Hydro Turbine Design Chart: Specific-Speed Nomogram

Choosing which turbine goes into a hydropower plant falls out of a single dimensionless number, the specific speed Ns, computed from a site's head, its available flow, and the runner's rotational speed. This 2D companion to the 3D spinning-runner simulator plots the identical physics as the log-log head/flow design chart real engineers read: drag a point across it to set head and flow together, watch the shaded region and the efficiency-vs-Ns curve update live, and see a spinning 2D schematic of whichever runner — Pelton, Francis, or Kaplan — the specific speed calls for. Force a mismatched runner from the dropdown to see exactly how much efficiency a wrong pick costs, plotted directly on that runner's own curve.