Hydrodynamic flow conditions and calcium carbonate scale in dripper labyrinth with varied geometric configurations

Abstract

Clogging of drippers by calcium carbonate (CaCO₃) scale is a major limitation to drip irrigation when calcareous water is used. This study investigates how hydrodynamic conditions and labyrinth geometry influence CaCO₃ nucleation, deposition, and scaling patterns in drippers. Fifteen dripper prototypes with different geometries were evaluated, grouped as Type I (with well-developed vortices) and Type II (with more uniform flow). Tests were performed using water with different saturation levels (LSI = 1.3 and 1.7) in a closed hydraulic circuit. Discharge variation rate (Dra) and internal images of the labyrinths were used to assess clogging. Computational Fluid Dynamics (CFD) simulations provided velocity, shear rate, and turbulent kinetic energy (TKE) fields. Type I prototypes exhibited greater resistance to clogging compared to Type II, with flow cross-sectional area and the tooth height/channel width ratio (H/W) being key geometric factors. Higher H/W ratios led to scaling patterns more closely aligned with low-velocity, low-shear, and low-TKE zones, especially in peripheral areas. This indicates that local flow structures strongly influence CaCO₃ scaling. In Type I emitters, hydrodynamic forces contributed not only to deposition but also to crystal removal and breakage. Scanning electron microscopy further revealed that the more turbulent flow in Type I prototypes altered the morphology of CaCO₃ deposits, supporting the hypothesis that hydrodynamic play a critical role in scale formation and emitter performance.