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 non-uniformity 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, especially the complex three-dimensional and oscillatory behaviors 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 the most frequently adopted experimental techniques. The review also helps identifying knowledge gaps in the literature that need to be addressed in future investigations.

The wake of polygonal cylinders with side number N = 2 ∼ ∞ is systematically studied based on fluid force, hot-wire, particle image velocimetry and flow visualisation measurements. Each cylinder is examined for two orientations, with a flat surface or a corner leading and facing normally to the free stream. The Reynolds number Re is 1:0 × 10⁴ × 1:0 × 10⁵, based on the longitudinally projected cylinder width. The time-averaged drag coefficient C_D and fluctuating lift coefficient on these cylinders are documented, along with the characteristic properties including the Strouhal number St, flow separation point and angle θ_s, wake width and critical Reynolds number Re_c at which the transition from laminar to turbulent flow occurs. It is found that once N exceeds 12, Re_c depends on the difference between the inner diameter (tangent to the faces) and the outer diameter (connecting corners) of a polygon, the relationship being approximately given by the dependence of Re_c on the height of the roughness elements for a circular cylinder. It is further found that C_D versus ξ or St versus ξ for all the tested cases collapse onto a single curve, where the angle ξ is the corrected θ_s associated with the laterally widest point of the polygon and the separation point. Finally, the empirical correlation between C_D and St is discussed.