The interaction between upstream flow disturbances and aeroelastic structures has been of recent interest to research groups in both academic and military research fields. Upstream bluff bodies have been shown to modify the behavior of downstream aeroelastic structures, including producing limit cycle oscillations (LCOs) in stationary structures and annihilating, increasing, and decreasing the amplitude of LCOs in aeroelastic structures already exhibiting LCO behavior. Previous studies in this research group have shown that these effects are largely dependent on the frequency and phase of the vortices produced by the upstream bluff body. However, in existing work, the bluff bodies used to interact with downstream aeroelastic structures have largely been stationary and therefore only produce vortices at a constant frequency. This study will examine the ability of an oscillating cylinder with an attached splitter plate to produce well-behaved, periodic, vortex wakes at a range of oscillation frequencies, resulting in a range of vortex shedding frequencies.Building upon previous work which examined an oscillating cylinder with an attached splitter plate in water, this study will use a similar experimental design optimized for airflow. It has been shown that the relationship between the Strouhal numbers of a stationary cylinder and an oscillating cylinder with attached splitter plate of the same diameter plays a role in the formation of the well-behaved von Karman vortex street desired. The Strouhal number of the oscillating cylinder with attached splitter plate is calculated by using the prescribed oscillation frequency, which also corresponds to the vortex shedding frequency produced by the oscillating bluff body. The ratio St/Stn, where St is the forced Strouhal number of the oscillating cylinder and Stn is the natural Strouhal number of a stationary cylinder, provide that values which fall between 0.8 and 1.4 produce the well-behaved wake desired for further study.Using this Strouhal ratio, bluff bodies were designed for use in subsonic wind tunnel experiments with flow conditions based on previous studies. Following this initial design, computational simulations were performed to verify that these designs would produce the desired wake at a range of oscillation frequencies. Preliminary results showed good agreement with predicted behavior, showing a well-defined, von Karman vortex street in cases where the Strouhal ratio fell within the acceptable range. Additionally, simulations were run which prescribed oscillation frequencies outside of the acceptable range, resulting in undesirable wakes downstream of the bluff body, again validating the predicted behavior.In tandem with the computational studies, an experimental study was designed to further verify the ability of the oscillating bluff bodies to produce well-behaved, periodic, vortex wakes at a range of oscillation frequencies. This setup will include real-time monitoring of the oscillatory motion of the bluff body, as well as downstream flow velocity gathered using hotwire anemometry. Following the completion of the experimental study, the results will be compared with those from the computational studies to validate the efficacy of the oscillating cylinder with attached splitter plate as a controllable bluff body system for use in future aeroelasticity work.

Flow Disturbance Generators Based on Oscillating Cylinders With Attached Splitter Plates

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.