Under-Expanded Jets

Dear Colleagues,

Fundamental understanding of the under-expansion process and under-expanded jets is highly beneficial to engineers and scientists of various fields, from aerospace engineering to geophysics. Under-expanded jets are complex high speed flows, which are formed in various engineering applications and devices such as exhaust plumes of aircrafts (rockets and missiles), supersonic combustors, actuators, ejectors and high pressure gaseous injectors. This type of jet can also be observed in geophysical systems (volcanic eruption) and in accidental release of hazardous gases (such as hydrogen) from tiny cracks in high pressure pipelines and reservoirs.

General characteristics of under-expanded jets in the aforementioned examples are similar, however different nozzle diameters, nozzle (hole) shapes, jet/ambient fluids and nozzle pressure ratios would result in significantly different flow behaviours. Although overall structures of under-expanded jets have been comprehensively identified, many specific characteristics and quantitative aspects are still to be determined. Furthermore, there are very limited quantitative data available for under-expanded jets issued form small-size and particularly millimetre-size nozzles. Therefore, this Special Issue aims to provide quantitative insights into the key sonic and mixing characteristics of under-expanded jets particularly those issued from millimetre-size nozzles.

Authors are encouraged to submit high quality manuscripts on analytical, computational (high fidelity modelling) and experimental (advanced quantitative measurement techniques) studies in the field of under-expanded jets. The topics of interest may include, but are not restricted to, free and impinging jets, co and cross-flows, near-nozzle shock structures, Mach disk dimensions and curvature, vortical and coherent structures and shear layers, turbulent mixing characteristics, aeroacoustics and screech tone, shock-shear interactions, viscous effects, farfield characteristics, effects of the ambient medium thermodynamic conditions, effects of the nozzle diameter and topology (lip geometry and exit profile), hydrodynamic instabilities, compressible in-nozzle flows, different jet/ambient fluids, computational modelling with real fluid equation of state and properties, reacting under-expanded jets, numerical methods, such as advanced shock capturing techniques.

Dr. Paul Bruce
Dr. Arash Hamzehloo
Guest Editors

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