Networked-oscillator-based modeling and control of unsteady wake flows

Area of Science:

• Fluid dynamics
• Nonlinear dynamics
• Control theory

Background:

• Bluff body flows exhibit complex energy dynamics.
• Controlling these flows is crucial for applications like drag reduction.
• Existing models like Galerkin reduced-order models have limitations.

Purpose of the Study:

• To develop a networked-oscillator model for analyzing and controlling kinetic energy transfer in periodic bluff body flows.
• To accurately capture nonlinear interactions among flow modes.
• To design a feedback controller for wake unsteadiness suppression and drag reduction.

Main Methods:

• Networked-oscillator analysis using spatial proper orthogonal decomposition (POD) modes.
• Tracking impulse responses to perturbations to identify oscillator interactions.
• Linear regression to construct the networked-oscillator model.
• Model-based feedback controller design.

Main Results:

• The networked-oscillator model accurately describes modal perturbation dynamics, outperforming empirical Galerkin models.
• The model reveals energy exchange among flow modes.
• A feedback controller successfully suppressed modal amplitudes, reducing wake unsteadiness and drag.
• The approach was validated on 2D unsteady flow over a circular cylinder.

Conclusions:

• The networked-oscillator approach provides a robust framework for characterizing modal interactions in unsteady bluff body flows.
• This method enables effective control of fundamental energy transfers for flow stabilization and drag reduction.