Role of Duty Cycle in Burst-Modulated Synthetic Jet Flow Control

TL;DR

This study experimentally examines how duty cycle and blowing ratio influence synthetic jet flow control over a stalled airfoil, highlighting optimal parameters for reattachment, lift, and stability.

Contribution

It provides new insights into the effects of burst modulation parameters on flow reattachment, lift enhancement, and flow stability in synthetic jet control.

Findings

Flow reattachment occurs at a threshold momentum coefficient.

Low duty cycles achieve substantial lift with high power efficiency.

Higher duty cycles improve flow stability but reduce power efficiency.

Abstract

The effect of duty cycle (DC) and blowing ratio on synthetic jet flow control over a stalled NACA 0025 airfoil at Re_c=10^5 was investigated experimentally. A finite-span microblower array operating with burst modulation was tested across a wide range of control parameters to assess aerodynamic performance, power consumption, and flow stability. Flow reattachment was achieved once a threshold momentum coefficient was met via increasing either the DC or blowing ratio. Control effectiveness increased sharply upon reattachment, with additional momentum providing incremental improvements in lift, spanwise control, and flow stability, though these effects eventually saturated. Substantial lift improvements are observed at DCs as low as 5%, indicating that brief, high-momentum bursts were the most power-efficient for achieving reattachment. However, flow stability was reduced at low DCs due to the inconsistent streamwise dissipation of spanwise vortices responsible for flow control. Higher DC control strategies resulted in more consistent boundary layer control. These results provide a framework for selecting control strategies that balance aerodynamic performance and stability with power efficiency.