<p>The different types of jet flow problems have long been of interest to the industry. In the case of rocket engines, under-expanded jets are the primary cause of shock waves formation immediately outside of the nozzle exit. Under-expanded jets are formed when the high-pressure fuel is injected into the combustion chamber. The formulations of these unsteady flow structures, and its development to fully turbulent steady state flows are of interest to designers. PLIF experiments on the temporal development of jet flows reveal the existence of highly under-expanded flow, moderately under-expanded and subsonic flow structures, during ‘the injection to the fully developed turbulent flow’ development process. However, these visualization experiments revealed limited or no influences on the instability features within the jet flow. The instabilities within the jets are directly responsible for the turbulence transition process. Further, these instabilities lead directly to the development of fully turbulent flows, the much-needed mixing process within the combustion chamber. Jet flow problems can be simulated by computers in a low-cost way compared to real experiments. Various fluid structures and behavior states can be analyzed in detail by CFD simulation. The ‘Integro-Differential Scheme’ (IDS) investigation proposed herein, seeks to investigate the detailed unsteady flow structures within jet flows. In the recent past, IDS has been significantly adapted to capture eddy and has been proven to solve Rayleigh Taylor instability problems. So, this numerical study seeks to identify the existing instability characteristics within the jets with the goal of manipulating them to enhance the development of turbulent flows. This CFD simulation not only focuses on a series of main fluid characteristic structures such as shock waves. More attention is paid to the capture of some details such as eddy and vortex. This is a challenge for any CFD approach. In the process of investigating these jets, the IDS numeral method is expected to fully reproduce the basic physics of under-expanded jets. In terms of setting fluid flow field, IDS needs to refer to the initial conditions and boundary conditions of different experiments and articles to generate a variety of fluid scenarios. The results of the simulated jet flow will be compared in terms of its barrel shock structures and normal shocks with existing LES and PLIF studies. In addition, IDS is an unsteady solver means the time-dependent flow structures within the jet flow will be demonstrated, and where applicable, will be manipulated and its influences compared to existing PLIF studies.</p>

An IDS Investigation of the Instability Features Within Jet Flows

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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