
Supplementary Material: Example Problems and Solutions
Appendix B – Problem 17
B.17 Consider a water distribution system (comprising 24 pipe elements outside the pump station area with a total length of 4180m) shown in the following map. Numbers shown next to the pipe elements are their lengths in meters. The inset shown on the map represents the pump station piping. The material for all pipes is mild steel with an approximate wave speed of 1000 m/s for all sizes. The maximum steady state velocity in the entire distribution network is 2.5 m/s and the smallest pipe diameter is 100 mm.
a. If the smallest pipe element in the entire network controls the computational time step, obtain a suitable computational time step for MOC-based solution for this network that minimizes the numerical stability issues [Hint: use the CFL condition].
b. Determine the total number of pipe sections (as described in section B.4) associated with the computational time step determined in part (a).
c. Determine the total number of friction elements (as defined in section 1.7) needed to model this network using the WPM-based solution limiting the maximum frictional headloss in each pipe element to (i) 5m, (ii) 10m, and (iii) 20m.
d. If a modeler is trying to limit the total number of pipe sections in an MOC-based solution technique to 5 times the total friction elements used in WPM-based solution technique, what should be the upward revision for the pipe lengths be, and what is the associated computational time step?
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