Effect of Inclination on Vortex Shedding Frequency Behind a Bent Cylinder: An Experimental Study

Abstract

This paper presents experimental results on the vortex shedding frequency measured behind a bent cylinder. Experiments were conducted in a wind tunnel covering Reynolds numbers between 50 and 500, a range of interest for flow sensing, flow control, and energy harvesting applications. The bent cylinder comprised a vertical leg always oriented at normal incidence with respect to the free-stream flow, and an inclined leg whose inclination was varied during the tests between 90° and 15°. The bent cylinder was oriented in the wind tunnel with the vertical leg upstream and the inclined leg downstream, and the vortex shedding frequency was measured with hot-wire anemometry at several locations behind the inclined leg. The present bent cylinder design improves upon those previously considered by providing a finer control on the upstream boundary condition acting upon the inclined leg, which in the present design is not affected by the yaw angle of the inclined leg. With the exception of free-end effects, only noticeable for certain inclinations and Reynolds number values, inclination effects were surprisingly not observed, and the frequency of vortex shedding measured behind the inclined leg of the bent cylinder was consistent (within a few percent) with the cross-flow vortex shedding frequency at the same flow velocity. The present results corroborate and significantly extend the limited observations on bent cylinders available in the literature, further highlighting the importance of the upstream boundary condition on the vortex shedding process with inclined cylinders.

Experiments on Flexible Filaments in Air Flow for Aeroelasticity and Fluid-Structure Interaction Models Validation

“…Measuring the flow field in the present case would require a three-dimensional flow visualization with sub-millimeter space resolution and high-frequency (on the order of several kHz) time resolution. Even for the simplest test case documented here, which corresponds to Filament 6 statically reconfigured at a flow velocity of 1 m/s (corresponding to a Reynolds number of Re = 133), measuring the flow field would require the resolution of a vortex street where vortices of sub-millimetric size are shed at a frequency of about 100 Hz [41]. As previously noted, in FSI test cases it is normally preferred to have flexible structures which undergo large deformations with moderate motion frequency whilst interacting with a flow of moderate Reynolds number, thereby avoiding the complications of simulating highly turbulent flows.…”

Dynamics and Wake Interference Mechanism of Long Flexible Circular Cylinders in Side-by-Side Arrangements

“…Vortex shedding of two flexible cylinders is a complex phenomenon influenced by various factors such as aspect ratio, end-effects, and structural vibrations. Studies by Ramberg [14] and Silva-Leon and Cioncolini [15] have explored the impact of boundary conditions on cylinder vortex shedding, highlighting a significant correlation with cylinder end-conditions shaping threedimensional flow features in the wake. Interestingly, except for free-end effects, the vortex shedding frequency remains consistent, suggesting that bent cylinders are less affected by end-conditions.…”