Detection and analysis of coherent structures in turbulent annular swirling jets

Adding swirl to jet flows has severable favorable effects in many engineering applications. It is well known for instance that swirl enhances mixing and recirculation in jet flows. Despite the favorable effects of swirl, addition of swirl can also exhibit unfavorable effects. At certain levels of swirl, large scale coherent structures are formed such as vortex breakdown or the Precessing Vortex Core. These structures involve instabilities which can create resonance effects and can harm the working of the installation. Since there are still some issues and unknown physical mechanisms involved that lead to this coherent structure instabilities in swirling jets and sudden expansion flows, this research project involves a thorough analysis of both flow fields to identify the underlying flow physics. The flow fields will be studied and analysed by a combination of experimental measurements, numerical simulations and stability analyses.