Characterization of emitter clogging substances boundary in subsurface drip irrigation with biogas slurry using porous media model

Subsurface drip irrigation (SDI) is a highly efficient and safe method for water reuse, particularly with biogas slurry. However, emitter clogging risks are high and it was hard to visualize the process. This study developed a high-precision numerical simulation method using 3D industrial computed tomography scanning, inverse modeling, and numerical simulation. We investigated the spatial distribution of clogging substances at various clogging levels. A new simulation method based on a porous media boundary was compared with the traditional fixed boundary method, showing improved accuracy. The results indicated that the cumulative growth of clogging substances on different walls of emitter increased with larger clogging degree, which also resulted in significantly different distributions. As the clogging degree increased to 50 %, the maximum and minimum values of the average volume of clogging substances appeared at the upstream face (2.36 mm3) and the downstream face (1.38 mm3), respectively. Compared to the traditional fixed-boundary simulation method, the method based on permeable porous media boundary improved the relative accuracy of the flow rate by 3.41 %-6.86 %. Furthermore, for the hydrodynamic parameters of emitter flow channel cross-section, the average velocity, average shear force, and average turbulent kinetic energy were 3.54 %-5.75 %, 14.93 %-16.26 %, and 11.16 %-30.46 % lower than those predicted by the fixed boundary module, respectively. The traditional fixed-boundary numerical simulation method tends to underestimate the clogging degree of the emitter and the influence of the clogging substances on the internal hydrodynamic characteristics to a certain extent. In summary, the results of this study can contribute to the development of anti-clogging emitter and facilitate the implementation of SDI system using biogas slurry.