A novel fluidic approach on transonic flow control at high deflection angles using Coanda effect

A fluidic approach is experimentally investigated for flow control of a transonic rectangular jet by combining Coanda attachment over a quarter-circular flap with secondary injection. The objective is to achieve more effective and practical adjustment of flow deflection across a wide range of angles. The study is conducted through experimental investigations aimed at examining the influence of key parameters, including the injection angle position (30°, 60°, and 90°), nozzle pressure ratio (NPR) (ranging from 1.8 to 3), and injection pressure ratio (IPR) (ranging from 1.25 to 6), on the flow field, flow angle, and total thrust of the nozzle. The results demonstrate that secondary jet injection over the flap at 60° and 90° positions provides an approximately linear and continuous adjustment of the deflection angle, with smaller thrust losses compared to the 30° injection case. In contrast, injection at the 30° position induces nonlinear behavior and sudden jumps in the deflection angle due to upstream flow separation, leading to greater thrust loss. The oscillation amplitude remains within a limited range, generally of the order of 1° across the tested cases, although the 90° position shows somewhat higher fluctuations under certain NPR–IPR combinations, while the 60° position exhibits the most balanced overall behavior. The findings suggest that this method can be effective, reliable, and suitable for practical applications, while also contributing to a deeper understanding of fluidic flow control using the Coanda effect. The proposed innovative technique offers advantages such as improved reliability, adjustability, and enhanced flow control.