One-way coupling of surface vibration and Kármán vortex street instability

Wiberg, Derrick DeMont

Permalink

https://hdl.handle.net/2142/129325 Copy

Description

Title

One-way coupling of surface vibration and Kármán vortex street instability

Author(s)

Wiberg, Derrick DeMont

Issue Date

2025-05-07

Director of Research (if dissertation) or Advisor (if thesis)

Ansell, Phillip J

Department of Study

Aerospace Engineering

Discipline

Aerospace Engineering

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Fluid-structure interaction
• Cylinder
• Kármán vortex street
• Surface vibration
• Wall-bounded flow
• Wind tunnel
• Aerodynamics

Abstract

An experimental study of the one-way coupling between a vibrating surface and the Kármán vortex street flow instability was conducted to identify criteria for effective flow control via fluid structure interaction. This investigation was motivated by the desire to inform the design of passive metamaterials for flow control wherein spectral scales of structural dynamics are matched with those of fluid instabilities. To that end, the interaction between the periodic vortex shedding in the wake of a cylinder and a surface vibrating at equivalent or near-equivalent frequencies of this flow instability was examined. Wind tunnel experiments at Reynolds numbers ranging from Re = 1.3 × 10^4 to Re = 3.7 × 10^4 were conducted to evaluate wall pressure and flow field characteristics in the wake of a circular cylinder located near a vibrating wall section. By actively controlling the surface vibration, the effects of the vibration frequency and amplitude on vortex shedding behavior were studied. Other parameters of interest to the fluid-structure coupling were also examined including the proximity of the vibrating surface to the cylinder and the freestream conditions. It was determined that through active excitation of the vibrating surface, the vortex shedding behavior could be biased to phase-lock with the surface motion. This phase-locking effect was facilitated by the proximity of the excitation frequency to the mean shedding frequency combined with high displacement amplitude to produce sufficient spectral power in relation to the baseline vortex shedding spectral power. Additionally, it was determined that physical proximity of the vibrating surface to the source of the instability (in this case, the underside of the cylinder), along with test conditions at lower Reynolds numbers resulted in greater phase-locking authority. The phase-locking phenomenon was found to be correlated to a subtle increase in overall circulation in the near-wake, suggesting a sustainment of circulation due to surface vibration. Phase locking was also accompanied by significant alterations to the dominant spatial modes of the resulting flow, as identified by proper orthogonal decomposition. These results obtained through active one-way coupling will provide a helpful basis for the design of passive two-way coupled materials for flow control of a variety of flow instabilities.

Graduation Semester

2025-05

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/129325

Copyright and License Information

Copyright 2025 Derrick Wiberg

Owning Collections