Numerical study of wall effects of a viscoplastic fluid over a stationary cylinder

Abstract

This thesis investigates the effects of the boundary layer developed on the bottom wall on the flow characteristics. The boundary layer is the region attached to the wall up to where the velocity is roughly 99 percent of the free stream velocity. Its thickness is computed by both theoretical analysis and simulations. As the results by theoretical analysis are found not appropriate as the Reynolds number is too small, we rely on the results obtained from the simulations. When 𝐺 = 0.5𝐷, the cylinder is completely inside the boundary layer. In contrast, when 𝐺 = 4.5𝐷 and 9.5𝐷, the cylinder is entirely outside it. Results are presented and analysed for numerous flow characteristics, such as streamline patterns, vorticity contours, unyielded (solid-like) zones, and hydrodynamic force coefficients.