On the Advection–Diffusion Process With Developing Eddies in Karst Conduits

Abstract Understanding the fluid flow and solute transport in karst conduits is significant for preventing pollutants (treated as solutes) in karst areas. This study evaluates the evolution of eddies in semi‐circular rough conduits under different hydrodynamic conditions and their effects on solute transport. As inlet flow velocity increases, the non‐Fickian coefficient (a parameter used for qualifying the tailing of BTCs) increases first then decreases afterward. A critical equilibrium concentration is found when the concentration of the main flow stream and the concentration of the eddy zone reaches the same value, signaling the moment at which the mass transfer (due to diffusion) between the main flow stream and the eddy zone drops to zero. Such a critical equilibrium concentration and its corresponding moment of occurrence are found to follow two distinctive logarithmic functions of the inlet flow velocity. These findings provide crucial technical support for groundwater pollution control in karst areas.