Large eddy simulation of inertial fiber deposition mechanisms in a vertical downward turbulent channel flow

The deposition pattern of elongated inertial fibers in a vertical downward turbulent channel flow is predicted using large eddy simulation and Lagrangian particle tracking. Three dominant fibers deposition mechanisms are observed, namely, diffusional deposition for small inertial fibers, free-flight deposition for large inertial fibers, and the interception mechanism for very elongated fibers. The fibers are found to exhibit orientation anisotropy at impact, which is strongly dependent on the fiber elongation. An increase in the fiber elongation increases the wall capture efficiency by the interception mechanism. The diffusional deposition mechanism is shown to dominate for fibers with large residence time, t⁺res, in the accumulation zone and small deposition velocities, v⁺z, while the free-flight mechanism governs deposition for fibers with small t⁺res and large v⁺z. This study describes how particles deposit on a surface and, ultimately for many practical applications, how such deposition may promote fouling.