Helical modes in a hydrodynamically self-excited jet
Low-density jets are a canonical model of a hydrodynamic oscillator. They are known to exhibit global instability in the form of self-excited axisymmetric oscillations, but are not generally known to support self-excited helical oscillations. In fact, the existence of helical modes in such jets has been predicted only a few times before (e.g. in the local linear spatiotemporal stability analysis of Coenen, Sevilla, and Sanchez [Physics of Fluids (20) 2008]) but helical modes have yet to be detected in real-world experiments. In this project, you will perform laboratory experiments to search for the existence of helical modes in low-density jets, potentially opening up new pathways through which such global hydrodynamic instabilities can be used in industrial and environmental applications such as aircraft engines and pollutant dispersion.