Effects of surface roughness and wall confinement on bluff body aerodynamics at large-gap regime

A purely Lagrangian vortex method is employed to investigate turbulent flows past a rough circular cylinder under moving wall effect at large-gap regime, namely h * / d * = 0.45 and 0.80 ( h * establishes the gap height between the moving wall base and the cylinder underside, and d * defines the outer cylinder diameter), yielding data in a transition regime, between the supercritical and transcritical regimes. In the large-gap regime, strong vortical structures are cyclically generated at the rear part of the cylinder. The numerical simulations utilize a two-dimensional model to simulate surface roughness effect. That model is inspired in a point set strategically located close to a body surface to inject momentum in its boundary layer and thus to capture a delay in the separation point of flow. Special attention is directed toward the relative roughness size variation, being that each test case always starts from an upper-subcritical Reynolds number of Re = 1.0 × 10 5 . The present work contributes in the literature: (i) providing a detailed study of temporal evolution of pressure distribution, simultaneously computed with the integrated aerodynamic loads (drag and lift forces), Strouhal number and angle of boundary layer separation and (ii) examining the possibility of predicting suppression of vortex shedding. Such approach has been successfully applied within the study of bluff body aerodynamics at small-gap regime (i.e., h * / d *