2-D URANS vs. experiments of flow induced motions of two circular cylinders in tandem with passive turbulence control for 30,000

Abstract

The flow induced motions (FIM) of two rigid circular cylinders, on end linear-springs, in tandem are studied using two-dimensional Unsteady Reynolds-Averaged Navier-Stokes (2-D URANS) simulations verified by experimental data. Passive turbulence control (PTC) is being used in the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan to enhance FIM of cylinders in the VIVACE (Vortex Induced Vibration for Aquatic Clean Energy) Converter to increase its efficiency and power density in harnessing marine hydrokinetic energy. Simulation is performed using a solver based on the open source CFD tool OpenFOAM, which solves continuum mechanics problems with a finite-volume discretization method. The simulated Reynolds number range for which experiments were conducted in the MRELab is 30,000<Re<105,000, which falls in the TrSL3 regime (Transition in Shear Layer), where the shear layers are fully saturated and consequently lift is high. The amplitude and frequency results are in excellent agreement with experimental data showing the initial and upper branches in VIV, transition from VIV to galloping, and galloping. Vortex structures are studied using high-resolution imaging from the CFD results showing typical 2S structure in the initial branch and both 2P+2S and 2P in the upper branch of VIV. In the galloping branch, amplitudes of 3.5 diameters are reached before the channel stops are hit.