The Flow Around Surface-Mounted, Prismatic Obstacles Placed in a Fully Developed Channel Flow (Data Bank Contribution)

TLDR

The study aims to highlight fundamental differences between nominally two‑dimensional and fully three‑dimensional obstacle flows. The authors examined surface‑mounted prismatic obstacles of varying spanwise dimensions in a fully developed channel flow (Re ≈ 8 × 10⁴–1.2 × 10⁵) using crystal violet, oil‑film, laser‑sheet visualizations and static pressure measurements. Results show that for width‑to‑height ratios above 6 the wake’s middle region remains nominally two‑dimensional, while wider obstacles exhibit a quasi‑regular pattern of saddle and nodal points in the separated region, indicating inherent three‑dimensional effects in such flows.

Abstract

The flow field around surface-mounted, prismatic obstacles with different spanwise dimensions was investigated using the crystal violet, oil-film and laser-sheet visualization techniques as well as by static pressure measurements. The aim of this study is to highlight the fundamental differences between nominally two-dimensional and fully three-dimensional obstacle flows. All experiments were performed in a fully developed channel flow. The Reynolds number, based on the height of the channel, lay between 8 × 104 and 1.2 × 105. Results show that the middle region of the wake is nominally two-dimensional for width-to-height ratios (W/H) greater than 6. The separated region in front of wider obstacles is characterized by the appearance of a quasi-regular distribution of saddle and nodal points on the forward face of the obstacles. These three-dimensional effects are considered to be inherent to such separating flows with stagnation.