Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session J33: Flow Control II: Actuator Design and Analysis |
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Chair: Haiyang Hu, University of Alabama in Huntsville Room: 255 E |
Sunday, November 24, 2024 5:50PM - 6:03PM |
J33.00001: Demonstration of an Actuator Array to Generate Wave-Like Perturbations through Surface Deformations Miriam Theobald-Deschine, Greeshma C Daniel, Luke Sylliaasen, Ebenezer P Gnanamanickam An actuator mechanism was demonstrated to generate traveling wave-like perturbations at the wall using surface deformations. The mechanism consisted of individually controllable solenoid actuators that introduced active surface deformations. Each solenoid actuator was designed to generate a positive (into the flow), controllable surface deformation that resembled a "Gaussian-bump" on a smooth, flexible surface. These surface deformations were designed with a maximum amplitude of less than or about 30 wall units. The actuators were arranged in a two-dimensional array to actuate in the streamwise and spanwise directions. As the actuators were individually controllable, various formations of surface perturbations could be introduced. These include traveling streamwise (with and against the flow), spanwise, and combined streamwise-spanwise surface perturbations. Further, these surface deformations can be produced in continuous or burst (or impulsive) mode. Preliminary, demonstrative measurements in a zero-pressure gradient turbulent boundary layer with a nominal friction Reynolds number of 2400 were presented. |
Sunday, November 24, 2024 6:03PM - 6:16PM |
J33.00002: Experimental characterisation of the internal flow field of a fluidic oscillator Chris J Nicholls, Michael Fenelon, Yang Zhang, Louis N Cattafesta We report on the characterization of a fluidic jet oscillator using PIV, PTV, and pressure measurements. The fluidic actuator has a single feedback channel configuration originally studied by Spyropoulos (1964) that incorporates acoustic excitation for phase synchronization. The device contains a splitter to produce a pulsed jet with potential applications in flow control problems. The synchronization of an array of such devices is of particular interest in many applications. Recent work has demonstrated that acoustic excitation can change the oscillation frequency in a fluidic oscillator and control the oscillation phase (Nicholls & Bacic, 2023). The goal is to understand the physical mechanism associated with synchronous vs. asynchronous mode of operation. |
Sunday, November 24, 2024 6:16PM - 6:29PM |
J33.00003: A Novel Synthetic Jet Created by a Deformable Dynamic Surface. Chukwudum Eluchie, Cong Wang, Bair Brandt, Joseph Pieper The conventional synthetic jet actuator typically involves an actuator oscillating periodically within a surface cavity to produce a zero-mass-flux jet. Recently, it was discovered that an oscillating deformable air-water interface at specific modes can generate a synthetic jet with high energy efficiency (Wang & Gharib, 2022). In this study, we investigate a generalized synthetic jet actuator using various elastic surface materials (e.g., latex membrane) and working fluids (e.g., water), and systematically compare it with the traditional design. We will highlight some notable features of the new synthetic jet, including lower excitation requirements and higher momentum flux. These fundamental findings could improve the performance capabilities of synthetic jet actuators for various flow control applications. |
Sunday, November 24, 2024 6:29PM - 6:42PM |
J33.00004: Open-loop active flow control of a periodically moving body based on resolvent analysis Ching-Te Lin, Min-Lin Tsai, Hsieh-Chen Tsai We design an open-loop active flow control for separated flows around a rigid body undergoing a periodic motion based on resolvent analysis. A linear time-periodic system for control is obtained by linearizing the non-inertial incompressible vorticity equation in the body-fixed frame about a time-averaged base flow. Using the Lyapunouv–Floquet transformation, the linear time-periodic system is transformed into a similar linear time-invariant system, whose resolvent is analyzed to obtain optimal locations and Strouhal number to excite the transformed linear system. A plunging circular cylinder is selected as a demonstration of the developed method. The cylinder is plunging at a Strouhal number of 0.36 and a Reynolds number of 500. The current Floquet-resolvent analysis reveals that the transformed linear system can be excited with actuations near the separation points on the cylinder surface at an optimal Strouhal number of 0.1464. Simulations show that the active control with tangential actuations is capable of reducing the lift fluctuation by up to 25.7% when the flow is actuated near the predicted harmonic and subharmonic frequencies of the optimal Strouhal number. |
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