VIV and galloping of single circular cylinder with surface roughness at 3.0×104≤Re≤1.2×105

Passive Turbulence Control (PTC) in the form of selectively distributed surface roughness is used to alter Flow Induced Motion (FIM) of a circular cylinder in a steady flow. The objective is to enhance FIM's synchronization range and amplitude, thus maximizing conversion of hydrokinetic energy into mechanical energy by oscillator in vortex-induced vibration and/or galloping. Through additional viscous damping, mechanical energy is converted to electrical harnessing clean and renewable energy from ocean/river currents. High Reynolds numbers (Re) are required to reach the high-lift TrSL3 (Transition-Shear-Layer-3) flow regime. PTC trips flow separation and energizes the boundary layer, thus inducing higher vorticity and consequently lift. Roughness location, surface coverage, and size are studied using systematic model tests with broad-field laser visualization at 3.0×104

► Passive Turbulence Control (PTC) is applied on a circular cylinder in steady flow to alter its FIM. ► PTC as selectively distributed roughness is modeled by its placement angle, height and width. ► PTC parametric study is performed for 3.0×104≤Re≤1.2×105. ► At the upper end of the range, amplitude of 3 cylinder diameters is achieved in galloping. ► Amplitude increases with Reynolds number within the upper branch of VIV and in galloping.