Effectiveness of micro synthetic jet actuator enhanced by flow instability in controlling laminar separation caused by adverse pressure gradient

This paper aims to understand how a micro synthetic jet actuator works effectively to prevent the boundary layer flow from laminar separation aused by adverse pressure gradient. Experimental results showed that synthetic jets were effective when the forcing frequency was a lower frequency f the Tollmien–Schlichting (T–S) wave, which received amplification from the base flow. They demonstrated the feasibility of controlling a largecale structure feature, such as flow separation, using a micro actuator which requires very low power supply (±7.5 V) and generates inaudible noise n a boundary layer with the Reynolds number of 1.78× 105–2.24× 105. The interaction between the synthetic jet and the base flow is analyzed, nd the significance of using the instability to make the synthetic jets effective is discussed. To enable a micro actuator to work effectively on reventing the boundary layer flow from laminar separation, the key issue is to use the synthetic jet actuator as an instability trigger to trigger T–S nstability which resonates with the Kelvin–Helmortz (K–H) instability to accelerate the viscous transition. The triggered T–S waves are amplified nd enhanced by the non-viscous K–H instability of the base flow and consequently become effective in controlling the K–H instability. As a rigger rather than a force generator, the synthetic jet actuator actuates independently to its size and weight. 2006 Elsevier B.V. All rights reserved.