Numerical and experimental study on hydraulic performance of emitters with arc labyrinth channels

An integral 3D numerical model based on the structural characteristics of the emitter with arc labyrinth channels was constructed to simulate the relationship between flow rates and pressure heads as well as the flow field distribution in the small channels by computational fluid dynamics (CFD). Meanwhile, the emitter prototypes fabricated by stereolithography technology were used in the flow rate experiments. The calculation results obtained revealed turbulence model can supply a better agreement with the experimental data than laminar flow model under pressure ranges of 40–160 kPa. Most pressure losses are occurred in labyrinth channels and the losses within each arc unit are constants under different inlet conditions. In addition, laser-Doppler velocimetry (LDV) was employed to measure the flow fields of the magnified model with a magnifying scale of 15:1 according to the channel structure of the emitter, and the measured velocity distribution in the cross-section is in good agreement with calculation results. It was found that reversed flow happened near the upper fringe of the flow path, and that in the longitudinal symmetric plane mainstream velocity regions and low velocity regions could be observed clearly. The vortexes of different sizes were developed in low velocity regions, which may be one of the reasons leading to channel clogging.