Abstract
Flow Induced Motions (FIM) of a single, rigid, circular cylinder on end-springs are investigated for Reynolds number 30,000 < Re < 110,000. Passive Turbulence Control (PTC) in the form of roughness strips is applied to enhance FIM and increase the efficiency of the VIVACE (Vortex Induced Vibration for Aquatic Clean Energy) converter in harnessing marine hydrokinetic energy. Numerical simulations are performed using a solver for two-dimensional Unsteady Reynolds-Averaged Navier-Stokes equations, which is developed based on OpenFOAM using a finite-volume discretization method. The results are in excellent agreement with experiments conducted in the Marine Renewable Energy Laboratory (MRELab) at the University of Michigan. Amplitude and frequency are predicted correctly in the initial and upper VIV branches, in VIV-to-galloping transition, and in galloping. The 2S (S = Single) vortex pattern is observed in the initial VIV branch and the 2P + 2S (P = Pair) in the upper branch for 30,000 ≤ Re ≤ 80,000. Transition from VIV to galloping initiates at Re = 90,000 with a P + 2S + P + S pattern. Maximum amplitude of 3.5D (D = Diameters) is achieved and more than seven vortices per cycle are observed in fully developed galloping. With PTC, the VIVACE converter can harness hydrokinetic energy from currents or tides over the entire range of FIM synchronization. Energy conversion efficiency reaches 37% in simulations and 28% in experiments.