Santara → Siwana Gravity Main
Interactive valve and water hammer simulator. Click any valve on the schematic, or use the switches in the table, to open or close it. The flows, hydraulic grade line and pressures update at once. The water hammer section simulates what happens when a valve is closed quickly.
Pipeline schematic
Horizontal position is to scale by chainage. Line thickness shows diameter and line colour shows flow. Click a valve to toggle it: green is open, red is closed. The bottom strip gives the pressure at each 5 km node, and the blinking red dot marks the point of maximum pressure. Strip values above the permissible pressure are shown in red.
Longitudinal profile: ground, pipe and hydraulic grade line
Pressure head at pipe centreline
Santara supply: safe operating range
Each offtake's flow control valve takes its design share of whatever arrives at Santara, so a surplus or shortfall is spread in the ratio of the design flows (J1 31%, J2 40%, Siwana 20%, J3 6%, Offtakes A and B 3%). The chart shows the highest and lowest pressure on the main at each supply level, for the current valve settings. Drag the Santara supply slider in the control bar to move along it.
Junctions and valves
Node pressures along the main line
Pressures every 1 km, with junctions and diameter changes highlighted. Once you run the water hammer analysis, its maximum and minimum pressures appear here too.
Show node table
Water hammer: fast valve closure
When a valve closes quickly, the moving water column is stopped suddenly. That sends a pressure wave travelling at about 1,000 m/s: a surge upstream of the valve and a pressure drop downstream. The wave reflects back and forth along the 80 km main until friction damps it. If the downstream pressure falls to vapour pressure, the water column separates, and the columns can slam back together with a second surge. Choose a valve and a closure time, then run the analysis.
Pipe and material properties (MS Fe250)
Wave speed is calculated from the Korteweg formula, a = √(K/ρ) / √(1 + (K/E)(D/t)(1 − ν²)), with K = 2.19 GPa and ν = 0.3 for a buried pipe restrained against axial movement. If you edit the wave speed field, your value is used instead. The default stress limits follow common IS 5822 practice; confirm them against the code you design to.
Model settings and assumptions
How the simulation works
- Steady state: demand-driven. Every open offtake draws its design flow, which assumes flow-control valves at the ESRs and CWRs. Friction is Hazen-Williams with C = 140, plus 10% for other losses, as in the design sheet.
- With the default boundary, the HGL at Ch 0 rises from 224.0 m toward the 257.5 m static head as the flow drawn falls. With everything closed, the whole main is at the sheet's "d/s valve closed" static case.
- The sheet has a 2.63 m head drop at Ch 45,700–45,725, at the 1000→900 mm reducer, that pipe friction doesn't explain. It is kept as a local loss.
- Pressure is HGL minus the pipe centreline level (invert + D/2). 1 kg/cm² = 10 m of water.
- Water hammer: solved with the method of characteristics, time step 0.1 s, about 800 computational nodes, and the same Hazen-Williams friction. Diameter changes within 175 m of a junction are moved to that junction. Offtakes and the Siwana inlet behave as orifices that discharge to atmosphere. In-line valves are butterfly-type, with a fully open loss coefficient of ζ = 0.3.
- Column separation uses the discrete vapour cavity model: pressure is capped at −9.8 m (vapour), and a cavity forms and later collapses. Results after a cavity collapses are indicative only.
- The source at Ch 0 is treated as a reservoir with the calibrated entry loss, so any pipeline upstream of Ch 0 is not modelled. Air valves, surge vessels and pressure relief valves are not modelled either, so the results are for an unprotected main. Use them for screening, and confirm with a detailed transient study.