The effects of gap ratio and upstream wall-roughness on the spatio-temporal turbulent flow dynamics surrounding a square cylinder

Abstract

Turbulent flow around a square cylinder offset at different heights from upstream smooth and rough walls are investigated using time-resolved particle image velocimetry. The Reynolds number based on the freestream velocity and cylinder height was 12 750 and the turbulent boundary layer thickness was 3.6 and 7.2 times the cylinder height for the upstream smooth and rough wall respectively. The first portion of this thesis discusses the effects of wall roughness for cylinders with a gap underneath the cylinder of 0.0, 0.3, 0.5, and 2.0 times the cylinder height. The second portion of this two-manuscript based thesis presents a discussion on gap ratio effects on flow around a square cylinder with an upstream rough wall for additional cases with a gap size of 1.0, 4.0 and 8.0 times the cylinder height. An extensive investigation into the turbulent statistics and coherent structures within the flow field is presented.