Multicylinder Flow Induced Motions: Enhancement by Passive Turbulence Control at 28,000<Re<120,000

Abstract

The VIVACE converter was introduced at OMAE2006 as a single, smooth, circularcylinder module. The hydrodynamics of VIVACE is being improved continuously to achieve higher density in harnessed hydrokinetic power. Intercylinder spacing and passive turbulence control (PTC) through selectively located roughness are effective tools in enhancement of flow induced motions (FIMs) under high damping for power harnessing. Single cylinders harness energy at high density even in 1 knot currents. For downstream cylinders, questions were raised on energy availability and sustainability of highamplitude FIM. Through PTC and intercylinder spacing, strongly synergetic FIMs of 2/3/4 cylinders are achieved. Twocylinder smooth/PTC, and three/fourcylinder PTC systems are tested experimentally. Using the “PTCtoFIMâ€‌ map developed in previous work at the Marine Renewable Energy Laboratory (MRELab), PTC is applied and cylinder response is measured for inflow centertocenter distance 2D5D (D = diameter), transverse centertocenter distance 0.5–1.5 D, Re خµâ€‰[28,000–120,000], m* خµâ€‰[1.677–1.690], U خµâ€‰[0.36–1.45 m/s], aspect ratio l/D = 10.29, and m*خ¶â€‰خµâ€‰[0.0283–0.0346]. All experiments are conducted in the low turbulence free surface water (LTFSW) channel of MRELab. Amplitude spectra and broad fieldofview (FOV) visualization help reveal complex flow structures and cylinder interference undergoing VIV, interference/ proximity/wake/soft/hard galloping. FIM amplitudes of 2.2–2.8D are achieved for all cylinders in steady flow for all parameter ranges tested.