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.
Highlights
Vortex shedding is the oscillating flow pattern that can be observed when a fluid flows past a body, and is characterized by a regular pattern of staggered vortices that form and periodically detach at the back of the body
Besides measuring the vortex shedding frequency behind the inclined leg of the bent cylinder, for the sake of verifying the stability and reproducibility of the experimental setup, one additional vortex shedding frequency was measured behind the vertical leg of the bent cylinder
Shedding frequency behind the inclined leg of the bent cylinder, for the sake of verifying the stability and reproducibility of the experimental setup, one additional vortex shedding frequency was measured behind the vertical leg of the bent cylinder
Summary
Vortex shedding is the oscillating flow pattern that can be observed when a fluid flows past a body, and is characterized by a regular pattern of staggered vortices (so-called vortex street) that form and periodically detach at the back of the body. Vortex shedding is rather ubiquitous in practical applications, and can, for example, be observed with suspension cables, transmission lines, chimneys and slender structures in wind; risers and mooring cables in marine applications; bridge piers; tubes and rods in fluid machinery; aircraft and missiles under maneuvering conditions; and vegetation in wind or water flow. The periodic shedding of vortices induces a periodic fluctuation of the fluid forces acting on the body, which in turn can trigger vortex-induced vibration if the body is flexible or otherwise free to oscillate. Additional influencing parameters include the speed of sound for non-subsonic flows; end-effects such as the junction between the body and a wall or other surfaces, or free-ends and tips; and structural vibrations or body movement when present
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