Why do viscoplastic fluids adhere to moving surfaces?

Viscoplastic fluids, characterized by their high apparent viscosity below a critical yield stress, pose significant challenges in industrial applications due to their tendency to adhere to processing surfaces. This study investigates the adhesion phenomenon using a simplified four-sided driven cavity model, implemented via a multiple relaxation time lattice Boltzmann method coupled with the Bingham–Papanastasiou regularization. By systematically varying the Bingham and Reynolds numbers, our simulations reveal the formation of distinct un-yielded regions, including a central rigid-body plug and wall-attached zones, which are responsible for the observed adhesion. Detailed analyses of velocity fields, vorticity distributions, shear stress profiles, and local Reynolds numbers elucidate the complex interplay between inertial forces, yield stress effects, and shear-rate-dependent viscosity. Comparisons with benchmark finite volume method solutions confirm the model's fidelity and highlight the advantages of the mesoscopic approach in capturing the physics of viscoplastic flow. The insight gained from this study provides a mechanistic understanding of how operating conditions and cavity geometry influence the adherence of viscoplastic fluids, with implications for optimizing industrial mixing processes and reducing surface fouling.