Distribution of local pressure and skin friction around a circular cylinder in cross-flow up to Re = 5 × 10⁶

Abstract

In a large range of Reynolds numbers, 6 × 104 < Re < 5 × 106, the flow around single cylinders with smooth surfaces has been investigated. The high values of the Reynolds numbers were obtained in a test channel which could be pressurized up to 40 bar of static pressure. New experiments were performed to measure the local pressure and skin friction distribution around the cylinder. From these results the total drag, the pressure drag and the friction drag were calculated. By means of the skin friction distribution the position of the separation points, separation bubbles or transition points can be localized. These data allow one to define three states of the flow: the subcritical flow, where the boundary layer separates laminarly; the critical flow, in which a separation bubble, followed by a turbulent reattachment, occurs; and the supercritical flow, where an immediate transition from the laminar to the turbulent boundary layer is observed at a critical distance from the stagnation point. According to the total drag coefficient the values found in this paper connect the subcritical region represented by the measurements of Wieselsberger (1923) and Fage & Warsap (1930) with the supercritical range in which Roshko (1961) carried out his experiments.

Simulation of viscous flow around a circular cylinder near a moving ground

“…Another experimental investigation made by Son and Hanratty (1969) determined a value of θ = 78º for the separation angle. A very interesting observation was made by Achenbach (1968) for Re = 1.0 x 10 5 (sub-critical flow): it was found that the laminar boundary layer separates at θ = 78º. Just before transition into the critical region at Re = 2.6 x 10 5 , the boundary layer is still laminar and separates at an angle equal θ = 94º.…”

Effects of a synthetic jet acting on a separated flow over a hump

“…The point of zero shear stress for the time-averaged flow is delayed ( θ zss = 107.6 • ) compared with the natural case, and the instantaneous stagnation point behind the separation vortex appears farther downstream ( θ stg ≈ 120 • -135 • ). These angles are still upstream of the turbulent separation point over a cylinder ( θ zss = 140 • reported by Achenbach 1968). The effects of the actuation become clear on comparing the time-averaged pressure fields between these two cases.…”

Subgrid-Scale Modeling of Turbulent Flow Around Circular Cylinder by Mesh-Free Vortex Method

“…Due to the fact that 2 F has a fast decay far from the reference vortex, it is essential to calculate the length of the radial distance from the reference vortex that captures only those vortices actually exerting influence on the local turbulence around the reference vortex. The two other parameters that affect the turbulence model in addition to f 1 In order to analyze the effect of the turbulent parameters in our simulations, we carry out numerical experiments to investigate the external ring semi-thickness,  re , and the mean density of vortices per unit area,  r , defined as the number of vortices in the ring divided by the ring area, averaged over all the vortices in the cloud. First, the factor f 2 associated with  re is analyzed through its dependence on  r .…”

“…The numerical results for the drag coefficient are compared in Fig. 11 with the experimental results of Achenbach (1968), obtained in a low-pressure wind tunnel (ND channel) and a pressurized wind tunnel (HD channel), for several aspect ratios of the cylinder (defined as the ratio of length to diameter). Achenbach, in turn, presents in his paper experimental results obtained by Wieselsberger (1923), Fage and Warsap (1930) and Roshko (1961).…”

“…5 No. 2 (2011) distribution on the cylinder surface, the timevarying positions of the separation points and the Strouhal number (Roshko, 1961;Achenbach, 1968;Bearman, 1969 Alfonsi and Giorgini, 2002). In this context, the Vortex Method (VM) is particularly suitable to simulate flows around bodies because it focuses attention only on the rotational flow regions (Sarpkaya, 1994; Cottet and Koumoutsakos, 2000; Kamemoto and Tsutahara, 2000).…”