Hydraulic analysis of trickle lateral

Soom, Mohd Amin Mohd (1989) Hydraulic analysis of trickle lateral. University of Southampton, Doctoral Thesis.

Abstract

This thesis reviews the current method in hydraulic analysis of trickle irrigation lateral and presents a new approach. An experimental investigation into the influence of emitter barb protrusion on the flow regime in the pipe, the energy loss and the flow through the emitter is described. The Darcy-Weisbach equation with a combined friction factor for the smooth pipe and local loss due to emitter connection is used in a step by step evaluation of head loss. The effects of temperature changes on emitter discharge and lateral flow rates are considered. The new approach gives a more accurate result than the current method. Several combinations of emitter barb shape and location of offtake have been experimented in a laboratory set-up to reduce the drag force on the protrusion. The pressure compensating effect of upstream protrusion on orifice emitters has been evaluated. An orifice emitter immediately downstream of a hemispherical protrusion is pressure compensating. The emitter requires low operating pressure, has turbulent flow regime and large opening. Energy loss across the hemispherical protrusion is very low due to delayed separation. The drag coefficient is about two-third that of truncated cone emitters. The theory of isolated roughness (semi-smooth) flow regime is extended for use in trickle lateral. The relationship between the combined friction factor for the pipe and emitter barb protrusion and Reynolds number was studied. Values of drag coefficient were derived.

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