Simulation of jet cleaning: Diffusion model for swellable soils

Abstract A physical-numerical simulation model for the cleaning of swellable soils by diffusive dissolution or cohesive separation of small soil particles, which was developed targeting a low computational effort, is presented and validated. The flow calculation, based on the Reynolds averaged Navier Stokes equations (RANS), and the calculation of the soil transport, modelled following the unsteady RANS concept, are performed successively. The behaviour of the soil is modelled as a transient Dirichlet boundary condition, its parameters being determined in laboratory experiments using plane channel flow. A validation is performed for a coherent water jet impinging vertically on a substrate, which is covered by a starch-based model soil, at a distance of 100 mm to the nozzle. Using a nozzle diameter of 1.69 mm and pressures in the nozzle ranging from 1.5 to 5 bar, corresponding to Reynolds numbers between 17700 and 55600, the wall shear stress in this configuration exceeds the values given in the laboratory tests by two orders of magnitude. Despite this difference, the simplicity of the model and the complexity of the test case, the simulated cleaning times correspond very well to the measured values. Thus, the targeted scalability and transferability of the model to other flow configurations are ensured.