Influence of Free-Stream Turbulence on Dynamic Strain Measurements of a Cantilevered Cylinder in a Turbulent Cross-Flow

The relationship between different "flavours" of free-stream turbulence and the developed fluctuating strain within/deflections of a circular cylinder is analysed. Regardless of the influence of the free-stream turbulence, bluff bodies at sufficiently high Reynolds number produce turbulent wakes in which multiple turbulent length/time scales exist concurrently and interact with the body's structure, imprinting these multi-scale physics onto the structural response. The present analysis aims to provide more insight on the effect of different free-stream characteristics on the experienced fluctuating loads acting on cantilevered structures, imposed by the conditions both upstream and downstream of the body. A set of experiments is carried out in a water channel, combining simultaneous particle image velocimetry (PIV) and strain measurements, using Rayleigh backscattering sensors (RBS), along four representative polar position sensing lines, to characterise the cylinder's response before and after the shear-layer separation. The cylinder is mounted as a cantilever beam, supported at one end, with 95% of its body submerged and exposed to the influence of the flow at Re= 25000, whilst being subjected to the rising tip vortices developing at its free end. The presence of free-stream turbulence is shown to be more relevant to the standard deviation of the strain development along the upstream face of the wake-generating body with little change observed on the downstream face of the body when comparing turbulent/non-turbulent cross-flow.