Influence of Lobe Pitch on the Supersonic Jet Dynamics From a Corrugated Convergent–Divergent Nozzle With Triangular Lobes

Abstract The application of corrugated nozzles has gained significant global interest due to their potential advantages in jet propulsion applications for reducing jet noise, mixing enhancement, and weakening shock waves. However, a comprehensive analysis of the flow-field dynamics of a corrugated lobed nozzle is limited. To this end, this study numerically investigated the influence of lobe pitch on supersonic jet dynamics in a corrugated convergent–divergent (CD) nozzle. Three nozzles with different lobe pitches (6.90, 8.67, and 11.69 mm) were designed and numerically predicted at a nozzle pressure ratio of 5. The results were compared between different lobe pitch cases, and the results were also compared with the experimental data of the baseline, circular CD nozzle. The results indicated the formation of a moderately expanded shock wave in all nozzles, characterized by a diamond-like structure. Notably, the nozzle with the largest lobe pitch (11.69 mm) exhibited a shorter potential core, reduced supersonic core lengths, and an earlier emergence of the peak of the fluctuating quantities. The results presented in this study highlight the importance of optimizing the lobe pitch while designing a corrugated CD nozzle. The results indicate that a minimum number of lobes is preferable due to its inverse correlation with lobe pitch, resulting in better jet flow characteristics emanating from the corrugated CD nozzle.