Flow Field Characteristics of a Supersonic Jet Influenced by Downstream Microjet Fluidic Injection

TL;DR

This study numerically investigates how downstream microjet fluidic injection enhances mixing in a supersonic jet, revealing improved mixing, vortex generation, and potential noise reduction compared to previous experimental findings.

Contribution

It provides new insights into the physics of microjet injection effects at smaller flow ratios and demonstrates its effectiveness in enhancing mixing and reducing noise in supersonic jets.

Findings

Enhanced jet mixing due to microjet injection and vortex formation

Attenuation of downstream turbulence production

Potential for jet noise reduction

Abstract

Mixing characteristics of a supersonic jet influenced by a Downstream Microjet Fluidic Injection (DMFI) system are numerically investigated. The DMFI system is built on the observation of a previous experimental study that utilized transverse fluidic injection from four equally spaced injection ports placed on an injection tube at a distance downstream of a 1.5 Mach number nozzle. The measurements from these previous experiments demonstrated thickening and mixing enhancement of the jet shear layer as a result of fluidic injection. The current numerical study examines the underlying physics of the flow field, as well as the effectiveness of the DMFI system at smaller mass flow rate ratios compared to those utilized in the previous experiments. Results indicate good agreement with the trend observed by the experimental study, and considerable improvement in enhancement of the jet mixing is observed. The observed mixing enhancement is attributed to the presence of the microjet tube and fluidic injection and the consequent generation of streamwise vortices, as well as the natural separating bow shock due to the transverse flow injection. DMFI system is shown to enhance the early mixing, resulting in attenuation of the downstream turbulence production. Furthermore, the DMFI system is demonstrated to be an effective method of mixing enhancement for supersonic jets with a potential for reducing the jet noise radiation.