Fluid Dynamics Behind a Circular Cylinder Embedded With an Active Flapping Jet Actuator

Abstract

The effects of an active flapping jet actuator on the wake flow dynamics behind a circular cylinder in wind tunnel tests were investigated. An active flapping jet actuator was embedded in the cylinder in advance to invoke a spontaneous flapping jet into the cylinder's wake. The experiment, which was performed in a wind tunnel with a Reynolds number of Re = 1.99 × 104, was based on the oncoming wind speed, cylinder diameter, and kinematic viscosity of the air at the laboratory's temperature. The flow field structures behind the cylinder model with different dimensionless jet momentum coefficients, Cu, were obtained using the high-speed particle image velocimetry technique. The proper orthogonal decomposition (POD) method was used to represent the variation of the POD mode energy, mode coefficients, and the reconstructed spreading vorticity. The dynamic temporal evolution and time-averaged results in the near wake region of the cylinder with and without active flapping-jet control were calculated and analyzed to illustrate the rich phenomena produced by, and the control effect of, the flapping jet. For Cu values up to 0.0554, the periodic vortex shedding was pushed to farther wakes. Meanwhile, the time-averaged wake changed considerably, and the distributions of the turbulent kinetic energy and Reynolds shear stress decreased significantly. A data-driven dynamic mode decomposition method was used to extract the coherent structure of the wake of the cylinder embedded with the flapping jet actuator. The Strouhal number of the main mode of the Cu = 0.0865 case was different from the natural case.

Cylinder wake flow in confined channel and its active control by sweeping jets

“…18 shows the cumulative energy content of the first 100th POD eigenvalues with different 𝐶 𝜇 . The first two modes occupy a higher energy proportion for natural flow conditions, which consistent with other studies (Feng et al, 2011, Gao et al, 2021. Subsequently, the cumulative sum of the mode energies increases as the number of modes increases.…”

“…Following Konstantinidis et al (2007), Feng et al (2011), andGao et al (2021), the proper orthogonal decomposition (POD) method was used to analyze the flow dynamics and flow control effects. POD has been proven to be an effective method for extracting dominant features from experimental data, and there are various examples using POD to deduce the wake vortex shedding modes from the first few POD modes and reconstruct the vortex shedding process.…”

“…References such as Woszidlo et al (2019) and Hussain and Khan (2022) provide valuable insights into SWJ actuator fundamentals. Researchers, including Zhou et al (2023) and Gao et al (2021), have also successfully applied SWJs to cylinder wake active flow control.…”

A comparative study of data-driven modal decomposition analysis of unforced and forced cylinder wakes

“…1(a). Gao et al (2022) and Chang et al (2022) used a flapping jet to control the vortex shedding in a circular cylinder wake flow. The former performed POD analysis of the coherent structures in a cylindrical wake, and the latter focused on DMD analysis of the dynamic structure and spatiotemporal flow field.…”

“…Based on Park et al (2008), the PIV system uncertainties in this paper were approximately 1%. More detailed information on wind tunnels, the PIV equipment, and the flapping jet actuator characteristics can be found in previous works (Chang et al, 2022;Gao et al, 2022).…”