The Oscillations of Large Circular Stacks in Wind.

Abstract

The results of an experiment on the response of model stacks free to oscillate under the influence of aerodynamic forces in a compressed air tunnel are presented. Reynolds number had a considerable influence on the response in both subcritical and supercritical smooth flow. For both models with polished and with slightly roughened surfaces, large peak amplitudes of oscillation found at subcritical Reynolds numbers decreased as the critical regime was approached. For the models with roughened surfaces, further increases of Reynolds number produced continuously higher peak amplitudes and the reduced velocity giving the peak amplitudes decreased from approximately 6.5 to 5. For the polished models no such similar peaks were found in the supercritical regime up to R = 2 X 106, the maximum available, but peak amplitudes occurred at reduced velocities of 10 and 13. For all Reynolds numbers the amplitude of oscillation had a considerable effect on the characteristics of the vortex shedding forces on the stacks. Notationcylinder diameter non-dimensional aerodynamic damping coefficient, 2m8JpD2= K,/pNDa, where K,, is the multiplier of velocity R to give phase component of aerodynamic force length of model equivalent mass per unit length frequency of oscillation of stack (Hz) frequency of shedding of vortex pairs from the sides of a cylinder (Hz) Reynolds number VD/v wind velocity reduced velocity (V/ND) displacement natural logarithm of the ratio of the amplitudes of successive cycles of oscillation (logarithmic decrement), S, refers to structural damping, S, refers to aerodynamic damping (usually negative) normalized displacement, x / D kinematic viscosity of air density of air

Effects of Free-End Condition on End-Cell-Induced Vibration

“…That vibration will be called the &&end-cell-induced vibration (ECIV)'' in this study. Wootton (1969) carried out wind tunnel experiments using circular stack models and measured the transverse-wind response, which indicates the occurrence of ECIV at a wind speed twice as high as the wind speed where VIV occurred. He inferred that the cause of ECIV is associated with the tip of the model, but no evidence was presented in his paper.…”

Across-wind response of tall circular chimneys to vortex shedding

“…Vortex induced oscillations significantly influence the across-wind load and response of a chimney. Several researchers have significantly contributed to this important problem and these include studies by Wootton (1969), Vickery and Basu (1983), Ruscheweyh (1989), ESDU (1996), and Flaga, Lipecki (2010). In a recent paper, Niemann et al (2014) have observed that available design models for vortex resonance, especially at relatively low Scruton numbers often provide considerable scatter in their results.…”

“…In this method, a value of 0.45 for the parameter 'fact' has been earlier suggested, although it was realized that 'fact' is expected to vary as a function of the normalized response. In the present paper, by including additional experimental data reported by Wootton (1969) is not universally constant since it depends on individual test conditions. However, by applying a correction factor to the correlation length, the authors have shown that (Arunachalam et al, 2001) the modified value of C L VS , ‵ denoted as C L V , ‵ takes a mean value of 0.089 (with cove ¼ 18%) corresponding to a turbulence intensity level of 7.5%.…”

Some Experiments on Flow-Induced Vibration of a Circular Cylinder With Surface Roughness

“…However, when the cylinder has a certain structural damping and the mass-ratio is large, such as in the air, it is more usual to obtain oscillation in the transverse direction than in the streamwise one. Free-oscillation tests of a circular cylinder in the transverse direction were conducted by many researchers, e.g., by Scruton (1963), Feng (1968), Wootton (1969), Brika & Laneville (1994), and so on. While the largest part of research e!orts have been focused on transverse vibration, there are some studies on the streamwise vibration of circular cylinder in the subcritical regime below the critical Reynolds number.…”

“…For example, King, Prosser & Johns (1973) carried out experiments on streamwise vibration of a #exible cantilevered beam of circular cylinder in a water channel. Many studies of free-oscillation tests of smooth circular cylinders, however, have been limited to the subcritical #ow regime, below the critical Reynolds number, except for the studies by Wootton (1969), who carried out experiments on the cylinders with smooth and roughened surfaces at high Reynolds numbers.…”