Performance increment of bell nozzles: Implementation of passive flow control methods for analyzing the effects of various modifications on aerodynamic and aeroacoustic capabilities

• This study implements passive flow control methods to the supersonic Convergent-Divergent (C-D) nozzle created using isentropic flow equations, to analyses aerodynamic and acoustic parameters. The alterations comprise serrated perturbations and dimples. • The boundary layer thickness diminishes by a factor of 2.2 for serrations and by a factor of 1.1 for the least effective dimples. • Additionally, the findings demonstrated that the addition of dimples resulted in a peripheral improvement of 0.15 % in the exit Mach number. • All adjustments regarding flow control are effective. The performance differs with each geometry concerning other parameters. During high-speed operation, in Convergent-Divergent (C-D) nozzles, the thickness of boundary layer increases drastically, developing lambda shocks, shock trains and pressure oscillations at the exit leading to imperfect expansion at the exit. Capturing these shockwaves and the Shear-Boundary layer interactions are not achievable in conventional design conditions since these shocks appear in off-design conditions. This study focuses on the overall performance improvement due to the incorporation of profile modifications associated with passive flow control. Six geometries are analyzed with equally numbered volume increment and decrement geometries. The created models resemble dimples and serrations in various forms with the aim of increasing aerodynamic efficiency and the overall performance. The thickness of the boundary layer is also considered. The results indicated that the incorporation of dimples produced a marginal increase in the Mach number at the exit of 0.15 %. The boundary layer thickness also reduces by a factor of 2.2 for serrated models and 1.1 for even the least efficient modifications. There is also a marginal increment of velocity with 0.03 % for serrated airfoils and for models with dimples, decrement of 2.178 % is seen. The exit Mach shows a 7.69 % increase for serrated model. But compared to modifications of the serration, there is a decrease in overall exit temperature by 2.75 %. Few passive flow- control methods might affect the performance of the nozzles. However, this study shows the advantage of energy efficient passive flow control methods over conventional bell nozzles.