A three-dimensional large eddy simulation(LES) of a highly underexpanded jet with nozzle pressure ratio(NPR) of 5.60 and the magnitude of flow Reynolds number of 105 was carried out based on high-pressure gas jet injection model and high-resolution mesh. The near-field wave structures of the highly underexpanded jet were successfully captured by LES

and also agreed well with the available references data. The quantitative investigation of the radial distributions of streamwise velocity and nitrogen mass fraction was performed to reveal the self-similarity characteristics of the highly underexpanded jet.Result showed that

the self-similarity characteristics of radial profiles of streamwise velocity and nitrogen mass fraction previously observed for subsonic jets were also confirmed in the downstream jet core for the current highly underexpanded jet. The flow where the self-similarity started was still supersonic

showing a distinctive feature for the self-similarity characteristics of highly underexpanded jets. The proposed Gauss fitting formulas can well present the self-similarity characteristics of the regions close to or far away from the jet centerline. In addition

the development feature of the jet shear layer was studied

the jet growth rate obtained was compared with the previous experimental results

and the possible explanation for the difference was observed.