Raimund Bürger, Julio Careaga, Stefan Diehl:
A simulation model for settling tanks with varying cross-sectional area
A quasi--one-dimensional model of the process of continuous sedimentation in vessels with variable cross-sectional area is presented. The partial differential equation (PDE) model extends the settler model advanced in [R. Bürger, S. Diehl, S. Farås, I. Nopens, E. Torfs, Water Sci. Tech. 68 (2013) 192-208], which assumes a constant cross section. A reliable numerical method that handles the special features of the nonlinar PDE is presented along with an advantageous time step condition for continuous and batch sedimentation under the condition of a variable cross-sectional area. Simulations of continuous sedimentation show the effect of the change of cross-sectional area in the concentration inside the vessel and in the underflow. Simulations of batch settling in cones illustrate the versatility of the numerical scheme to include a vertex, where the area shrinks to zero.