Turbulence characterization in multiphase slurry flow through annular jet pumps: A mixture model approach

Annular jet pumps (AJPs) are promising passive devices for transporting multiphase mixtures such as slurry in mining and dredging industries due to their modularity and lack of moving parts. However, accurately predicting turbulent characteristics and performance in such multiphase flows remains a significant challenge due to complex particle-fluid interactions and geometry-induced flow separation. This study aims to map the performance of modular AJPs handling sand-water slurry using a multiphase mixture model to assess both hydraulic performance and turbulence behavior. The novelty lies in the combined use of the Schiller-Naumann drag model, Krieger's viscosity model, and the realizable k − ε turbulence model, enabling improved prediction of turbulence parameters across a wide range of flow conditions. A parametric analysis is carried out to investigate the effects of key parameters, including the primary fluid's volumetric flow rate, nozzle convergence angle, volume fraction of the dispersed phase, and particle size, on crucial turbulence characteristics: Turbulent Kinetic Energy (TKE), Turbulent Dissipation Rate (TDR), and Turbulent Dynamic Viscosity (TDV). This parametric study is conducted for a primary fluid flow rate ranging from 6 m³ /h to 10 m³ /h, convergence angles of 21° to 27°, sand particle volume fractions from 0 % to 40 %, and particle sizes from 2 × 10⁻⁴ m to 10⁻³ m. A high-quality structured mapped mesh is employed (average element quality = 0.9815, average skewness = 0.0185, orthogonality ≈ 0.98, target y + ≈ 50), and mesh independence is confirmed with deviations under 1.5 % in key parameters. The mixture model demonstrates excellent agreement with experimental pressure gradient data, achieving a mean absolute error (MAE) of 0.133 kPa/m and a root mean square error (RMSE) of 0.141 kPa/m, corresponding to deviations between 3.63 % and 4.84 %. This model also successfully captures turbulence anisotropy and streamwise variations in turbulent kinetic energy and eddy viscosity across multiple transverse planes. These findings advance the understanding of energy-efficient slurry transport and provide a predictive framework for optimizing AJP geometry for industrial applications. It also offers valuable insights into how geometric and flow parameters influence turbulence behavior, paving the way for the optimized design and operation of AJPs to improve slurry transport performance and enhance understanding of multiphase flow phenomena in industrial systems.