Selective Roughness in the Boundary Layer to Suppress Flow-Induced Motions of Circular Cylinder at 30,000<Re<120,000

Abstract

A passive control means to suppress flow-induced motions (FIM) of a rigid circular cylinder in the TrSL3, high-lift, flow regime is formulated and tested experimentally. The developed method uses passive turbulence control (PTC) consisting of selectively located roughness on the cylinder surface with thickness about equal to the boundary layer thickness. The map of "PTC-to-FIM," developed in previous work, revealed robust zones of weak suppression, strong suppression, hard galloping, and soft galloping. PTC has been used successfully to enhance FIM for hydrokinetic energy harnessing using the VIVACE Converter. PTC also revealed the potential to suppress FIM to various levels. The map is flow-direction dependent. In this paper, the "PTC-to-FIM" map is used to guide development of FIM suppression devices that are flow-direction independent and hardly affect cylinder geometry. Experiments are conducted in the Low Turbulence Free Surface Water Channel of the University of Michigan on a rigid, horizontal, circular cylinder, suspended on springs. Amplitude and frequency measurements and broad field-of-view visualization reveal complex flow structures and their relation to suppression. Several PTC designs are tested to understand the effect of PTC roughness, location, coverage, and configuration. Gradual modification of PTC parameters, leads to improved suppression and evolution of a design reducing the VIV synchronization range. Over a wide range of high reduced velocities, VIV is fully suppressed. The maximum amplitude occurring near the system's natural frequency is reduced by about 63% compared to the maximum amplitude of the smooth cylinder.

URANS vs. experiments of flow induced motions of multiple circular cylinders with passive turbulence control

“…Park et al (2012) thoroughly investigated the effects of PTC on VIV and galloping of a circular cylinder, and produced the PTC-to-FIM Map based on the amplitude response of the cylinder. All modeling parameters of PTC are defined in Fig.…”

“…In addition, contrary to the traditional engineering challenge of reducing FIM to prevent structural damage, the VIVACE (vortex induced vibration for aquatic clean energy) team at the University of Michigan works towards increasing the oscillatory response of a cylinder in FIM (Bernitsas et al, 2008Raghavan, 2009, 2011;Raghavan and Bernitsas, 2011;Chang et al, 2011;Ding et al, 2013;Kim et al, 2013;Lee and Bernitsas, 2011;Park et al, 2012Park et al, , 2013. Their purpose is to harness marine hydrokinetic energy from ocean/river currents and maximize the power density of VIVACE by using multiple cylinders in synergistic FIM .…”

“…Passive turbulence control (PTC) in the form of sand strips used in this work both in experiments and simulations result not rotationally symmetric body and, thus, galloping. The PTC-to-FIM was developed by Park et al (2012). The motion of the cylinder in the range of lock-in can be roughly described by a linear model.…”

Selective Surface Roughness to Suppress Flow-Induced Motion of Two Circular Cylinders at 30,000 < Re < 120,000

“…Flow-induced motions (FIMs) of a single circular cylinder have been studied widely [1][2][3][4][5]. In industrial applications though, arrays of multiple circular cylinders are used more frequently, such as tube arrays in heat exchangers, offshore structures, bridge cables, power transmission lines, and chimneystacks.…”

“…PTC was successful in enhancement by initiating gallop ing and achieving amplitude of three diameters (3D) [21], It was also used for suppression of FIM reducing the maximum VIV am plitude by 60% and the synchronization range by 50% compared to the smooth cylinder [5]. This method, called passive turbulence control (PTC), was designed for the purpose of enhancement or suppression of FIM of a single cylinder.…”