Turbulent flow interaction with a circular cylinder

Abstract

This paper presents a comprehensive experimental study on the unsteady pressure exerted on the surface of a round cylinder in smooth and turbulent flows. A highly instrumented cylinder with several static pressure taps and dynamic pressure transducers at different spanwise and peripheral locations was used, enabling extensive dynamic surface pressure, coherence and turbulence length-scale analysis. The effects of the free-stream turbulence and turbulent length scale are investigated by placing the turbulent-generating grids within the wind tunnel duct. For both the laminar and turbulent incident flows, the surface pressure results show the emergence of the fundamental, first and second harmonics at most peripheral angles, while at the cylinder base the surface pressure spectra is dominated by the first harmonic. It has also been observed that an increase in the level of the turbulence intensity results in the increase of the energy level of unsteady pressure acting on the cylinder. An increase in the length scale of the incoming flow structures is shown to result in an increase in the energy level of the tonal frequencies and the broadband content of the surface pressure spectra. The spanwise coherence results have also shown that an increase in the length scale of the flow structures increases the spanwise correlation length of the flow structures at the vortex shedding frequency at the stagnation point, while at the cylinder base, the spanwise correlation length decreases at the vortex shedding frequency.

Scale-Resolving Simulations of a Circular Cylinder Subjected to Low Mach Number Turbulent Inflow

“…The present work considers the flow around a circular cylinder at a Reynolds number of Re = U ∞ D/ν = 14, 700 and Ma = U ∞ /c 0 = 0.029, and replicates the measurement setup of Maryami et al [12]. For the chosen experimental condition, a freestream turbulence intensity of 5.1% and an integral length scale of 0.0239 m (1.086 cylinder diameters) have been reported.…”

“…Therefore, spectra and Reynolds stresses were monitored directly above the cylinder (x/D = 0, y/D = +4.5) to be compared with measurements. Figure 5 presents the inflow velocity spectrum computed for all cases, also showing data measured by Maryami et al [12]. The frequency axis has been normalised to give the Strouhal number.…”

“…From the experimental data given by Norberg [33] and numerical results by Liefvendahl and Bensow [19], the spanwise correlation length for the considered Reynolds number is known to be between approximately four and five cylinder diameters. In the experiments of Maryami et al [12], the cylinder span was 21 diameters, ensuring that the end effects play a minimum role on the flow. In the present simulations, S/D sim = 15 was used as a compromise between computational cost and the desire to avoid a significant influence of the boundaries and boundary conditions on the spanwise correlation of the flow.…”

“…The development and validation of numerical models for predicting inflow turbulence (IT) noise during design has a long history, from semi-analytical approaches [8] to advanced computational fluid dynamics (CFD) simulations [9]. Due to the physical complexity and high computational cost associated with inflow turbulence problems, simplified geometries are often preferred for these purposes, such as circular cylinders [10][11][12] and airfoils [9,13]. Nevertheless, these cases represent a challenge from a numerical point of view, due to the complex interaction of the inflow turbulence with the body's leading edge and-in the case of the cylinder-the boundary layer and wake [14].…”

“…Before this can be achieved, it is necessary to validate the ability of the inflow turbulence generator to reproduce realistic inflow turbulence and correctly simulate the interactions of turbulence with complex flow around realistic geometries. To this end, the present study investigates the flow around a circular cylinder for which extensive experimental hydrodynamic validation data are available for several inflow turbulence intensities (TI) [11,12]. We also present results for inflow turbulence intensities above those measured, in order to further study the trends for high TI.…”