TIME-DEPENDENT FLOW IN A PENSTOCK DURING HEAD-GATE CLOSURE

This paper is concerned with the study of the time-dependent water and air flow in a penstock caused by closing the head gate. Two approxima te techniques are Employed. The first approach uses simple global argu ments based on mass and momentum conservation, and the time-dependent Bernoulli equation is used to derive evolution equations for the fluxe s of wafer and air through the various components of the system. To co mplement this approach, the time-dependent Navier-Stokes equations wer e solved with a substantially reduced Reynolds number. Both approaches suggested that the pressure in the penstock remained above 1/2 atm, a nswering a question posed by Electricorp, New Zealand.