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Hot-wire measurements were taken in the wake of ten finite length circular cylinders, six of which were also tapered, in a uniform flow in a low speed wind tunnel. The Reynolds number based on mean cylinder diameter ranged from 2100 ≤ Re ≤ 5500, the aspect ratio (AR) of the cylinders varied from 16 ≤ AR ≤ 64, and the taper ratio (RT) varied from 21.3 ≤ RT ≤ 96. The vortex shedding along the spans of the cylinders coalesced into discrete cells, the range of Strouhal numbers and the number of cells being a function of the cylinder aspect ratio and taper ratio. It was found that the number of discrete cells is linearly related to a cylinder geometry ratio (CGR) defined as CGR = AR(1 + AR/RT).

An experimental wind tunnel study was performed to assess the effect of aspect ratio and rotational speed of circular cylinders of varying diameter on the flow patterns behind the cylinders in the presence of a uniform upstream crossflow. Six circular cylinders of constant length but different diameters, producing aspect ratios 6 ≤ AR ≤ 32 were examined at a single upstream velocity such that the Reynolds number varied between 1920 ≤ Re ≤ 10240. Rotational speeds from stationary up to 3600 rpm were applied to the cylinders, so that the maximum relative velocity α = πfD/U∞ = 0.80. Mean velocity profiles were measured three diameters downstream of the cylinder axis at 6 equidistant locations, and PSD power spectral density were generated for 26 equidistant locations along the cylinder, to create a comprehensive record of spanwise variations under all rotational conditions. For the highest aspect ratio tested, the wake velocity profiles were independent of rotational speed at all spanwise locations, whereas at lower aspect ratios, the maximum velocity defect diminished with increasing rotational speed along most of the span and became asymmetric near the free end. Two distinct shedding cells were found only for a cylinder with an aspect ratio of twelve at three relative spin rates of 0.067, 0.27, and 0.4. In cases where only a single cell existed, increased rotational speed produced a higher vortex shedding frequency on a given aspect ratio cylinder.

An experimental investigation into the flow field behind baseballs at two different seam orientations as well as a smooth sphere of the same diameter was undertaken at Reynolds numbers of 5 × 104 and 1 × 105. The rotational speed of the three spheres varied from 0 to 2400 rpm, with data collected in increments of 400 rpm which correspond to relative spin rates between 0 and 0.94. Mean velocity profiles, turbulence in intensity profiles, and power spectral density of the signals were taken using hot-wire anemometry. The smooth sphere wake was seen to change in orientation over a range of relative rotational speeds. The Strouhal number remained constant around 0.24 for relatively low spin rates. The seams on the baseball suppressed any measurable vortex shedding once rotation began, also eliminating any significant change in wake orientation as evidenced by the mean velocity deficit and turbulence intensity profiles. It was concluded that the so-called inverse Magnus effect recorded by previous investigators at a specific Reynolds number / relative rotational speed of a sphere exists only for a smooth sphere and not for a sphere where the boundary layer separation is governed by raised seams.

An experimental study was undertaken to investigate the influence of leading edge geometry and of relative curvature on the formation of a boundary layer on the surface of a cylinder aligned axially in a uniform flow. Hot wire anemometry was used to measure mean and fluctuating velocity components at a number of axial locations from the leading edge of cylinders of three different relative curvatures and two different leading edge shapes. In all cases a minimum relative axial length of greater than ten radii was examined, hence allowing adequate inspection of the formation region. Six cylinders were employed in the study, three with a blunt leading edge, and three with an ellipsoid of 3:1 ratio leading to the constant radius length. The Reynolds number based on cylinder radius (Rea = Uoa/v) varied from 3000 ≤ Rea ≤ 9000. The elliptical leading edge cylinders experienced laminar boundary layers, and the blunt cylinders created a separated bubble region followed by the development of a turbulent boundary layer. The laminar boundary layer was smaller than what a flat plate would produce at a corresponding length, and its experimental data generated profiles could be universalized with previously developed similarity variables. The turbulent boundary layer assumed a nearly constant velocity profile in the region 10 ≤ x/a ≤ 40, and its height grew proportionally to x1/3 rather than to x4/5 as for a flat plate. Streamwise turbulence intensities diminished rapidly with vertical distance from the surface of the cylinder, and also assumed a constant profile as relative axial distance increased. Over the limited range examined, changes in curvature were of secondary importance on relative boundary layer growth.

An experimental study was undertaken to examine two phenomena associated with a jet issuing from a forward-facing circular cylinder (with a length to outer radius ratio of 6.8) into a counterflow: (1) the effect of the counterflow on the internal velocity profile near the injector exit, and (2) the combined jet and counterflow influence on the external surface boundary layer profiles. Wind tunnel experiments, utilizing hot-wire anemometry, were conducted at very low jet-to-counterflow velocity ratios between 0 and 0.41 and Reynolds numbers based on cylinder outer diameter of 2.6×104 and 5.2×104. It was found that the flow at the internal location was negligibly affected by the counterflow, with the profiles exhibiting typical turbulent pipe flow behavior. However, close to the injector exit plane, the counter-flow accelerated the exiting jet in an annular region adjacent to the cylinder inner wall, creating a high velocity region which reversed direction upon exiting. The exit flow reversal around the lip of the cylinder was manifested downstream as an addition of momentum to the flow field. Boundary layer measurements were taken at seven streamwise locations along the upper surface of the cylinder. A dimensionless parameter constructed from both a traditional flat plate turbulent boundary layer scaling and a geometric curvature ratio was used to plot all data, which collapsed to a single curve at all locations in the absence of a jet, while in the presence of the jet, the only differences in the profiles were close to the surface. Independently of jet-to-counterflow velocity ratio, the boundary layer on the cylinder was seen to grow in the streamwise direction at a rate proportional to x25 rather than x45 as occurs with a turbulent boundary layer on a flat plate, even though the boundary layer height to curvature ratio was relatively low (≈ 1), and hence would have been expected to approximate flat plate behavior.