A review of experiments on stationary bluff body wakes

Abstract

Experimental studies dealing with the wake of isolated stationary bluff-bodies are reviewed. After briefly recalling the pioneering works in this domain, the paper focuses on recent research conducted with the latest experimental methods and techniques. The review encompasses a range of topics, including, the effects of bluff-body geometry (non-circular cross sections and nonuniformity in spanwise direction), steady and unsteady (periodic and non-periodic) inflow conditions; surface proximity (rigid wall, confinement and water free surface) and non-Newtonian fluids. Focus is brought to the flow physics of the wakes, including especially the complex threedimensional and oscillatory behaviours induced by the periodic vortex shedding phenomenon. The paper aims to offer a critical and systematic review of new knowledge and findings on the subject area, as well as emerging? and the most frequently adopted experimental techniques. The review also helps identifying knowledge gaps in the literature that need to be addressed in future investigations.

Hierarchy of coherent vortices in turbulence behind a cylinder

“…Here, we must note that the sustaining mechanism of the large-scale vortices, which are the origins of the energy cascade, can be different from that in turbulence without flow separation, for example, periodic turbulence (Goto et al 2017), zero-pressure-gradient turbulent boundary layers (Motoori & Goto 2019) and turbulent channel flow (Motoori & Goto 2021). We must also note that the flow state behind a cylinder is different depending on the ranges of the Reynolds number Re D = U ∞ D/ν (Williamson 1996;Forouzi Feshalami et al 2022), where U ∞ is the upstream uniform velocity magnitude, D is the diameter and ν is the kinematic viscosity of the fluid. For Re D ≈ 50-190, Kármán vortices are shed alternately from the cylinder.…”

“…Although the transition mechanisms in a wide range of Re D have been extensively investigated by experiments (see the reviews by Williamson 1996;Forouzi Feshalami et al 2022) and LES (e.g. Breuer 1998;Lehmkuhl et al 2014;Rodríguez et al 2015), there are only a few studies of DNS that focus on energy cascade and its relation to multiscale flow structures.…”

“…We must also note that the flow state behind a cylinder is different depending on the ranges of the Reynolds number (Williamson 1996; Forouzi Feshalami et al. 2022), where is the upstream uniform velocity magnitude, is the diameter and is the kinematic viscosity of the fluid. For , Kármán vortices are shed alternately from the cylinder.…”

“…Although the transition mechanisms in a wide range of have been extensively investigated by experiments (see the reviews by Williamson 1996; Forouzi Feshalami et al. 2022) and LES (e.g. Breuer 1998; Lehmkuhl et al.…”

Influence of nano- and micro-roughness on vortex generations of mixing flows in a cavity

“…There are many examples of laminar or turbulence flow regimes where the useful impact of the different roughnesses was discovered, e.g., in jets, wakes, or pipe flows in which the small or large coherent vortex structures were periodically or chaotically generated by such rough surfaces. [5][6][7][8] Unfortunately, for all mentioned complex flow cases, it usually becomes impossible to separate and estimate a pure impact of the roughness only on one flow component, e.g., the vortex formation, because the feedback mechanism of different flow instabilities usually is present. The dynamic interactions with other coherent structures in the flows should strongly influence the growth of vorticity over any rough walls, too.…”